News & Views
The Mars Astrobiology Explorer-Cacher
(MAX-C): A Potential Rover Mission for 2018
Final Report of the Mars Mid-Range Rover Science Analysis Group (MRR-SAG) October 14, 2009
Table of Contents
1. Executive Summary 127
2. Introduction 129
3. Scientific Priorities for a Possible Late-Decade Rover Mission 130
4. Development of a Spectrum of Possible Mission Concepts 131
5. Evaluation, Prioritization of Candidate Mission Concepts 132
6. Strategy to Achieve Primary In Situ Objectives 136
7. Relationship to a Potential Sample Return Campaign 141
8. Consensus Mission Vision 146
9. Considerations Related to Landing Site Selection 147
10. Some Engineering Considerations Related to the Consensus Mission Vision 152
11. Acknowledgments 156
12. Abbreviations 156
13. References 156
1. Executive Summary
This report documents the work of the Mid-Range Ro-ver Science Analysis Group (MRR-SAG), which was
assigned to formulate a concept for a potential rover mission
that could be launched to Mars in 2018. Based on pro-
grammatic and engineering considerations as of April 2009,
our deliberations assumed that the potential mission would
use the Mars Science Laboratory (MSL) sky-crane landing
system and include a single solar-powered rover. The mis-
sion would also have a targeting accuracy of *7 km
(semimajor axis landing ellipse), a mobility range of at least
10 km, and a lifetime on the martian surface of at least 1
Earth year. An additional key consideration, given recently
declining budgets and cost growth issues with MSL, is that
the proposed rover must have lower cost and cost risk than
Members: Lisa M. Pratt, Chair, Indiana University; Carl Allen, NASA Johnson Space Center; Abby Allwood,
Jet Propulsion Laboratory, California Institute of Technology; Ariel Anbar, Arizona State University; Sushil
Atreya, University of Michigan; Mike Carr, U.S. Geological Survey, retired; Dave Des Marais, NASA Ames
Research Center; John Grant, Smithsonian Institution; Daniel Glavin, NASA Goddard Space Flight Center; Vicky
Hamilton, Southwest Research Institute; Ken Herkenhoff, U.S. Geological Survey; Vicky Hipkin, Canadian
Space Agency, Canada; Barbara Sherwood Lollar, University of Toronto, Canada; Tom McCollom, University of
Colorado; Alfred McEwen, University of Arizona; Scott McLennan, State University of New York, Stony Brook;
Ralph Milliken, Jet Propulsion Laboratory, California Institute of Technology; Doug Ming, NASA Johnson Space
Flight Center; Gian Gabrielle Ori, International Research School of Planetary Sciences, Italy; John Parnell, Uni-
versity of Aberdeen, United Kingdom; Franc?ois Poulet, Universite? Paris-Sud, France; Frances Westall, Centre
National de la Recherche Scientifique, France.
Ex Officio Members: David Beaty, Mars Program Office, Jet Propulsion Laboratory, California Institute of
Technology; Joy Crisp, Mars Program Office, Jet Propulsion Laboratory, California Institute of Technology;
Chris Salvo, Jet Propulsion Laboratory, California Institute of Technology; Charles Whetsel, Jet Propulsion
Laboratory, California Institute of Technology; Michael Wilson, Jet Propulsion Laboratory, California Institute
of Technology.
ASTROBIOLOGY
Volume 10, Number 2, 2010
? Mary Ann Liebert, Inc.
DOI: 10.1089=ast.2010.0462
127
those of MSL?this is an essential consideration for the
Mars Exploration Program Analysis Group (MEPAG). The
MRR-SAG was asked to formulate a mission concept that
would address two general objectives: (1) conduct high-
priority in situ science and (2) make concrete steps toward
the potential return of samples to Earth. The proposed
means of achieving these two goals while balancing the
trade-offs between them are described here in detail. We
propose the name Mars Astrobiology Explorer-Cacher
(MAX-C) to reflect the dual purpose of this potential 2018
rover mission.
A key conclusion is that the capabilities needed to carry
out compelling, breakthrough science at the martian surface
are the same as those needed to select samples for potential
sample return to document their context. This leads to a
common rover concept with the following attributes:

 Mast- or body-mounted instruments capable of estab-
lishing local geological context and identifying targets
for close-up investigation. This could consist of an op-
tical camera and an instrument to determine mineralogy
remotely. Documentation of the field context of the
landing site would include mapping outcrops and other
accessible rocks, characterization of mineralogy and
geochemistry, and interpretation of paleoenvironments.

 A tool to produce a flat abraded surface on rock
samples.

 A set of arm-mounted instruments capable of interro-
gating the abraded surfaces by creating co-registered
two-dimensional maps of visual texture, major element
geochemistry, mineralogy, and organic geochemistry.
This information would be used to understand the di-
versity of the samples at the landing site, formulate
hypotheses for the origin of that diversity, and seek
candidate signs of past life preserved in the geological
record. This information could also be used to select an
outstanding set of rock core samples for potential return
to Earth.

 A rock core acquisition, encapsulation, and caching
system of the standards specified by the MEPAG Next
Decade Science Analysis Group (ND-SAG) (2008). This
cache would be left in a position (either on the ground or
on the rover) where it could be recovered by a future
potential sample return mission.
We propose the following summary primary scientific
objectives for the potential MAX-C mission: At a site in-
terpreted to represent high habitability potential with high
preservation potential for physical and chemical bio-
signatures: evaluate paleoenvironmental conditions, charac-
terize the potential for preservation of biotic or prebiotic
signatures, and access multiple sequences of geological units
in a search for evidence of past life or prebiotic chemistry.
Samples necessary to achieve the proposed scientific objec-
tives of the potential future sample return mission should be
collected, documented, and packaged in a manner suitable
for potential return to Earth.
The scientific value of the MAX-C mission would be sig-
nificantly improved if it were possible to accommodate a
small secondary payload. Highest priorities, as judged
by this team, are basic atmospheric monitoring, an atmo-
spheric-surface interactions instrument package, and a
magnetometer.
The most important contribution of the proposed MAX-C
mission to a potential sample return would be the assembly
of a returnable cache of rock core samples. This cache
would place the program on the pathway of a potential
3-element Mars sample return campaign [sampling rover
mission, combined fetch rover plus Mars Ascent Vehicle
(MAV) mission, and orbital retrieval mission]. By preparing
a cache, the proposed MAX-C rover would reduce the
complexity, payload size, and landed operations time of a
potential follow-on mission that would land the potential
MAV, thus reducing the overall risk of that follow-on mis-
sion. This reduction in mass would facilitate bringing a po-
tential sample return mission?s landed mass within heritage
(MSL) entry, descent, and landing capabilities. Even though
caching would consume mission resources (e.g., money,
mass, and surface operation time) that could alternatively be
used for in situ scientific operations, the benefit to a potential
sample return campaign would be compelling.
The proposed MAX-C rover would be smaller than MSL,
but larger than the Mars Exploration Rovers (MERs). This
makes a reflight of the MSL Cruise=Entry, Descent, and
Landing system a prudent cost-effective choice to deliver the
proposed MAX-C rover to the surface of Mars. Recent high-
level discussions between NASA and ESA have explored the
idea of delivering the ESA ExoMars rover and the proposed
NASA MAX-C rover to Mars together in 2018 on a single
launch and MSL-type Entry, Descent, and Landing (EDL)
system. This combined mission concept has been evaluated
only briefly thus far. The implementation discussion in this
report reflects a proposed NASA-only MAX-C mission, but
the general capabilities would not be expected to change
significantly for a joint mission architecture.
The proposed MAX-C mission would be launched in May
2018 and arrive at Mars in January 2019 at Ls? 3258
(northern mid-winter). Given the favorable atmospheric
pressure at this season, performance of the MSL delivery
system might allow altitudes up to ?1 km, but altitude
would trade off against the landed mass. There are also
unfavorable effects on the atmosphere from an increased
probability of dust storms, but the combined effects of these
factors have not yet been fully evaluated. Latitude access for
a solar-powered rover with a minimum of a 1-Earth-year
primary mission lifetime is restricted to between 258N and
158S.
The mission concept would require near-term technology
development in four key areas:

 Coring, encapsulation, and caching: Lightweight tools
and mechanisms to obtain and handle cored samples.

 Scientific payload: Instruments capable of achieving the
primary scientific objectives need to be matured, par-
ticularly for microscale mapping of mineralogy, organic
compounds, and elemental composition.

 Planetary protection=contamination control: Methodol-
ogies for biocleaning, cataloging of biocontaminants,
and transport modeling to ensure cached samples
would be returnable.

 Rover navigation: Enhanced onboard image processing
and navigation algorithms to increase traverse rate.
As the next lander mission in the Mars Exploration Pro-
gram, the proposed MAX-C mission would be a logical step
in addressing MEPAG?s goals, especially for astrobiological
128 MRR-SAG
and geological objectives. It could be flown alone or with
ExoMars and could be sent to a previously visited site or a
new more-compelling site selected from orbital data, with
sample return objectives included in the site selection criteria.
It would be capable of yielding exciting in situ mission re-
sults in its own right as well as making a significant feed-
forward contribution to a potential sample return, and it
would likely become the first step in a potential sample re-
turn campaign.
2. Introduction
2.1. Background
As noted by MEPAG (2009), Mars has crustal and atmo-
spheric characteristics that make it a priority exploration
target for understanding the origins of life. The essential
energy, water, and nutrient requirements to support and
sustain life are currently present, and the martian geological
record offers tantalizing clues of many ancient habitable
environments (e.g., Knoll and Grotzinger, 2006; Squyres et al.,
2008; Hecht et al., 2009). Recent data from orbiting and
landed instruments have been studied by multiple teams
of researchers, revealing a complexly dynamic planet with
formation of rock units and structures influenced by impact
events, crustal melting, tectonism, fluid=rock interactions,
weathering, erosion, sedimentation, glaciation, and climate
change (see, e.g., Christensen et al., 2003; Neukum et al., 2004;
Howard et al., 2005; Tanaka et al., 2005; Bibring et al., 2006;
Hahn et al., 2007; Arvidson et al., 2008; Frey, 2008; Murchie
et al., 2009; Smith et al., 2009b; Squyres et al., 2009). If life
emerged and evolved on early Mars, then it is possible, and
indeed likely, that physical or chemical biosignatures are
preserved in the exposed rock record. These extraordinary
discoveries and inferences make a compelling case for a
rover mission designed to explore for evidence of past
martian life.
In the 2006 reports of the Mars Advance Planning Group
(Beaty et al., 2006; McCleese et al., 2006), a mission concept
was introduced that was generically referred to as ??Mars
mid-rover.?? This was envisioned as a mission that could be
considered for flight in 2016 or 2018, in follow-up to the MSL
and ExoMars rovers. The mission concept involved twin
??MER-derived rovers directed to different sites to explore the
geological diversity on Mars and, perhaps, search for organic
material.?? In February 2008, the MEPAG Mars Strategic
Science Assessment Group discussed the possible purpose
and value of a single mid-range rover in more detail, given
our discoveries at Mars through 2007, and concluded that
there could be three significant benefits:

 ??Characterization of a new site follows up on discovery
of diverse aqueous deposits

 Investigation of each type of deposit promises signifi-
cant new insights into the history of water on Mars

 Provides additional context for proposed MSR samples??
The MRR concept was also included in the planning work
of the Mars Architecture Tiger Team (MATT) (Christensen
et al., 2008, 2009). By the time of the MATT-3 report (Chris-
tensen et al., 2009), the potential mission was referred to with
several different working names, including both Mid-Range
Rover and Mars Prospector Rover, and the mission con-
cept was generically envisioned as including a single ??MER-
or MSL-class rover with precision landing and sampling=
caching capability.??

 An at least MER-class rover would be deployed to new
water-related geological targets.

 Precision landing (<6 km diameter error ellipse) would
enable access to new sites.

 The concept would allow investigators to conduct
independent science but with scientific and technical
feed-forward to Mars Sample Return (MSR).

 As a precursor, this concept should demonstrate feed-
forward capabilities for MSR and might open the pos-
sibility for payload trade-offs (e.g., caching and cache
delivery) with the proposed MSR lander.
Although the strategic importance of a rover mission in
about 2016?2018 to Mars exploration was recognized in each
of the above planning documents, the specific purpose, rover
size, and even the number of rovers was deferred to a future
science planning team. For example, none of the above re-
ports penetrated the details of the possible scientific objec-
tives (and the reasons why those objectives are important),
how this mission would fit within an evolving program-
matic context (most importantly, its relationship to MSL and
a possible MSR mission), the investigation strategy, and the
preliminary attributes of the rover needed to carry out these
objectives. MEPAG has therefore requested an analysis of
scientific priorities and engineering implications for this
mission concept.
2.2. MRR-SAG Charter
The Mars Exploration Program Analysis Group chartered
a Mid-Range Rover Science Analysis Group (MRR-SAG) to
analyze

 possible scientific objectives of such a mission,

 the potential contribution of such a mission to the pos-
sible future return of samples from Mars, any long-lead
technologies that would enable or enhance the potential
Mid-Range Rover (MRR) mission and possible subse-
quent sample return.
The complete charter is provided in MEPAG MRR-SAG
(2009).
The MRR-SAG was given the following guidelines for the
analysis:

 The MRR mission should include a single solar-powered
rover, with a targeting accuracy of 3 km semimajor axis
landing ellipse, a rover range of at least 5 km, a lifetime
greater than 1 Earth year, and no requirement to visit a
Planetary Protection Special region.

 The mission should have two purposes?to conduct
high-priority in situ science and to prepare for potential
sample return.

 Given the forecasted budgetary environment, it is im-
perative to find mission options that would be lower
cost and lower cost-risk than MSL.
After the charter was provided, engineers with expertise
in Mars EDL capabilities determined, during the MRR-SAG
deliberations, that the targeting accuracy and rover range
guidelines needed adjustment. More-realistic capabilities,
which were used for the MRR mission concept analyzed in
PROPOSED MARS ASTROBIOLOGY EXPLORER-CACHER (MAX-C) 129
this report, are a semimajor axis landing ellipse of *7 km
and a rover range of at least 10 km.
The following specific tasks were assigned:
(1) Evaluate the possible and probable discoveries from
MSL and ExoMars that would feed forward to the 2018
(or 2020) opportunity.
(2) Analyze the high-priority in situ science that could be
accomplished based on Task 1, the MEPAG Goals
Document (MEPAG, 2008), and recent National Re-
search Council (NRC) reports. Propose draft state-
ments of the scientific objectives for this mission.
Evaluate the kinds of instruments, kinds of landing
sites, and nature of surface operations that would be
needed to achieve the scientific objectives.
(3) Determine the most important ways (scientific and
technical) in which this mission could contribute to a
potential sample return.
(4) Analyze the trade-offs associated with simultaneously
optimizing Tasks (2) and (3).
(5) Analyze the incremental value to either in situ science
or potential sample return feed-forward or both, which
could be achieved with a modest increase in budget
over the baseline assumptions specified above.
As a consequence of feedback from the Mars Architecture
Review Team on a presentation of preliminary findings
partway through the analysis, and in consultation with the
MEPAG Chair and Mars Program administrators, the SAG
responded to additional questions with the intent to clarify
findings on the above tasks and explore more completely the
engineering complexity of a sample cache.
The membership of the MRR-SAG is listed on page 127.
Team members were selected by the MEPAG Executive
Committee to represent the diversity in expertise within the
Mars Program. They have considerable experience in Mars
science, in previous and ongoing Mars spacecraft missions,
and from membership on MEPAG and other NASA advisory
groups. The 27-member team has 6 non-US members, 4 of
whom are involved in ExoMars. The team also included
three Jet Propulsion Laboratory ( JPL) engineers. The SAG
also elicited assistance from about 30 other scientists and
engineers (see Acknowledgments) in areas where additional
expertise was needed.
Right before the MEPAG meeting ( July 29?30, 2009), news
stories reported the possibility that NASA and ESA might
decide to fly a joint mission and send the ExoMars rover and
a NASA rover smaller than MSL on the same landing system
in 2018. This new scenario would delay the launch of Exo-
Mars from the 2016 launch opportunity to 2018. Because of
the timing of this news, a detailed analysis of the option to
fly an MRR with ExoMars was beyond the scope of the MRR-
SAG. However, even if flown together, the two rovers would
probably have different lifetimes and strategies and would
eventually end up traversing to different locations. To min-
imize risk and maximize scientific return, the concept of the
MRR as proposed in this report would still be a sensible one,
even if flown together with ExoMars. We leave the detailed
analysis of this option to future study groups.
To provide a name that fit the mission concept better,
the MRR-SAG changed the name of their concept from
the generic Mid-Range Rover (MRR) to Mars Astrobiology
Explorer-Cacher (MAX-C) toward the end of their deliber-
ations in August 2009, and this updated name is used in the
rest of this report.
3. Scientific Priorities for a Possible Late-Decade
Rover Mission
The Mars Exploration Program Analysis Group actively
maintains a prioritized, consensus-based list of four broad
scientific objectives that could be achieved with use of the
ongoing flight program (MEPAG, 2008):

 Determine whether life ever arose on Mars,

 Understand the processes and history of climate on
Mars,

 Determine the evolution of the surface and interior of
Mars,

 Prepare for human exploration.
At present, the emphasis of the Mars Exploration Pro-
gram is on the objective of determining whether life ever
arose on the planet. Searching for signs of life on another
planetary body requires a detailed understanding of the
diversity of life as well as the environmental limits and
evolutionary adaptations of life for different physical and
chemical settings on Earth. Exploration for life on Mars re-
quires a broad understanding of integrated planetary pro-
cesses in order to identify those locations where habitable
conditions are most likely to exist today or to have existed
in the past, and where conditions are, or were, favorable for
preservation of the evidence of life if it ever existed. Any
endeavor to search for signs of life, therefore, must also seek
to understand

 The geological and geophysical evolution of Mars,

 The history of Mars? volatiles and climate,

 The nature of the surface and subsurface environments,
now and in the past,

 The temporal and geographic distribution of liquid
water,

 The availability of other resources (e.g., energy) neces-
sary for life.
Over most of the last decade, the Mars Exploration Pro-
gram has pursued a strategy of ??follow the water?? (formally
introduced in 2000; see documentation in MEPAG, 2008).
While this strategy has been highly successful in the Mars
missions of 1996?2007 (MPF, MGS, ODY, MER, MEX, MRO,
and PHX), it is increasingly appreciated that assessing the
full astrobiological potential of martian environments re-
quires going beyond the identification of locations where
liquid water was present (e.g., Knoll and Grotzinger, 2006;
Hoehler, 2007). Thus, to seek signs of past or present life on
Mars, it is necessary to characterize more comprehensively
the macroscopic and microscopic fabric of sedimentary ma-
terials, identify organic molecules, reconstruct the history of
mineral formation as an indicator of preservation potential
and geochemical environments, and determine specific
mineral compositions as indicators of oxidized organic ma-
terials or coupled redox reactions characteristic of life. This
type of information would be critical to selecting and caching
relevant samples in an effort to address the life question in
samples intended for study in sophisticated laboratories on
Earth.
130 MRR-SAG
Two landed Mars missions are currently in development.
Although neither has yet returned data, for the purpose of
planning, we need to be cognizant of their objectives and
possible results. NASA?s MSL, scheduled for launch in 2011,
has the following objectives (Crisp et al., 2008):

 Assess the biological potential of at least one target en-
vironment,

 Characterize the geology and geochemistry of the
landing region,

 Investigate planetary processes relevant to past habit-
ability,

 Characterize the broad spectrum of surface radiation.
ExoMars, which ESA plans to launch in 2018, has the fol-
lowing objectives (Vago et al., 2006):

 Search for signs of past and present life on Mars,

 Characterize the water=geochemical distribution as a
function of depth in the shallow subsurface,

 Study the surface environment and identify hazards to
potential future human missions,

 Investigate the planet?s subsurface and deep interior to
better understand the evolution and habitability of
Mars.
The ??Follow the Water?? theme has served Mars explora-
tion well by connecting discipline goals in our investigations
of Mars just as those processes (geological, geophysical,
meteorological, chemical, and potentially biological) have
been connected through Mars? history. As the numerous
missions to Mars have revealed the diversity of its environ-
ments and the complexity of its history, other themes have
emerged, which MEPAG has considered and NASA, to some
extent, has adopted:

 Introduced in 2000: Follow the Water (MGS, ODY,
MER, MEX, MRO, PHX)

 Introduced in 2004: Understand Mars as a System (All
missions)

 Introduced in 2005: Seek Habitable Environments
(MSL, MSR)
As summarized by MEPAG (2009), the focus of potential
missions should be to explore habitable environments of
the past and present, including the ??how, when, and why?? of
environmental change. Although quantitatively assessing
environmental habitability is the objective of MSL, the
growing body of information about the diverse aqueous
environments of Mars indicates that we are ready for more
ambitious next steps. The NRC (2007) recently concluded,
??The search for evidence of past or present life, as well as
determination of the planetary context that creates habitable
environments, is a compelling primary focus for NASA?s
Mars Exploration Program.?? These considerations have led
MEPAG to adopt (at the July 2009 MEPAG meeting) ??Seek
the Signs of Life?? as its next broad strategy (MEPAG,
2009; Mustard, 2009). There is a drive to have the proposed
MAX-C rover mission be the first major mission designed to
support this new strategy (see Fig. 3.1).
Sample return from Mars has been advocated by numer-
ous scientific advisory panels for over 30 years, most
prominently beginning with the NRC?s (1978) strategy for
the exploration of the inner Solar System, and most recently
by MEPAG?s ND-SAG (2008) panel. It remains the highest-
priority potential future mission in the Mars Exploration
Program. Analysis of samples here on Earth has enormous
advantages over in situ analyses. Instead of a small, pre-
determined set of analytic techniques applied to samples
analyzed in situ, a return of samples would enable the ana-
lytical approach to be all-encompassing and flexible. State-of-
the-art analytical resources of the entire scientific community
could be applied to the samples, and the analytical emphasis
could shift as the meaning of each result becomes better
appreciated. Sample return has, however, been repeatedly
deferred mainly for budgetary reasons.
The possible strategy of using rovers prior to MSR to collect
and cache geological samples for possible subsequent return to
Earth has been discussed as far back as at least the mid-1990s.
The brief mention by Shirley and Haynes (1997) clearly shows
that this was being discussed as a conceptual planning option
at that time.MacPherson et al. (2002) and Steele et al. (2005) also
briefly discussed sample caching, but particularly noted the
potential difficulties of surface rendezvous. These reportswere
written in the context of MERs that were designed to last for
only 90 sols and to travel 600m (Crisp et al., 2003), so the
challenges of physically recovering potential caches appeared
quite daunting. The first detailed discussion of caching was
presented by MacPherson et al. (2005). They pointed out some
of themajor advantages of caching, including reducing timeon
the surface for the potential MAV and improving sample
documentation by a prior mission that would have more time,
and the engineering advantages of sending the potential MSR
lander into known terrain. In the Mars Advance Planning
Group programmatic planning report (Beaty et al., 2006),
sample caching was recognized as a strategy by which to in-
crease the scientific value of a potential future sample return. It
would improve the quality of the sample collection returnedby
a potential MSR by allowing more information to go into
sample selection decisions. This was followed up by the NRC
(2007), which recommended ??sample caching on all surface
missions that follow theMars Science Laboratory, in away that
wouldprepare fora relatively early returnof samples toEarth.??
In mid-2007, NASA directed that a very simple cache (McKay
et al., 2007; Karcz et al., 2008b; design documented by Karcz
et al., 2008a) be added to the MSL rover. At the time, MSL was
very advanced in its design process, which resulted in a
number of significant constraints. Although they endorsed the
potential value of sample caching, Steele et al. (2008) and the
MEPAG ND-SAG (2008) raised serious concerns regarding
sample quality for this specific implementation. In November
2008, given the advanced state ofMSL?s design, it was decided
that this cache could not be added without significant conse-
quences in other areas, and the cachewas descoped fromMSL.
Finally, a number of the MSR-related white papers submitted
to the 2009 Planetary Decadal Survey discussed the potential
strategic importance ofMSR-related sample caching, including
Borg et al. (2009), Farmer et al. (2009), Hand et al. (2009), Hayati
et al. (2009), Jakosky et al. (2009), MEPAG (2009), Neal et al.
(2009), and Steele et al. (2009).
4. Development of a Spectrum of Possible
Mission Concepts
To assess whether the prospective rover mission could
meet the scientific goals of the Mars program within the
constraints provided, the panel undertook the exercise of
PROPOSED MARS ASTROBIOLOGY EXPLORER-CACHER (MAX-C) 131
defining and evaluating potential mission scenarios with
which to achieve current program priorities and determine
the rover capabilities required to accomplish the mission
objectives. Building on the long history of scientific explo-
ration on Mars, it is possible to frame a diverse array of
highly informed and specific scientific objectives that lay
out a path for far-reaching insights to the planet. Many of
the key scientific objectives could be addressed with an
in situ rover mission, and the MRR-SAG committee com-
piled a list of 28 such objectives that they felt could be
addressed by a potential MAX-C mission. Some of the ob-
jectives pertain to application of specific types of measure-
ments (or approaches to measurements) that would be
valuable for addressing several different scientific questions,
whereas others describe the important scientific objectives
themselves, without specification of measurements or ap-
proaches. Thus, there are many conceptual overlaps and
interrelationships within the list. Six broad scientific themes
emerged from the list:

 The search for extant life on Mars

 The search for evidence of past life on Mars

 Understanding martian climate history

 Determination of the ages of geological terrains on Mars

 Understanding surface-atmosphere interactions on Mars

 Understanding martian interior processes
The possible scientific objectives and scientific themes
could be organized into eight mission concepts (Table 4.1).
These mission concepts encompass one or more of the sci-
entific themes listed above. The MEPAG Goals Committee
reviewed these mission concepts for completeness and clar-
ity. They pointed out some ways of consolidating the list to
make it more useful, which helped to focus in on the defi-
nition of the various concepts, but they did not contribute
any additional new mission concepts. This helped give us
confidence that we had sufficiently covered the full spectrum
of high-priority options. SAG members self-selected into
eight subgroups (one for each mission concept) that worked
to identify fundamental scientific questions, essential infor-
mation needed, landing site considerations, and mission
implementation. These eight mission concepts are described
more fully in MEPAG MRR-SAG (2009).
The MRR-SAG also identified several possible augmen-
tations to these missions, which might be accommodated if
sufficient funding were available. These augmentations
(landed atmospheric science, paleomagnetic measurements,
and radiometric dating) are described in Section 5.3 and in
more depth in MEPAG MRR-SAG (2009). Note that two of
the mission concepts (#3 Radiometric Age Determination
and #6 Deep Drilling) could also be considered as augmen-
tations to other mission concepts.
5. Evaluation, Prioritization of Candidate
Mission Concepts
5.1. Concept prioritization
The SAG prioritized the candidate mission concepts using
the following criteria: scientific value, scientific risk, and
breakthrough potential. The priority rankings are given in
Table 5.1. Three concepts (reference #4, #2, and #5) clearly
ranked higher than the rest. Several mission concepts were
determined to be not currently viable, for various reasons. A
mission to obtain absolute radiometric ages for surface mate-
rials (Concept #3) was considered to offer potential future
promise, but technologies that allow age determinations in situ
appear not yet to be mature or cost effective (e.g.,Conrad et al.,
2009).Amission to investigatemethane seeps (Concept #7) had
strong astrobiological interest, but the SAG did not see a clear
path that would provide sufficient information on the spatial
FIG. 3.1. Timeline of launch dates for missions already launched (red), missions in development (orange), and proposed
missions (yellow). The proposed MAX-C mission could be the first step in a potential Mars sample return campaign,
representing a transition from earlier missions that ??followed the water?? and missions currently in development that will
focus on habitability. Modified after Mustard (2009).
FINDING: Several rover-based mission concepts with com-
pelling scientific objectives have been identified for the 2018
opportunity.
132 MRR-SAG
distribution of such seeps to allow targeting for the 2018 launch
opportunity, even with a potential Trace Gas Mapper in 2016
(Smith et al., 2009a). This could be revisited later if a Trace Gas
Mapper is selected, and after its capabilities have been defined.
A potential mission to polar layered deposits (Concept #8)
was not considered viable because the SAGwas informed that
it appears there are no reasonably achievable trajectories to
high-latitude sites in the 2018 launch opportunity.Moreover, a
rover mission trying to last a year would have a severe power
challenge at such high latitude. In addition to the rankings,
members of the team were invited to add comments that ex-
plained the reasons behind their rankings. These comments
were compiled by concept and,within each concept, organized
into positive and negative remarks. A summary of the more
notable points that were raised is given in MEPAG MRR-SAG
(2009).
The MRR-SAG team had a mixture of scientific expertise
that could be broadly grouped into three categories: geolo-
gists, astrobiologists, and atmospheric scientists plus geo-
physicists. Because perspective on relative priority for
concepts as diverse as these can be quite dependent on dis-
cipline balance, we show in Table 5.2 the relative priorities of
the eight mission concepts as judged by these three discipline
groups. Most importantly, Concepts #2 and #4 were rated the
top two priorities by each of the three discipline groups, and
Concept #5 was rated a third priority by two of the groups
and fourth by the other. The differences between these
groups were that the atmospheric scientists saw higher value
in Concept #1 (relating to mid-latitude ice), the astrobi-
ologists saw higher value in Concept #7 (methane), and the
geologists saw higher value in Concept #3 (age dating).
However, the convergence of all sectors of the team on
Concepts #2, #4, and #5 is an important foundation for for-
mulating a consensus mission concept.
5.2. Integration into a single mission concept
It is increasingly appreciated that assessing the full astro-
biological potential of martian environments requires going
beyond the identification of locations where liquid water is,
Table 4.1. Mission Concepts and Proposed Primary Objectives
Ref # Mission concept Primary scientific objectives
1 Mid-latitude ice analysis Characterize periglacial sites for habitability, evaluate in situ resource potential
of shallow ice deposits (similar to Phoenix, but mid-latitude).
2 Noachian-Hesperian
boundary
Understand environmental change across this important boundary, define its age,
explore implications of boundary for habitability and biosignature preservation
potential.
3 Radiometric dating Determine absolute ages of a stratigraphic sequence relevant to astrobiology?in
support of another concept or to provide calibration for crater retention.
4 Mission to Early
Noachian terrain
Address questions about early Mars history, possible transition from prebiotic
to biotic chemistry and primitive cells, potential biological evolution in relation
to changes in the magnetic field, atmosphere, and impact rate.
5 Astrobiology new terrain Search for evidence of life and habitability in an astrobiologically significant
terrain type that has not yet been explored.
6 Deep drilling (*2m) Understand surface oxidation and its effect on carbon and life. (Overlaps
with ExoMars goals.)
7 Methane seep Analyze methane and reduced gases emitted from the subsurface and assess
their possible connection to life.
8 Traverse and analyze polar
layered deposits
Assess global climate change and secular evolution of water.
Note: numbers are the SAG?s reference numbers only, and do not indicate rankings.
Table 5.1. Scientific Prioritization of the Eight Mission Concepts
PRIORITY
Concept # Mission Concept Science value Science risk Breakthrough potential OVERALL
4 Astrobiology Mission to Early
Noachian Mars
2.7 2.3 2.6 2.5
2 Stratigraphic Sequence near
Noachian-Hesperian Boundary
2.6 2.2 2.5 2.4
5 Astrobiology: New Terrain 2.5 2.1 2.4 2.3
7 Detection of Methane Emission
from the Martian Subsurface
2.3 1.2 2.5 2.1
3 Radiometric Dating 2.3 1.5 2.1 1.9
6 ??Deep?? Drilling 1.9 1.6 1.9 1.8
8 Polar Layered Deposits Traverse 1.8 1.7 1.7 1.7
1 Mid-Latitude Shallow Ice 1.7 1.9 1.7 1.5
MRR-SAG members scored each concept from 1 (low value, high risk, low breakthrough potential) to 3 (high value, low risk, high
breakthrough potential). Average scores of the MRR-SAG votes are listed above. Green boxes highlight the averaged scores >2.5.
PROPOSED MARS ASTROBIOLOGY EXPLORER-CACHER (MAX-C) 133
or was, present (e.g., Knoll and Grotzinger, 2006). Thus, to
seek signs of past or present life on Mars, basic requirements
include more comprehensive characterization of the macro-
scopic and microscopic fabric of sedimentary materials, de-
tection of organic molecules, reconstruction of the history of
mineral formation as an indicator of preservation potential
and geochemical environments, and determination of specific
mineral compositions as indicators of oxidized organic ma-
terials or coupled redox reactions characteristic of life. This
essential science lies at the heart of each of the top three
candidate mission concepts: #2, #4, and #5. Example landing
sites for these concepts are shown in Fig. 5.1.
This leads us to conclude that a single rover with the same
general capabilities could be used to explore a wide range of
landing sites of relevance to all three of the candidate mis-
sions. Each of these three candidate mission concepts relates
to astrobiology, and all entail understanding paleoenviron-
mental conditions. Understanding preservation potential
would be important for all three candidate mission concepts,
and all are of interest for assessing possible evidence of past
life or prebiotic chemistry. A single general mission im-
plementation would allow the Mars Exploration Program to
respond to discoveries over the next several years in any of
the above areas with the distinction between these scenarios
resolved in a landing site competition.
It is possible to frame a single statement of scientific ob-
jective (see below) that encompasses all three of these mis-
sion concepts. First, since one of the Mars Exploration
Program?s current strategies is to evaluate differences in
habitability potential as a function of both space and time, it
is presumed that sites with comparatively high potential will
have been identified as input to both mission planning and
site selection. This is a crucial prioritization strategy that
would allow the proposed MAX-C rover to be inserted into
an environment with high scientific potential. Second, each
of the high-priority mission concepts relates to ancient en-
vironments on Mars rather than modern environments.
Thus, the scientific objectives relate to the kinds of things
investigators would want to do in such an environment,
which include evaluating paleoenvironmental conditions,
characterizing the potential for the preservation of biotic or
prebiotic signatures, and accessing multiple sequences of
geological units in a search for possible evidence of ancient
life or prebiotic chemistry.
Table 5.2. Top Four Mission Concepts (Indicated
by Reference Numbers) in Overall Science Priority,
by MRR-SAG Member Primary Discipline
Overall
Science
Priority
Geologists
(12 voting)
Astrobiologists
(8 voting)
Atmospheric
Scientists and
Geophysicists
(3 voting)
1 #4 #4 #2
2 #2 #2 #4
3 #3 #5 #5
4 #5 #7 #1
FIG. 5.1. (Left) Example of a location that might be suitable for Mission Concept #4 (Early Noachian Astrobiology):
megabreccia with diverse lithologies in the watershed of Jezero Crater. Subframe of a HiRISE color image PSP_006923_1995.
(Center) Example of a location that might be suitable for Mission Concept #2 (Stratigraphic Sequence at the Noachian-
Hesperian Boundary): stratigraphy of phyllosilicate-bearing strata in the Nili Fossae region, where CRISM detected phyl-
losilicates in the Noachian strata and megabreccia. Subframe of a HiRISE image PSP_002176_2025. (Right) Example of a
location that might be suitable for Mission Concept #5 (Astrobiology?New Terrain): potential chloride-bearing materials in
Terra Sirenum. Subframe of a HiRISE image PSP_003160_1410. Credit for all three images: NASA=JPL-Caltech=University of
Arizona.
MAJOR FINDING: A single rover with the same general capa-
bilities and high-level scientific objectives could explore one
of a wide range of landing sites relevant to the top three mis-
sion concepts. The differences between the concepts primarily
relate to where the rover would be sent, rather than how it
would be designed.
PROPOSED PRIMARY IN SITU SCIENTIFIC OBJECTIVES:
At a site interpreted to represent high habitability potential,
and with high preservation potential for physical and chemical
biosignatures:

 evaluate paleoenvironmental conditions,

 characterize the potential for the preservation of biotic or
prebiotic signatures, and

 access multiple sequences of geological units in a search
for possible evidence of ancient life or prebiotic chemistry.
134 MRR-SAG
5.3. The possibility of one or more secondary
scientific objectives
At this stage of planning, it is not clear what the final
resource constraints on a possible next-decade rover mission
would be. For this reason, it is important to consider the
possibility of secondary scientific objectives, for which it may
ultimately be possible to fit necessary instruments within the
mission?s resource limitations. A number of ideas were
raised during the course of the team?s deliberations. On the
basis of its collective sense of current scientific priorities and
engineering=financial feasibility, the MRR-SAG recognized
two broad classes of investigation that appear to be partic-
ularly good candidates for the potential MAX-C mission,
which relate to landed atmospheric science and paleomag-
netic studies. In both cases, additional expertise was solicited
to document the possible scientific objectives and possible
implementation strategies?these amplified analyses are
presented in MEPAG MRR-SAG (2009).
Landed atmospheric science. An important scientific
objective related to landed atmospheric science would be to
determine the relationships that govern surface=atmosphere
interaction through exchange of volatiles (including trace
gases), sediment transport, and small-scale atmospheric
flows, all of which are necessary to characterize Mars? pres-
ent climate. Measurement of wind velocities, surface and air
temperatures, relative humidity, dust emission (either
through saltation impact or otherwise), air pressure, and
trace gas fluxes are all necessary to determine the relation-
ships that control surface=atmosphere interactions. To char-
acterize the exchange of momentum, heat, volatiles, and
sediment between the surface and atmosphere, it would be
necessary to have a dedicated suite of instruments that
functions for extended periods of time and obtains precise
measurements of high frequency so that subsecond, hourly,
diurnal, seasonal, and interannual variations are resolved
and monitored (Rafkin et al., 2009). With the current lack of
martian observations, empirical relations acquired on Earth
are typically applied to estimate fluxes between the martian
surface and atmosphere, with unknown errors. Thus, these
data would be essential for understanding the current cli-
matic state of Mars, determining potential sources of trace
gases that might lead to the discovery of life, and con-
straining atmospheric models that are needed to ensure safe
landing conditions for potential future spacecraft.
Within MEPAG MRR-SAG (2009), draft priorities within a
multiple set of possible landed atmospheric scientific inves-
tigations are described, which could determine the relation-
ships that govern surface=atmosphere interaction through
exchange of volatiles (including trace gases), sediment
transport, and small-scale atmospheric flows. Of everything
in the list, the most important is judged to be measurement
of the atmospheric pressure, which is the ??heartbeat?? of the
atmospheric system (Rafkin et al., 2009) and would provide
a measure of the total atmospheric mass, which is related
to formation and sublimation of the polar ice caps (Titus
et al., 2009).
Paleomagnetic studies. Objectives for paleomagnetic
investigations are described in detail in MEPAG MRR-SAG
(2009) and are also advocated in the Decadal Survey white
paper by Lillis et al. (2009). Mars presently does not have a
core dynamo magnetic field, but the discoveries of intense
magnetic anomalies in the ancient southern cratered terrane
by the Mars Global Surveyor mission (Acun?a et al., 1998) and
remanent magnetization in martian meteorite ALH 84001
(Kirschvink et al., 1997; Weiss et al., 2002) provide strong
evidence for a martian dynamo active during the Noachian
epoch. The time of origin and decay of this global field is
poorly constrained but has critical implications for planetary
thermal evolution (Stevenson, 2001), the possibility of an
early giant impact (Roberts et al., 2009), the possibility of
early plate tectonics (Nimmo and Stevenson, 2000), and the
evolution of the martian atmosphere and climate ( Jakosky
and Phillips, 2001). Paleomagnetic studies have yielded two
pieces of information: the intensity and the direction of an-
cient fields. Because the original stratigraphic orientations of
martian meteorites are unknown, all Mars paleomagnetic
studies, to date, have only been able to measure the pa-
leointensity of the martian field (Weiss et al., 2008). In situ
paleomagnetic studies from a Mars rover would provide unprece-
dented geological context and the first paleodirectional information
on martian fields. The data could be used to address at least
four very important scientific questions:
(1) When was the martian magnetic field present, and
when did it disappear? Did the death of the martian
dynamo lead to atmospheric loss and climate change?
(2) Did ancient magnetic fields definitely arise from a core
dynamo?
(3) How did the martian paleofield vary in time? Did it
experience reversals and secular variation, and if so
what were their frequencies?
(4) Did Mars experience plate tectonics or true polar
wander?
Unlike landed atmospheric science packages (which
have flown on missions, including Viking and Pathfinder,
and will also be on the upcoming MSL mission), a paleo-
magnetism package has never been flown on any martian
lander.
Other possible secondary objectives considered included a
geochronology experiment, a seismic investigation, and sci-
entific objectives related to drill acquisition of subsurface
samples. The judgment of the SAG was that, though there
are very strong scientific reasons for these investigations,
they are of a character that would be more appropriate as the
primary objective of a separate mission, not as a secondary
objective squeezed into a mission that has an alternate pri-
mary purpose. If the resource parameters of the mission
change significantly in the future, these possibilities should
certainly be reconsidered.
Balancing all the above possibilities with the realities
of limitations on mass and money, the SAG concludes that
at least one secondary payload should be accommodated and
that the single highest priority is an atmospheric pressure
sensor.
FINDING: Inclusion of at least one secondary scientific ob-
jective would substantially enhance the scientific return of the
proposed mission. The single highest priority would be to
monitor the atmospheric pressure as a function of time at the
martian surface.
PROPOSED MARS ASTROBIOLOGY EXPLORER-CACHER (MAX-C) 135
6. Strategy to Achieve Primary In Situ Objectives
If rocks and outcrops are limited in extent within the
landing ellipse (which may be a necessary condition to
ensure safe landing), the important process of quickly
constraining geological setting, selecting sample locations,
and providing context for samples might be challenging.
Indeed, the MER experience shows that considerable time
would be spent locating outcrops and evaluating them
upon arrival. These considerations lead to the following
finding:
In addition, interpretation of the geological setting and
placement of observations in stratigraphic context could be
significantly enhanced by subsurface sensing, such as
ground-penetrating radar or seismic profiling (although the
latter is unlikely to be feasible). The potential MAX-C tra-
verse capability would affect the specific requirements for
remote sensing (resolution, downlink volume). Orbital data
would be very useful for strategic traverse planning but not
sufficient for tactical planning.
Implementation of the proposed MAX-C mission objec-
tives would require interpretation of the origin and subse-
quent modification of rocks with as-yet unknown mineral
composition, macroscale structure, and degree of heteroge-
neity. Given these unknowns, it is challenging to identify the
specific set of measurements that would be required in
the future by such a rover mission. However, relevant ex-
perience from study of ancient terrestrial strata, martian
meteorites, and from MER indicates that the proposed ro-
ver?s interpretive capability should include

 Mineralogical remote sensing at *1mrad=pixel or bet-
ter, signal-to-noise ratio (S=N) >100;

 Geomorphological context (optical) imaging at
*0.3mrad=pixel or better;

 Abrasion of *3 cm diameter areas on rocks;

 Measurements of the abraded rock surfaces:

 Optical texture at *30 mm=pixel resolution or better,
S=N> 100,

 Mineralogical two-dimensional mapping with
*0.3mm spatial resolution, S=N> 100,

 Organic detector two-dimensional mapping with
*0.1mm spatial sampling,

 Elemental chemistry two-dimensional mapping with
*0.1mm spatial resolution (if not possible to ac-
commodate, then bulk chemical composition mea-
sured on a few cm diameter spot).
For three primary reasons, we propose that the measure-
ment strategy focus on interrogation of abraded surfaces: (1)
We know from the results of MER that a variety of micro-
scopic textures are present on Mars (see Fig. 6.1); (2) We
know that surface analysis techniques have significantly
lower cost and risk in comparison to acquiring rock chips or
powders (comparative experience from MER and MSL); and
(3) A number of suitable instruments are either already de-
veloped or under development in each of these four areas
identified (see Section 6.1). This class of instruments makes
use of a relatively smooth, abraded rock surface, such as is
produced by the Rock Abrasion Tool (RAT) grinder on MER
(Gorevan et al., 2003). Note that this strategy and the mission
objectives would require access to outcrops, a consideration
that has implications for the landing site attributes.
For measurements of mineralogy and chemistry, instru-
ments used to interrogate smoothed rock surfaces directly
FIG. 6.1. MER close-up visual examination has revealed interesting textures on relatively smooth rock surfaces of martian
rocks, as shown in these example images. Credit: NASA=JPL-Caltech=USGS. Detailed results from the MER Microscopic
Imager investigations are described in Herkenhoff et al. (2004, 2006, 2008). Micro-mapping could be used to study origins of
minerals, depositional=formation sequences, presence and duration of liquid water, and the presence and nature of any
organic deposits or biominerals.
FINDING: The proposed MAX-C mission must have the ca-
pability to define geological setting and remotely measure
mineralogy in order to identify targets for detailed interroga-
tion by the arm-mounted tools from a population of candidates
and place them in stratigraphic context.
FINDING: Outcrop access is fundamental to the MRR mission
concept. This has implications for landing site selection.
136 MRR-SAG
typically cannot match the analytical accuracy and precision
attained by instruments that ingest samples. However, the
data quality would be sufficient to meet key scientific ob-
jectives, and the ability of such instruments to characterize
intact outcrops would offer substantial advantages. Al-
though in the past we have used instruments that average
the analytic data over an area at least centimeters in size (e.g.,
Christensen et al., 2004; Clark et al., 2005; McLennan et al.,
2005; Squyres and Knoll, 2005; Arvidson et al., 2006; Gellert
et al., 2006; Glotch et al., 2006; Morris et al., 2006a, 2006b,
2008; Squyres et al., 2006), spatial resolution down to scales of
tens of micrometers is readily achievable with newer in-
strumentation (see Section 6.1). Some instruments can pro-
duce data in a two-dimensional scanning mode, which
would be exceptionally powerful. If observations of texture,
mineral identification, major element content, and organic
materials are spatially co-registered, they can interact syn-
ergistically to strengthen the ultimate interpretations. This
two-dimensional micro-mapping approach is judged to have
particularly high value for evaluating potential signs of an-
cient microbial life, key aspects of which are likely to be
manifested at a relatively small scale. We conclude that the
two-dimensional micro-mapping investigation approach is
an excellent complement to the data anticipated from MSL,
which will have higher analytical precision but lower spatial
resolution.
In MEPAG MRR-SAG (2009), a more detailed description
of the proposed ??science floor?? replaces two-dimensional
elemental mapping with bulk elemental analysis on a 1.5?
2.5 cm diameter spot, relaxes the recommended required
resolution of the mineralogical remote sensing and visible
imaging, and relaxes the recommended required spatial
resolution of in situ mineralogical mapping and organic
compound measurements.
The panel concluded that recommendation of specific
instruments to accomplish the recommended required
measurements should be left to a future Science Definition
Team but recognized the need for a straw-man payload to
support engineering trade studies and mission planning.
We have carefully evaluated the available means of col-
lecting these kinds of data without acquisition of rock chips
or powders and have learned that a number of suitable
instruments are either already developed or under devel-
opment (at least Technology Readiness Level-3) in each of
these four areas identified. This class of instruments makes
use of a relatively smooth, abraded rock surface, such as is
produced by the RAT on MER. We expect there to be some
dependency of the accuracy and precision of measurement
results on the physical character of the abraded surface.
Some kinds of measurements of surfaces are affected by
surface roughness, flatness, and so on. Setting specific re-
quirements in this area would need further study by a
successor team.
6.1. Some classes of instruments relevant
to primary in situ objectives
The MRR-SAG arranged for a survey of the status and
capabilities of various remote sensing and in situ instruments
that could meet the proposed MAX-C objectives (credit to
Dr. Sabrina Feldman, JPL). We found that there are a number
of potentially important instruments that could meet the
recommended measurement requirements of the proposed
mission that currently have a Technology Readiness Level
(TRL) of at least TRL-3, though only a fraction are as ad-
vanced as TRL-6 (the state of readiness needed by the time of
mission Preliminary Design Review). Continuing develop-
ment of these instruments would be very important in sup-
porting a good instrument competition in response to an
Announcement of Opportunity for the proposed MAX-C
mission.
Some examples of these instruments that could be flown
on the proposed MAX-C mission are described below. The
purpose is not to advocate that these particular instruments
should be a part of the proposed mission. Rather, these de-
scriptions could be used by scientists to consider the full
scientific potential of this sort of mission and by engineers to
check the feasibility of accommodating an instrument suite
that could meet the recommended measurement objectives
formulated in this report.
6.1.1. Multispectral Microscopic Imager (robotic arm?
mounted). Microimaging capability?in the form of a geo-
logist?s hand lens?has long been an essential tool for
terrestrial field geology. Imagery at the hand-lens scale
(several cm field of view resolved to several tens of mi-
crons) provided by the Microscopic Imagers on the MERs
and the Robotic Arm Camera (Keller et al., 2008) on the
Phoenix lander has proven so vital to the success of these
missions and to the Mars Exploration Program (Herkenhoff
et al., 2004, 2006, 2008) that a microimager is one of the
two instruments now recognized as essential for Mars
surface missions (MEPAG ND-SAG, 2008). The micro-
textures of rocks and soils, defined as the microspatial in-
terrelationships between constituent mineral grains, pore
spaces, and secondary (authigenic) phases (e.g., cements) of
minerals, provide essential data for inferring both primary
formational processes and secondary (postformational)
diagenetic processes. Such observations are fundamental
for properly identifying rocks, interpreting the paleoenvir-
onmental conditions they represent, and assessing the po-
tential for past or present habitability. Multispectral,
visible-to-near-infrared microimages could provide context
information for evaluating the spatial (and implied tem-
poral) relationships between constituent mineral phases
characterized by other mineralogical methods that lack
context information. Microimaging could also provide
highly desirable contextual information for guiding the
subsampling of rocks for potential caching or additional
analyses with other in situ instruments. Figure 6.2 shows
3-band-color-composite images, both natural color and
false color, composed of bands selected and extracted from
a 21-band visible=near-infrared image set acquired by the
Multispectral Microscopic Imager (Sellar et al., 2007; Nun?ez
et al., 2009a, 2009b).
The images reveal important information about the de-
positional processes that formed this volcaniclastic sedi-
mentary rock and also about the microscale aqueous
FINDING: There are a number of potentially useful instru-
ments that could meet the measurement requirements of the
proposed mission that currently have a Technology Readiness
Level (TRL) of at least TRL-3.
PROPOSED MARS ASTROBIOLOGY EXPLORER-CACHER (MAX-C) 137
environments that existed within the rock during its early
postburial history. The Multispectral Microscopic Imager is
estimated to have a mass of about 1.6 kg and consume
*19W peak including electronics.
6.1.2. XRF Chemical Micro-Mapper (robotic arm?moun-
ted). X-Ray fluorescence (XRF) chemical micro-mapping
produces a series of high-resolution element maps that show
the spatial distribution of chemical elements in rocks. These
hand-lens scale maps can be digitally overlaid to reveal co-
variations between elements and relationships between
chemical composition and visible textures and microstruc-
tures. This information can be used to

 Determine the mineral composition of individual grains,
cements, alteration rims, fracture-fills, and so on;

 Detect otherwise cryptic features such as textural com-
ponents that have the same mineralogy, but slightly
different elemental composition;

 Verify mineralogical interpretations and identify min-
eral types that can be difficult to constrain with other
spectral techniques.
X-Ray fluorescence micro-mapping is inspired by state-of-
the-art benchtop chemical mapping instruments. These in-
struments use a capillary optic (Ohzawa, 2008) to focus an X-
ray beam down to a 100mm spot. The beam is raster scanned
across the sample surface, while XRF spectra are rapidly ac-
quired at close spacing, which gradually builds up a raster
image for each element measured (e.g., Fig. 6.3). Up to 14
single-element maps are acquired simultaneously, detecting
elements fromNa to U, over a map size of up to 10 cm10 cm.
The flight instrument would also consist of a capillary
focusing optic, miniature X-ray tube, detector array, and
two-dimensional translation stage (all mounted on the arm)
operated with a high-voltage power supply and detector
electronics (mounted in the rover body and connected via
insulated cable along the rover?s robotic arm). The estimated
total mass of a flight X-Ray Micro-Mapper is *2.5 kg, with
power consumption of *30W. Preliminary estimates sug-
gest that the X-Ray Micro-Mapper could analyze a 1 cm2 area
of an abraded rock surface on Mars at 100mm resolution in
about 3 hours.
The scientific value of the technique has been validated
through studies of *3.5 billion-year-old rocks containing the
oldest evidence of life on Earth: element maps acquired with
a commercial X-ray guide tube X-ray analytical microscope
have revealed mineralogy and key aspects of rock fabrics
that constrained paleoenvironmental conditions, habitability,
and biogenicity in Early Archean stromatolites (Fig. 6.3)
(Allwood et al., 2009). In the context of planetary exploration,
chemical mapping would have even greater value and pro-
vide a valuable substitute for thin section petrography (a
fundamental part of geological studies on Earth, but complex
and resource intensive for robotic planetary exploration).
Using XRF to map covariations among elements against a
backdrop of optical imagery would achieve many key ob-
jectives of thin section petrography.
6.1.3. Alpha particle X-ray elemental chemistry instrument
(robotic arm?mounted). An alternative to the XRF Chemi-
cal Micro-Mapper (Section 6.1.2) is provided by an alpha
particle X-ray spectrometer (APXS). An APXS provides bulk
chemical analysis averaged over an area a few cm in diam-
eter. The advantages of the APXS include flight heritage, fast
analyses, and small data size.
An APXS similar to the one built for MSL could provide
bulk elemental composition measurements (Na to Br) on
rock or soil surface target areas *1.7 cm in diameter, to a
depth of 5?50 mm. The MSL APXS has significant heritage
from the APXS instruments flown on Spirit and Opportunity
(Rieder et al., 2003; Gellert et al., 2006, 2009). A thermoelectric
cooler allows operation up to martian ambient temperatures
FIG. 6.2. Natural-color image (left) composed of 660, 525, and 470 nm bands; and false-color image (right) composed of
1450, 1200, and 880 nm bands; displayed in red, green, and blue, respectively; selected subframe shown here is 2020mm
(full field is 4032mm) with a resolution of 62.5 mm=pixel. This sample was ground to a roughness similar to that provided
by the RATs on the MERs. Interpretation: volcanic breccia. Angular clasts of a fine-grained silicic volcanic rock have been
cemented by calcite and hematite. Angular shapes and poor size sorting of clasts indicate minimal transport. This, along with
the uniformity of clast compositions (monolithologic), suggests deposition near the volcanic source, perhaps as an airfall tuff
(lapillistone).
138 MRR-SAG
of 58C. Measurements can be taken by deploying the ro-
ver?s robotic arm to place the instrument?s sensor head in
close contact with a sample. The sensor head containing ra-
dioactive 244Cm sources bombards the sample with emitted
alpha particles and X-rays. From the X-rays measured by the
sensor head detector (equivalent to particle-induced X-ray
emission and X-ray fluorescence techniques), the rough
abundance of major elements can be obtained in 15 minutes,
or a complete chemical analysis, including some trace ele-
ments, can be obtained in 2?3 hours, which requires a total of
*6W with no cooler or *10W with the cooler (only re-
quired at the highest ambient temperatures) with an instru-
ment mass of 1.7 kg. The 10mm2 silicon drift detector can
achieve a full-width at half maximum at 5.9 keV of *140 eV
and covers the X-ray energy range from 700 eV to 25 keV
with 1024 channels. In addition, backscatter peaks of pri-
mary X-ray radiation allow detection of bound water and
carbonate at levels of around 5wt % (Campbell et al., 2008).
6.1.4. Green Raman imager (robotic arm?mounted).
Raman spectroscopy is a point analysis method that uses
energy loss from an excitation laser source due to lattice or
molecular vibrations to discern the identity of the targeted
material. Raman imaging is a new technique that rasters the
point excitation source across an area to produce images
instead of point measurements, and results in far more in-
formation. For example, a point Raman instrument on Mars
could discover jarosite, but this reveals little more than is
already known, namely, that jarosite exists in martian min-
eralogy. A Raman image containing jarosite (Fig. 6.4) would
enable us to determine whether the jarosite exists as wind-
blown fines, a weathering rind component, in a cement, in a
breccia, as an alteration vein, as a constituent in a layered
deposit, or as a deposit that fills vesicles, and so on (Vicenzi
et al., 2007; McCubbin et al., 2009). Each of these settings can
be used to describe the origin and alteration history of the
target material. While commercial Raman imaging instru-
ments are common and have achieved considerable matu-
rity, no Raman imaging instrument, to date, has been
developed for space flight. The Mars Microbeam Raman
Spectrometer is the closest to this achievement (Wang et al.,
2003), as it can make linear scans and was proposed as part
of the Athena rover payload. It was also considered for, but
not flown on, the MERs. Commercial instruments can image
areas 100mm2 up to multi-cm2, with pixel sizes from *1mm2
down to 360 nm2. The primary limitation arises from native
sample fluorescence, but there are technical means to mini-
mize that effect. Mineral sensitivity is extraordinary and
ranges from clay minerals to opaque minerals, to the full
range of carbonaceous species (Schopf et al., 2002; Steele et al.,
2007; Fries et al., 2009; Papineau et al., 2009) from diamond to
organic compounds, and to every known silicate mineral. No
sample preparation is necessary, but some surface grinding
may be preferable. The flight instrument mass is estimated to
be <6 kg and the power required <30W, including elec-
tronics with a field of view of 1 cm2 and a resolution of 4mm.
6.1.5. Deep ultraviolet Raman=fluorescence mapper (ro-
botic arm?mounted). Deep ultraviolet (DUV) Raman spec-
troscopy is well suited to in situ analysis of many
carbonaceous compounds (Asher and Johnson, 1984; Storrie-
Lombardi et al., 2001; Hug et al., 2006; Frosch et al., 2007;
Bhartia et al., 2008). Rayleigh enhancement with deep UV
excitation generates *20 times greater signal strength than
the same measurement made with a green excitation laser
and greater than 100 over a red (785 nm) excitation laser.
Resonance Raman effects in carbonaceous compounds under
UV excitation produce additional signal improvement that
FIG. 6.3. Stromatolite from the Archean Strelley Pool Formation (Pilbara, Australia). Top left image is a polished slab,
showing irregularly laminated dolomite and chert. Remaining images are element maps produced by XRF mapping over the
same area. The lower right image consists of overlaid iron (red) and calcium (blue) maps, showing dolomite laminae and
iron-rich dolomite cavity-lining cements that confirmed the presence of fenestrae?a key microbial fabric component. An
APXS measurement would chemically homogenize the detailed variations existing at this scale.
PROPOSED MARS ASTROBIOLOGY EXPLORER-CACHER (MAX-C) 139
ranges up to 8 orders of magnitude (Asher and Johnson,
1984; Storrie-Lombardi et al., 2001). Examples of resonantly
enhanced bonds include, but are not limited to, water, C?H,
CN, C?O, C?C, NHx, NOx, SOx, POx, ClO4, and OH with
sensitivities in the sub?parts per million (Dudik et al., 1985;
Asher et al., 1986; Burris et al., 1992; Ianoul et al., 2002). In
addition to the resonance enhancements, with excitation
below 260 nm, Raman and fluorescence regions do not
overlap (Asher and Johnson, 1984; Frosch et al., 2007). This
enables simultaneous measurement of Raman spectra and
fluorescence backgrounds (Bhartia et al., 2008).
Coupling DUV Raman with DUV native fluorescence
would enable characterization of biological materials as well
as structure and arrangement of aromatic rings with sensi-
tivities at the sub?part per billion (Bhartia et al., 2008; Rohde
et al., 2008) (Fig. 6.5). These combined data sets make it
possible to map the distribution of organic compounds and
water (Fig. 6.6). This instrument can achieve a field of view
of 1 cm2, with spatial resolution of 10mm, as a rover arm?
mounted instrument mapping at a standoff distance of
2.5 cm. The mass and power consumption for this instrument
is estimated to be *5 kg and <20W, including electronics.
6.1.6. Imaging spectrometer (mast-mounted). The Mast-
Mounted Imaging Spectrometer is a passive instrument that
operates in the visible and short-wave infrared portion of the
spectrum to provide detailed mineral maps of the sur-
rounding terrain and the mineral composition of specific
rocks and outcrops. Spatial resolution varies with distance
from the target, reaching down to a few mm at distances
below 10m (example shown in Fig. 6.7). The instrument is
capable of generating 3608 panoramic image mosaics and
providing compositional information for each pixel in the
images. Its spectral range and spectral resolution are similar
to those of the orbiting CRISM and OMEGA instruments,
which allows for extension of the orbital measurements to
higher spatial resolution in addition to providing ??ground
truth?? data. Short-wave infrared spectroscopy has proven to
be highly effective in mapping aqueous alteration deposits
on Mars from orbit (Noe Dobrea et al., 2009) and has been
used to identify minerals such as hydrous sulfates and
phyllosilicates on the martian surface (e.g., Bibring et al.,
2005; Gendrin et al., 2005; Langevin et al., 2005), carbonates
(Ehlmann et al., 2008), opaline silica (Milliken et al., 2008),
and mineralogically complex regions with multiple types of
FIG. 6.4. (Left) 20 reflected light image of martian meteorite MIL 03446. (Right) Raman image from image at left. Red:
jarosite. Green: goethite. Blue: clay minerals. This alteration vein is martian in origin as shown by D=H abundance ratio and
the fact that the vein is truncated by the meteorite fusion crust (not shown). Data courtesy of M. Fries and A. Steele,
Geophysical Laboratory, Carnegie Institution of Washington.
FIG. 6.5. DUV (<250 nm) excitation of native fluorescence from a basalt vesicle (dark area) from Svalbard, Norway. Left is a
visible reflectance image. Center is a native fluorescence image. Fluorescence analysis (Bhartia et al., 2008) indicates the
presence of 2-ring aromatics (yellow regions) as possible mantle-derived organic compounds. Right is a visible and fluo-
rescence overlay. White scale bar: 2mm. Sample courtesy of A. Steele, Geophysical Laboratory, Carnegie Institute of Wa-
shington. For further information on the geology and geochemistry of a basalt from this locality, see Steele et al. (2007).
140 MRR-SAG
clay minerals including iron- and aluminum-rich varieties
(e.g., Bishop et al., 2008).
This medium- to low-risk instrument is expected to have a
3 kg mass and power requirements of 6W, including elec-
tronics, optics, and thermal control. The instrument has no
mechanisms other than the scanning in x and y provided by
the mast. A single data set will typically comprise an area of
344344 spatial pixels (1mrad2) with a single-line field of
view of 1mrad20 degrees. Each pixel is simultaneously
imaged in *420 spectral bands over a range of 400?2500 nm
where the spectral resolution is 5 nm.
6.2. Instrument development
Preliminary scheduling for a mission project of this kind
indicates that the instrument competition might take place
in late 2012, with instrument selection about 6 months after
that. Candidate instruments need to be at about TRL-5 or
greater to be credibly proposed. This means that during the
next 2 years significant instrument funding through NA-
SA?s Mars Instrument Development Program (MIDP), Pla-
netary Instrument Definition and Development Program
(PIDDP), and similar programs would need to be made
available to the community. Instrument competitions
should include specific needs related to the proposed MAX-
C mission. As discussed above, because many of the in-
struments of high relevance to the MAX-C mission concept
are at a readiness state less than TRL-5, the definition of a
straw-man payload suite, which must be done immediately
for engineering trade studies, will necessarily be immature.
To the extent possible, the results of early engineering trade
studies should be fed back into instrument development
constraints and priorities.
7. Relationship to a Potential Sample
Return Campaign
To analyze the relationship of the proposed MAX-C mis-
sion to the possible future return of samples from Mars, it is
FIG. 6.6. DUV excited H2O Raman map of an altered basalt
from the Mojave Desert, acquired from a 2m standoff (im-
age? 20.37.6 cm). (Top) Visible reflectance image, white
regions are composed of carbonates. (Center) False-color
map of the OH-stretch Raman band showing the distribution
of hydrated minerals (magenta color) indicating extent of
fluidic alteration. (Bottom) Overlay of the reflectance and
Raman map indicates carbonate deposited by aqueous
transport and mixed with hydrous mineral phases. White
scale bar: 5 cm.
FIG. 6.7. (Right) Example color image mosaic of Cape St. Mary, a promontory on the rim of the Victoria Crater, Mars,
acquired by Pancam on Opportunity rover. The observation spans 368208 (620344 pixels). (Left) A 1010 square pixel area
is expanded, showing the ability to resolve differences within layers. Pancam image credit: NASA=JPL-Caltech=Cornell
University. The Mast-Mounted Imaging Spectrometer would provide visible through shortwave infrared spectra for each
pixel.
MAJOR FINDING: For these instruments to be mature enough
to be selectable for flight (i.e., TRL-6), a commitment must be
made now and sustained for the next several years to improve
the maturity of the most promising candidate instruments.
PROPOSED MARS ASTROBIOLOGY EXPLORER-CACHER (MAX-C) 141
necessary first to consider some of the aspects of sample
return. The potential sample return objectives, sample ac-
quisition and preservation requirements and strategies,
and sample context requirements are relevant planning
considerations. In Section 7.2, we discuss how the proposed
MAX-C mission would fit into a larger possible mission ar-
chitecture configuration. The expectation is that the potential
MAX-C sample cache would be a returnable and scientifi-
cally enticing cache that the science community would be
eager to see returned to Earth (Section 7.3).
7.1. Proposed Mars sample return scientific objectives
and required measurements
7.1.1. Potential sample return scientific objectives. A
potential sample return campaign would carry an unprece-
dented combination of cost and risk, and because of this
must return unprecedented scientific value. The value of a
potential Mars sample return has been discussed in the lit-
erature for at least 30 years (see, for example, NRC, 1978,
1990a, 1990b, 1994, 1996, 2003, 2006, 2007), and the scientific
rationale for returning samples has evolved over time. Early
studies (e.g., NRC, 1978) emphasized the need for samples to
better understand the evolution of the planet. Emphasis in
the last two decades, on the other hand, has been on the
search for past and present life (e.g., NASA, 1995; NRC 2007).
Answering the life question (??Are we alone???) is now one of
the most important strategic drivers for NASA (NASA
Strategic Plan), and the Mars Exploration Program has
therefore long carried the objective ??determine whether life
ever arose on Mars?? as one of its top priorities. Returning
samples from Mars is considered essential for meeting that
objective.
In accordance with these considerations, the MEPAG ND-
SAG (2008) reached the following conclusions after carrying
out a detailed analysis of the scientific trade space associated
with the objectives and implementation options of a poten-
tial sample return campaign:

 Many scientific objectives could be achievable with a
sample return campaign (11 objectives listed in MEPAG
ND-SAG, 2008), depending on where it would be sent,
what kinds of samples it could acquire, and in what
condition they would be returned. Unfortunately, some
objectives require relatively specific samples, and there
is probably no single place on Mars where a suite of
samples could be collected that would achieve all these
objectives. Thus, planning for a potential sample return
must involve careful consideration of the priority of its
scientific objectives, the influence this prioritization has
on choice of landing site, and criteria for selection of
samples at that site.

 The most important scientific objectives of a potential
sample return mission should relate to ??the life ques-
tion?? (see also NRC, 2007; iMARS Working Group, 2008;
MEPAG, 2009).
Because of the significance of the life question to Mars
exploration, we conclude that returned samples from Mars
must make a substantial contribution in that area. For many
reasons, however, a significant contribution must also be
made toward at least one of the other high-priority objectives
that have been defined by the Mars scientific community.
7.1.2. The kinds of samples needed to achieve these
objectives: diverse, intelligently collected samples. The
NRC (1978) first concluded that a potential Mars sample
return mission must return ??an intelligently selected suite of
martian samples,?? and this recommendation has been re-
inforced by subsequent panels ever since. A primary theme
of the ND-SAG report was to emphasize the need for careful
selection to ensure geological diversity (MEPAG ND-SAG,
2008). This is especially true for addressing the life question,
because detecting and interpreting potential evidence of
microbial life requires assessment of the paleoenvironment,
its habitability and biosignature preservation potential, and
the relationships of potential biosignatures within the pa-
leoenvironmental context. Moreover, the sampling should
take strategic advantage of the contextual framework to al-
low robust testing of different hypotheses that arise. Evi-
dence of life is not likely to be something that resides in a
single sample: rather, evidence of life emerges from an as-
semblage of observations, strategically analyzed and inte-
grated across all scales of observation. This is unequivocally
illustrated by the challenges and spirited debate surrounding
the search for Earth?s earliest biosignatures (e.g., Walsh, 1972;
Lowe, 1980, 1983, 1992, 1994; Walter et al., 1980; Buick et al.,
1981; Awramik et al., 1983; Walter, 1983; Walsh and Lowe,
1985; Byerly et al., 1986; Schopf and Packer, 1987; Schopf,
1993, 2006; Grotzinger and Knoll, 1999; Hofmann et al., 1999;
Hofmann, 2000; Ueno et al., 2001; Westall et al., 2001, 2006;
Brasier et al., 2002, 2006; Van Kranendonk et al., 2003; Lind-
say et al., 2003a, 2003b, 2005; Tice and Lowe, 2004; Moorbath,
2005; Allwood et al., 2006, 2009; McCollom and Seewald,
2006; Westall and Southam, 2006; Westall, 2007).
One advantage of returning samples is that the investi-
gations could generate results much more definitive than
those achievable by in situ techniques alone. This lesson has
been learned over and over again by geologists working in
the field on Earth. However, an extension of this lesson is
that the scientific productivity of the samples would be
strongly dependent on their character. For example, as
pointed out by the ND-SAG (2008), returning 24 identical
rocks would have no more scientific value than returning
one. For this reason, we introduce the concept of ??out-
standing samples,?? or perhaps more properly, ??outstanding
sample suite.?? On the one hand, we agree with the posi-
tion (most recently summarized by NRC, 2007) that there is
no such thing as ??the ideal sample?? and that delaying a
potential sample return campaign until it is discovered is
illogical. On the other hand, even though any sample re-
turned from Mars would be useful for some aspect of sci-
entific inquiry, it is also true that not all samples would be
equally useful for the kinds of scientific questions we are
FINDING: For a potential Mars sample return mission to de-
liver value commensurate with the cost and risk, it must ad-
dress a major life-related objective as well as one or more of
the major geological objectives defined by the MEPAG ND-
SAG (2008).
FINDING: Particularly in the case of a ??signs of life?? objective,
a potential sample return mission should be designed to return
a set of intelligently collected, diverse samples.
142 MRR-SAG
trying to answer. Moreover, the concept of a suite of samples
is rooted in the premise that the differences between samples
is as important, or even more so, than the absolute properties
of any of them. Thus, a well-collected suite of samples would
be one that represents the range of natural variability of a
key martian geological process. A couple of examples to il-
lustrate the point are shown in Fig. 7.1.
In both of the examples in Fig. 7.1, there is more than one
way to assemble an effective suite of samples, and equally
effective suites could be collected at other nearby localities.
The common point, however, is the identification of samples
that span the range of natural local diversity is required in
order to make effective sample selection decisions. Such
samples would be more than ??ordinary?? and less than the
??right?? sample?for this we use the term ??outstanding??
samples. Clearly, the acquisition of a set of outstanding
samples would take planning and effort.
Seeking signs of life demands a host of scientific investi-
gations that would yield important in situ results in their own
right. Furthermore, such results would also provide essential
information for addressing other high-priority scientific ob-
jectives. Thus, very little scientific trade-off is required be-
tween simultaneously optimizing feed-forward to a ??signs of
life?? potential sample return campaign and conducting sig-
nificant in situ science inmultiple high-priority research areas.
7.1.3. Measurements needed to make sample selection
decisions and to document sample context. As noted by
the MEPAG ND-SAG (2008), to interpret analytical results
obtained from potential returned samples, the geological
context of the landing site should be fully documented. Such
documentation should include mapping bedrock and other
surficial rocks, mineralogy, geochemistry, and petrology.
Thus, any potential sample suite must be characterized in
situ and be designed to leverage the geological context to aid
in the interpretation of eventual Earth-based laboratory an-
alyses. Achieving these requirements would substantially
influence landing site selection and rover operation proto-
cols. The importance of access to outcrops would necessitate
either significant traverse capability or hazard avoidance
during descent (see Section 10.2).
The MEPAG ND-SAG (2008) proposed two instrument
suites for a potential sample return mission: one designed for
a mission sent to a previously visited site and the other for a
mission going to a new site (Table 7.1). The MRR-SAG agrees
that, at the bare minimum, the potential sample acquisition
rover must make the ND-SAG?s minimum observations for a
new site:
(1) Color stereo imaging,
(2) Microscopic imaging,
(3) Elemental and mineralogical determinations,
FIG. 7.1. Two examples (S.W. Squyres, written communication, 2008) highlighting the importance of sample selection tools
in understanding the range of natural variation, which is crucial in assembling a suite of outstanding samples. (Left) False-
color rendering of a Pancam image mosaic from Opportunity rover on Sol 173 ( July 19, 2004). The view, looking back up
toward the rim of Endurance Crater, shows the rover?s tracks and the first seven holes made by the RAT as the rover moved
down layers of exposed rock. Image credit: NASA=JPL-Caltech=Cornell. (Right) A new type of basalt was detected with Spirit
rover?s Mini-TES at the summit of Husband Hill (McSween et al., 2006), at this location shown in a Navcam mosaic from Sol
598. The rock named Irvine, which was part of an aligned set of similar rocks (some of which are circled in yellow), was more
closely examined with instruments on the robotic arm. Characterization of the difference between the alkaline basalt Irvine
and other more common subalkaline basalts allowed interpretation of the liquid line of descent?this would not have been
possible if this type of sample had not been recognized. In addition to the need for macroscopic target selection, sample
acquisition decision-making would also need to incorporate observations from finer scale, such as those in Fig. 6.1 and
possibly also the other figures in Section 6. Image credit: NASA=JPL-Caltech.
FINDING: To meet the high expectations, a potential sample
return mission should return ??outstanding samples?? that have
the potential to generate results more definitive than those
achievable in situ and could make a significant contribution to
addressing MEPAG?s life-related scientific objectives.
PROPOSED MARS ASTROBIOLOGY EXPLORER-CACHER (MAX-C) 143
(4) Detection of reduced carbon,
(5) Ability to remove weathered or dust-coated surfaces
(i.e., an abrasion tool).
The ND-SAG noted that it is theoretically possible for a
potential sampling rover that revisits a previously explored
route at a well-characterized site to carry reduced instru-
mentation (indicated by the pink boxes in Table 7.1). How-
ever, this would mean that the potential rover might need to
revisit exact positions, and possibly the same RAT holes, if
the compelling rock features are difficult to find and docu-
ment with just cameras (as the ND-SAG recommended).
Since such a mission would have to rely on cameras for all of
its selection and documentation of samples, the risk of not
being able to reoccupy exact locations that were character-
ized by the previous (MER or MSL) mission is a potentially
crucial vulnerability with extremely negative consequences
to the scientific return. The MRR-SAG concluded that the
same payload would be required, whether the potential
sample acquisition rover is sent to a new or a previously
visited site (Table 7.1, right two columns). In addition, the
MRR-SAG updated Table 7.1 to indicate that the mineralogy
information should assist with both the location of samples
from a distance (purple boxes in Table 7.1) and the charac-
terization of samples at higher spatial resolution. The ND-
SAG did not specify the exact nature of the recommended
required mineralogy measurements, other than the need to
differentiate rock types and effects of natural processes.
The MRR-SAG notes that this recommended minimum
required set of observations would be greatly improved with
various ??upgrades,?? if they could be accommodated. Such
upgrades would include the capability to evaluate chemistry
and mineralogy of small-scale features and capability of
evaluating constituents of interest to astrobiology in addition
to reduced carbon (such as N, S, and biosignatures). Based
on experience from MER, where the science team had diffi-
culties inferring orientation of underground bedding, the
inclusion of a subsurface sounding instrument such as
ground-penetrating radar would also add valuable context.
The potential sample acquisition rover should carefully
document the context of its collected samples and should be
robust against any challenges impinging on the proposed
scientific objectives. For example, several likely scenarios
exist where the potential sample acquisition rover might be
unable to access and sample the exact spot(s) where MSL
might make compelling discoveries. Indeed, a well-equipped
potential sample acquisition rover could make its own novel
discoveries at a MER or MSL site. The ability of a potential
sample acquisition rover to stand alone in its ability to exe-
cute a scientifically valuable mission would also add con-
siderable robustness to a potential sample return campaign.
Of course, future MER or MSL discoveries could help to
optimize the measurement capabilities of a sample acquisi-
tion rover and thereby enhance even further the scientific
return of the overall potential sample return campaign.
7.2. How the proposed MAX-C mission fits
in a potential 3-element sample return campaign
Given current understanding of celestial dynamics and
engineering approaches to optimize spacecraft design, it is
Table 7.1. Recommended Required Instrumentation for a Potential Caching Rover
that is Directed to a New Landing Site or to a Previously Visited Site
ND-SAG MRR-SAG
What would be needed Measurement New site Previous site New site Previous site
Ability to locate samples Color stereo imagery YES YES YES YES
Remote mineralogy YES YES
Ability to determine fine rock
textures (grain size, crystal
morphology), detailed context
Microscopic imagery YES YES YES YES
Ability to differentiate rock types,
effects of different natural processes
Mineralogy YES NO YES YES
Ability to differentiate rock types,
effects of different natural processes
Bulk elemental
abundance
YES NO YES YES
Ability to detect organic carbon Organic carbon
detection
YES NO YES YES
Ability to remove weathered or
dust-coated surface and see
unweathered rock
Abrasion tool YES NO YES YES
The left-hand part of this table was developed by the ND-SAG (2008; Table 6). The MRR-SAG reached consensus on the right two columns,
identifying the same payload that would be required for a new site as for a previously visited site.
FINDING: The potential rover needed to do scientific sample
selection, acquisition, and documentation for potential return
to Earth should have similar measurement capabilities, whe-
ther it is sent to an area that has been previously visited or to a
new unexplored site.
FINDING: (1) The potential sample acquisition rover must
provide the data needed to find and select samples and to es-
tablish their context over a wide range of scales. (2) The base-
line instrument package might need to be modified, depending
on the specifics of what the MERs or MSL find, if the potential
sample acquisition rover returns to one of those previously
visited sites.
144 MRR-SAG
widely accepted that the return of samples from Mars would
involve a potential campaign of multiple missions (see e.g.,
iMARS Working Group, 2008; Borg et al., 2009). The pro-
posed MAX-C mission would be intended to be the first step
of a potential 3-element campaign (Fig. 7.2), followed by
another potential mission (MSR-Lander) carrying a small
rover that would fetch the proposed MAX-C cache (i.e.,
surface rendezvous) and also carrying a MAV capable of
launching a container holding the proposed cache into orbit
for rendezvous with an orbiter mission. A 3-element archi-
tecture would offer some major financial advantages in the
form of smoothing future budget peaks for the Mars flight
program (e.g., Li, 2009).
7.2.1. Considerations related to a potential 3-element
campaign. Exploring a site prior to sending the potential
sample return system (i.e., lander and MAV) would reduce
both engineering and scientific risk for the overall potential
sample return campaign. Many scientists and engineers have
previously concluded that it would be too risky to send the
mission that would land the MAV to a site other than one
that has been previously visited (MacPherson et al., 2005;
discussions at the MSR workshop in Albuquerque, May
2008); and, after extensive debate within the team, the MRR-
SAG strongly endorses that conclusion.
We would know that the samples exist, are retrievable,
and are of sufficient scientific interest before committing to
sending the potential lander mission with the MAV. More-
over, we would have completed exploration and documen-
tation of the geological context with a payload optimized for
science. Sending the MAV in a launch opportunity after the
proposed MAX-C rover would allow it to be launched with a
more modest fetch rover (requiring a minimal payload and
briefer surface operations time).
For the potential 3-element approach, the MAV would not
be put ??at risk?? until after the cache has been prepared, thus
making it more likely that the proposed MAX-C rover would
be allowed to visit a site that has not been previously
ground-truthed. Allowing a broader range of landing sites to
be considered is a significant scientific benefit of a potential
3-element campaign (as discussed in Section 9.2). The in-
tention would be to fly the MAV in a follow-on launch op-
portunity, but the go=no-go decision could be made after the
proposed MAX-C mission. In a 3-element campaign, after
arrival on Mars, the proposed MAX-C rover would likely
have plenty of operations time (depending on rover lifetime
and which launch opportunity would be used for the mis-
sion carrying the MAV) to collect a thoughtfully selected,
thoroughly documented, diverse set of samples from a well-
characterized geological setting.
In a 3-element campaign, the proposed MAX-C rover mis-
sion would be required to make quality sample selection de-
cisions, document the context of the samples chosen, and
acquire and cache the samples chosen. The instruments nec-
essary to provide the informational basis for these decisions
would also need to be present to achieve the in situ objectives.
In summary, the proposed MAX-C rover could benefit the
potential sample return campaign in the following ways:
(1) Developing and accomplishing rock coring and en-
capsulation.
(2) Assembling a cache containing sample suites acquired
from a diverse set of sampling locations.
(3) Accomplishing #1 and #2 above, consistent with sam-
ple return planetary protection and contamination
control requirements (MEPAG MRR-SAG, 2009).
(4) Preparing and operating a new generation of instru-
ments optimized for sample selection and site charac-
terization.
(5) Further verifying the performance of the MSL EDL
system and improving targeting accuracy. This would
also benefit the later potential mission carrying the
MAV and fetch rover.
FIG. 7.2. Schematic diagram depicting the 3-element mission campaign concept to accomplish a potential return of samples.
FINDING: A potential 3-element MSR campaign would result
in great simplification of the MSR-Lander mission. By reducing
the number of miracles that mission would require, the overall
campaign would be more technically feasible.
FINDING: In order for a potential sample return campaign to
be of acceptable risk (both science and engineering), the po-
tential MSR-Lander mission should be sent to a site previously
explored by a rover or lander.
PROPOSED MARS ASTROBIOLOGY EXPLORER-CACHER (MAX-C) 145
On the other hand, sample caching would consume critical
mission resources (e.g., money, mass, and surface operation
time) that could have been used for in situ scientific opera-
tions. For example, a drill on an instrument arm would in-
crease the vibration isolation design requirements for the
scientific instruments on the arm.
7.2.2. Possible risk reduction engineering measurements
in a potential 3-element campaign. By virtue of the poten-
tial 3-element campaign, the proposed MAX-C rover might
be able to carry out certain specific tests that would buy
down engineering risks for the follow-on parts of the cam-
paign. We present one example related to electrical fields but
encourage further discussion by future planning teams.
Theoretical predictions and laboratory simulations suggest
that electrostatic charging could be a serious risk to the
launch of a MAV from the martian surface, but scientists do
not have sufficient information to confirm the magnitude of
the risk (Melnik and Parrot, 1998; Farrell et al., 1999; Farrell
and Desch, 2001; Michael et al., 2008). Electrical discharge in
dust storms (Farrell et al., 1999) and rocket-triggered light-
ning along the exhaust trail of a MAV during ascent from
Mars (MEPAG HEM-SAG, 2008) are a possible concern. The
potential MAX-C rover could include a device that monitors
electric fields (e.g., Farrell et al., 1999; Berthelier et al., 2000) to
determine the magnitude of the risk and affect the design of
the MAV so that it would be robust in the local martian
conditions. An electric field probe with a mass of *0.5 kg
requiring *1W has some MIDP heritage (MEPAG HEM-
SAG, 2008). Future design teams should determine the spe-
cific nature of the electric field information needed to sig-
nificantly reduce risk of the MAV launch, and assess the
feasibility of achieving and accommodating those measure-
ments with an in situ instrument.
There could be other measurements like this, or engi-
neering design implementations of the proposed MAX-C
mission that should be considered, that would reduce the
cost and risk of the other missions that are part of the overall
potential sample return campaign. This is left to future study
groups and engineering teams to determine.
7.3. The proposed MAX-C sample
cache?intent to return
It is not possible to know in advance what would be dis-
covered at any individual landing site on Mars. Our orbital
data sets are of very high quality, but we know from the ex-
perience at both MER sites that orbital data can give incom-
plete representations of the surface geology. For example, at
the Opportunity site, the orbital data show the presence of
hematite but not sulfate; and, in actual fact, both can be de-
tected from the ground. However, a crucial point is that this
committee has concluded that, to within reasonable levels of
confidence, a high-quality landing site for the assembly of a
sample cache can be selected from orbital data, and the intent
is that the samples selected at that site would actually be re-
turned if the follow-upMSRmissionwere approved. It would
be unwise to make this decision formally before the potential
sample collection and caching missions take place, and it is
possible to envision scenarios in which the proposed MAX-C
cache would end up with lower-than-expected scientific pri-
ority (for example, if the rover fails to access certain high-
priority sampling targets). However, the baseline intention is
that the proposed MAX-C cache would be returned, and
mission planning should be carried out on this basis.
8. Consensus Mission Vision
As discussed at the recent ( July 29?30, 2009) MEPAG
meeting at Brown University (http:==mepag.jpl.nasa.gov=
meeting=jul-09=), the Mars Exploration Program appears to
be moving forward from a strategy of ??follow the water?? and
examining habitable environments toward one of ??seek signs
of life.?? Also included in the strategy is preparation for a
potential Mars sample return. To further focus the proposed
MAX-C mission toward a single concept, the MRR-SAG
considered how the investigations and measurements pro-
posed for the top three concept missions meet the overall
vision of a mission to the martian surface that would (1) have
the in situ scientific exploration capability to respond to
discoveries by prior landers or orbital mapping missions, (2)
be able to collect, document, and cache samples for potential
return to Earth by a potential future mission, (3) be a key
stepping stone to seeking signs of life on Mars, and (4) do all
this within the constraints of a rover intermediate in size to
MER and MSL. Additionally, the MAX-C mission concept
must take into account areas in which it would complement,
and be complemented by, ESA?s ExoMars mission.
8.1. Consensus mission concept
As described in Sections 6 and 7.1, the measurements
needed to achieve the proposed in situ objectives are the
same measurements needed to select samples for potential
return to Earth and document their context.
This consensus mission concept has recommended objec-
tives consisting of three components:
(1) A set of primary objectives related to the exploration of
a site on Mars. Given current scientific priorities, the
proposed rover would need to visit a site with high
preservation potential for physical and chemical
biosignatures and, at that site, achieve the following
primary objectives: (a) evaluate paleoenvironmental
conditions, (b) characterize, in situ, the potential for
the preservation of biotic or prebiotic signatures, and
MAJOR FINDING: The instruments needed to achieve the
proposed in situ objectives are the same instruments needed to
select samples for potential return to Earth and document their
context. Because of the compelling commonalities, it makes
sense to merge these two purposes into one mission.
FINDING: The proposed MAX-C mission would help prepare
for a potential sample return in at least five critical areas?
thereby significantly reducing the ??number of miracles??
needed for an overall sample return campaign.
FINDING: Caching samples on the proposed MAX-C mission
would be of major engineering benefit to potential sample re-
turn, but this would come at a cost to in situ science of the
proposed MAX-C mission. The importance of a sample return
makes this trade worthwhile.
146 MRR-SAG
(c) access a sequence of geological units in a search for
evidence of past life or prebiotic chemistry. Note that
steps (a) and (b) above cannot be done once for the
planet, such that the investigation would be consid-
ered complete?these activities would need to be done
at every site where the potential signs of life are being
investigated.
(2) A primary objective to collect, document, and package
in a manner suitable for return to Earth by a potential
future mission at least some of the samples needed to
achieve the scientific objectives of a sample return
mission. These samples should include some of the
rocks that contain the essential evidence for the inter-
pretations reached as part of Objective #1 above but
would also certainly include additional types of sam-
ples. As documented by the ND-SAG (2008), a poten-
tial sample return would have important objectives
beyond those related to the life goals, and multiple
sample types would be implied, including samples of
rock, soil, and atmosphere. It is yet to be determined
whether the proposed MAX-C mission should be de-
signed to collect rock samples only or collect soil
samples as well (it might be possible to collect soil
samples via the proposed mission that would carry the
MAV).
(3) At least one secondary scientific objective, the highest
priority of which is related to measuring the surface
atmospheric pressure as a function of time.
In summary, the proposed MAX-C mission should pro-
vide insight into the paleoenvironment of the landing site
to help constrain the conditions in which life might have
evolved on Mars. Visiting terrains that represent key peri-
ods in martian history (e.g., the early Noachian, or the
Noachian-Hesperian boundary) could enable investigation
of a prebiotic environment or an environment that repre-
sents a period when Mars? climate and geology might have
been in transition and affected the development of primi-
tive cellular life. Investigation of an astrobiologically rele-
vant environment represented by a novel terrain not
previously explored could permit tests of hypotheses that
relate to life in certain types of compositional or geomor-
phological environments. Detailed characterization of the
geology of the landing site is critical to our understanding
of conditions that may have enabled or challenged the
development of life or that might have context that would
guide the search for evidence of ancient life or prebiotic
chemistry within the landing site region and more broadly
across Mars. The concept of the payload needed to achieve
all the objectives, including caching samples, is summarized
in Fig. 8.1.
With respect to potential sample return, the proposed
MAX-C mission could contribute greatly to our prepared-
ness by caching samples, conducting site characterization
(accomplished in large part via the primary in situ scientific
objectives), and demonstrating key capabilities such as
sample acquisition and manipulation, sample encapsulation
and canister loading, and planetary protection and contam-
ination control. Inclusion of these scientific approaches and
technological components on the proposed MAX-C mission
could, via early demonstration of sample acquisition and
storage capabilities, substantially reduce the risks associated
with sample return and enhance the quality and value of the
science and technology required for a follow-on potential
sample return mission.
9. Considerations Related to Landing
Site Selection
In this section, the possible implications of novel dis-
coveries by preceding missions on the design and im-
plementation of the proposed MAX-C mission are
considered, and a strategy is revealed for selecting a site
that could bolster the scientific return of a potential sample
return mission.
Discoveries by preceding orbiters and landers could
impact the execution of the proposed MAX-C mission in
several important ways. For instance, a compelling dis-
covery at a particular locality would clearly impact the
proposed MAX-C site selection process. Furthermore, the
particular features identified at such a site might influence
the selection of scientific instruments that would be re-
quired to perform the key types of measurements at the
site. Geographical and other attributes of a landing site
could influence the engineering design of the spacecraft.
Possibilities such as these require consideration for how a
future mission might adapt to such discoveries. Another
consideration should be that, if the proposed MAX-C mis-
sion is sent to a previously visited site, then Mars explo-
ration resources would become heavily concentrated at that
single site, which would thereby potentially reduce (or
slow) our efforts to better understand global martian geo-
logical diversity and character of diverse habitable envi-
ronments.
FINDING: The best way to evaluate the multiple candidate
sites from which to consider returning samples is via an open
landing site selection competition with sample return selection
criteria. A mission such as the proposed MAX-C presents the
first opportunity to evaluate new high-potential sites via such a
competition.
SUMMARY OF SCIENTIFIC OBJECTIVES PROPOSED FOR
THE MAX-C MISSION CONCEPT:
(1) Primary Scientific Objectives: At a site interpreted to rep-
resent high habitability potential, and with high preserva-
tion potential for physical and chemical biosignatures:

 evaluate paleoenvironmental conditions

 characterize the potential for the preservation of biotic
or prebiotic signatures

 access multiple sequences of geological units in a
search for possible evidence of ancient life or prebi-
otic chemistry
(2) Samples necessary to achieve the proposed scientific ob-
jectives of the potential future sample return mission
would be collected, documented, and packaged in a manner
suitable for potential return to Earth.
(3) Secondary Scientific Objective: Address the need for
long-term atmospheric pressure data from the martian
surface.
PROPOSED MARS ASTROBIOLOGY EXPLORER-CACHER (MAX-C) 147
9.1. Discoveries potentially affecting
landing site selection
Site selection is centrally important for pursuing key sci-
entific objectives by reading a well-preserved geological re-
cord of ancient planetary processes and environments. Site
selection is particularly critical for astrobiology, given the
challenges associated with locating evidence of life on Mars,
which might be akin to ??finding needles [biosignatures] in a
haystack [the vast martian surface].?? Recent discoveries have
revealed many different types of sites that were (or are)
potentially habitable and might preserve evidence of life.
Each of these types must be evaluated to determine its po-
tential value as an exploration target. For example, in the
search for evidence of past environments and life, each of
the following key questions sets the stage for addressing the
question that follows it: Was a particular local environment
habitable at some time in the past? If so, did local conditions
favor the preservation of evidence of environments and life?
If so, are any organic compounds or other potential bio-
signatures present? If so, does the evidence indicate specifi-
cally that at least some chemical species, isotopic patterns,
minerals, rock textures, or gaseous species probably origi-
nated from martian life and that an abiotic origin is unlikely?
Findings by the Mars orbiters and landers that precede the
proposed MAX-C mission would enhance the potential
MAX-C site selection process (Fig. 9.1) and optimize the
spacecraft design and scientific payload.
9.1.1. Orbiters. Recent remote sensing observations il-
lustrate how an ongoing orbital campaign will help to
evaluate candidate sites with regard to habitability and the
potential preservation of a record of past environments and
life. Minerals associated with aqueous processes occur in
perhaps nine or more classes of deposits characterized by
distinct mineral assemblages, morphologies, and geological
settings (Murchie et al., 2009). Phyllosilicates appear in nu-
merous different settings, including the following: composi-
tionally layered strata that are hundreds of meters thick and
overlie eroded Noachian terrains, lower layers of deposi-
tional fans within craters, potential chloride-rich deposits on
inter-crater plains, and deep bedrock exposures in thousands
of craters (e.g., Schwenzer et al., 2009) and escarpments.
Carbonates appear in thin unit(s) along the western margin
of the Isidis Basin. Hydrated silica accompanies hydrated
sulfates in thin layered deposits in Valles Marineris. Hy-
drated sulfates and crystalline ferric minerals co-occur in
thick, layered deposits in Terra Meridiani and in Valles
Marineris. Sulfates, ferric minerals, and kaolinite appear in
deposits within some highland craters. While these discov-
eries exemplify successful outcomes of the Mars exploration
theme ??Follow the Water,?? additional orbital observations
would be required to determine which of these numerous
localities has the greatest probability of supporting life in the
past and preserving an accessible biological record.
Assemblages of minerals formed in ancient environments
frequently can indicate whether an environment provided
FIG. 8.1. MAX-C payload concept.
FIG. 9.1. Discoveries made by orbiters and landers during
the next several years will influence substantially the selec-
tion of the proposed MAX-C candidate landing sites.
148 MRR-SAG
the requirements to sustain life, which would include es-
sential nutrients, biochemically useful energy, and liquid
water with a sufficiently high chemical activity to sustain life.
The suites of minerals that have been detected to date indi-
cate a range of soluble cations, pH, Eh, and water activities
(Murchie et al., 2009). When combined with chemical mod-
eling, these observations provide a basis for constraining the
pH and water activities of their environments of formation
(Tosca et al., 2008). For example, most smectite clays form in
near-neutral waters, whereas kaolinite and hydrated silica
can also form under weakly acidic conditions. Carbonates
typically form in weakly alkaline environments and precip-
itate at water activity values that can sustain microbial life as
we know it. Accordingly, deposits that are probably Noa-
chian age and contain phyllosilicates and carbonates appar-
ently formed in environments that had pH and water activity
values consistent with habitable conditions (Murchie et al.,
2009). Phyllosilicates in ancient plains sediments appear to
be dominantly detrital and also lack evidence for sulfates or
carbonates, which is consistent with the possibility that the
water activity might have been high. Phyllosilicates that lie
deeper in the crust and have been exhumed locally probably
formed in neutral to mildly acidic pH conditions. Orbiters
have not yet detected mineralogical evidence indicating that
these deposits formed in environments that had high sali-
nities.
In contrast, late Noachian and younger evaporite deposits
may have formed in water environments that were margin-
ally habitable at best due to low water activity, at least at the
time when their most soluble salt components were precip-
itated. The Meridiani layered deposits at the Opportunity
landing site contain highly soluble magnesium sulfates and
jarosite and thus apparently formed in waters that were both
acidic and highly saline (Knoll et al., 2005; Tosca et al., 2008).
The presence in some intra-crater phyllosilicate deposits of
hydrated Fe and Mg sulfates and the acid sulfate alunite
indicates extreme salinities and low pH. Monohydrated Fe
and Mg sulfates in some Valles Marineris deposits precipi-
tated from brines whose water activities were perhaps
too low to sustain active metabolism. In contrast, gypsum
(CaSO4  2H2O) is estimated to have precipitated from mar-
tian brines whose water activities were higher (Tosca et al.,
2008) and, therefore, might have sustained biological activ-
ity. Occurrences of hydrated silica might have been less sa-
line and only mildly acidic (Murchie et al., 2009).
Potential visible, near-infrared, and mid-infrared orbital
observations will clarify the relative merits of these sites to
the extent that investigators can test the multiple hypotheses
for the origins of aqueous mineral-bearing deposits. Such
efforts will provide additional constraints on the habitability
of their depositional environments. Any such insights would
impact substantially the potential MAX-C site selection
process. The potential future Trace Gas Mission (Smith et al.,
2009a) might also provide information of interest to the
MAX-C mission concept, though MAX-C, as proposed in this
report, would be focused on the search for signs of life in
ancient rocks.
Also critically important is the extent to which geological
deposits have preserved key information about the ancient
habitable environment in which they formed. Fossilization
processes are intimately tied to the physical, chemical, and
biological conditions that accompany the formation and
long-term persistence of geological deposits (Farmer and Des
Marais, 1999). For example, chemically reducing conditions
are better than oxidizing conditions in promoting the pres-
ervation of sedimentary organic matter. On Earth, minerals
differ in their effectiveness as agents of preservation. Phyl-
losilicates and sulfates are excellent for preserving organic
compounds and isotopic biosignatures, but they are less ef-
fective for preserving morphological fossils. Phyllosilicates
can enhance the retention of organic compounds by binding
molecules to charged mineral surfaces and incorporating
them into mineral structures as interlayer cations (Keil et al.,
1994; Kennedy et al., 2002; Wattel-Koekkoek et al., 2003;
Mayer, 2004). Silica and, to a lesser extent, carbonates can
preserve all types of biosignatures. Microbial fossils can be
preserved by entombment in fine-grained mineral precipi-
tates, such as silica, phosphate, carbonate, or metallic oxides
and sulfides. Sedimentary precipitates like silica and phos-
phate minerals can become very chemically stable and thus
have very long residence times in Earth?s crust. These min-
erals host the best-preserved microbial fossils in Earth?s early
geological record.
Orbital observations of the abundance and geological
context of minerals such as these could support a prioriti-
zation of candidate MAX-C landing sites regarding their
potential to have preserved an accessible record of ancient
habitable environments. The numerous promising sites that
have already been identified are widely distributed across a
range of geographic locations and elevations. Further ac-
quisition and analysis of orbiter data are needed to ensure a
set of good choices for possible near-future landed missions.
9.1.2. Landers. Landers provide more-detailed and
precise analyses of particular sites than is possible from or-
bital observations and make it possible to address questions
such as: did environmental conditions at the site indeed
favor habitability and preservation of a record? If so, are any
organic compounds or other potential biosignatures present?
If so, does the evidence indicate specifically that at least some
chemical species, isotopic patterns, minerals, rock textures,
or gaseous species probably originated from martian life and
that an abiotic origin is unlikely?
The MSL mission is very well equipped to address these
astrobiology questions as well as additional key objectives
that address geological and climate history. Efforts by MSL
to map the distribution of such minerals at various spatial
scales will influence substantially the way phyllosilicates,
sulfates, and silica are viewed as indicators of aqueous
activity and habitability and as preservation media for bio-
signatures. The findings from MSL could, in turn, signifi-
cantly impact potential future mission scientific objectives,
the development of flight instruments needed for sample
selection, and the choice of a specific landing site for po-
tential sample return.
Given the care of the MSL site selection process and the
great potential for MSL discoveries, the MSL site might be-
come one of the finalists for the proposed MAX-C mission,
though a potential sample return would have a wider range
MAJOR FINDING: An ongoing program of orbital observa-
tions would be essential to provide a robust site selection
process for the proposed MAX-C mission.
PROPOSED MARS ASTROBIOLOGY EXPLORER-CACHER (MAX-C) 149
of scientific objectives than MSL. It is likely that discoveries
from orbit would also provide compelling competing sites to
the finalists. Selecting a new location would broaden the
diversity of explored astrobiologically relevant environments
by visiting a site that is both promising and qualitatively
distinct from previously visited sites.
That said, MSL?s substantial capabilities and its ??front row
seat?? location on the ground will greatly enhance its pros-
pects for achieving compelling discoveries (see Table 9.1).
MSL should confirm, at a level of confidence unachievable
from orbit, whether a habitable environment indeed existed
at some time in the past and whether the depositional con-
ditions favored good preservation of information about that
environment. Mineral assemblages might indicate that fluids
once existed and had water activities high enough to sustain
active metabolism.
The Mars Science Laboratory might find possible evidence
of prebiotic chemistry or life (Table 9.1). Organic materials
could have molecular compositions that are either meteoritic
or indigenous to Mars and could have had either an abio-
logical or biological origin. MSL might find isotopically light
carbon or sulfur in minerals or organic matter.
Even more compelling would be probable evidence of
prebiotic chemistry or life. Examples include organic com-
pounds that resemble microbial organic constituents on
Earth or have compositions distinctly different from mete-
oritic materials. Microscale sedimentary fabrics and shapes
also could suggest biological origins. Discrete cohesive or-
ganic layers might resemble the remains of microbial bio-
films. Sedimentary fabrics might indicate stromatolites or
microbialite-like structures. And patterns of stable isotopic
abundances in combination with petrographic observations
that indicate a biological origin would be highly significant.
One very specific hypothetical MSL mission scenario il-
lustrates the case where the potential MAX-C site selection
process might consider the MSL site and additional
sites identified from orbit. For example, MSL finds well-
preserved deposits from a past habitable environment,
and these deposits contain organic matter of indeterminate
origin(s). These findings would be ??possible evidence of life,??
but meteoritic organic compounds could not be excluded.
In this scenario, the site would be designated a ??finalist??
for the proposed MAX-C mission, but if orbital observa-
tions have also identified other as yet unvisited localities
that are highly promising, these would also be designated
as finalists.
In another ??possible evidence of life?? hypothetical sce-
nario, MSL explores a cross section of materials that orbital
observations indicate were deposited in aqueous environ-
ments. The rover only reaches phyllosilicate deposits shortly
before the end of the mission, and organic compounds of
possible martian origin are finally discovered. Assessment of
orbital imagery has revealed an even stronger connection
between these types of phyllosilicates and long-lived liquid
water on the martian surface. Such observations would
warrant designating this as a potential ??MAX-C finalist site.??
Table 9.1. Examples of Significant Observations that Might Compel the Selection
of a Site for the Proposed MAX-C Mission
Observed by
Lander Orbiter
Example observations suggesting
site was favorable in terms of
habitability and=or preservation
x x (1) Minerals that indicate extended activity
of liquid water
x x (2) Minerals that indicate reducing conditions
x x (3) Signs of early mineralization (favoring
biosignature preservation)
x x (4) Morphological features indicating aqueous
transport and aqueous sedimentation
x x (5) Evidence of a hydrothermal system
x x (6) High diversity of deposits favorable for
habitability (e.g., phyllosilicates, silica, carbonates, sulfates)
x x (7) Layered deposits with conspicuous lateral
continuity
Example observations suggesting
possible evidence of life or prebiotic
chemistry
x (1) Organic materials with molecular composition
that could be meteoritic or indigenous with an
abiological or biological origin
x (2) Isotopically light sulfur or carbon, etc., in minerals
Example observations suggesting
probable evidence of life or prebiotic
chemistry
x (1) Organic materials with composition distinct from
meteoritic organics
x (2) ??Complex?? organic material with overall
composition similar to microbial organics on Earth
x (3) Ancient organic deposits with microbial mat-like
characteristics (e.g., cohesive, discrete layers)
x (4) Isotopic fractionation patterns with
petrographic=petrologic observations suggesting primary,
possibly biological origin
x (5) Stromatolitic or microbialite-like structures
150 MRR-SAG
Remote sensing observations can also have ??possible
evidence of life?? scenarios. For example, a spacecraft cor-
roborates the detection of atmospheric methane and dem-
onstrates that higher methane concentrations appear to
originate from a region that harbored ultramafic rocks, ser-
pentine, and other evidence of aqueous alteration. Such a
discovery might make this region a ??finalist site.??
A ??probable evidence of life?? scenario occurs if MSL confirms
that the site has preserved a record of a past habitable en-
vironment and the spacecraft also discovers martian organic
matter and possibly additional features for which martian
life is the most probable source. Although such evidence
might not yet provide proof of past martian life, it would
provide a compelling argument that a potential sample re-
turn mission should go there in order to obtain potentially
compelling evidence in Earth-based laboratories. In this
scenario, the proposed MAX-C mission would likely be sent
to the MSL site.
The MERs are still continuing their investigations, and one
of them may yet encounter some new compelling deposits
with chemical, mineralogical, and textural characteristics that
compel us to make it a potential MAX-C ??finalist site.?? The
MER payload capabilities are limited compared to the MSL
rover?s, but we should leave open the possibility for new
discoveries, as indicated in Fig. 9.1.
However, sending the proposed MAX-C mission to a
previously visited site would reduce the range of geological
environments visited. Mars exploration resources would be
concentrated at a single site, which would thereby poten-
tially reduce (or at least slow) our efforts to better under-
stand global martian geological diversity of habitable
environments. Finally, a requirement to return to a previous
site would preclude a potential sample return mission from
visiting a compelling new site identified from orbit after the
proposed MAX-C mission (though it is likely that a suffi-
ciently compelling observation would lead to a change in the
requirement).
9.2. Selection of a landing site of high potential interest
The site visited by a potential sample returnmission should
contain samples of high relevance to the life question, and a
MAX-C site selection competition would provide an oppor-
tunity to evaluate candidates. Over the past 35 years, theMars
program has successfully visited six landing sites. However,
three of those sites (Viking 1 and 2, and Pathfinder) are clearly
not of broad enough interest to justify an astrobiology-focused
MSR mission. The Phoenix site is likely not accessible to the
potential sample return flight system and in any case would
probably not be judged to be scientifically compelling from a
??signs of life?? viewpoint. Both of the MERs have encountered
and documented past geological environments that are po-
tentially habitable and thus hold interest for sample return.
The two MERs are still operating and could yield new dis-
coveries that might make one of their landing sites more en-
ticing for sample return. Thus, two of six past sites are possible
candidates for a potential astrobiology-focused sample return
mission. However, with the recent improvement in our
knowledge ofmartian surface geology (notably from theMars
Reconnaissance Orbiter,MRO), there is a consensus that, from
the perspective of potential sample return, more promising
sites than these almost certainly exist.
As our knowledge of the martian surface has increased,
there has been a parallel increase in the number and nature
of sites that have the potential to contain outstanding sam-
ples for a possible sample return. In the area of astrobiology,
the NRC (2007) recently listed some of the high-interest sites.
In addition, at recent Mars-related conferences (e.g., Lunar
and Planetary Science Conference, European Planetary Sci-
ence Congress, the American Geophysical Union, 7th Inter-
national Conference on Mars, European Geosciences Union),
the global Mars scientific community has developed multiple
additional site-specific astrobiology hypotheses, the testing
of which could substantially address the life question. The
four candidate MSL landing sites still under consideration as
of this writing are also of interest from an astrobiological
perspective. However, sample return scientific objectives go
beyond astrobiology and habitability. For example, as re-
cently discussed at the conference ??Ground Truth from Mars:
Science Payoff from a Sample Return Mission?? (April 21?23,
2008, Albuquerque, New Mexico, http:==www.lpi.usra.edu=
meetings=msr2008=), other kinds of geological materials of
interest include sulfate minerals (which may contain a record
of Mars near-surface processes), igneous rocks (which are
fundamental to understanding the martian interior), hydrous
minerals (which may contain a record of fluid-atmospheric
evolution and secondary alteration), a full spectrum of sed-
imentary rocks, samples that represent a depth profile, and
others.
As with all landed missions to Mars, the best way to
evaluate the multiple sample return landing site possibilities,
priorities, and advocacy positions is through an open com-
petitive landing site selection process. Developing a con-
sensus for a potential sample return landing site would be
essential for generating a broad, politically valuable support
base. The proposed MAX-C mission represents the first op-
portunity to hold an open, competitive selection process to
identify a landing site with consideration of potential sample
return criteria.
It is extremely important that a broad spectrum of landing
site possibilities be available for this landing site competition.
Recent results from orbital missions, highlighted by those
from MRO, indicate that many candidate landing sites for
the proposed MAX-C mission will likely be located in the
ancient terrains of the Southern Highlands, where the record
of aqueous alteration and processes is best preserved and
exposed. Experience with the MSL and previous landing site
selection activities has shown that a range of candidate
MAX-C sites should be available for exploration if elevations
up to ?1 km could be accessed, but restriction to progres-
sively lower elevation would result in loss of a rapidly in-
creasing number of attractive sites (see Fig. 9.2).
FINDING: The landing site selection process for a potential
sample return mission should start as soon as possible to take
full advantage of the currently orbiting high-resolution in-
struments.
FINDING: There are many candidate sites of high interest for a
potential sample return beyond those previously visited or to
be visited by MSL.
PROPOSED MARS ASTROBIOLOGY EXPLORER-CACHER (MAX-C) 151
10. Some Engineering Considerations Related
to the Consensus Mission Vision
10.1. Solar power and thermal considerations
The proposed architecture would use solar arrays to
power the rover. This would drive the power and thermal
design and would result in a practical limit to latitude access
for the mission. The desired mission duration of at least
1 Earth year (half a Mars year) and the season at landing
would result in a requirement to be able to operate in nearly
any seasonal extreme. In northern latitudes it would be
winter at arrival and summer at the end of the mission. The
opposite seasons are experienced for southern landing sites.
Due to the eccentricity of the martian orbit, northern lati-
tudes are less severe on the power=thermal design than
southern latitudes, which would allow effective operation at
sites as far north as 258N and as far south as 158S.
10.2. Entry, descent, and landing,
and rover traverse capabilities
The performance of the EDL system is an important factor
in defining the accessible landing sites on Mars and in sizing
some key rover attributes. The major EDL performance at-
tributes relevant to this discussion are delivered mass,
landing altitude, and landing ellipse size. In general, less
mass can be delivered to a higher altitude, more mass to a
lower altitude, but there are limits to this trade due to other
engineering constraints (e.g., structural design, guidance and
control considerations). The size of the landing ellipse is in
part dependent upon EDL phase a priori attitude knowledge
errors that propagate through the entry phase. The ellipse
can be tightened up incrementally by tightening up the
knowledge errors. Landing ellipse size is primarily of interest
when improved access to specific features on Mars is to be
considered. Given that scientifically interesting features often
represent terrain that is too dangerous on which to land, the
landing ellipse is often driven to be placed right up against,
but not on top of, features of interest. The result is that access
is often a product of both ellipse size and traverse capability
that is sufficient to get outside of that ellipse in a reasonable
amount of time relative to the mission lifetime.
The mass of the proposed MAX-C rover is estimated to be
in a mass class much smaller than MSL but larger than the
MERs. This makes a reflight of the MSL Cruise=EDL system
the prudent choice to deliver the proposed MAX-C rover to
the surface of Mars. The proposed MAX-C mission would
arrive at Mars in January of 2019 at an Ls? 3258 (northern
midwinter). Given the favorable atmospheric pressure at this
time of the martian year, performance of the MSL delivery
system could possibly allow altitudes up to ?1 km, de-
pending upon the final landed mass. There are also unfa-
vorable effects on the atmosphere from possible dust storms,
FIG. 9.2. Mercator projection of ? gridded Mars Orbiter Laser Altimeter (MOLA) topography of Mars from 908S to 908N
latitude, showing the areas below ?1 km elevation in blue and dark green. Elevation is relative to the MOLA datum (Smith
et al., 2001). This map uses an areocentric coordinate convention with west longitude positive. Image Credit: NASA=
JPL-Caltech=GSFC.
FINDING: A significant number of candidate landing sites, of
high relevance to the objectives of the proposed MAX-C mis-
sion, with elevations less than ?1km MOLA datum are known.
It is very important for this proposed mission to preserve the
option of accessing the Southern Highlands, for which this
threshold is a practical minimum.
152 MRR-SAG
and the combination of all of this has not been fully evalu-
ated at this time. The landing ellipse size could be reduced
from the MSL 10 km radius capability to as small as 7 km
(Wolf and Ivanov, 2008). A traverse capability complemen-
tary to this would be provided to allow access outside of the
landing ellipse.
To achieve the scientific objectives, it would be important
for the rover to have sufficient ability to apply its payload to
particular features of interest (outcrops, layers, etc.). The
proposed rover would have a mobility system physically
similar to that of the MERs, only slightly larger. The traverse
capabilities of the MERs are seen as the standard for such
feature access. The key parameters behind a rover?s ability to
traverse slopes, sandy terrain, and rock fields are as follows:

 Ground Pressure: Defined as the ratio of the weight of
the vehicle to the effective contact patch of its wheels.
Ground pressure for the proposed MAX-C rover would
be as good as, or better than, that of the MERs, which
would allow safe and effective traverse on loose or
sandy slopes of as high as 10?12 degrees.

 Static Stability Angle: Defined as the complement of the
angle from the ground up to the rover center of mass,
measured from the various outer edges and pivot points
of the rover suspension. The proposed MAX-C rover
would be designed with a sufficiently high static sta-
bility angle to allow safe and effective traverse on well-
consolidated or rock-plated terrain up to *30 degrees.

 Wheel Size and Belly Clearance: The diameter of the
wheels and the distance from the belly of the rover to
the ground defines the size of rock that is deemed an
obstacle. The proposed MAX-C rover would be de-
signed to be at least as large as the MERs in these pa-
rameters, which would allow effective traverse in rock
fields at least as dense as encountered by the MERs.
Another important capability for accessing features of in-
terest is traverse rate (or effective daily average rate). In some
landing sites, it might be desired to traverse distances as far
as 10 km to reach the features of interest. Given the modest
lifetime of 1 Earth year suggested for the proposed MAX-C
mission, the necessary traverse rate for the rover would need
to be improved over past experience. It is estimated that a
factor of 2?3 improvement over the actual MER capability
could be required. Through the use of improved algorithms
and hardware for navigation functions, it could be possible
to increase the traverse rate for the proposed MAX-C rover
by at least this much.
The MSL landing system (called ??sky crane??) would likely
be used for the proposed MAX-C mission and would result
in similar engineering constraints on the landing ellipse (to
first order) as those applied to MSL. By analogy with the
MSL landing site selection process, many of the highest-
priority landing locations identified from orbit cannot be
directly accessed and might require the ability to traverse
beyond the perimeter of the landing ellipse. Although good
FIG. 10.1. An example of a ??go to?? landing site that would be well suited for landing in the smooth safe area to the south
but then requiring a possibly long rover drive to get to the area of scientific interest on rougher terrain. Mosaic of CTX images
P05_003168_1825 and P06_003379_1827 shows a portion of a Northern Meridiani site that is no longer being considered for
MSL. Image credit: NASA=JPL-Caltech=MSSS.
PROPOSED MARS ASTROBIOLOGY EXPLORER-CACHER (MAX-C) 153
scientific targets exist within all the final candidate sites for
MSL, primary scientific targets are near the edge or outside
the ellipse for three of the final four candidate sites selected.
Figure 10.1 shows an example of a ??go to?? type of landing
site. Outcrop access would be essential to the scientific return
of the MAX-C mission concept. Areas of extensive outcrop
are typically associated with significant topography, which
correlates to landing hazard for an MSL landing system. An
alternative would be to land in a place where it is topo-
graphically rough but the landing ellipse contains all the
targets of interest, and use hazard avoidance technology
(Mourikis et al., 2009) during descent to land on a safe spot
(see Fig. 10.2 for an example of this kind of landing).
The use of hazard avoidance would reduce rover mobility
requirements and the risk of a surface rendezvous with a
potential sample return ??fetch?? rover. However, if hazard
avoidance is not possible due to risk or cost reasons, an in-
creased rover traverse capability could be relied on.
The capability to navigate on slopes of up to 30 degrees,
as both of the MERs have done, would be extremely useful
for the proposed MAX-C mission. Many of the geologically
interesting terrains on Mars expose stratified layers on
slopes in craters, channels, and hillsides. Access to these
kinds of slopes would allow the proposed MAX-C mission
to characterize a sequence of layers and lower the risk to
achieving the scientific objectives. Limiting this capability
could rule out certain landing sites, could cause a rover to
take a much longer path to get to a target of interest, or
could preclude access to certain targets of interest. Also,
another consequence of limiting the slope capability is that it
would increase the rover egress challenges for those archi-
tectures that include a landing pallet. Less slope capability
means that smaller rocks become landing hazards. The
ability to also acquire cores for the proposed cache while the
rover is parked on a slope is also highly desirable, though
this should be part of a future science=engineering trade
study.
10.3. Sample acquisition, mechanical
handling, and caching
10.3.1. Abrading. Abrading of surface material would
be accomplished through the use of a specialized abrading
bit placed in the coring tool (Zacny et al., 2008). The incre-
mental mass and complexity of this approach, given the
existence of the coring tool with bit change-out capability, is
small (much smaller than adding a separate abrading tool).
This tool would be intended to remove small amounts of
FIG. 10.2. An example of a landing site that could benefit from hazard avoidance during descent to avoid the rough terrain
outlined by red polygons. Mosaic of CTX images P01_001336_1560 and P06_003222_1561, showing the ellipse for the
Eberswalde candidate MSL landing site. Image credit: NASA=JPL-Caltech=MSSS, polygons generated by Eldar Noe Dobrea
and Matthew Golombek.
FINDING: The proposed MAX-C mission would require either
(a) the ability to traverse beyond the landing ellipse to targets
of interest or (b) hazard avoidance capability during EDL and
an ability to traverse to targets of interest within the ellipse.
154 MRR-SAG
surface material to allow instruments access past any dust or
weathering layer. It would abrade a circular area of similar
diameter to the core (8?10mm). Translation of the arm
would be used to scan or mosaic the individual abrasion
spots to expose larger areas. Design parameters would be
explored to strike a balance between the engineering desire
to use percussion for efficient abrading and the scientific
desire to have a smooth cut surface to observe. The surface
contamination due to abrasion would need to be constrained
so as not to interfere with organic compound detection, if
such an instrument is included in the payload.
10.3.2. Coring. Coring would be accomplished through
the use of a coring tool on a 5-degree-of-freedom arm, to
allow acquisition from a diverse set of targets. It could pro-
duce cores of approximately 10mm diameter up to 50mm
long, which would be encapsulated in individual sleeves
with pressed-in caps. The system would minimize mechan-
ical handling of the cored material through a design that
allows core acquisition to take place directly into the en-
capsulation sleeve. Bit change-out capability would also be
provided to allow for bit wear, breakage, and loss of any
kind.
Cores could be made available for observation through a
mechanism to allow placing them on an observation tray at
the front of the rover. In this tray, they would be accessible or
visible by instruments on both the arm and mast. Cores
placed in the tray could not later be encapsulated for
placement in the cache. Once placed in the tray, and subse-
quent to any interrogations by mast or arm-mounted in-
struments, cores would be discarded.
The nature of the coring tool would be rotary percussive
[like a common hammer drill, see Stanley et al. (2007) for an
example]. It does not cut the rock but rather fractures and
pulverizes it in the impact patch (the circumference of the
core). This percussive action results in minimal temperature
rise of the actual core, especially across the multi-hour ex-
traction process, but produces a slightly rougher surface than
a pure cutting tool would.
10.3.3. Caching. The rover would be equipped with a
mechanism for handling cores, capping their individual
sleeves, and retaining them in a hexagonal packed cylinder
[Fig. 10.3 shows one example of how a cache could be
configured. See Collins et al. (2009)]. The coring bit (with
sleeved core inside) would be released into the handling
system as part of the transfer mechanism for each core. Bit
change-out essentially would occur during transfer of every
cached core, which would make it advantageous to combine
the more general spare bit change-out function in the same
system. The sleeved core would be retrieved from the bit,
capped, and placed into the cache. Specification of the exact
size of the cache would be the subject of future trade-off
studies, but it appears it would be feasible to incorporate a
cache of 20?30 cores, plus some extra sleeves=caps to allow
for swap-out or loss for whatever reason. The proposed
MAX-C rover could be designed to place the cache on the
surface of Mars at a location favorable for subsequent re-
trieval by a rover from a potential future mission or to retain
the cache for retrieval directly from the proposed MAX-C
rover.
The entire core handling and caching assembly would be
enclosed and sealed with the only entry point being a small
port where the bit (with sleeved core inside) would be in-
serted for transfer. The bit port would be covered and ori-
ented facing down so nothing could fall into it. This is all
favorable for planetary protection and contamination con-
trol, which would impose rigorous requirements on this
mission in order to produce a cache that would be valid for
return to Earth (see MEPAG MRR-SAG, 2009).
The capability for the proposed MAX-C rover to drop off
the sample cache at a location favorable for retrieval by a
subsequent mission could make it much easier for a potential
??fetch?? rover to access quickly. Once the cache is dropped
off, the proposed MAX-C rover could go into more rugged
terrain for its own in situ science without increasing the risk
to a potential sample return. This would benefit the analysis
of potential returned samples by expanding the regional
context of those collected samples.
10.4. Overall risk and cost issues
The implementation described above would rely on sig-
nificant inheritance of MSL cruise and EDL spacecraft de-
signs to minimize cost and risk. Using an MSL design for
cruise stage, entry body, and sky-crane landing system
would be the proposed approach. This would result in
substantive inheritance from MSL in the flight design, test
design, and test and handling hardware. The intermediate
scale of the proposed rover would drive a new mechanical
and thermal development. The basis for the design would be
well understood since it could draw upon the experience of
MER and MSL. At the component level, the proposed rover
would draw heavily upon MSL heritage. The result would
represent a medium risk and medium cost for the rover.
FIG. 10.3. Schematic showing a possible design for a car-
ousel to hold sleeved rock cores. The center cache is re-
movable.
PROPOSED MARS ASTROBIOLOGY EXPLORER-CACHER (MAX-C) 155
A typical development schedule for this kind of project
would be approximately 6 years, Phase A through D, plus
some advanced technology development activities in the
years preceding that. Based on this schedule and a full JPL
Team X estimate, the MRR-SAG?s cost estimate is in the
range of 1.5?2.0 billion, real-year dollars for a possible launch
in 2018. The operations phase after launch plus 30 days is not
included in this estimate. The estimate does include a base-
line Atlas V 531 launch service at an estimated cost of *$290
million. Also included is *$70 million in technology devel-
opment activities to address the needs described in the next
section, with the exception of instrument technology. It is
assumed that key instrument technologies would be ad-
vanced as needed through other funding sources (i.e., MIDP
or other such activity) to an appropriate readiness level to
respond to an Announcement of Opportunity, from which
point the remaining development cost would be provided by
the project. For the entire estimate, cost reserves of 30% on
top of the base estimate are also included.
10.5. Summary of potential MAX-C technology
development needs
Several key technologies would need further development
(Hayati et al., 2009) to support the mission concept. These
include technologies in five areas:

 Coring, encapsulation, and caching: Lightweight
tools=mechanisms would be needed to obtain and
handle cored material.

 Instruments: Additional technology focus should be
applied to instruments that could address the mea-
surement needs posed herein, particularly the micro-
scale mineralogy, organic compounds, and elemental
composition mapping.

 Planetary protection=contamination control: Bioclean-
ing, cataloguing of biocontaminants, and transport
modeling to ensure cached samples would be return-
able.

 Rover navigation: Onboard image processing and nav-
igation to increase traverse rate.

 Entry, descent, and landing: Precision landing and
hazard avoidance.
10.6. A programmatic note
The proposed MAX-C mission concept has been studied
by the MRR-SAG since April, 2009. The strategy has been to
develop the most cost-effective concept to meet the in situ
scientific and caching objectives. The resulting proposed ro-
ver would be in a mass class much smaller than MSL but
larger than MER. This makes an MSL Cruise=EDL system the
prudent choice to deliver the proposed MAX-C rover to the
surface of Mars. Recent high-level discussions between
NASA and ESA have led to the possibility of delivering the
ESA ExoMars rover and the proposed NASA MAX-C rover
to Mars together in 2018 on a single launch vehicle with the
MSL EDL system. This combined mission concept has been
explored only briefly thus far. The implementation discus-
sion in this report reflects a proposed NASA-only MAX-C
mission, but the general capabilities for the proposed MAX-C
mission would be expected to be similar for a dual mission
architecture.
11. Acknowledgments
We are grateful to these outside experts who assisted our
team in answering questions: Fernando Abilleira, F. Scott
Anderson, Paul Backes, Don Banfield, Luther Beegle, Rohit
Bhartia, Jordana Blacksberg, Diana Blaney, Karen Buxbaum,
Shane Byrne, John Eiler, Sabrina Feldman, Lori Fenton,
Kathryn Fishbaugh, Marc Fries, Matt Golombek, Bob Ha-
berle, Samad Hayati, Michael Hecht, Arthur (Lonne) Lane,
Lucia Marinangeli, Richard Mattingly, Tim Michaels, Denis
Moura, Zacos Mouroulis, Mike Mumma, Scot Rafkin, Carol
Raymond, Glenn Sellar, Christophe Sotin, Rob Sullivan, Tim
Swindle, Marguerite Syvertson, Ken Tanaka, Peter Thomas,
Lawrence A. Wade, Ben Weiss, Richard Zurek, and the
MEPAG Goals Committee. Some of this research was car-
ried out at the Jet Propulsion Laboratory, California In-
stitute of Technology, under a contract with the National
Aeronautics and Space Administration. In the early parts of
this study, the contributions of Hap McSween were im-
portant.
12. Abbreviations
APXS, Alpha Particle X-Ray Spectrometer
DUV, deep ultraviolet
EDL, entry, descent, and landing
JPL, Jet Propulsion Laboratory
MATT, Mars Architecture Tiger Team
MAV, Mars Ascent Vehicle
MAX-C, the Mars Astrobiology Explorer-Cacher
MEPAG, Mars Exploration Program Analysis Group
MER, Mars Exploration Rover
MIDP, Mars Instrument Development Program
MOLA, Mars Orbiter Laser Altimeter
MRO, Mars Reconnaissance Orbiter
MRR, Mid-Range Rover
MRR-SAG, Mid-Range Rover Science Analysis Group
MSL, Mars Science Laboratory
MSR, Mars Sample Return
ND-SAG, Next Decade Science Analysis Group
NRC, National Research Council
PIDDP, Planetary Instrument Definition
and Development Program
RAT, Rock Abrasion Tool
S=N, signal-to-noise ratio
TRL, Technology Readiness Level
XRF, X-ray fluorescence
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Address correspondence to:
Lisa Pratt
Indiana University
E-mail: prattl@indiana.edu
David Beaty
Mars Program Office
Jet Propulsion Laboratory
California Institute of Technology
E-mail: David.Beaty@jpl.nasa.gov
Abigail Allwood
Mars Program Office
Jet Propulsion Laboratory
California Institute of Technology
E-mail: Abigail.C.Allwood@jpl.nasa.gov
Submitted 2 December 2009
Accepted 6 January 2010
PROPOSED MARS ASTROBIOLOGY EXPLORER-CACHER (MAX-C) 163