The Argyre Region as a Prime Target for in situ
Astrobiological Exploration of Mars
Alberto G. Faire´n,1,2 James M. Dohm,3 J. Alexis P. Rodrı´guez,4 Esther R. Uceda,5 Jeffrey Kargel,6
Richard Soare,7 H. James Cleaves,8,9 Dorothy Oehler,10 Dirk Schulze-Makuch,11,12 Elhoucine Essefi,13
Maria E. Banks,4,14 Goro Komatsu,15 Wolfgang Fink,16,17 Stuart Robbins,18 Jianguo Yan,19
Hideaki Miyamoto,3 Shigenori Maruyama,8 and Victor R. Baker6
Abstract
At the time before *3.5Ga that life originated and began to spread on Earth, Mars was a wetter and more
geologically dynamic planet than it is today. The Argyre basin, in the southern cratered highlands of Mars,
formed from a giant impact at *3.93Ga, which generated an enormous basin approximately 1800 km in
diameter. The early post-impact environment of the Argyre basin possibly contained many of the ingredients
that are thought to be necessary for life: abundant and long-lived liquid water, biogenic elements, and energy
sources, all of which would have supported a regional environment favorable for the origin and the persistence
of life. We discuss the astrobiological significance of some landscape features and terrain types in the Argyre
region that are promising and accessible sites for astrobiological exploration. These include (i) deposits related
to the hydrothermal activity associated with the Argyre impact event, subsequent impacts, and those associated
with the migration of heated water along Argyre-induced basement structures; (ii) constructs along the floor of
the basin that could mark venting of volatiles, possibly related to the development of mud volcanoes; (iii)
features interpreted as ice-cored mounds (open-system pingos), whose origin and development could be the
result of deeply seated groundwater upwelling to the surface; (iv) sedimentary deposits related to the formation
of glaciers along the basin’s margins, such as evidenced by the ridges interpreted to be eskers on the basin floor;
(v) sedimentary deposits related to the formation of lakes in both the primary Argyre basin and other smaller
impact-derived basins along the margin, including those in the highly degraded rim materials; and (vi) crater-
wall gullies, whose morphology points to a structural origin and discharge of (wet) flows. Key Words: Mars—
Surface processes and composition of Mars—Liquid water—Geological conditions for the development of
life—Planetary habitability and biosignatures. Astrobiology 16, 143–158.
lDepartment of Planetology and Habitability, Centro de Astrobiologı´a (CSIC-INTA), Madrid, Spain.
2Department of Astronomy, Cornell University, Ithaca, New York, USA.
3The University Museum, The University of Tokyo, Tokyo, Japan.
4Planetary Science Institute, Tucson, Arizona, USA.
5Facultad de Ciencias, Universidad Auto´noma de Madrid, Madrid, Spain.
6Department of Hydrology and Water Resources, University of Arizona, Tucson, Arizona, USA.
7Department of Geography, Dawson College, Montreal, Canada.
8Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, Japan.
9The Institute for Advanced Study, Princeton, New Jersey, USA.
10Jacobs/LZ Technology, JETS Contract, NASA Johnson Space Center, Houston, Texas, USA.
11Center of Astronomy and Astrophysics, Technical University Berlin, Berlin, Germany.
12School of the Environment, Washington State University, Pullman, Washington, USA.
13Higher Institute of Applied Sciences and Technology, University of Gabes, Gabes, Tunisia.
14Smithsonian Institution, National Air and Space Museum, Center for Earth and Planetary Studies, Washington, DC, USA.
15International Research School of Planetary Sciences, Universita` d’Annunzio, Pescara, Italy.
16College of Engineering, Department of Electrical and Computer Engineering, University of Arizona, Tucson, Arizona, USA.
17Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, California, USA.
18Southwest Research Institute, Boulder, Colorado, USA.
19RISE Project Office, National Astronomical Observatory of Japan, Oshu, Japan.
ª Alberto G. Faire´n, et al., 2016; Published by Mary Ann Liebert, Inc. This Open Access article is distributed under the terms of the
Creative Commons Attribution Noncommercial License (http://creativecommons.org/license/by-nc/4.0/) which permits any noncommercial
use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited.
ASTROBIOLOGY
Volume 16, Number 2, 2016
Mary Ann Liebert, Inc.
DOI: 10.1089/ast.2015.1396
143
1. Introduction
Earth has been an enduringly dynamic and water-influenced planet since early in its geological history.
There is evidence of water-deposited rocks in the oldest
petrological record of Earth (e.g., Mojzsis et al., 2001) and
evidence of continent/ocean structure almost as ancient (e.g.,
Polat, 2012; Maruyama et al., 2013a; Ge et al., 2014), as well
as magmatism involving a water-rich interior—and pre-
sumed degassing—at least as early as 4.2Ga (Iizuka et al.,
2006). Earth’s biosphere originated and evolved very early in
its geological history. There is evidence for Paleoarchean life
dating back to*3.4 to 3.5Ga from both organic microfossils
and stromatolites (e.g., Schopf et al., 2002, 2007a, 2007b;
Knoll, 2004; Allwood et al., 2006; Schopf, 2006; Stu¨eken
et al., 2015), and those microfossils exhibit relatively diverse
morphologies and complexity (Oehler et al., 2010; House
et al., 2013), suggesting an even earlier origin of life that can
be unambiguously identified in the geological record. Con-
sistent with this view is isotopic evidence suggestive of the
presence of biological activity dating as far back as 3.8Ga
(Mojzis et al., 1996). Because Paleoarchean life appears to
have been relatively diverse, life’s origin on Earth is likely to
have occurred even earlier than these dates suggest (Eiler,
2007; Abramov and Mojzsis, 2009; Oehler et al., 2010;
House et al., 2013; Maruyama et al., 2013b; Patel et al.,
2015), possibly even during the Hadean more than 4.0 billion
years ago.
At the time when life originated and began to radiate on
Earth, Mars was a wetter and more geologically dynamic
planet than it is today, with a global hydrological cycle.
Mirroring conditions of the Late Hadean or Paleoarchean
Earth, early Mars comprised a landmass (the southern cra-
tered highlands acting as a ‘‘supercontinent’’); a large
ocean, countless crater-hosted lakes, and continental-scale
ice sheets (Baker et al., 1991; Kargel and Strom, 1992;
Kargel et al., 1995; Cabrol and Grin, 1999; Carr and Head,
2003; Faire´n et al., 2003; Head et al., 2005; Di Achille and
Hynek, 2010); a relatively thick atmosphere, capable of
supporting stable and widespread hydrological activity; and
diverse energy sources (such as solar or thermally induced
chemical disequilibrium, see Baker et al., 2007; Faire´n,
2010, and references therein). Interaction among the land-
mass, ocean, and atmosphere through hydrological cycling
driven by internal (heat flow) and external (the Sun) energy
sources is considered key to Mars being habitable during its
early evolution (Dohm and Maruyama, 2014).
At the surface, early Mars may have supported an Earth-
like erosional regime and relatively warmer and wetter con-
ditions than today (e.g., Baker et al., 2007), perhaps having
prevailing modern Earth-like periglacial/glacial conditions,
whichmay have been sufficient for life to originate and evolve
(Faire´n et al., 2003, 2010; Kargel, 2004). Moreover, subsur-
face conditions could have been even warmer and wetter,
generating local settings that had potentially habitable con-
ditions for far longer periods—perhaps continuously since the
Noachian period. Given that early Mars may have hosted
habitable conditions approximating those of early Earth, then
whatever steps that led to the emergence and early evolution
of life on Earth also may have occurred independently on
Mars. Alternatively, life could have been transferred from
Earth to Mars or vice versa (e.g., Schulze-Makuch et al.,
2008; Faire´n et al., 2010) when habitable conditions were
present on Mars.
The geological and hydrological evolution of the Argyre
basin and its margins, located in the southern hemisphere of
FIG. 1. Location map of Argyre, showing the main features discussed in this article. Base is a Mars Orbiter Laser
Altimeter (MOLA) map. (Color graphics available at www.liebertonline.com/ast)
144 FAIRE´N ET AL.
Mars (Fig. 1), points to a habitable environment where life
could have originated (or been transferred to), persisted, and
evolved. The early post-impact environment of the Argyre
basin possibly contained many of the ingredients we think
today are necessary for life: abundant and long-lived liquid
water, biogenic elements, and energy sources. Here we sug-
gest that, early inMars’ geological history, the Argyre impact
basin and margins supported (and perhaps still support at
depth) an environment that is favorable for the origin, de-
velopment, and maintenance of microbial life.
2. Geological History
The Argyre province (30S to 65S, 290E to 340.0E;
Fig. 2) is a major geological province in the southern cra-
tered highlands of Mars. Geological and hydrological his-
tories have been detailed through a mapping investigation
with Viking, Mars Global Surveyor (MGS), Mars Odyssey
(ODY), and Mars Reconnaissance Orbiter (MRO) data
(Dohm et al., 2015). A synthesis of Argyre’s history is pro-
vided here, using the formal chronostratigraphic systems
(Noachian, Hesperian, and Amazonian) devised by Scott and
Carr (1978), as well as the series (upper, middle, and lower
divisions of systems) defined by Tanaka (1986).
The Argyre basin formed from a giant impact estimated to
have occurred at *3.93Ga (Robbins et al., 2013), near the
end of the Late Heavy Bombardment (Claeys andMorbidelli,
2011; Fassett andMinton, 2013). The impact left an enormous
basin, approximately 1800 km in diameter. The Argyre event
occurred at a time when Mars was experiencing major
changes in global planetary conditions, including termination
of the internal dynamo, the thinning of the atmosphere, and
consequential changes in climate (e.g., Faire´n et al., 2003;
Baker et al., 2007; Faire´n, 2010).
The Argyre basin is the best-preserved large multiringed
impact structure on Mars. This is more noticeable when
Argyre is compared to the larger and more highly degraded
*4.0Ga Hellas impact basin (Robbins et al., 2013); the
distinction is indicative of major planetary-system changes
occurring during the estimated 70-million-year time range
between the formation of Argyre andHellas. The giant impact
event resulted in the construction of the primary Argyre
crater, the uplift of a mountainous rim, and the production of a
complex system of tectonic structures. These include small
FIG. 2. Geological map of the Argyre and surrounding region of Mars showing stratigraphy and structure. Highlighted are
the major valley systems, Uzboi Vallis (Uzboi), Surius Vallis (SV), Dzigai Vallis (DV), Nia Vallis (NV), and the Argyre
western-margin-paleolake basin (AWMP). (Color graphics available at www.liebertonline.com/ast)
ASTROBIOLOGICAL EXPLORATION OF ARGYRE, MARS 145
and large (as much as thousands of kilometers in length) ex-
tensional and compressional structures, such as structurally
controlled fault scarps, broad ridges, valleys, and mountain
ranges within several hundred kilometers of the basin margin.
With time, erosional and depositional processes have highly
resurfaced the Argyre basin and rim materials continuously
since the excavation of the impact basin (Fig. 3).
3. The History of Water and Volatiles
in the Argyre Region
Topographic, geomorphological, spectroscopic, and iso-
topic investigations (e.g., Hiesinger and Head, 2002; Kargel,
2004; Banks et al., 2008, 2009; Buczkowski et al., 2010;
Jones et al., 2011; El Maarry et al., 2013; Soare et al.,
2014a, 2014b; Webster et al., 2015) provide information for
reconstructing the hydrological history of Argyre, including
long-term water enrichment up to the present day. These
investigations provide some evidence for a broad integration
of hydrogeological activity within the basin extending to
possible headwaters in the highlands south and east of the
basin, and to the Uzboi-debouchment area, northeast of the
basin, and possibly associated with flooding of the northern
plains (i.e., possibly above the Opportunity Landing site)
during the Noachian and Early Hesperian (Faire´n et al.,
2003, 2004); this hydrological system had the Argyre
impact-derived lake as the primary contributor of Uzboi
Valles (Dohm et al., 2015).
3.1. The geomorphological perspective
Some of Argyre’s impact-generated basement structures
possibly reach great depths (potentially reaching the lower
crust and likely the Moho of Mars) and could have served as
conduits for the migration of water, volatiles, and internal
heat into the basin from thousands of kilometers away, such
as extending well within the Tharsis province and from
depths potentially reaching Mars’ lower crust and upper
mantle (Dohm et al., 2001a, 2001b, 2013). These processes
may still be occurring presently (Soare et al., 2014a), though
presumably at a slower pace than in the earlier history of
the basin. This would contribute to a long-term supply of
mineral-enriched water in the subsurface and at the surface
of the basin.
Water enrichment could have been augmented by hy-
drothermal activity associated with the Argyre excavation,
with impact-driven, long-term heat energy being supplied
potentially for millions of years; for example, Abramov and
FIG. 3. Examples of big impact
craters excavated on the Argyre
province. (A) The outlet channel of
the Uzboi Vallis system debouching
into the 140 km wide Holden crater.
Holden’s rim is cut with gullies, and
at the end of some gullies are fan-
shaped deposits of material trans-
ported by water, and sediments
containing clays. (B) Close-up view
of the 230 km diameter crater Galle,
to the east of the Argyre Planitia. A
large stack of layered sediments
form an outcrop in the southern part
of the crater, and several parallel
gullies originate at the inner crater
walls of the southern rim. (C) The
150 km diameter crater Hale, with
its terraced walls, central peak, and
a part of the inner ring. The wall of
Hale crater has a large number of
gullies, and its surface shows a
network of fluvial channels. (D) The
network of fluvial channels, which
may have been caused by running
water, to the west of Hale crater. (E)
Hooke crater, with a diameter of
138 km, comprises two different
impact structures, with a smaller
impactor blasting a depression off-
center in the floor of a larger, pre-
existing crater. The newer crater in
the center is filled with a large
mound topped by a dark dune field.
The mound appears to be composed
of layered material, possibly alternating sheets of sand and frost. Dark dunes spread southward from the smaller crater,
partially covering the floor of the main crater. Much of the low-lying region to the south, as well as the central mound inside
Hooke crater, is covered with a thin, white coating of carbon dioxide frost. Image credits: ESA/DLR/FU Berlin (G.
Neukum). (Color graphics available at www.liebertonline.com/ast)
146 FAIRE´N ET AL.
Kring (2005) estimated about 10 million years of continuing
hydrothermal activity for a Hellas-sized basin, depending on
the permeability of the subsurface. Following the same
reasoning, Argyre would potentially have had long-lived
heat energy, even factoring the smaller size and younger age
of Argyre with respect to Hellas. This energy supply, cou-
pled with heat releases from the largest and most enduring
volcanic province in the Solar System, the nearby Tharsis
superplume (Dohm et al., 2001b, 2007; Baker et al., 2007),
could have provided long-term hydrothermal activity near
the surface after the impact excavation. To a lesser extent,
and in geologically more recent times, the Elysium super-
plume (e.g., Baker et al., 2007) and the Tharsis/Elysium
corridor region (Dohm et al., 2008), as well as changes in
obliquity (e.g., Laskar et al., 2004), also could have con-
tributed to the alteration of the interior surfaces of the Ar-
gyre basin and associated rim materials.
As a consequence of the water enrichment, the primary
Argyre basin contained a large water body that was suffi-
cient in size to have sourced Uzboi Vallis (Dohm et al.,
2015). This conclusion is based on several lines of evidence
including (i) crater retention ages that are similar among the
high-standing Argyre rim materials and intervening valley-
and basin-infill materials, and (ii) spatial associations
(stratigraphic relations and relative elevations) among the
source region of Uzboi Valles, terraces, benches, and a
possible spillway that connected a paleolake in Douglass
impact crater with the primary Argyre basin, all of which are
near the zero-elevation datum (i.e., 0 km as a potential
equipotential surface). It is even possible that a more ex-
tensive water body could have formed due to the impact,
reaching an elevation of 1.0 km or more above the zero-
elevation datum. This is suggested by the Geographic In-
formation Systems (GIS) mapping of elongated basins with
valley networks along their margins and dendritic valleys. If
the water column reached 1.0 km in elevation, then the body
of water with a maximum depth reaching *4.0 km would
have had an estimated volume of *3 · 106 km3, approxi-
mating the volume of the Mediterranean Sea, as well as a
comparable maximum depth of 5.3 km (Fig. 4).
Following the formation of lakes and associated growth
of glaciers, the water bodies would have waned over time,
and eventually the lakes would have become frozen, as the
planet cooled and impact-generated heat dissipated over
time. Evidence has been provided for wet-based alpine and
continental-scale glaciation in southern Argyre and the ad-
joining highlands (Kargel and Strom, 1992; Kargel, 2004;
Banks et al., 2008, 2009), with a proposed glacial system
extending as far as the south polar region and eastward half-
way to Hellas (Baker et al., 1991; Kargel and Strom, 1992;
Hiesinger and Head, 2002). Baker et al. (1991) considered
that a latitude limit of south polar glaciation occurred roughly
halfway through the Argyre basin, leaving the southern part
glaciated, although ElMaarry et al. (2013) found evidence for
glaciation also occurring farther north. This is also supported
by the presence of sinuous ridges in areas surrounding
southern Argyre Planitia (Seibert and Kargel, 2001; Banks
et al., 2008). The sinuous ridges have been hypothesized by
several investigators to be eskers or fluvial sediments de-
posited in open-walled channels within an ice sheet (e.g.,
Kargel and Strom, 1992; Seibert and Kargel, 2001; Kargel,
2004; Banks et al., 2008, 2009). Recentmapping suggests that
these ridges formed during the Late Hesperian–Early Ama-
zonian (Dohm et al., 2015). The esker development correlates
to major Tharsis outgassing, flood erosion of some circum-
Chryse outflow channels, and widespread glacial activity
(Baker et al., 1991; Kargel et al., 1995; Dohm et al., 2001b,
2007; Rodriguez et al., 2014) recorded in the youngest Argyre
plains-forming basin floor deposits of the distinct strati-
graphic sequences in the basin (unit HAb4a; Dohm et al.,
2015). There has been significant activity since this major
stage of Tharsis development, including geologically recent
and possibly present-day resurfacing of all the geological
units of the Argyre Province (Dohm et al., 2015), which are
tied to variable endogenic and exogenic activities at local to
global scales on Mars (Kargel, 2004; El Maarry et al., 2013;
Rodriguez et al., 2014; Soare et al., 2014a, 2014b).
Periglacial activity has also been identified in and around
the Argyre impact basin, including the development of
small-scale mounds. These mounds could be open-system
FIG. 4. (Left) Schematic paleolake map of the Argyre basin using a maximum topographic elevation of 0 km based on
MOLA topography (regions in blue). An estimated extent of the hypothesized Argyre lake based on geomorphological and
topographical analyses, as well as detailed geological mapping, is also shown (red line). In addition to the estimated extent,
dendritic channel systems (SP), local basins (B) that occur among the crater rim materials, and the Uzboi Vallis system
(UV) correspond to the blue-highlighted region. Also shown is a small extent (near base level) of AWMP. The volumes of
the hypothesized AWMP and Argyre lakes are estimated to be 1.6 · 104 and 1.9 · 106 km3, respectively, using MOLA.
Ever-changing conditions in the Argyre basin include the possible interplay between lakes, ice sheets, and glaciers through
time, as well as waning water bodies. (Right) Similar to left, but at 1 km with an estimated volume of 3.1 million km3,
nearing that of the Mediterranean Sea. SWB is the drainage basin located southwest of the Argyre basin; DV is a distinct
dendritic valley located southeast of the primary Argyre basin. (Color graphics available at www.liebertonline.com/ast)
ASTROBIOLOGICAL EXPLORATION OF ARGYRE, MARS 147
pingos (OSPs, see following section), perennially ice-cored
mounds fed by hydraulically driven water. These mounds
are located downslope of gullies inset within fractures and
faults, suggesting structurally controlled groundwater flow
and the migration of heat from the interior of Mars (Soare
et al., 2014a).
Subsequent modification of the regional landscape seems
to reflect the influence of fluvial, alluvial, glacial, perigla-
cial, and eolian processes (Kargel and Strom, 1992; Parker
et al., 2000; Hiesinger and Head, 2002; Kargel, 2004; Banks
et al., 2008, 2009; Soare et al., 2014a, 2014b; Dohm et al.,
2015). Within and around the basin, resurfacing has included
physical and chemical erosion, the emplacement of diverse
sedimentary deposits, the accumulation and ablation of gla-
cial ice, major etching of the rim materials, and the highly
localized flow of gully-associated water. Also, possible fog
concentration, including moisture, could have periodically
embanked against topographic highs and bottle-necked into
valleys and basins in Argyre, providing suitable environ-
mental conditions for fog-dependent ecosystems, similarly to
fog-driven ecosystems on Earth (e.g., Hock et al., 2007;
Warren-Rhodes et al., 2007; Borthagaray et al., 2010; Azu´a-
Bustos et al., 2011; Latorre et al., 2011).
3.2. The geochemical perspective
At the time of the impact excavation of Argyre, at
3.93Ga, water probably was abundant on Mars’ surface,
according to data obtained by the Curiosity rover. Curios-
ity’s Sample Analysis at Mars (SAM) experiment mea-
sured thermally evolved water and hydrogen gas from the
‘‘Cumberland’’ rock target in Gale crater (Webster et al.,
2015). The samples were Hesperian in age and used to de-
termine the deuterium to hydrogen (D/H) isotope ratio,
which can be used to infer the amount of water at the time of
formation of Cumberland. The D/H ratio in Cumberland was
measured to be about half that of the ratio found in martian
atmospheric water vapor today, suggesting that Mars re-
tained much of its surface water at the time when Cum-
berland formed. Because Argyre was excavated at least 100
million years before the formation of Gale (Gale has an age
of 3.8–3.6Ga, see Greeley and Guest, 1987, and Thomson
et al., 2011), water should have been more abundant at the
time of Argyre’s formation than when Gale formed, because
the surface of Mars should have experienced wetter condi-
tions at earlier times (e.g., Faire´n et al., 2003; Kargel, 2004).
Additional investigations through Curiosity have indicated
that Mars had the required climate and atmospheric condi-
tions in terms of pressure and temperature to harbor large
crater lakes, streambeds, and deltas long after the excavation
of Gale in the early Hesperian period and for tens of mil-
lions of years after (Williams et al., 2013; Grotzinger et al.,
2014). Considering Argyre’s older age of *3.93Ga, it is
likely that water was even more abundant in the early his-
tory of Argyre than of Gale.
Multiple spectroscopic analyses of the basin have helped
unveil this history of Argyre’s water. More than 100 CRISM
(Compact Reconnaissance Imaging Spectrometer for Mars,
a visible-infrared spectrometer aboard MRO) targeted ob-
servations of the Argyre basin area have been acquired, with
the result that (i) phyllosilicates have been identified in lo-
cations where aqueous activity has modified the landscape
within the basin, and (ii) signatures of olivine in the rim
materials of Argyre point to the impact having exposed parts
of the upper mantle through the inversion of stratigraphy
(Buczkowski et al., 2010). Rock outcrops exposed along
the large Argyre impact-derived concentric structures show
evidence of high calcium pyroxene materials and phyllosili-
cates, such as magnesium-rich chlorite and iron-magnesium
smectite (Buczkowski et al., 2010). Ancient subglacial drain-
age of a south polar ice-sheet, together with widespread gla-
ciers on Argyre’s rim, would have delivered large volumes of
clays to the basin’s basal stratigraphy. The reduced perme-
ability of these ancient clay deposits would have promoted
the development of regional aquifers within the floor of Ar-
gyre. Aqueous activity also is indicated by the phyllosilicates
identified in Hale crater ejecta, which are consistent with
those observed in western Argyre, CRISM-based signatures
of which include chlorite and iron-magnesium smectite along
with some prehnite (Buczkowski et al., 2010). Aqueous ac-
tivity likely included hydrothermalism, related to the Hale
impact into the water-enriched Uzboi-Vallis source area
(Dohm et al., 2015).
4. The Argyre Region as a Prime Site
for Astrobiological Exploration
4.1. Water on Mars and habitability
Early Mars is thought to have been relatively habitable
(see previous sections). The Argyre impact event occurred
during the Late Heavy Bombardment, when Mars had a
much thicker atmosphere than today; CO2 atmospheric
pressures are estimated to have been at about 0.5–1 bar
(Carr, 1999) to 1.5 bar (Phillips et al., 2001). Dynamical
simulations also suggest that Mars acquired less total bulk of
water than Earth, about 0.06–0.27 of Earth’s oceans (Lunine
et al., 2003); however, this estimate actually represents
more water content per planetary volume in Mars than in
Earth, which is consistent with the position of Mars in the
Solar System retaining more volatiles. Evidence for ancient
oceans on the northern plains of Mars comes both from
geological and geomorphological analyses (e.g., Faire´n
et al., 2003, and references therein) and from spectroscopic
investigations (e.g., Villanueva et al., 2015, consider a
global equivalent layer—GEL—of about 130m on early
Mars).
The above-described amounts of water are also consistent
with a deposited volume estimated to be at least 1/10 that of
the volume of water on Earth during the Late Heavy
Bombardment, shortly following the Argyre impact event,
as well as the volume of water mobilized to the surface from
subsurface reservoirs of ground ice and water. This estimate
includes the Noachian Contact 1-Meridiani shoreline, which
would have enclosed a volume of water of more than 108
km3 or roughly 1/6 that of the Pacific Ocean (Faire´n et al.,
2003; Ormo¨ et al., 2004); a lake body of 3 · 106 km3 volume
in Argyre, approximating that of the Mediterranean Sea; and
another lake in Hellas (Moore and Wilhelms, 2007), which
is estimated here as roughly equivalent to that of the Argyre
lake. This estimate does not account for other possible lakes
in the southern highlands, such as those that occupied
smaller impact basins (Cabrol and Grin, 1999). A significant
amount of water was, therefore, present at the time of the
Argyre impact event (also see Di Achille and Hynek, 2010)
148 FAIRE´N ET AL.
at, and in, the encompassing region of the target site of the
giant impact.
Through time, near-surface liquid water and water-ice
dissipated, though it was not totally depleted, as there was
subsequent Tharsis-driven, transient hydrological cycling
(including enhanced geological and climatic activities, see
Dohm et al., 2001b; Faire´n et al., 2003; Baker et al., 2007).
On present-day Mars, D/H data from meteorites indicate
that a GEL of undetected subsurface water/ice that ranges
from about 102 to 103 m (Kurokawa et al., 2014; Usui et al.,
2015) should exist. This value far exceeds the sum of the
observable present water inventory (*20–30m GEL) on
Mars, as was estimated by Christensen (2006), and the hy-
pothesized deep-aquifer water reservoir that exists today
(another 20m GEL), which was calculated by Villanueva
et al. (2015) as a conservative minimum volume. The modern
phases of aqueous activity would have allowed potential
living organisms to become more active and widespread,
while during intervening phases, life might have remained in
a dormant or at least stationary state (Schulze-Makuch et al.,
2005).
4.2. The habitability of Argyre
Argyre’s unique geological setting may have contributed
to the existence of life and may have significant implications
for the search for life on Mars. Conditions compatible with
current models for the origin of life were likely present in, or
around, Argyre for at least tens of millions of years after the
impact. These could have included intermittent and standing
bodies of liquid water (e.g., Faire´n et al., 2003) with a variety
of solutes depressing the melting point of water when con-
ditions on Mars turned colder globally (Faire´n et al., 2009);
the presence of various mineral surfaces including clays
(Cleaves et al., 2012); impact-induced and volcanically in-
duced hydrothermal circulation (Ciba Foundation, 2008);
solar radiation; and the input of organic materials from in-
terplanetary dust particles, carbonaceous chondrites, and
comets (Flynn, 1996). The long-term persistence of these
factors in Argyre alsomake it an exceptional candidate for the
persistence of life on Mars, as well as the preservation of
biomarkers in clays or evaporates (Aubrey et al., 2006;
Summons et al., 2011). Most of the above-mentioned factors
would have been available for long periods of Mars’ history,
sustaining structurally and thermally stable aquifers.
In particular, water-rich, hydrothermal systems are not
only possible sites for the origin of life, but they also pro-
vide excellent environmental conditions to preserve miner-
alized and organic fossils by favoring rapid entombment of
cellular structures in precipitating mineral phases. For ex-
ample, fossil-containing Archean rocks on Earth are often
heavily metamorphosed deep-water sediments, hydrothermal
deposits, or alternating layers of sediments and igneous rocks.
Some of these rocks have preserved fossilized organic re-
mains for at least 2.7 billion years (Rasmussen et al., 2008).
Similar fossil remains could exist in sedimentary deposits
(e.g., Komatsu and Ori, 2000) within the Argyre basin. The
preservation of such fossil remains would have been aided by
the pervasive low temperatures, as well as the development of
glacial and periglacial conditions both within and around the
basin. Evidence for glacial and periglacial activity is wide-
spread throughout the geological history of Mars (e.g., Faire´n
et al., 2011), andmore data from several locations continue to
be investigated, including Gale crater (Faire´n et al., 2014).
The continued supply of heat and gases in the Argyre
basin could have resulted in an entrenched and long-lasting
autotrophic microbial biosphere based on subsurface hy-
drothermal vent systems, possibly generating methane as an
end product of their metabolism (e.g., Schulze-Makuch et al.,
2005, 2008; Komatsu et al., 2011). Global atmospheric
methane of present-day Mars was reported by Formisano
et al. (2004), Mumma et al. (2004), and Krasnopolsky et al.
(2004), with apparent regional enrichments (Geminale et al.,
2008; Mumma et al., 2009). All these methane detections
have been challenged (Zahnle et al., 2011). TheMars Science
Laboratory (MSL) mission’s Curiosity rover has recently
identified variable methane concentrations at a maximum of
7 ppb, using SAM (Webster et al., 2015). Reported signatures
of methane might be further examined through India’s on-
going Mars Orbiter Mission (Mangalyaan) (Lele, 2014) and
the upcoming European Space Agency’s 2016 ExoMars or-
biter (Zurek et al., 2011). Any methane detection could be a
result of biogenic or abiotic processes, and additional char-
acterizations would have to be evaluated to determine the
likely source of that methane.
Finally, a key factor that supports the habitability of Ar-
gyre is the presence of ice at the surface coexisting with
aqueous liquids. At lower latitudes, there were aqueous
liquids, but the case for coexisting ice is less clear (e.g.,
Faire´n, 2010). This is important because the coexistence of
ice with aqueous liquids means that ice was on the liquidus
(or down to the eutectic) state, which further means that the
water activity (the thermodynamic activity of H2O; see, e.g.,
Grant, 2004, Marion and Kargel, 2008) was not as low as
might otherwise be the case. Taking terrestrial environments
as an example, where there exist highly arid hypersaline en-
vironments (e.g., Death Valley), water activities are ex-
tremely low, and biodiversity is also extremely low, despite
Earth’s long-existing biosphere and ample opportunity to
evolve and adapt. This argues that life is indeed extremely
challenged with water activity declines, due to extremely low
relative humidities and extreme evaporation (e.g., Knoll
et al., 2005;Marion and Kargel, 2008). Liquid water may still
exist, but it is not so suitable for life (Grant, 2004).When ice is
present, that buffering factor maintains water thermodynamic
activity at higher and less life-adverse levels, preserving
lower salinity and potentially truly ‘‘freshwater’’ environ-
ments. Such large buffering masses of ice make it harder to
completely desiccate a body of water, which could therefore
contribute to maintaining long-term stable, habitable envi-
ronments for potential life-forms.
4.3. Astrobiologically relevant landforms in Argyre
Now we highlight some specific landscape features in
Argyre that are promising sites for astrobiological explora-
tion. These include the following:
(1) Hydrothermal deposits, including those related to the
hydrothermal activity associated with the Argyre
impact event, subsequent impacts, and those associ-
ated with the migration of heated water along Argyre-
induced basement structures. Echaurren and Ocampo
(2004) determined impact conditions and predicted
possible hydrothermal zones generated after the im-
ASTROBIOLOGICAL EXPLORATION OF ARGYRE, MARS 149
FIG. 5. Examples of gullies, possible grabens and OSPs, faults and fractures. All panels from HiRISE image
ESP_020720_1410. (A) Overview of the site, showing lobes, mantle deposits, and gullies. (B) Locations of insets (C–E) and
the downslope position of the putative OSPs relative to the gullies (arrows), and lobes (arcuate ridges) interpreted to be
glacial moraines. (C) Top of the alcove of the eastern gully, showing an abrupt start of the channel embedded in a
grabenlike elongated depression. A possible landslide scar is located at the northern tip of the cavity. (D) Top of the alcove
of the western gully, with rill-like features running into the grabenlike cavity; the features seem to originate upslope from
the nonpolygonized terrain. Note the polygonal network within the cavity and in the surrounding terrain; black arrow points
to location with low-centered polygons. (E) Midpart of the eastern gully, with multiple terraces (i) and multiple self-
blocking digitate deposits (ii), as indicated by black arrows. Note the distinct lineaments, which we interpret to be fractures
and faults. Image credits: NASA/JPL/University of Arizona.
150 FAIRE´N ET AL.
pact. The presence of uplifted mantle and lower
crustal materials in the basin means that primordial
materials composed of P, K, Al, Ca, Fe, and other
elements necessary for life to form may have been
exposed to the surface and near-surface environ-
ments. Internal heat and water, and other volatiles at
depth, may have migrated along the impact-induced
basement structures. The interaction among primor-
dial crustal materials and hydrothermal activity
would be favorable from the metabolic energy per-
spective (e.g., Schulze-Makuch et al., 2007).
(2) Candidate vent structures along the floor of the Ar-
gyre basin. The youngest basin unit, mapped as unit
HAb4a (Dohm et al., 2015), comprises landforms
interpreted to mark venting related to flooding, the
rapid emplacement and burial of flood deposits and
associated volatiles, and eventual release to form vent
structures. For example, Argyre Mons is a newly
identified feature interpreted to have formed from
subterranean gas releases (e.g., mud volcanoes),
magmatic-driven activity, or an impact event, with
gas release being the favored hypothesis (Williams
et al., 2014). Numerous and widespread vent struc-
tures in the northern plains, interpreted to be mud
volcanoes, are likely the result of rapid emplacement
of Tharsis-triggered circum-Chryse floodwaters and
sediments and associated ocean formation (Skinner
and Tanaka, 2007; Skinner and Mazzini, 2009;
Oehler and Allen, 2010; Komatsu et al., 2011, 2012)
and have been reported to be prime astrobiological
targets (Mahaney et al., 2004).
(3) Possible ice-cored mounds, including candidate OSPs
(Soare et al., 2014a; see Fig. 5). On the basis of the
available photogeology, the OSPs within the Argyre
basin are recent features, dating from the Late Am-
azonian (and possibly still having some activity), and
their proposed hydraulic, tectonic, and hydro-tectonic
models of formation and functioning involve freeze-
thaw cycling. The OSPs within the floor of Argyre
basin could bear exceptional astrobiological interest,
because the heat gradients produced hydrothermal
activity, which in turn resulted in upwelling processes,
enhancing the prospect of fossilized and extant life.
The upwelling of deep-seated water from aquifers, rich
in volatiles and organic material, would act as exhu-
mation pockets into ancient environments; therefore
the groundwater or deeply seatedwater associated with
OSP formation could be capable of delivering evi-
dence of past/current microbial activity in the subsur-
face to the surface or near-surface. In addition, the
protecting layers that formed after the wet eolian sed-
imentation or icy periods would provide a protected
environment for existing life or its remains, as man-
tling by eolian drifts could have reduced the rates of
sublimation. In summary, OSPs, as indicated through
investigations of analogous terrestrial settings, could
be host to past (and maybe present) heat fluxes, ice,
liquid water, and nutrients (e.g., Dohm et al., 2004;
Hock et al., 2007; Warren-Rhodes et al., 2007).
(4) Sedimentary deposits left behind by glaciers along
the basins’ margins as evidenced by ridges inter-
preted to be eskers (e.g., Kargel and Strom, 1992;
Kargel, 2004; Banks et al., 2008; Fig. 6). The ridges
occur in the Late Hesperian–Early Amazonian basin
floor deposits and thus are interpreted to be emplaced
during this time period, which is coeval with major
Tharsis-driven activity (Dohm et al., 2001b; Faire´n
et al., 2003). This highlights the far-reaching sedi-
mentological record in the deep Argyre basin devel-
oped over time. The eskerlike features could be
composed of sediment from environments nearby and
distant (e.g., south polar region), laid down during
glacial outburst floods debouching under confined
ice-covered lakes.
(5) Sedimentary deposits related to the formation of lakes
in both the primary Argyre basin and other smaller
impact-derived basins along the margin (including
those in the highly degraded rim materials). Lakes
could have been formed by the glacial flood outbursts
mentioned above, and they would be therefore related
to major changes in environmental and hydrological
conditions associated with major outgassing of
Tharsis during the Late Hesperian and Early Ama-
zonian (conditions also related to the formation of the
younger northern plains ocean, see Faire´n et al.,
2003). In addition to floodwaters derived by wet-
based glacial activity (Kargel, 2004), the floodwaters
could also have originated from a raised hydraulic
head, migration of water and other volatiles along
Argyre-induced basement structures, and spring-fed
(artesian) release. If the water was subterranean-
derived, such as related to Tharsis activity (including
migration from great distances along basement
structures) (Dohm et al., 2015), then the astro-
biological potential would be heightened.
(6) Crater-wall gullies (Fig. 3B) occurring upslope of the
pingo-like mounds described below (Fig. 5). The
morphology of the gully landforms points to ‘‘wet’’
flows, and the crater-wall structures in which they are
embedded could be indicative of groundwater dis-
charge (Soare et al., 2014a). Against the general
backdrop of boundary conditions inconsistent with
the flow of liquid water at the surface, gully dis-
charges might be markers of aqueous activity and
bearers of nutrients if not fossilized microbes.
5. Strategies for Future Robotic Exploration
The main challenge for the exploration of Argyre is the
basin’s latitude. Most of Argyre is located between 45 and
55 in the southern hemisphere, and this latitude would
present a major energy challenge even for a RTG (radio-
isotope thermoelectric generator)–powered mission (Ander-
son, 2005), such as the Curiosity rover. For a solar-powered
mission, Argyre’s latitude would be troublesome, although
not overwhelmingly so, especially if duration is not a large
prerequisite; for example, the Phoenix lander successfully
operated for 157 martian sols in the northern high latitudes.
On the other hand, the low elevation of the Argyre floor is
a plus for parachute-aided landings, because lower eleva-
tions would provide a longer atmospheric column for the
parachutes to open and achieve the desired deceleration of
the spacecraft during the entry, descent, and landing (EDL)
phase.
ASTROBIOLOGICAL EXPLORATION OF ARGYRE, MARS 151
FIG. 6. (A) View of Southeastern Argyre basin centered at 6248’S, 4656’W. The image shows an integrated fluvial and
glacial geological setting that includes deeply dissected upland valleys connected to the upper sedimentary strata that
occupy the basin’s floor. (B) Close-up view centered at 574’S, 4621’W, on the terminal zone of Surius Vallis, where some
plains are marked by possible esker ridges. (C) The plains shown in (B) include a large depression (Cleia Dorsum) where
the regional upper stratigraphy appears exposed, including a region where scarps likely expose glacial and older fluvial
deposits (dashed box). These strata appear lightly cratered and thus likely spent a much longer time buried before being
exhumed by regional erosional processes, making them an even better exobiological target (CTX view centered at 5516’S,
4539’W). (Color graphics available at www.liebertonline.com/ast)
152
With these engineering constraints in mind, it is important
to revisit the merits of Argyre as a promising target for the
astrobiological exploration of Mars. If there are compelling
scientific reasons to propose the exploration of the potential
biological attributes of Argyre, then there are compelling
reasons to elevate the discussion of the engineering con-
straints currently imposed on missions and hence reconsider
mission architectures. When these engineering issues are
solved, we propose that Argyre could be reached by a tier-
scalable exploration mission architecture, in which a flotilla
of vehicles is used for the regional investigation of several
different areas. The large size and diversity of landforms
within the Argyre impact basin make it an ideal case for
tier-scalable reconnaissance, a redundant exploration
strategy based on the deployment, operation, and control of
vehicles in multiple areas of interest using hierarchical
levels of oversight called tiers—each tier controlling the
vehicles within the tier beneath it (Fink et al., 2005, 2008;
Kean, 2010; Fig. 7). Multi-tiered and autonomous robotic
exploration architectures on Mars would comprise an orbiter
(or orbiters) in conjunction with aerial platforms (e.g.,
blimps) along with rovers (Fink et al., 2005, 2008), minia-
ture landing science stations (Schulze-Makuch et al., 2012),
sensorwebs (Delin et al., 2005), and autonomous drilling
sciencecraft (Ori et al., 2000; Dohm et al., 2011), all of
which would help verify the analyses provided in such an
investigation through contextual in situ evidence.
Particularly appealing for in situ investigations is the rich
variety of water- and ice-mobilized sedimentary deposits
and extant ice deposits, as described above. We propose
focusing the astrobiological exploration on the southeast-
ern part of the Argyre basin, near Cleia Dorsum, elevation
-2600m (Fig. 6). In this setting, basal fluvial and overlying
glacial deposits seem to be exposed as well-preserved,
laterally extensive layers, and topographically the site is
low. This is an area of eskerlike ridges, probably glacial
river–deposited or debris flow–deposited, containing ma-
terial derived from the highlands, and situated within
reachable distance for a tier-scalable reconnaissance sys-
tem (60 km max) of lobate debris aprons (icy glacierlike
forms), layered rock sequences near the eskerlike ridges
(ancient lake deposits), and U-shaped valleys and cirque-
like amphitheatres (remnants of wet-based glacial bedrock
scour).
Many of these extant environments in Argyre could be
suitable for terrestrial extremophiles; therefore it is reason-
able to speculate that a Mars-adapted biology would likewise
be able to survive in them. The tier-scalable reconnaissance
system could confirm whether and where there has been
venting of the martian internal heat energy along the impact-
FIG. 7. Tier-scalable reconnaissance:
three-tiered utilization on Mars. Tier 1:
space-borne orbiter; tier 2: airborne blimps;
tier 3: ground-based rovers. (Color graphics
available at www.liebertonline.com/ast)
ASTROBIOLOGICAL EXPLORATION OF ARGYRE, MARS 153
induced faults (structural conduits), as well as evidence for
groundwater influx with nutrient-enriched rock materials,
such as primordial crustal materials enriched in biogenic ele-
ments. Such exploration would require careful mission prepa-
ration, including proper sterilization of the spacecraft
components to ensure compliance with planetary protection
policies, as the possible presence of current liquid water or
water ice near the surface at these featuresmay categorize them
as ‘‘Mars Special Regions,’’ that is, places where terrestrial
organisms might be able to replicate (Rummel et al., 2014).
6. Conclusions
We propose that the Argyre province should be consid-
ered a prime target for the search for past or present life on
Mars. This is based on evidence of its long-term water en-
richment, heat generation from the Argyre basin–forming
impact, basement structures that could have channeled water
and heat into the basin from far-reaching geological prov-
inces and from great depths, and potential nutrient-enriched
primordial crustal materials that could have been transferred
to near-surface and surface environments through impact-
induced uplift and inversion. We have highlighted the
astrobiological significance of some particular landscape
features in Argyre that may be especially promising and ac-
cessible sites for the astrobiological exploration of the basin,
including hydrothermally altered mineral assemblages, pos-
siblemud volcanoes, ice-coredmounds, sedimentary deposits
of glacial and lacustrine origin, and crater-wall gullies. To-
day, the Argyre province also could host extant ice, perhaps
near-surface liquid groundwater in places, possible fog con-
centrations, and potential vents with exhalation of volatiles.
Tier-scalable reconnaissance may improve chances for high
data return from these complex landscapes, because prime
microenvironmental targets may be located in rugged loca-
tions, which otherwise would be exceedingly challenging to
explore through traditional mission designs.
Acknowledgments
The research leading to these results is a contribution
from the Project ‘‘icyMARS,’’ funded by the European
Research Council, Starting Grant no 307496. J.M.D. was
supported by the NASA PG&G Program and JSPS KA-
KENHI Grant Number 26106002 [Hadean BioScience
(Grant-in-Aid for Scientific Research on Innovative
Areas)]. J.M.D. and H.M. express their gratitude to the
Tokyo Dome Corporation for their support of the TeNQ
exhibit and the branch of Space Exploration Education &
Discovery, the University Museum, the University of To-
kyo. H.J.C. would like to thank the Tokyo Institute of
Technology’s Earth-Life Science Institute for funding
during the preparation of this manuscript. D.Z.O. is
grateful to the Astromaterials Research and Exploration
Science Division at Johnson Space Center for support.
D.S.-M. was supported by European Research Council,
Advanced Grant ‘‘Habitability of Martian Environments,’’
no 339231. The authors want to thank Chris McKay for a
constructive review of this paper.
Author Disclosure Statement
No competing financial interests exist.
References
Abramov, O. and Kring, D.A. (2005) Impact-induced hydro-
thermal activity on early Mars. J Geophys Res 110,
doi:10.1029/2005JE002453.
Abramov, O. and Mojzsis, S.J. (2009) Microbial habitability of
the Hadean Earth during the Late Heavy Bombardment.
Nature 459:419–422.
Allwood, A.C., Walter, M.R., Kamber, B.S., Marshall, C.P., and
Burch, I.W. (2006) Stromatolite reef from the Early Archaean
era of Australia. Nature 441:714–718.
Anderson, D.J. (2005) NASA Radioisotope Power Conversion
Technology NRA Overview, TM-2005-213981, National
Aeronautics and Space Administration, Glenn Research
Center, Cleveland, OH.
Aubrey, A., Cleaves, A.H.J., Chalmers, J.H., Skelley, A.M.,
Mathies, R.A., Grunthaner, F.J., Ehrenfreund, P., and Bada,
J.L. (2006) Sulfate minerals and organic compounds on Mars.
Geology 34:357–360.
Azu´a-Bustos, A., Gonza´lez-Silva, C., Mancilla, R.A., Salas,
L., Go´mez-Silva, B., McKay, C.P., and Vicun˜a, R. (2011)
Hypolithic cyanobacteria supported mainly by fog in the
coastal range of the Atacama Desert. Microb Ecol 61:568–
581.
Baker, V.R., Strom, R.G., Gulick, V.C., Kargel, J.S., Komatsu,
G., and Kale, V.S. (1991) Ancient oceans, ice sheets and the
hydrological cycle on Mars. Nature 352:589–594.
Baker, V.R., Maruyama, S., and Dohm, J.M. (2007) Tharsis
superplume and the geological evolution of early Mars. In
Superplumes: Beyond Plate Tectonics, edited by D.A. Yuen,
S. Maruyama, S.-I. Karato, and B.F. Windley, Springer,
Dordrecht, the Netherlands, pp 507–523.
Banks, M.E., McEwen, A.S., Kargel, J.S., Baker, V.R., Strom,
R.G., Mellon, M.T., Pelletier, J.D., Gulick, V.C., Keszthelyi,
L., Herkenhoff, K.E., Jaeger, W.L., and the HiRISE Team.
(2008) High Resolution Imaging Science Experiment (HiR-
ISE) observations of glacial and periglacial morphologies in
the circum-Argyre Planitia highlands. J Geophys Res 113,
doi:10.1029/2007JE002994.
Banks, M.E., Lang, N.P., McEwen, A.S., Kargel, J.S., Baker,
V.R., Strom, R.G., Grant, J.A., Pelletier, J.D., and the HiRISE
Team. (2009) An analysis of the sinuous ridges in the southern
Argyre Planitia, Mars using HiRISE and CTX images and
MOLA data. J Geophys Res 114, doi:10.1029/2008JE003244.
Borthagaray, A.I., Fuentes, M.A., and Marquet, P.A. (2010)
Vegetation pattern formation in a fog-dependent ecosystem. J
Theor Biol 265:18–26.
Buczkowski, D.L., Murchie, S., Clark, R., Seelos, K., Seelos, F.,
Malaret, E., and Hash, C. (2010) Investigation of an Argyre
basin ring structure using Mars Reconnaissance Orbiter/
Compact Reconnaissance Imaging Spectrometer for Mars. J
Geophys Res 115, doi:10.1029/2009JE003508.
Cabrol, N.A. and Grin, E.A. (1999) Distribution, classification
and ages of martian impact crater lakes. Icarus 142:160–
172.
Carr, M.H. (1999) Retention of an atmosphere on Early Mars. J
Geophys Res 104:21897–21909.
Carr, M.H. and Head, J.W., III. (2003) Oceans on Mars: an
assessment of the observational evidence and possible fate. J
Geophys Res 108, doi:10.1029/2002JE001963.
Christensen, P. (2006) Water at the poles and in permafrost
regions of Mars. Elements 2:151–155.
Ciba Foundation. (2008) Evolution of Hydrothermal Ecosys-
tems on Earth (and Mars?), Ciba Foundation Symposium
202, Wiley, Chichester, UK.
154 FAIRE´N ET AL.
Claeys, P. and Morbidelli, A. (2011). Late Heavy Bombard-
ment. In Encyclopedia of Astrobiology, Springer, Berlin, pp
909–912.
Cleaves, H.J., Scott, A.M., Hill, F.C., Leszczynski, J., Sahai, N., and
Hazen, R. (2012) Mineral-organic interfacial processes: potential
roles in the origins of life. Chem Soc Rev 41:5502–5525.
Delin, K.A., Jackson, S.P., Johnson, D.W., Burleigh, S.C., Woo-
drow, R.R., McAuley, J.M., Dohm, J.M., Ip, F., Ferre, T.P.A,
Rucker, D.F., and Baker, V.R. (2005) Environmental studies
with the sensor web: principles and practice. Sensors 5:103–117.
Di Achille, G. and Hynek, B.M. (2010) Ancient oceans on Mars
supported by global distribution of deltas and valleys. Nat
Geosci 3:459–463.
Dohm, J.M. and Maruyama, S. (2014) Habitable trinity.
Geoscience Frontiers 6:95–101.
Dohm, J.M., Tanaka, K.L., and Hare, T.M. (2001a) Geologic
Map of the Thaumasia Region of Mars, U.S. Geological
Survey Investigations Series I-2650, USGS Information
Services, Denver, CO.
Dohm, J.M., Ferris, J.C., Baker, V.R., Anderson, R.C., Hare,
T.M., Strom, R.G., Barlow, N.G., Tanaka, K.L., Kle-
maszewski, J.E., and Scott, D.H. (2001b) Ancient drainage
basin of the Tharsis region, Mars: potential source for outflow
channel systems and putative oceans or paleolakes. J Geo-
phys Res 106:32943–32958.
Dohm, J.M., Ferris, J.C., Barlow, N.G., Baker, V.R., Mahaney,
W.C., Anderson, R.C., and Hare, T.M. (2004) The North-
western Slope Valleys (NSVs) region, Mars: a prime candi-
date site for the future exploration of Mars. Planet Space Sci
52:189–198.
Dohm, J.M., Maruyama, S., Baker, V.R., and Anderson, R.C.
(2007) Traits and evolution of the Tharsis superplume, Mars.
In Superplumes: Beyond Plate Tectonics, edited by D.A.
Yuen, S. Maruyama, S.-I. Karato, and B.F. Windley,
Springer, Dordrecht, the Netherlands, pp 523–537.
Dohm, J.M., Anderson, R.C., Barlow, N.G., Miyamoto, H.,
Davies, A.G., Taylor, G.J., Baker, V.R., Boynton, W.V.,
Keller, J., Kerry, K., Janes, D., Faire´n, A.G., Schulze-
Makuch, D., Glamoclija, M., Marinangeli, L., Ori, G.G.,
Strom, R.G., Williams, J-P., Ferris, J.C., Rodı´guez, J.A.P., de
Pablo, M.A., and Karunatillake, S. (2008) Recent geological
and hydrological activity on Mars: the Tharsis/Elysium cor-
ridor. Planet Space Sci 56:985–1013.
Dohm, J.M., Miyamoto, H., Ori, G.G., Faire´n, A.G., Davila,
A.F., Komatsu, G., Mahaney, W.C., Williams, J.-P., Joye,
S.B., Di Achille, G., Oehler, D.Z., Marzo, G.A., Schulze-
Makuch, D., Acocella, V., Glamoclija, M., Pondrelli, M.,
Boston, P., Hart, K.M., Anderson, R.C., Baker, V.R., Fink,
W., Kelleher, B.P., Furfaro, R., Gross, C., Hare, T.M., Frazer,
A.R., Ip, F., Allen, C.C.R., Kim, K.J., Maruyama, S.,
McGuire, P.C., Netoff, D., Parnell, J., Wendt, L., Wheelock,
S.J., Steele, A., Hancock, R.G.V., Havics, R.A., Costa, P.,
and Krinsley, D. (2011) An inventory of potentially habitable
environments on Mars: geological and biological perspec-
tives. In Analogs for Planetary Exploration, edited by W.B.
Garry and J.E. Bleacher, Geological Society of America
Special Paper 483, Geological Society of America, Boulder,
CO, pp 317–347.
Dohm, J.M., Miyamoto, H., Maruyama, S., Baker, V.R., An-
derson, R.C., Hynek, B.M., Robbins, S.J., Ori, G., Komatsu,
G., El Maarry, M.R., Soare, R.J., Mahaney, W.C., Kim, K.J.,
and Hare, T.M. (2013) Mars evolution. In Mars: Evolution,
Geology, and Exploration, edited by A.G. Faire´n, Nova
Science Publishers, New York, pp 1–33.
Dohm, J.M., Hare, T.M., Robbins, S.J., Williams, J.-P., Soare,
R.J., El-Maarry, M.R., Conway, S.J., Buczkowski, D.L.,
Kargel, J.S., Banks, M.E., Faire´n, A.G., Schulze-Makuch, D.,
Komatsu, G., Miyamoto, H., Anderson, R.C., Davila, A.F.,
Mahaney, W.C., Fink, W., Cleaves, H.J., Yan, J., Hynek, B.,
and Maruyama, S. (2015) Geological and hydrological his-
tories of the Argyre province, Mars. Icarus 253:66–98.
Echaurren, J.C. and Ocampo, A.C. (2004) Calculation and
prediction of hydrothermal zones and impact conditions on
Argyre Planitia, Mars [abstract 5009]. In 67th Annual Meeting
of the Meteoritical Society, Lunar and Planetary Institute,
Houston.
Eiler, J.M. (2007) The oldest fossil or just another rock? Science
317:1046–1047.
El Maarry, M.R., Dohm, J.M., Michael, G., Thomas, N., and
Maruyama, S. (2013) Morphology and evolution of the ejecta
of Hale Crater in Argyre basin, Mars: results from high res-
olution mapping. Icarus 226:905–922.
Faire´n, A.G. (2010) A cold and wet Mars. Icarus 208:165–175.
Faire´n, A.G., Dohm, J.M., Baker, V.R., de Pablo, M.A., Ruiz,
J., Ferris, J.C., and Anderson, R.C. (2003) Episodic flood
inundations of the northern plains of Mars. Icarus 165:53–67.
Faire´n, A.G., Ferna´ndez-Remolar, D., Dohm, J.M., Baker, V.R.,
and Amils, R. (2004) Inhibition of carbonate synthesis in
acidic oceans on early Mars. Nature 431:423–426.
Faire´n, A.G., Davila, A.F., Gago-Duport, L., Amils, R., and
McKay, C.P. (2009) Stability against freezing of aqueous
solutions on early Mars. Nature 459:401–404.
Faire´n, A.G., Davila, A.F., Lim, D., Bramall, N., Bonaccorsi,
R., Zavaleta, J., Uceda, E.R., Stoker, C., Wierzchos, J.,
Amils, R., Dohm, J.M., Andersen, D., and McKay, C. (2010)
Astrobiology through the ages of Mars. Astrobiology 10:821–
843.
Faire´n, A.G., Davila, A.F., Gago-Duport, L., Haqq-Misra, J.D.,
Gil, C., McKay, C.P., and Kasting, J.F. (2011) Cold glacial
oceans would have inhibited phyllosilicate sedimentation on
early Mars. Nat Geosci 4:667–670.
Faire´n, A.G., Stokes, C., Davies, N., Schulze-Makuch, D.,
Rodrı´guez, J.A.P., Davila, A.F., Uceda, E.R., Dohm, J.M.,
Baker, V.R., Clifford, S.M., McKay, C.P., and Squyres, S.W.
(2014) A cold hydrological system in Gale Crater, Mars.
Planet Space Sci 93–94:101–118.
Fassett, C.I. and Minton, D.A. (2013) Impact bombardment of
the terrestrial planets and the early history of the Solar Sys-
tem. Nat Geosci 6:520–524.
Fink, W., Dohm, J.M., Tarbell, M.A., Hare, T.M., and Baker,
V.R. (2005) Next-generation robotic planetary reconnais-
sance missions: a paradigm shift. Planet Space Sci 53:1419–
1426.
Fink, W., Tarbell, M.A., and Jobling, F.M. (2008) Tier-scalable
reconnaissance—a paradigm shift in autonomous remote
planetary exploration of Mars and beyond. In Planet Mars
Research Focus, edited by L.A. Costas, Nova Science Pub-
lishers, New York, pp 17–48.
Flynn, G.J. (1996) The delivery of organic matter from aster-
oids and comets to the early surface of Mars. In Worlds
in Interaction: Small Bodies and Planets of the Solar System,
edited by H. Rickman and M.J. Valtonen, Springer,
Dordrecht, the Netherlands, pp 469–474.
Formisano, V., Atreya, S., Encrenaz, T., Ignatiev, N., and
Giuranna, M. (2004) Detection of methane in the atmosphere
of Mars. Science 306:1758–1761.
Ge, R., Zhu, W., Wilde, S.A., and He, J. (2014) Zircon U–Pb–
Lu–Hf–O isotopic evidence for ‡3.5 Ga crustal growth, re-
ASTROBIOLOGICAL EXPLORATION OF ARGYRE, MARS 155
working and differentiation in the northern Tarim Craton.
Precambrian Res 249:115–128.
Geminale, A., Formisano, V., and Giuranna, M. (2008) Me-
thane in martian atmosphere: average spatial, diurnal, and
seasonal behavior. Planet Space Sci 56:1194–1203.
Grant, W.D. (2004) Life at low water activity. Philos Trans R
Soc Lond B Biol Sci 359:1249–1267.
Greeley, R. and Guest, J.E. (1987) Geologic Map of the Eastern
Equatorial Region of Mars, IMAP I-1802B (1:15,000,000),
U.S. Geological Survey, Denver, CO.
Grotzinger, J.P., Sumner, D.Y., Kah, L.C., Stack, K., Gupta, S.,
Edgar, L., Rubin, D., Lewis, K., Schieber, J., Mangold, N.,
Milliken, R., Conrad, P.G., Des Marais, D., Farmer, J., Sie-
bach, K., Calef, F., III, Hurowitz, J., McLennan, S.M., Ming,
D., Vaniman, D., Crisp, J., Vasavada, A., Edgett, K.S., Malin,
M., Blake, D., Gellert, R., Mahaffy, P., Wiens, R.C., Maurice,
S., Grant, J.A., Wilson, S., Anderson, R.C., Beegle, L., Ar-
vidson, R., Hallet, B., Sletten, R.S., Rice, M., Bell, J., III,
Griffes, J., Ehlmann, B., Anderson, R.B., Bristow, T.F.,
Dietrich, W.E., Dromart, G., Eigenbrode, J., Fraeman, A.,
Hardgrove, C., Herkenhoff, K., Jandura, L., Kocurek, G., Lee,
S., Leshin, L.A., Leveille, R., Limonadi, D., Maki, J.,
McCloskey, S., Meyer, M., Minitti, M., Newsom, H., Oehler,
D., Okon, A., Palucis, M., Parker, T., Rowland, S., Schmidt,
M., Squyres, S., Steele, A., Stolper, E., Summons, R., Trei-
man, A., Williams, R., and Yingst, A. (2014) A habitable
fluvio-lacustrine environment at Yellowknife Bay, Gale
Crater, Mars. Science 343, doi:10.1126/science.1242777.
Head, J.W., Neukum, G., Jaumann, R., Hiesinger, H., Hauber,
E., Carr, M., Masson, P., Foing, B., Hoffmann, H., Kre-
slavsky, M., Werner, S., Milkovich, S., van Gasselt, S., and
the HRSC Co-Investigator Team. (2005) Tropical to mid-
latitude snow and ice accumulation, flow and glaciation on
Mars. Nature 434:346–351.
Hiesinger, H. and Head, J.W. (2002) Topography and mor-
phology of the Argyre basin, Mars: implications for its geo-
logic and hydrologic history. Planet Space Sci 50:939–981.
Hock, A.N., Cabrol, N.A., Dohm, J.M., Piatek, J., Warren-
Rhodes, K., Weinstein, S., Wettergreen, D.S., Grin, E.A.,
Moersch, J., Cockell, C.S., Coppin, P., Ernst, L., Fisher, G.,
Hardgrove, C., Marinangeli, L., Minkley, E., Ori, G.G.,
Waggoner, A., Wyatt, M., Smith, T., Thompson, D., Wagner,
M., Jonak, D., Stubbs, K., Thomas, G., Pudenz, E., and
Glasgow, J. (2007) Life in the Atacama: a scoring system for
habitability and the robotic exploration for life. J Geophys
Res Biogeosciences 112, doi:10.1029/2006JG000321.
House, C.H., Oehler, D.Z., Sugitani, K., and Mimura, K. (2013)
Carbon isotopic analyses of ca. 3.0Ga microstructures imply
planktonic autotrophs inhabited Earth’s early oceans. Geol-
ogy 41:651–654.
Iizuka, T., Horie, K., Komiya, T., Maruyama, S., Hirata, T.,
Hidaka, H., and Windley, B.F. (2006) 4.2Ga zircon xenocryst
in an Acasta gneiss from northwestern Canada: evidence for
early continental crust. Geology 34:245–248.
Jones, A.P., McEwen, A.S., Tornabene, L.L., Baker, V.R.,
Melosh, H.J., and Berman, D.C. (2011) A geomorphic anal-
ysis of Hale Crater, Mars: the effects of impact into ice-rich
crust. Icarus 211:259–272.
Kargel, J.S. (2004) Mars: A Warmer Wetter Planet, Praxis-
Springer, London.
Kargel, J.S. and Strom, R.G. (1992) Ancient glaciation on Mars.
Geology 20:3–7.
Kargel, J.S., Baker, V.R., Beget, J.E., Lockwood, J., Pewe, T.L.,
Shaw, J.S., and Strom, R.G. (1995) Evidence of ancient
continental glaciation in the martian northern plains. J Geo-
phys Res 100:5351–5368.
Kean, S. (2010) Making smarter, savvier robots. Science 329:
508–509.
Knoll, A.H. (2004) Life on a Young Planet: The First Three
Billion Years of Evolution on Earth, Princeton University
Press, Princeton, NJ.
Knoll, A.H., Carr, M., Clark, B., Des Marais, D.J., Farmer, J.D.,
Fischer, W.W., Grotzinger, J.P., McLennan, S.M., Malin, M.,
Schro¨der, C., Squyres, S., Tosca, N.J., and Wdowiak, T.
(2005) An astrobiological perspective on Meridiani Planum.
Earth Planet Sci Lett 240:179–189.
Komatsu, G. and Ori, G.G. (2000) Exobiological implications
of potential sedimentary deposits on Mars. Planet Space Sci
48:1043–1052.
Komatsu, G., Ori, G.G., Cardinale, M., Dohm, J.M., Baker,
V.R., Vaz, D.A., Ishimaru, R., Namiki, N., and Matsui, T.
(2011) Roles of methane and carbon dioxide in geological
processes on Mars. Planet Space Sci 59:169–181.
Komatsu, G., Okubo, C.H., Wray, J.J., Gallagher, R., Orosei,
R., Cardinale, M., Chan, M.A., and Ormo, J. (2012) Small
mounds in Chryse Planitia, Mars: testing a mud volcano
hypothesis [abstract 1103]. In 43rd Lunar and Planetary
Science Conference, Lunar and Planetary Institute,
Houston.
Krasnopolsky, V.A., Maillard, J.P., and Owen, T.C. (2004)
Detection of methane in the martian atmosphere: evidence for
life? Icarus 172:537–547.
Kurokawa, H., Sato, M., Ushioda, M., Matsuyama, T.,
Moriwaki, R., Dohm, J.M., and Usui, T. (2014) Evolution
of water reservoirs on Mars: constraints from hydrogen
isotopes in martian meteorites. Earth Planet Sci Lett 394:
179–185.
Laskar, J., Correia, A.C.M., Gastineau, M., Joutel, F., Levard,
B., and Robutel, P. (2004) Long term evolution and chaotic
diffusion of the insolation quantities of Mars. Icarus 170:
343–364.
Latorre, C., Gonza´lez, A.L., Quade, J., Farin˜a, J.M., Pinto, R.,
and Marquet, P.A. (2011) Establishment and formation
of fog-dependent Tillandsia landbeckii dunes in the
Atacama Desert: evidence from radiocarbon and stable iso-
topes. J Geophys Res Biogeosciences 116, doi:10.1029/
2010JG001521.
Lele, A. (2014) Mission Mars: India’s Quest for the Red Planet,
Springer, New Delhi.
Lunine, J.I., Chambers, J., Morbidelli, A., and Leshin, L.A.
(2003) The origin of water on Mars. Icarus 165:1–8.
Mahaney, W.C., Milner, M.W., Netoff, D.I., Malloch, D.,
Dohm, J.M., Baker, V.R., Miyamoto, H., Hare, T.M., and
Komatsu, G. (2004) Ancient wet aeolian environments on
Earth: clues to presence of fossil/live microorganisms on
Mars. Icarus 171:39–53.
Marion, G. and Kargel, J.S. (2008) Cold Aqueous Planetary
Geochemistry with FREZCHEM: From Modeling to the
Search for Life at the Limits, Springer, Berlin.
Maruyama, S., Ikoma, M., Genda, H., Hirose, K., Yokoyama,
T., and Santosh, M. (2013a) The naked planet Earth: most
essential pre-requisite for the origin and evolution of life.
Geoscience Frontiers 4:141–165.
Maruyama, S., Aono, A., Ebisuzaki, T., and Dohm, J.M.
(2013b) Birth place of life on the Hadean Earth: the role of
primordial continent [abstract 66-10]. In 125th Anniversary
Annual Meeting & Expo, Geological Society of America,
Boulder, CO.
156 FAIRE´N ET AL.
Mojzis, S.J., Arrhenius, G., McKeegan, K.D., Harrison, T.M.,
Nutman, A.P., and Friend, C.R.L. (1996) Evidence for life on
Earth before 3,800 million years ago. Nature 384:55–59.
Mojzsis, S.J., Harrison, T.M., and Pidgeon, R.T. (2001)
Oxygen-isotope evidence from ancient zircons for liquid
water at the Earth’s surface 4300 Myr ago. Nature 409:178–
181.
Moore, J.M. and Wilhelms, D.E. (2007) Geologic Map of Part
of Western Hellas Planitia, Mars, U.S. Geological Survey
Scientific Investigations Map SIM-2953, USGS Information
Services, Denver, CO.
Mumma, M.J., Novak, R.E., DiSanti, M.A., Bonev, B.P., and
Dello Russo, N. (2004) Detection and mapping of methane
and water on Mars. Bulletin of the American Astronomical
Society 36:1127.
Mumma, M.J., Villanueva, G.L., Novak, R.E., Hewagama, T.,
Bonev, B.P., DiSanti, M.A., Mandell, A.M., and Smith, M.D.
(2009) Strong release of methane on Mars in northern sum-
mer 2003. Science 323:1041–1045.
Oehler, D.Z. and Allen, C.C. (2010) Evidence for pervasive
mud volcanism in Acidalia Planitia, Mars. Icarus 208:636–
657.
Oehler, D.Z., Robert, F., Walter, M.R., Sugitani, K., Meibom,
A., Mostefaoui, S., and Gibson, E.K. (2010) Diversity in the
Archean biosphere: new insights from NanoSIMS. Astro-
biology 10:413–424.
Ori, G.G., Marinangeli, L., and Komatsu, G. (2000) Martian
paleolacustrine environments and their geological constraints
on drilling operations for exobiological research. Planet
Space Sci 48:1027–1034.
Ormo¨, J., Dohm, J.M., Ferris, J.C., Lepinette, A., and Faire´n,
A.G. (2004) Marine-target craters on Mars? An assessment
study. Meteorit Planet Sci 39:333–346.
Parker, T.J., Clifford, S.M., and Banerdt, W.B. (2000) Argyre
Planitia and the Mars global hydrologic cycle [abstract 2033].
In 31st Lunar and Planetary Science Conference, Lunar and
Planetary Institute, Houston.
Patel, B.H., Percivalle, C., Ritson, D.J., Duffy, C.D., and Su-
therland, J.D. (2015) Common origins of RNA, protein and
lipid precursors in a cyanosulfidic protometabolism. Nat
Chem 7:301–307.
Phillips, R.J., Zuber, M.T., Solomon, S.C., Golombek, M.P.,
Jakosky, B.M., Banerdt, W.B., Smith, D.E., Williams,
R.M.E., Hynek, B.M., Aharonson, O., and Hauck, S.A.
(2001) Ancient geodynamics and global-scale hydrology on
Mars. Science 291:2587–2591.
Polat, A. (2012) Growth of Archean continental crust in oceanic
island arcs. Geology 40:383–384.
Rasmussen, B., Fletcher, I.R., Brocks, J.J., and Kilburn, M.R.
(2008) Reassessing the first appearance of eukaryotes and
cyanobacteria. Nature 455:1101–1104.
Robbins, S.J., Hynek, B.M., Lillis, R.J., and Bottke, W.F.
(2013) Large impact crater histories of Mars: the effect of
different model crater age techniques. Icarus 225:173–184.
Rodriguez, J.A.P., Gulick, V.C., Baker, V.R., Platz, T., Faire´n,
A.G., Miyamoto, H., Kargel, J.S., Rice, J.W., and Glines, N.
(2014) Evidence for Middle Amazonian catastrophic flooding
and glaciation on Mars. Icarus 242:202–210.
Rummel, J.D., Beaty, D.W., Jones, M.A., Bakermans, C.,
Barlow, N.G., Boston, P.J., Chevrier, V.F., Clark, B.C., de
Vera, J.-P.P., Gough, R.V., Hallsworth, J.E., Head, J.W.,
Hipkin, V.J., Kieft, T.L., McEwen, A.S., Mellon, M.T., Mi-
kucki, J.A., Nicholson, W.L., Omelon, C.R., Peterson, R.,
Roden, E.E., Sherwood Lollar, B., Tanaka, K.L., Viola, D.,
and Wray, J.J. (2014) A new analysis of Mars ‘‘Special Re-
gions’’: findings of the second MEPAG Special Regions
Science Analysis Group (SR-SAG2). Astrobiology 14:887–
968.
Schopf, J.W. (2006) Fossil evidence of Archaean life. Philos
Trans R Soc Lond B Biol Sci 361:869–885.
Schopf, J.W., Kudryavtsev, A.B., Agresti, D.G., Wdowiak, T.J.,
and Czaja, A.D. (2002) Laser-Raman imagery of Earth’s
earliest fossils. Nature 416:73–76.
Schopf, J.W., Walter, M.R., and Ruiju, C. (2007a) Earliest
evidence of life on Earth. Precambrian Res 158:139–140.
Schopf, J.W., Kudryavtsev, A.B., Czaja, A.D., and Tripathi,
A.B. (2007b) Evidence of Archean life: stromatolites and
microfossils. Precambrian Res 158:141–155.
Schulze-Makuch, D., Irwin, L.N., Lipps, J.H., LeMone, D.,
Dohm, J.M., and Faire´n, A.G. (2005) Scenarios for the evo-
lution of life on Mars. J Geophys Res 110, doi:10.1029/
2005JE002430.
Schulze-Makuch, D., Dohm, J.M., Fan, C., Faire´n, A.G., Ro-
driguez, J.A.P., Baker, V.R., and Fink, W. (2007) Exploration
of hydrothermal targets on Mars. Icarus 189:308–324.
Schulze-Makuch, D., Faire´n, A.G., and Davila, A.F. (2008) The
case for life on Mars. International Journal of Astrobiology
7:117–141.
Schulze-Makuch, D., Head, J.N., Houtkooper, J.M., Knoblauch,
M., Furfaro, R., Fink, W., Faire´n, A.G., Vali, H., Kelly Sears,
S., Daly, M., Deamer, D., Schmidt, H., Hawkins, A.R., Sun,
H.J., Lim, D.S.S., Dohm, J., Irwin, L.N., Davila, A.F.,
Mendez, A., and Andersen, D. (2012) The Biological Oxidant
and Life Detection (BOLD) mission: a proposal for a mission
to Mars. Planet Space Sci 67:57–69.
Scott, D.H. and Carr, M.H. (1978) Geologic Map of Mars, IMap
I-1083, U.S. Geological Survey, Denver, CO.
Seibert, N.M. and Kargel, J.S. (2001) Small-scale martian po-
lygonal terrain: implications for liquid surface water. Geo-
phys Res Lett 28:899–903.
Skinner, J.A. and Mazzini, A. (2009) Martian mud volcanism:
terrestrial analogs and implications for formational scenarios.
Mar Pet Geol 26:1866–1878.
Skinner, J.A. and Tanaka, K.L. (2007) Evidence for and im-
plications of sedimentary diapirism and mud volcanism in the
southern Utopia highland-lowland boundary plain, Mars. Ic-
arus 186:41–59.
Soare, R.J., Conway, S.J., Dohm, J.M., and El-Maarry, M.R.
(2014a) Possible open-system (hydraulic) pingos in and
around the Argyre impact regions of Mars. Earth Planet Sci
Lett 398:25–36.
Soare, R.J., Conway, S.J., Dohm, J.M., and El-Maarry, M.R.
(2014b) Possible ice-wedge polygons and recent landscape
modification by ‘‘wet’’ periglacial processes in and around
the Argyre impact basin, Mars. Icarus 233:214–228.
Stu¨eken, E.E., Buick, R., Guy, B.M., and Koehler, M.C. (2015)
Isotopic evidence for biological nitrogen fixation by
molybdenum-nitrogenase from 3.2 Gyr. Nature 520:666–669.
Summons, R.E., Amend, J.P., Bish, D., Buick, R., Cody, G.D.,
Des Marais, D.J., Dromart, G., Eigenbrode, J.L., Knoll, A.H.,
and Sumner, D.Y. (2011) Preservation of martian organic and
environmental records: final report of the Mars Biosignature
Working Group. Astrobiology 11:157–181.
Tanaka, K.L. (1986) The stratigraphy of Mars. J Geophys Res:
Solid Earth 91, doi:10.1029/JB091iB13p0E139.
Thomson, B.J., Bridges, N.T., Milliken, R.E., Baldridge, A.,
Hook, S.J., Crowley, J.K., Marion, G.M., de Souza Filho,
C.R., Kargel, J.S., Brown, A.J., and Weitz, C.M. (2011)
ASTROBIOLOGICAL EXPLORATION OF ARGYRE, MARS 157
Constraints on the origin and evolution of the layered mound
in Gale crater, Mars, using Mars Reconnaissance Orbiter
data. Icarus 214:413–432.
Usui, T., Alexander, C.M.D., Wang, J., Simon, J.I., and Jones,
J.H. (2015) Meteoritic evidence for a previously unrecog-
nized hydrogen reservoir on Mars. Earth Planet Sci Lett
410:140–151.
Villanueva, G.L., Mumma, M.J., Novak, R.E., Ka¨ufl, H.U.,
Hartogh, P., Encrenaz, T., Tokunaga, A., Khayat, A., and
Smith, M.D. (2015) Strong water isotopic anomalies in the
martian atmosphere: probing current and ancient reservoirs.
Science 348:218–221.
Warren-Rhodes, K., Weinstein, S., Dohm, J.M., Piatek, J.,
Minkley, E., Hock, A., Pane, D., Ernst, L.A., Fisher, G.,
Emani, S., Waggoner, A.S., Cabrol, N.A., Wettergreen, D.S.,
Apostolopoulos, D., Coppin, P., Grin, E., Diaz, C., Moersch,
J., Ori, G.G., Smith, T., Stubbs, K., Thomas, G., Wagner, M.,
and Wyatt, M. (2007) Searching for microbial life remotely:
satellite-to-rover habitat mapping in the Atacama Desert,
Chile. J Geophys Res 112, doi:10.1029/2006JG000283.
Webster, C.R., Mahaffy, P.R., Atreya, S.K., Flesch, G.J., Mis-
chna, M.A., Meslin, P.Y., Farley, K.A., Conrad, P.G.,
Christensen, L.E., Pavlov, A.A., Martı´n-Torres, J., Zorzano,
M.P., McConnochie, T.H., Owen, T., Eigenbrode, J.L., Gla-
vin, D.P., Steele, A., Malespin, C.A., Archer, P.D., Jr., Sutter,
B., Coll, P., Freissinet, C., McKay, C.P., Moores, J.E.,
Schwenzer, S.P., Bridges, J.C., Navarro-Gonzalez, R., Gel-
lert, R., Lemmon, M.T., and the MSL Science Team. (2015)
Mars methane detection and variability at Gale Crater. Sci-
ence 347:412–414.
Williams, J.-P., Dohm, J.M., Lopes, R.M., and Buczkowski,
D.L. (2014) A large vent structure within Argyre basin, Mars
[abstract 2807]. In 45th Lunar and Planetary Science Con-
ference, Lunar and Planetary Institute, Houston.
Williams, R.M.E., Grotzinger, J.P., Dietrich, W.E., Gupta, S.,
Sumner, D.Y., Wiens, R.C., Mangold, N., Malin, M.C.,
Edgett, K.S., Maurice, S., Forni, O., Gasnault, O., Ollila, A.,
Newsom, H.E., Dromart, G., Palucis, M.C., Yingst, R.A.,
Anderson, R.B., Herkenhoff, K.E., Le Moue´lic, S., Goetz,
W., Madsen, M.B., Koefoed, A., Jensen, J.K., Bridges, J.C.,
Schwenzer, S.P., Lewis, K.W., Stack, K.M., Rubin, D., Kah,
L.C., Bell, J.F., III, Farmer, J.D., Sullivan, R., Van Beek, T.,
Blaney, D.L., Pariser, O., and Deen, R.G. (2013) Martian
fluvial conglomerates at Gale crater. Science 340:1068–1072.
Zahnle, K., Freedman, R.S., and Catling, D.C. (2011) Is there
methane on Mars? Icarus 212:493–503.
Zurek, R.W., Chicarro, A., Allen, M.A., Bertaux, J.-L., Clancy,
R.T., Daerden, F., Formisano, V., Garvin, J.B., Neukum, G.,
and Smith, M.D. (2011) Assessment of a 2016 mission con-
cept: the search for trace gases in the atmosphere of Mars.
Planet Space Sci 59:284–291.
Address correspondence to:
Alberto G. Faire´n
Centro de Astrobiologı´a
M-108, km 4
28850 Madrid
Spain
E-mail: agfairen@cab.inta-csic.es
Submitted 6 August 2015
Accepted 11 October 2015
Abbreviations Used
AWMP ¼ Argyre western-margin-paleolake basin
CRISM ¼ Compact Reconnaissance Imaging
Spectrometer for Mars
GEL ¼ global equivalent layer
MOLA ¼ Mars Orbiter Laser Altimeter
MRO ¼ Mars Reconnaissance Orbiter
OSPs ¼ open-system pingos
SAM ¼ Sample Analysis at Mars
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