Smithsonian
Contributions to Astrophysics
VOLUME 5, NUMBER 14
THE SPACE DENSITY OF ATMOSPHERIC DUST IN THE
ALTITUDE RANGE 50,000 TO 90,000 FEET
by PAUL W. HODGE AND FRANCES W. WRIGHT
SMITHSONIAN INSTITUTION
Washington, D.C.
1962
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The Space Density of Atmospheric Dust in the
Altitude Range 50,000 to 90,000 Feet'
By Paul W. Hodge2 and Frances W. Wright3
The importance of collecting and analyzing
meteoritic dust particles has been enhanced by
the recent suggestion of a remarkably localized
dust cloud about the earth (Whipple, 1961a),
and by the likelihood that this dust has a
lunar origin (Whipple, 1961b). Artificial satel-
lites efficiently provide the evidence for the
probable existence of the earth's dust belt;
however, they are not yet capable of capturing
samples of this material and returning them
to earth for analysis. For such highly desirable
samples we must at present rely on the earth's
atmosphere to act as a cushion, braking the
high-velocity particles and concentrating them
in sufficient numbers for collection on high-
flying aircraft and balloons.
The Smithsonian Astrophysical Observatory
has been employing jet aircraft and balloons to
collect particles from various levels of the
stratosphere. In previous publications we have
described a series of particle collections made
at altitudes of 30,000 to 50,000 feet (Hodge
and Rinehart, 1958; Hodge, 1961; Wright,
Hodge, and Fireman, 1961). Fireman and Kist-
ner (1961) and Riggs, Wright, and Hodge (1962)
have made chemical analyses of some of these
particles. The present paper presents results
1
 This work was supported in part by Contract AF 19(604)-6627 with
the Qeophysical Research Directorate, Air Force Cambridge Research
Center, Cambridge, Mass. We wish to acknowledge the excellent
assistance of the Flight Research Center of the National Aeronautics
and Space Administration, Edwards, California, and of Mr. Terry
Larson of the National Aeronautics and Space Administration.
1
 Smithsonian Astrophysical Observatory and Berkeley Astronomical
Department, University of California.
* Smithsonian Astrophysical Observatory and Harvard College Ob-
servatory, Cambridge, Mass.
of the first of a series of collections at altitudes
between 50,000 and 90,000 feet, made in
cooperation with the Flight Research Center
of the National Aeronautics and Space Adminis-
tration.
Collecting procedure
The collector.?The device used in the present
collecting program is a refinement of our
first collector, which was flown on a U-2 (see
photograph in the paper by Rados, 1960, that
describes our U-2 program). It is nearly
identical with the device flown on the B-52
(Hodge, 1961), although mounted on the air-
craft differently. Air is admitted to an ex-
pansion chamber and filtered by a Millipore
filter, which retains all particles down to the
submicron range. The shutter mechanism and
filter housing are so designed that exposure of
the filter to air at times other than the period
during which the shutter is open in flight is
minimized.
Location on aircraft.?The collector was flown
on an F-104A aircraft by the Flight Research
Center of the National Aeronautics and Space
Administration, out of Edwards, Calif. Plate 1
shows the device in place on the tip of the right
wing of the aircraft; an identical collector was
also mounted on the left wing, but it was not in
operation. The wing tip was chosen as a prime
location because contamination of the sample by
the body of the craft was minimized.
Flight characteristics.?A pressure switch in-
stalled on the wing activated the shutter at an
altitude of about 55,000 feet, so that dust was
collected continuously at all heights above this
limit. The flights of the F-104A on which
231
644484?62
232 SMITHSONIAN CONTRIBUTIONS TO ASTROPHYSICS VOL. B
collections were made were typically short-
duration, high-altitude climbs to above 80,000
feet. Collections were made on nine such
flights. Heights, velocities, temperatures and
wind characteristics for each flight are shown
in table 5.
Examination of samples
Microscope procedure.?We made a general
survey of each filter (40 mm in diameter) from
edge to edge, with a microscope of 200 X magni-
fication, and measured, described, and recorded
the position of all types of particles larger than
6/* (mean diameter).
Then, within the central exposed portion of
the filter (a circle of 14-mm diameter), we made
a survey under 400 X magnification, and meas-
ured, described, and recorded the positions of
all opaque particles with mean diameters larger
than 3/x. The numerical results of these two
scannings are shown in table 1.
Classification of particles.?We found that all
particles examined were included in the follow-
ing classification scheme:
1. Black, shiny metallic particles; they may be rough or
smooth. Designation, M.
2. Black, non-shiny particles. Designation, B.
3. Dark brown and dark gray particles. Designation,
Z>.
4. Gray, stone-colored chunks. Designation, Gy.
5. Colored particles, usually with smooth outlines; most
of these seem to be semitransparent. Designation,
C.
6. Transparent, clear particles. Designation, T.
7. Aluminum chips, from the walls of the collector.
Designation, Al.
8. Green-black ovals. Designation, Gn-B.
9. Metallic particles similar in appearance to iron filings.
Designation, M(C).
The second scan, within the 14-mm circle,
excluded the very numerous colored and trans-
parent particles.
The complete scanning data are given in
table 4.
Results
Description of flights and collections.?The
characteristics of the nine flights were all very
nearly the same. Exposure times averaged
95 seconds, with a dispersion of about 20
percent; maximum altitudes averaged 83,000
feet with a dispersion of only 9 percent. The
small differences in the exposure times or alti-
tudes of different flights are not expected to
affect greatly the number or nature of particles.
For this reason the observed numbers of par-
ticles are expected to reflect primarily differ-
ences in space density rather than in flight
characteristics.
Table 1 summarizes the individual flight
characteristics and scanning results, details of
which are given more completely in table 5.
Table 1 shows the total numbers of particles
(with mean dimensions greater than 3M) on the
exposed portions of each filter; this value was
computed from counts on smaller areas, and
over a different size range, by applying the
appropriate multiplication factors (e.g., the
known size distribution). The numbers of
opaque particles given in table 1 are those
directly observed and measured.
TABLE 1.?Flight characteristics and number of non-
aluminum particles
Filter
no.
G8
G16
N l
N2
N3
N4
N5
N7
N9
Exposure(sees)
103
77
92
94
87
96
100
102
103
Alt. range(1000 ft)
51 to 85
52 to 82
51 to 83
53 to 85
56 to 78
52 to 83
52 to 78
52 to 85
52 to 87
Total no.
particles(mean di-
ameter
>3M)
80
560
2080
160
40
80
80
5200
120
No. opaque
particles(mean di-
ameter
>3M)
43
69
359
81
15
40
18
510
63
From the data of table 1 three facts are
evident. (1) The total number of particles and
the number of opaque particles vary widely,
over a range of two orders of magnitude. (2)
The two values agree in their differences; when
the number of all types of particles is high, the
number of opaque particles is high. (3) The
ratio of total to opaque varies between 2 and 10,
and is larger when the actual values are larger.
Computed space densities.?Because the col-
lector's altitude and velocity varied widely
during the collections, we cannot obtain
straightforward space densities as a function of
height. Instead, we obtain a mean value,
weighted according to altitude by the volume
encountered as a function of altitude. This
space density is computed by
HODGE AND WRIGHT PLATE 1

SPACE DENSITY OF ATMOSPHERIC DUST 233
where p is the weighted mean density, k is the
efficiency of the collector, NQ is the number of
collected particles (total minus contamination),
and V is the volume encountered by the col-
lector (kV is the volume swept out).
In our case, iV0 is taken as equal to the value
given in table 1 if we assume no contamination
(thus giving an upper limit to p). The volume
encountered is taken to be
TABLE 2.?Particles per cubic meter (mean diam-
eter >3M).
V=A V\(t)dt,
where A is the area of the opening of the col-
lector (3X10-6m2); v(t) is the aircraft's velocity
as a function of time; and tx is the time of the
beginning, and t2 the time of the end of the
exposure.
We do not have direct values for v(t), but
we do know M(t), the Mach number as a func-
tion of time. This value is related to the
velocity of the plane with respect to the air by
v(t)=20.lM(t)JT(t),
where M(/) is the Mach number and T(t) is the
temperature in absolute units.
Thus we can compute the average space
density of particles by the equation
6X10" 'M(t)
particles/m3
This has been done numerically for the flights,
and results are given in table 2. The volume
of air sampled in each case is nearly one cubic
meter, and the value for kp~ is normally of the
order of 150 particles per cubic meter for all
particles with diameters greater than 3;u- The
average value is 156, excluding Nl and N7
(see below).
The efficiency k of the collector has been de-
termined from wind-tunnel tests carried out by
P. Stroom of General Mills. He made an ex-
perimental calibration by injecting particles
into the air stream, and then comparing the
number collected by our device and that col-
lected by a collector of known efficiency. The
calibration showed that at Mach 0.6 and alti-
tude 50,000 feet our collector is 15 percent
Filter no.
G8
G16
N l
N2
N3
N4
N5
N7
N9
kp
80
480
2290
192
38
82
85
5720
132
efficient. This low efficiency results from the
very small pore-size of the filters and from some
loss on the walls and other portions of the col-
lector. The central part of the collector re-
tained 7 percent of the particles; the remainder
were concentrated near the edges. Calcula-
tions based on pressure differentials measured
in the wind tunnel indicate that the efficiency
of filtering increases with velocity and decreases
with height. For a typical F-104A flight this
efficiency varies between 0.7 and 4.1 times that
of the nights at 50,000 feet and Mach 0.6.
Experimental tests with particles were not
carried out for Mach numbers greater than 0.6,
so that we estimate the efficiency from the
pressure data. We believe that a realistic time
average for the F-104A flights is an efficiency
of approximately 15 percent ? 3 . We adopt a
value of 0.15 for k; the derived space density p
is nearly 7 times the values of kp tabulated in
table 2. Thus the space density is normally of
the order of 1000 particles larger than 3/x per
cubic meter.
0.0
70
H (1000 ft . )
FIGURE l.?The volume of air, F, encountered by the collector
between heights H and H-f 5,000 feet, expressed as a
function of altitude.
234 SMITHSONIAN CONTRIBUTIONS TO ASTROPHYSICS
In figure 1, the volume of air encountered is
shown as a function of altitude for the typical
flight on which filter G8 was flown. The dia-
gram indicates that the volume of air is not a
rapidly varying function of altitude, and that,
within the accuracy to which we can discuss the
present data, the computed p is very nearly
equivalent to a mean space density for altitudes
between 55,000 and 85,000 feet.
On two filters, Nl and N7, the calculated
values of k~p are much greater than the average.
This seems to be the result not of contamina-
tion, but of the encounter of the aircraft with a
dust-enriched portion of air. We have found
that accidentally contaminated samples, such
as N6 and N8 (see table 4), contain large
amounts of aluminum particles, while the
amount of aluminum dust on filters Nl and N7
was equal to the normal background count.
In each case, and especially for filter Nl , there
is a large cluster of particles, nearly centered on
the filter, where most of the dust is located
(fig. 2). The remainder of the filter has the
density of particles typical of the other filters.
Thus the unusually high count is due ex-
clusively to the compact cluster, which appears
to consist of fragments of a larger, conglomerate
particle that may have disintegrated on contact
with the filter or while entering the collector.
Such a particle must have been relatively
fragile and of low density, with a diameter of
the order of 100/z and mass of the order of
10~7 gm. It is tempting to enquire whether
such a particle can be extraterrestrial in origin.
Meteor studies suggest that meteoroids are
primarily low-density, fragile bodies derived
from comets. Fragments of such bodies might
well have the appearance of the object we
collected. It is of great importance to check
such a possibility by means of more collections.
TABLE 3.?The size distribution of particles with mean
diameters larger than 3M; the limiting mean diameter
of opaque particles collected on these filters was 21ft.
TABLE 4.?Complete scanning data
Mean diameter
(microns)
3.0 to 5.9
6.0 to 8.9
9.0 to 11.9
12.0 to 14.9
15.0 to 17.9
18.0 to 20.9
Percent of
total sample
67.3
26.2
4.8
1.2
0.4
0.1
Filter
No.
G8
G16
N l
N2
N3
N4
N5
N6*
N7
N8*
N9
No. particles
of all types
in 14 mm2
with mean
diam. > 6 M
1
7
26
2
0.5
1
1
131.2
65
5
1.5
No. particles in 140
mean diameter
Total:
all but
CandT
43
69
359
81
15
40
18
441
510
260
63
B
and
M
34
40
309
38
12
24
6
86
227
32
28
Gy
3
12
87
5
1
1
1
36
39
35
3
mm2
> 3 M
M(O
0
4
1
0
0
0
0
133
6
151
2
with
Al
27
143
99
75
16
16
16
1592
122
947
2
? Unexposed and heavily contaminated; flown on left wing, new
collector.
From our limited data, assuming k=l for this
encounter, we calculate tentative space den-
sities of 0.1 such particle per cubic meter.
This corresponds to a rate of fall on the earth
of about 104 tons/day, using the method of
estimating the mass rate of fall described by
Fireman and Kistner (1961).
Conclusions
From microscopic studies of particles collected
in the upper atmosphere, we find that at alti-
tudes of 50,000 to 90,000 feet there are per
cubic meter approximately 1000 particles larger
than 3M in diameter. This is approximately
one-fourth of the value derived by identical
methods at altitudes of 40,000 to 50,000 feet.
The space density may fluctuate widely. A
maximum of roughly 30 percent of these are
opaque particles, so that the upper limit for the
space density of meteoritic dust in the atmos-
phere must be approximately 300 particles
larger than 3n per cubic meter. Using the
assumptions of Fireman and Kistner (1961), we
calculate an upper limit to the influx rate of
meteoritic material of roughly 104 tons/day.
The tentatively identified meteoric particles
give a lower limit of 104 tons/day for their influx
rate.
We plan to make further collections with a
more refined collecting device. These will
attempt to determine (1) the nature and num-
ber of the large fragile particles, such as those
SPACE DENSITY OF ATMOSPHERIC DUST 235
S
 "
X ?
2 m m
FIGURE 2.?The distribution of 359 opaque particles on filter Nl , showing the dump of particles believed to have resulted from the
disintegration of a larger fragile particle on impact or while entering the collector.
236 SMITHSONIAN CONTRIBUTIONS TO ASTROPHYSICS
on filter N l ; (2) the distribution with height of
the opaque particles to test the present indica-
tion of a lack of decrease with height; and (3)
the chemical composition of those particles
that from their distribution with height appear
to be extraterrestrial.
TABLE 5.?Flight data far filters
Explanation of column heads: (2), time after take-off; (3), Mach number
for plane's velocity; (4), the dynamic pressure of the air on the aircraft,
measured in pounds per square foot. The figures in columns (5), (6), and
(7) were obtained by a meteorological balloon on the day of the plane
flight.]
FILTER G8
Date of flight, June 21, I960. Altitude range at which filter was exposed,
51,600 to 85,400 feet. Mach number range during the exposure of the
fllter,0.65tol.70. Airplane beading, from magnetic north, 0.65?. Take-
ofl time, 0815 P.S.T. Length of time filter was exposed, 102.7 seconds.
General atmospheric conditions, clear, ground haze. Time of tempera-
ture and wind data, 0810 P.S.T.
(1) (2) (3) (4) (5) (6) (7)
Altitude
(ft.)
50,000
55,000
60,000
65,000
70,000
75,000
80,000
85,000
85,000
80,000
75,000
70,000
65,000
60.000
55,000
50,000
Time
(sec.)
75.5
79.8
84.0
88.7
93.3
98.8
107.8
122.5
130.0
146.0
154.0
159.5
164.5
169.7
174.5
179.5
Mach
no.
1.75
1.66
1.54
1.40
1.25
1.08
0.89
0.66
0.66
0.90
1.10
1.20
1.30
1.40
1.46
1.44
q
(p.s.f.)
515
370
250
145
100
60
30
15
12
35
60
95
140
205
285
355
Fn/TEB O1S
Temp.
(C)
-68 .3?
- 6 5 . 9
- 6 3 . 1
- 6 6 . 7
- 5 4 . 0
- 5 2 . 6
?49.3
- 4 5 . 8
Wind
speed
(knots)
35
14
03
12
18
21
30
31
Wind
direction
260?
265
040
099
104
100
080
090
Date of flight, July 15,1960. Altitude range, 51,600 to 82,000 feet. Mach
no. range, 0.75 to 1.58. Airplane heading, from magnetic north, 065?.
Take-off time, 0940 P.S.T. Length of time filter was exposed, 76.7
seconds. Oenerel atmospheric conditions, clear. Time of temperature
and wind data, 0820 P.S.T.
(U (2) (3) (4) (5) (8) (7)
FILTER N l
Date of flight, August 2, 1960. Altitude range, 51,000 to 83,200 feet.
Mach no. range, 0.44 to 1.65. Airplane heading, from magnetic north,
245?. Take-off time, 0949 P.S.T. Length of time filter was exposed,
91.7 seconds. General atmospheric conditions, clear. Time of tem-
perature and wind data, 0820 P.S.T.
(1) (2) (3) (4) (5) (6) (7)
50,000
55,000
60,000
65,000
70,000
75,000
80,000
85,000
80,000
75,000
70,000
65,000
60,000
55,000
50,000
21.5
25.6
29.7
33.8
38.1
43.6
52.6
?
86.5
97.2
102.7
107.1
111.
114.8
118.2
1.80
1.66
1.51
1.37
1.21
1.07
0.90
?
0.67
1.00
1.17
1.30
1.40
1.49
1.57
550
365
240
155
92
61
32
?
18
50
90
?
205
295
410
-65 .8?
- 6 5 . 4
- 6 0 . 8
- 5 8 . 4
- 5 3 . 2
- 5 1 . 9
- 4 8 . 3
- 4 7 . 8
18
16
12
16
19
29
24
27
203?
150
130
105
106
098
124
092
FILTER N2
Date of flight, August 9, 1960. Altitude range, 52,700 to 85,400 feet.
Mach no. range, 0.57 to 1.69. Airplane heading, from magnetic north,
265?. Take-off time, 0958 P.S.T. Length of time filter was exposed,
94 seconds. General atmospheric conditions, clear. Time of tempera-
ture and wind data, 0925 P.S.T.
(1) (2) (3) (4) (5) (6) (7)
50,000
65,000
60,000
65,000
70,000
75,000
80,000
85,000
85,000
80,000
75,000
70,000
65,000
60,000
55,000
60,000
30.4
35.0
39.2
43.6
48.7
55.7
61.8
76.0
86.5
100.5
107.2
113.0
120.4
123.0
127.1
131.0
1.83
1.69
1.51
1.36
1.16
0.95
0.83
0.59
0.59
0.82
0.99
1.13
1.35
1.42
1.51
1.56
550
370
235
160
95
46
28
11
11
28
50
84
190
220
300
400
FILTER N 3
-68 .4?
- 6 8 . 6
- 6 3 . 5
- 6 7 . 3
- 5 4 . 5
- 5 1 . 8
- 4 7 . 7
- 4 5 . 6
16
9
7
15
25
25
23
24
300'
114
062
096
090
097
090
094
Date of flight, August 12, 1960. Altitude range, 55,500 to 78,000 feet.
Mach no. range, 1.19 to 1.73. Airplane heading, from magnetic north,
246?. Take-off time, 1200 P.S.T. Length of time filter was exposed, 87
seconds. General atmospheric conditions, clear. Time of temperature
and wind data, 0730 P.S.T.
(1) (2) (3) (4) (5) (6) (7)
50.000
55.000
60.000
65.000
70,000
75,000
80.000
85.000
80.000
75,000
70,000
65,000
60.000
55,000
50.0P0
26.0
30.0
34.7
39.5
45. 3
51.2
61.0
?
82.0
93.5
101.0
106.8
112.2
117.0
121.8
1.71
1.61
1.46
1.30
1.14
1.00
0. SI
?
0. S7
1.10
1.26
1.36
1.45
1.48
1.47
?
?
?
146
86
53
28
?
26
50
87
132
?
?
?
- 6 7 . 7?
- 6 6 . 4
- 6 4 . 7
- 5 8 . 8
- 5 6 . 3
- 5 3 . 7
?50. 1
- 4 6 . 1
16
15
13
17
22
29
33
26
245?
188
156
108
72
84
90
90
50,000
55,000
60,000
65,000
70,000
75,000
80,000
85,000
80,000
75,000
70,000
65,000
60,000
55,000
60,000
235.4
241.2
247.0
253.7
262.3
273.0
_
_
301.4
310.3
318.2
325.5
331.3
336.3
1.80
1.74
1.65
1.53
1.38
1.25
_
1.25
1.35
1.46
1.57
1.65
1.69
555
420
285
190
115
75
80
120
175
265
385
480
-69 .9?
- 7 0 . 8
- 6 3 . 5
- 5 8 . 8
- 5 6 . 7
- 4 9 . 6
- 5 0 . 7
- 4 6 . 5
03
12
15
12
20
23
24
21
231
106
088
080
070
083
100
094
SPACE DENSITY OF ATMOSPHERIC DUST 237
TABLE 5.?Flight data for filters?Continued
FILTER N4
Date of flight, August 25, 1960. Altitude range, 51,600 to 82,700 feet.
Macb no. range, 0.66 to 1.74. Airplane heading, from magnetic north,
245?. Take-ofl time, 1150 P.S.T. Length of time filter was exposed,
96 seconds. General atmospheric conditions, clear. Time of tempera-
ture and wind data, 0935 P.S.T. Airplane missed runway on landing;
possible contamination by dust from crash trucks.
(1) (2) (3) (4) (5) (6) (7)
50,000
55,000
60,000
65,000
70,000
75,000
80,000
85,000
80,000
75,000
70,000
65,000
60,000
55,000
50,000
36.4
41.4
46.6
62.0
58.7
66.0
72.0
?
99.3
104.6
112.7
119.3
124.7
130.2
135.0
1.78
1.64
1.43
1.25
1.07
0.91
0.80
?
0.77
0.86
1.05
1.23
1.35
1.49
1.57
530
350
215
125
75
40
30
?
30
40
70
125
190
295
430
FILTER N5
-67 .3?
-67 .0
-60 .6
-57 .9
-53 .2
-51 .2
-48 .9
-45 .0
30
18
06
07
12
21
25
24
250?
257
190
143
120
100
100
090
Date of flight, August 31, 1960. Altitude range, 51,600 to 78,200 feet.
Mach no. range, 0.66 to 1.75. Airplane beading, from magnetic north,
245?. Take-off time, 1015 P.S.T. Length of time filter was exposed,
99.5 seconds. General atmospheric conditions, clear. Time of tempera-
ture and wind data, 0835 P.8.T. Dusty landing.
(1) (2) (3) (4) (5) (6) (7)
50,000
55,000
60,000
65,000
70,000
75,000
80,000
85,000
80,000
75,000
70,000
65,000
60,000
55,000
50,000
34.5
40.0
45.6
51.5
58.6
68.5
?
?
?
104.5
113.5
120.4
126.3
131.7
136.8
1.80
1.63
1.45
1.28
1.07
0.82
?
?
?
0.88
1.07
1.22
1.32
?
?
550
380
205
140
75
35
?
?
?
40
80
125
185
?
?
-61.8?
-64 .9
-61 .2
- 5 4 . 9
-54 .9
-53 .0
-50 .2
-47 .3
28
14
12
12
15
18
19
24
197
185
171
118
090
100
086
090
FlLTEB N7
Date of flight, October 4, 1960. Altitude range, 52,000 to 85,200 feet.
Mach no. range, 0.65 to 1.73. Airplane heading, from magnetic north,
245?. Take-off time, 0935 P.S.T. Length of time filter was exposed,
101.5 seconds. General atmospheric conditions, very clear, calm. Time
of temperature and wind data, 1000 P.S.T.
(1) (2) (3) (4) (5) (6) (7)
50,000
55,000
60,000
65,000
70,000
75,000
80,000
85,000
85,000
80,000
75,000
70,000
65,000
60,000
55,000
50,000
35.0
39.7
40.5
49.6
54.8
59.9
08.3
84.0
91.0
108.0
115.5
122.0
127.0
132.5
137.5
143.0
1.85
1.71
1.69
1.39
1.23
1.11
0.87
0.66
0.65
0.88
1.06
1.22
1.31
1.41
1.46
1.46
575
390
370
360
100
60
30
12
12
28
60
95
135
210
280
360
-60.3?
-62 .2
- 6 0 . 2
-57 .7
24
14
07
04
2.WO
230
224
229
Data not acquired for higher
altitudes.
FlLTEB N 9
Date of flight, October 4, 1960. Altitude range, 52,500 to 86,600 feet.
Mach no. range, 0.76 to 1.80. Airplane beading from magnetic north,
245?. Take-off time, 1345 P.S.T. Length of time filter was exposed,
102.6 seconds. General atmospheric conditions, clear, wind at 10 knots.
Time of temperature and wind data, 1000 F.S.T.
(1)
50,000
65,000
60,000
65,000
70,000
75,000
80,000
85,000
85,000
80,000
75,000
70,000
65,000
60,000
55,000
50.000
(2)
33.5
38.7
43.3
48.3
53.2
59.8
66.8
77.8
97.8
108.4
116.3
122.0
127.4
132.3
137.2
142.5
(3)
1.90
1.76
1.65
1.47
1.32
1.14
0.99
0.81
0.81
0.99
1.14
1.27
1.37
1.45
1.52
1.57
(4)
625
420
285
175
115
60
40
20
20
40
70
105
155
215
305
410
(5)
-60.3?
- 6 2 . 2
- 6 0 . 2
-57 .7
(6)
24
14
07
04
(7)
250?
230
224
229
Data not acquired for higher
altitudes
References
FIREMAN, E. L., AND KISTNEK, G.
1961. The nature of dust collected at high alti-
tudes. Geochim. et Cosmochim. Acta,
vol. 24, pp. 10-22.
HODGE, P. W.
1961. Sampling dust from the stratosphere.
Smithsonian Contr. Astrophys., vol. 5,
No. 10, pp. 145-152.
HODGE, P. W., AND RlNEHART, J. S.
1958. High-altitude collection of extraterrestrial
particulate matter Paper presented at
100th meeting of the American Astro-
nomical Society, Madison, Wis., June 29-
July 2. (Abstract published in Astron.
Journ., vol. 63, p. 306).
RADOS, R. M.
1960. The U-2 as an instrumented aircraft for
geophysical research. Weatherwise, vol.
13, p. 232 ff.
RIGGS, F. G., JR.; WRIGHT, F. W.; AND HODGE, P. W.
1962. Chemical analysis of 643 particles collected
by high-altitude aircraft and balloons.
Smithsonian Astrophys. Obs., Special
Report No. 99, 41 pp.
WHIPPLE, F. L.
1961a. The particulate contents of space. In
P. Campbell, ed., Medical and biological
aspects of the energies of space, pp. 49-
70. Columbia University Press, New
York.
1961b. The dust cloud about the earth. Nature,
vol. 189, pp. 127-128.
WRIGHT, F. W.; HODGE, P. W.; AND FIREMAN, E. L.
1961. A search for micrometeorites in the earth's
atmosphere. Paper presented at 108th
meeting of the American Astronomical
Society, Nantucket, Mass., June 18-21.
(Abstract published in Astron. Journ.,
vol. 66, pp. 298-299).
2 3 8 SMITHSONIAN CONTRIBUTIONS TO ASTROPHYSICS VOL. B
Abstract
Collections of participate matter have been made in the altitude range from 50,000 to 90,000 feet by means of
high-altitude, short-duration flights of an F-104A jet aircraft of the NASA Flight Research Center. The average
space density of particles larger than 3/x in diameter is estimated to be 1000 particles per cubic meter at these altitudes.
The derived space density varies considerably, as previously found for altitudes in the range from 40,000 to 50,000
feet. Only a small percentage of these particles are possibly meteoritic.