Utilizing the Termoskan data set of the Phobos '88 mission we have recognized a new feature on Mars: Ejecta blanket Distinct In the THermal infrared (EDITH). Virtually all of the more than one hundred of these features discovered in the Termoskan data are located on the plains near Valles Manneris. EDITH's have a startlingly clear dependence upon terrains of Hesperian age, implying a spatial or temporal dependence on Hesperian terrains. Almost no thermally distinct ejecta blankets are associated with any of the thousands of craters within the data set that occur on the older Noachian units. EDITH's also do not appear on the portions of the younger Tharsis Amazonian units seen in the data. The Hesperian terrain dependence cannot be explained by either atmospheric or impactor variations; Noachian and Hesperian terrains must have experienced identical atmospheric and impactor conditions during Hesperian times. Thermally distinct eject a blankets therefore reflect target material differences and/or secondary modification processes. A further discussion of EIDTH's is presented

Murray, Bruce C.

English

NASA Technical Reports Server

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NASA-CR-193298
FINAL TECHNICAL REPORT
to
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
From
California Institute of Technology
Division of Geological and Planetary Sciences
Pasadena, CA 91125
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"Spacecraft Studies of Phobos and Mars"
(NAGW-1426)
Principal Investigator:
Time Period:
Dr. Bruce C. Murray
6/1/88 - 10/31/90
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VProfessor, Planetary Science /
Division of Geological and
Planetary Science
California Institute of Technology
Pasadena, California 91125
(818) 356-3780
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FINAL TECHNICAL REPORT
GRANT: NAGW-1426
P.I.: Bruce Murray
Attached, please find summaries of the major work done under this grant. They are taken
from Betts and Murray [ 1993a], Betts and Murray [ 1993b], and Betts, et al. (abstract) [ 1990a].
The following publications and abstracts were produced at least in part from NAGW-
1426:
Publications
Betts, B. H. and B. C. Murray, Thermally Distinct Ejecta Blankets from Martian Craters, J.
Geophys. Res.-Planets, 98, 11,043-11,059, 1993a.
Betts, B. H. and B. C. Murray, Topical studies of the martian surface using the Termoskan data
set, J. Geophys. Res.-Planets, in review, 1993b.
Betts, B. H., Edited Termoskan data fries and descriptions, on the PDS (Planetary Data System)
Phobos "88 CD-ROM, produced in May 1992.
Murray,B.C., M.K.Naraeva, A.S.Selivanov, B.H.Betts, T.Svitek, V.D.Kharlamov,
A.V.Romanov, M.L.Santee, Y.M.Gektin, D.A.Fomin, D.A.Paige, A.S.Panfilov, D.Crisp,
J.W.Head, S.L.Murchie, and T.Z.Martin, Preliminary Assessment of Termoskan
Observations of Mars, Planetary and Space Science, Vol. 39, No. 1/2, pp. 237-265, 1991.
Abstracts
Betts, B. H. and B. C. Murray, Thermal Studies of Martian Channels and Valleys Using
Termoskan Data, Lunar Planet. Sci., XX/V, 103-104, 1993.
Betts, B. H. and B. C. Murray, Thermally Distinct Ejecta Blankets from Martian Craters, in
Workshop on the Martian Surface and Atmosphere Through Time (MSATT), LPI Tech.
Report 92-02, 19-20, 1992.
Betts,B.H. and B.C.Murray, Martian Fluidized Ejecta Blankets as Seen in the Phobos '88
Termoskan Data Set, Lunar Planet. Sci., XXII, 97-98, 1991.
Betts, B. H., T. Svitek, M. L. Santee, B. C. Murray, D. Crisp, D. A. Paige, M. Naraeva, and A.
Selivanov, "Preliminary quantitative assessment and analysis of Phobos 88 Termoskan
observations of Mars": Lunar Planet. Sci., XXI, 77-78, 1990a.
Betts, et al., (same as above), in Scientific Results of the NASA-Sponsered Study Project on
Mars: Evolution of Volcanism, Tectonics, and Volatiles (Solomon, S. C., V. L. Sharpton,
and J. R. Zimbelman, eds.), LPI Tech Rpt. 90-06, Lunar and Planetary Institute, Houston,
79-80, 1990b.
Betts,B.H., T.Svitek, M.L.Santee, B.C.Murray, D.Crisp, D.A.Paige, M.Naraeva, and
A.Selivanov, Preliminary Quantitative Assessment and Analyses of Phobos '88
Termoskan Observations of Mars, Brown-Vernadsky Microsymposium, 1990c.
Ksanfomality, L.V., V.I. Moroz, A.V. Zharkov, G.E. Nikitin, M.L. Santee,D. Crisp, T.Z.
Martin, D.A. Paige,B.H. Betts,B.C. Murray, F.D. Palluconi,P. Bibring, M. Comb,and
A. Soufflot, "Preliminary features of KRFM observationsof Mars": published at
InternationalSymposium:First Resultsof the Phobos-MarsMission and Future Space
Explorationof Mars,in Paris,France,Oct. 1989.
Selivanov, A., M.K. Naraeva, V. Kharlomov, A. Romanov, Y.M. Gektin, D.A. Paige, B.H.
Betts, and B.C. Murray, "Comparisons between infrared thermal emission measurements
of Mars by Phobos Termoskan and Viking IRTM": published at International
Symposium: First Results of the Phobos-Mars Mission and Future Space Exploration of
Mars, in Paris, France, Oct. 1989.
ABSTRACT
Utilizing the Termoskan data set of the Phobos '88 mission we have recognized a new
feature on Mars: Ejecta blanket Distinct In the THermal infrared (EDITH). Virtually all of the
more than one hundred of these features discovered in the Termoskan data are located on the
plains near Valles Marineris. EDrrHs have atstarflingly clear dependence upon terrains of
-. r
Hesperian age, implying a spatial or temporal dependence on Hesperian terrains. Almost no
thermally distinct ejecta blankets are associated with any of the thousands of craters within the
data set that occur on the older Noachian units. EDITHs also do not appear on the portions of
the younger Tharsis Amazonian units seen in the data. The Hesperian terrain dependence cannot
be explained by either atmospheric or impactor variations; Noachian and Hesperian terrains must
have experienced identical atmospheric and impactor conditions during Hesperian times.
Thermally distinct ejecta blankets therefore reflect target material differences and/or secondary
modification processes.
Not all lobate ejecta blankets are thermally distinct, but all EDITHs correlated with
visibly discernible ejecta blankets are associated with lobate ejecta blankets. The boundaries of
the thermally distinct areas usually follow closely the termini of the fluidized lobate ejecta
blankets, even when the ejecta blankets show a high degree of sinuosity. Thus, the thermally
distinct nature of EDITHs must be due to the primary ejecta formation process. The coupling of
these thermal anomalies to morphology is unlike most sharp martian inertia variations which are
decoupled from observed surface morphology. Some thermally distinct ejecta blankets occur
near otherwise similar craters that do not have thermally distinct ejecta blankets. Thus, wind
patterns or locally available aeolian material cannot provide a single overall explanation for the
observed variations. We compiled a database of 110 EDITH and non-EDITH craters ranging in
diameter from 4.2 km to 90.6 km. There are almost no correlations within the database other
than occurrence on Hesperian terrains.
We postulate that most of the observed EDITHs are due to excavation of thermally
distinctive Noachian age material from beneath a relatively thin layer of younger, more
2
consolidated Hesperian volcanic material. The plausibility of this theory is supported by much
geological evidence for relatively thin near-surface Hesperian deposits overlying massive
Noachian megabreccias on the EDrrH-rich plains units. We suggest that absence of thermally
distinct ejecta blankets on Noachian and Amazonian terrains is due to absences of distinctive
near-surface layering. Thermally distinct ejecta blankets are excellent locations for future
landers and remote sensing because of relatively.dust _ free surface exposures of material
excavated from depth.
3
ABSTRACT
The Termoskan instrument on board the Phobos '88 spacecraft acquired the highest spatial
resolution thermal data ever obtained for Mars. included in the thermal images are 2 km per
pixel, midday observations of several major channel and valley systems including significant
portions of Shalbatana Vallis, Ravi Vallis, AI-Qahira Vallis, Ma'adim Vallis, the channel
connecting Valles Marineris with Hydraotes Chaos, and channel mate ri.'aI, in Eos Chasma.
Termoskan also observed small portions of the southern beginnings of Simud, Tiu, and Ares
VaUes and some channel material in Gangis Chasma. Simultaneous broad band visible data were
obtained for all but Ma'adim Vallis. We find that most of the channels and valleys have higher
inertias than their surroundings, consistent with previous thermal studies of martian channels. We
show for the first time that thermal inertia boundaries closely match all flat channel floor
boundaries. Lower bounds on typical channel thermal inertias range from 8.4 to 12.5 (10 -3 ca1
cm -2 s-It2 Kq). Lower bounds on inertia differences with the surrounding heavily cratered plains
range from 1.1 to 3.5. Atmospheric and geometric effects are not sufficient to cause the inertia
enhancements. We agree with previous researchers that localized, dark, high inertia areas within
channels are likely aeolian in nature. However, our data show that aeolian deposits do not fill the
channels, nor are they responsible for the overall thermal inertia enhancement. Thermal
homogeneity and strong correlation of thermal boundaries with the channel floor boundaries lead
us to favor non-aeolian overall explanations. Flat floors and steep scalloped walls are observed in
most regions that show increased inertia. Therefore, we favor fretting processes over
catastrophic flooding for explaining the inertia enhancements. Fretting may have emplaced more
blocks on channel floors or caused increased bonding of fines due to increased availability of
water. Alternatively, post-channel formation water that was preferentially present due to the low,
flat fretted floors may have enhanced bonding of original frees or dust fallout.
2
PRELIMINARY QUANTITATIVE ASSESSMENTAND ANALYSES OF PHOBOS 88
TERMOSKAN OBSERVATIONS OF MARS; B. H..Betts, T. Svitek, M.. L. Santee, B. C.
Murray, D. Crisp, California Institute of Technology, D. A. Paige, University of California at
Los Angeles, M. Naraeva and A. Selivanov, Institute of Space Devices, Moscow.
In February and March, 1989, the-Termoskan instrument onboard the Phobos '88
spacecraft of the USSR acquired a limited set of very high resolution simultaneous observations
of the reflected solar and thermal emission fromMars' equatorial region. We have analyzed
quantitatively approximately 20% of the entire data set and here present three preliminary
analyses: a comparison of Termoskan data .with Viking Infrared Thermal Mapper (IRTM)'data;
an analysis of thermal infrared limb brightening seen on the morning limb and other preliminary
limb analysis results; and an analysis of one observatiom of the shadow of the moon Phobos as
observed on Mars by Termoskan.
THE EXPER/MENT: Termoskan was a two channel optical-mechanical scanning
radiometer with one visible channel (0.5-1.0 Ima and one thermal infrared channel (8.5-12.0 lun).
The instrument was fixed to the spacecraft, pointing in the anti-solar direction. Resolution per
pixel at nadir was 1.8 km for 3 of the 4 panoramas acquired and 300 meters for the remaining
panorama.
COMPARISON WITH IRTM OBSERVATIONS: TO determine the absolute accuracy
of the Termoskan data set, we compared it with thewell calibrated Viking IRTM measurements.
We compared brightness temperatures fa'om Termoskan infrared observations to brightness
temperatures from IRTM's 11 micron channel (9.8 to 12.5 lun). We constrained the IRTM data
to match approxin:ately the Termoskan data in season (Ls), longitude, latitude, and local time of
day. In order to _ompare the two data sets, we degraded the Termoskan resolution to a
resolution comparable to Viking. Figure 1 shows a representative Termoskan-IRTM comparison
which is consistent with other areas that we have compared. We fred that the Termoskan
brightness temperatures are approximately 3 K Warmer than corresponding IRTM brightness
temperatures; that relative features correlate very well in the two data sets; and that Termoskan
sees thermal variations even at the limit of its-spatial resolution.
TERMOSKAN LIMB PROFILES: Limb brightening in the Termoskan thermal infrared
channel from the morning limb was consistently observed. Figure 2 shows a sample morning
limb profile. We explain the peak in thermal brightness just off the limb as a consequence of an
ice or dust haze in equilibrium with the atmosphere, which is warmer than the pre-dawn surface.
Paige used a delta-Eddington spherical shell model developed for the Mars Observer limb
sounder PMIRR (Pressure Modulator Infrared Radiometer), and found that a water ice haze with
a scale height of 5 km (isothermal atmosphere at 200 K, surface at 175 K) could produce a
thermal brightness signature matching the one in Figure 2. The visible channel def'mes a highly
scattering atmosphere to extend 60 to 70 km above the limb. Figure 3 shows a sample evening
limb proftle. The absence of any infrared evening limb brightening is consistent with a surface
which is wanner than the atmosphere. On the evening limb a high haze was observed which
may correlate well with that seen by the Phobos '88 AUGUST experiment.
PHOBOS SHADOW MEASUREMENTS: Termoskan observed the shadow of Phobos
on the surface of Mars during two of its four scans. Due to the scanning nature of the instrument
and the similarity of the spacecraft's orbit to that of Phobos, the shadow appears elongated in the
images. We have looked at one shadowed region south of Arsia Mons. We used the observed
drop in visible flux within the shadowed area to model the solar insolation as a function of both
actual time since the beginning of eclipse and position in the scan. We then used this in an
adaptation of the Clifford et al., 1987 one dimensional, finite difference thermal model for a
homogeneous surface [1]. By comparing the model results with the temperature drops observed
in the infrared scan we f'md thermal inertias varying from 0.7 to 1.1 (10 -3 cal cm -2 s -t/2 K-l).
These values of thermal inertia are lower by factors of 2 to 4 compared to thermal inertias
derived from Viking IRTM measurements [2] for the same area. Viking-derived inertias are
sensitive to the upper few centimeters of the surface, whereas the Phobos shadow measurements
are sensitive only to the upper tenths of a mm of the surface due to the short duration of the
PRELIM. QUANT. ASSESS. OF PHOBOS 88 TEP_IOSKAN: Betts, B. H. et al.
eclipse. Our results imply that there is a thin layer of. highly insulating material, for example a
thin, loosely packed dust layer, on the surface which overlies a layer of less insulating material.
REFERENCES: (1) Clifford, S.M., C.J. Bartels, and E.P. Rubenstein (1987), Lunar and
Planetary Institute; (2) Kieffer, H.H., T.Z. Martin_ A.P. Peterfreund, B.M. Jakosky, E.D. Miner,
F.D, Palluconi (1977), Journal of Geophysical Research, 82 (28), pp. 4249-4291.
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the foo_ of each IRTM dala poim. _IRTM dlta Is constraka_ so malch d_e T_ data to
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warmer. Local tia'ae oI"day i_ the dala d'_wu nmlg_l _om about IL5 to I0.3.
105
VISIBLE AND INFRARED MORNING LIMB PROFILES
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Spacecraft studies of Phobos and Mars

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