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Detection of caves and cave-bearing geology on Mars

Authors:

Abstract

Regions on Mars likely to contain caves and/or cave-bearing geology are identified using multispectral imagery from orbital missions and the exploration of terrestrial analogs for the characterization of associated thermal, and geo-signatures.
DETECTION OF CAVES AND CAVE-BEARING GEOLOGY ON MARS. N. A. Cabrol1,2, E. A. Grin1,2, and
J. J. Wynne2,3. 1. NASA Ames Research Center, Space Science Division, MS 245-3. Moffett Field, CA 94035-
1000.; 2. SETI Carl Sagan Center, 515N. Whisman Road, Mountain View, CA 94043; 3. Merriam-Powell Center for
Environmental Research, Department of Biological Sciences, Northern University of Arizona, Flagstaff, AZ 86011.
Email: Nathalie.A.Cabrol@nasa.gov.
Overview: The objectives of the Earth-Mars Cave
Detection Project is to identify regions on Mars likely
to contain caves and/or cave-bearing geology through
(1) the analysis of multispectral imagery from past and
current orbital missions and other orbital assets (e.g.,
radar), and (2) the investigation of terrestrial analogs
for the identification of associated thermal, and geo-
signatures. The project’s deliverables include (a) the
localization and characterization of potential caves and
pits on Mars and their classification; (b) for terrestrial
analogs, the identification of geosignatures and texture
images, Energy Dispersive Spectra (EDS), and other
signatures, and the classification of mineral suites to be
expected under sets of conditions. The end product is a
database of morphological, geological, mineralogical,
signatures of significant astrobiological relevance for
future mission searching for the past and present
signatures of life on Mars and for human exploration.
Rationale: If early Mars once supported life, organ-
isms may have retreated underground to escape the
increasingly inhospitable surface conditions [e.g., 1-4].
If subsurface life does exist on Mars, energy would
either be derived heterotrophically or chemoautotro-
phically [5]. Numerous cave-dwelling chemoautothro-
phic microbes considered as analogues for Mars have
been identified [6]. These organisms fix carbon from
the air or rocks, live on oxidizable hydrogen sulfide [7]
or can process methane, carbon dioxide, or sulphate
ions [8]. It has been suggested that caves may provide
access to water resources on Mars [2,3,9]. Identifica-
tion of water and ice is central to both the search for
life and for future manned-missions. Whether from
orbit or from the ground, data now abounds to support
the presence of liquid water and ice throughout Mar-
tian history. Recent gullies plausibly formed by shal-
low and deep aquifers were identified [10-11]. Phyl-
losilicates and other abundant other hydrated minerals
[12] support the hypothesis of surface bodies of water;
groundwater and surface drainage have been suggested
[e.g., 13-16]. The MER mission has also identified an
acidic shallow water environment at Meridiani, which
may be conducive to cave formation [17].
Future human exploration and possible follow-on es-
tablishment of a permanent human presence will not
only need water for survival and fuel; it will also re-
quire construction of suitable shelters and will provide
near-complete protection against inhospitable surface
conditions [2]. Potential future use as human habitats
will first require detection of caves. To be efficient,
such detection must be performed in a systematic fash-
ion and with a high-degree of reliability. There is cur-
rently no tool, methodology, models, or instruments
dedicated to the detection of caves for planetary explo-
ration while their identification responds to NASA’s
highest priorities related to science (water and search
for life) and human exploration (e.g., Exploration Vi-
sion: help advance the plans for humans on Mars in 30
years).
Project Description: In response to this issue, we
developed a project with an overall goal to define mis-
sion and instrumentation requirements for detecting
caves on Mars using thermal infrared imagery. Spe-
cifically, the two main objectives are to:
(a) Characterize cave thermal behavior and evaluate
the potential to differentiate thermal signatures of
deep caves from shallow caves and collapse pits at
Mars analog sites (Atacama Desert, Chile and Mo-
jave Desert, California) where thermal data for
both caves and non-cave features is collected in
order to determine cave signatures and the differ-
ences between various types of caves. It also
quantifies the signatures of false positives and
false negatives;
(b) Develop models for martian caves that simulate
atmospheric and environmental conditions using
thermal behavior data and structural characteris-
tics from terrestrial caves. We model surface and
subsurface temperatures of caves and surrounding
terrain, Mars atmospheric conditions (lower pres-
sure, density, and heat capacity), entrance struc-
ture, albedo associated with martian geological
formations where caves are likely to occur, and
varying surface temperatures to reflect seasonality
and diurnality. The objective is to identify the op-
timal detectability of a cave given structure type
and geological substrate. The developed model is
used to identify times to conduct overflights using
the Quantum Well Infrared Photodetector (QWIP),
a thermal imaging sensor developed by NASA
Goddard Space Flight Center (GSFC). Overflights
will be used to determine detectability and resolv-
ability of each cave in the thermal infrared.
(c) Map potential caves and cave-bearing geology on
Mars by surveying the existing missions data-
bases. The results presented here relates to this ob-
jective.
1040.pdf40th Lunar and Planetary Science Conference (2009)
Typology of Martian Caves: The geological diver-
sity and evolution of Mars suggest that cave-types may
be as varied as on Earth. The existence of caves from
microscale to macroscale structures is predicted from
Mars geology and climate history. A first level ap-
proach is to consider caves as a result of aqueous (wa-
ter and ice), volcanic, and aeolian activity (individually
or combined). Another approach is to consider proc-
esses, i.e., tectonic and chemical activity, and erosion.
Tables 1 and 2 summarize plausible martian cave
types and their formation processes [after 18-19].
Table 1. Cave Formation Independent of Host Environment
Chemical Composition
Cave Type
Process
Morphology
Host Environment
Tectonic
Mass mov. in
regolith
Fossae
Cohesive, low
water content
Sink Hole
Soil piping
Chamber
Fine-grained, non-
cohesive
Subsurface
Erosion
Water drain-
age
Underground
conduit
Water-rich, porous
Valley and
Talus
Slope proc-
esses
Interconnected
holes
Coarse-grained
clastics
Channel bank
Flow scouring
Longitudinal
excavation
Cohesive
Lake shoreline
Wave scour-
ing, ice-push
Shore leveled
excavation
Fine-grained, non-
cohesive
Aeolian
Wind scouring
Holes
Loosely Cohesive
Table 2. Cave Formation Dependent on Host Environment
Chemical Composition
Cave Type
Process
Host Environ-
ment
Dissolution
Chemical
Soluble material
Lava blister
Exsolved away
gas
Basalt
Fracture
Mechanical
pressure
Varied materials
Lava tubes
Roof cooling
Lava flows
Ice
1. Steam from
volcanic origin
2. Tension, wind
ablation
Ice
Glacial
potholes
Ice melt blocks
Ancient segre-
gated ice envi-
ronment
Pseudo-
karsts
Thermokarst,
pressure or tem-
perature induced
melting
Poorly consoli-
dated sediment
Preliminary Results: 40,116 THEMIS images
were examined into the first year of the project. They
cover the Olympus, Chryse, Elysium, Hellas, Argyre,
and Memnonia regions of Mars. Among those, 1.7%
(N = 677) show features of interest ranging from
possible lava tubes, deep cavities associated with pit
chains morphology, faulting, sink holes near ancient
channels, ancient deep volcanic vents, and other
cavity-like features associated with periglacial
processes. Among those, 7.4% (N = 50) present
characteristics making them high-priority cave or
cavity candidates i.e. Figure 1.
Our poster will show the location of these features,
their morphology, and type. Next steps include com-
pleting the survey of the THEMIS imagery and, where
available, the compilation of images taken at different
times of the day for high-priority candidates in order to
assess depth and morphology; and to initiate the survey
of imagery from other missions i.e. MRO, MGS, MEx.
When completed, this project will provide a catalogue
that identifies the most promising targets for astrobiol-
ogy and human mission concept studies and a first-
level assessment of their interest and reachability.
Figure 1: THEMIS image ID V05709015 (subsample),
18m/pxl resolution.
References: [1] Ellery, A. et al., IJA, 1, 365 (2002);
[2] Wynne, J. et al., EPSL, 272, 240 (2008); [3] Wynne, J.
et al., 38th LPSC, # 2378, (2007); [4] Cushing, G. et al.,
GRL, L17201 (2007; [5] Mazur, P. et al., SSR, 22, 3
(1978); [6] Boston, P. et al., Astrob., 1, 25 (2001); [7]
Parnell, J. et al., Astrob., 2, 43 (2002); [8] Baker, V. et al.,
In: Resources of near-Earth space (J.S Lewis, Ed.), Univ.
Arizona Press, 765 (1993); [9] Malin, M. & K. Edgett,
Science, 302, 1931 (2000); [10] Heldmann, J. and M.
Mellon, Icarus, 168, 285 (2004); [11] Bibring, J-P., et al.,
Science, 307, 1576 (2005); [12] Baker, V. & D. Milton,
Icarus, 23, 27 (1974); [13] Carr, M. The Surface of Mars.
Yale Univ. Press (1981); [14] Carr, M. Water on Mars,
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of Mars, Univ. Texas Press, Austin (1982); [16] Malin,
M. & K. Edgett, Science, 302, 1931 (2003); [17] Squyres
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29th LPSC, (1998); [19] Grin, E. et al., Proc. Workshop on
Mars 2001, Houston, TX, 31 (1999).
Acknowledgment: This project is supported by
the NASA Astrobiology: Exobiology and Evolutionary
Biology program under grant # EXOB07-0040.
1040.pdf40th Lunar and Planetary Science Conference (2009)
... To date, Mars mission imaging has yielded views of vertical pits or shafts of various sizes and descriptions in volcanic terrains that may be associated with some form of extensional tectonics, collapse of material into an emptied magma chamber, or other processes (Wyrick et al., 2004;Cushing et al., 2007;Smart et al., 2011;Cushing, 2012;Halliday et al., 2012). Caves on Mars were speculated about before they were identified (e.g., Grin et al., 1998Grin et al., , 1999, and chains of collapse pits are now visible in many locations on Mars and interpreted as possible lava tubes, sinuous rilles, or other volcanic subterranean features (Boston, 2004;Cabrol et al., 2009); see Fig. 24. Such features appear to be a by-product of lava flows or dikes as they are here on Earth, and these can be made by a variety of mechanisms (Kempe et al., 2006;Kempe, 2009). ...
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Water on Mars The Channels of Mars, Univ
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