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Detection of caves and cave-bearing geology on Mars



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.
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.
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
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-
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
Host Environment
Mass mov. in
Cohesive, low
water content
Sink Hole
Soil piping
Fine-grained, non-
Water drain-
Water-rich, porous
Valley and
Slope proc-
Channel bank
Flow scouring
Lake shoreline
Wave scour-
ing, ice-push
Shore leveled
Fine-grained, non-
Wind scouring
Loosely Cohesive
Table 2. Cave Formation Dependent on Host Environment
Chemical Composition
Cave Type
Host Environ-
Soluble material
Lava blister
Exsolved away
Varied materials
Lava tubes
Roof cooling
Lava flows
1. Steam from
volcanic origin
2. Tension, wind
Ice melt blocks
Ancient segre-
gated ice envi-
pressure or tem-
perature induced
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,
Oxford Univ. Press (1996); [15] Baker, V. The Channels
of Mars, Univ. Texas Press, Austin (1982); [16] Malin,
M. & K. Edgett, Science, 302, 1931 (2003); [17] Squyres
S., et al., Science, 306, 1698 (2004); [18] Grin, E. et al.,
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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A committee of the Mars Exploration Program Analysis Group (MEPAG) has reviewed and updated the description of Special Regions on Mars as places where terrestrial organisms might replicate (per the COSPAR Planetary Protection Policy). This review and update was conducted by an international team (SR-SAG2) drawn from both the biological science and Mars exploration communities, focused on understanding when and where Special Regions could occur. The study applied recently available data about martian environments and about terrestrial organisms, building on a previous analysis of Mars Special Regions (2006) undertaken by a similar team. Since then, a new body of highly relevant information has been generated from the Mars Reconnaissance Orbiter (launched in 2005) and Phoenix (2007) and data from Mars Express and the twin Mars Exploration Rovers (all 2003). Results have also been gleaned from the Mars Science Laboratory (launched in 2011). In addition to Mars data, there is a considerable body of new data regarding the known environmental limits to life on Earth—including the potential for terrestrial microbial life to survive and replicate under martian environmental conditions. The SR-SAG2 analysis has included an examination of new Mars models relevant to natural environmental variation in water activity and temperature; a review and reconsideration of the current parameters used to define Special Regions; and updated maps and descriptions of the martian environments recommended for treatment as ‘‘Uncertain’’ or ‘‘Special’’ as natural features or those potentially formed by the influence of future landed spacecraft. Significant changes in our knowledge of the capabilities of terrestrial organisms and the existence of possibly habitable martian environments have led to a new appreciation of where Mars Special Regions may be identified and protected. The SR-SAG also considered the impact of Special Regions on potential future human missions to Mars, both as locations of potential resources and as places that should not be inadvertently contaminated by human activity.
Conference Paper
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Research has shown one example differentiating caves from non-cave anomalies in the Mojave Desert, CA. This work has important implications for detecting caves on the Moon and Mars.
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From the perspective of energy expenditure, ice is the most economical water resource to target for exploration on Mars. Theoretical stability criteria indicate the planetary-scale potential for ground ice poleward of about 40° latitude. Geologic indicators can constrain the exploration. Particularly useful in this regard are fluidized ejecta blankets, periglacial features, and relict glacial landforms. The relationship of such geomorphological indicators to the modern water resources is dictated by the processes responsible for water cycling in the Martian past and the extension of those processes to the present. The geomorphological evidence indicates extensive water cycling in the geologic past. Exploration strategies can develop around the resource potential of hydrated minerals, hydrothermal systems, and ground ice based on an evolving practical experience as resources are discovered.
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Landforms representative of sedimentary processes and environments that occurred early in martian history have been recognized in Mars Global Surveyor Mars Orbiter Camera and Mars Odyssey Thermal Emission Imaging System images. Evidence of distributary, channelized flow (in particular, flow that lasted long enough to foster meandering) and the resulting deposition of a fan-shaped apron of debris indicate persistent flow conditions and formation of at least some large intracrater layered sedimentary sequences within fluvial, and potentially lacustrine, environments.
The discovery of presumably geologically recent gully features on Mars (Malin and Edgett, 2000, Science 288, 2330–2335) has spawned a wide variety of proposed theories of their origin including hypotheses of the type of erosive material. To test the validity of gully formation mechanisms, data from the Mars Global Surveyor spacecraft has been analyzed to uncover trends in the dimensional and physical properties of the gullies and their surrounding terrain. We located 106 Mars Orbiter Camera (MOC) images that contain clear evidence of gully landforms, distributed in the southern mid and high latitudes, and analyzed these images in combination with Mars Orbiter Laser Altimeter (MOLA) and Thermal Emission Spectrometer (TES) data to provide quantitative measurements of numerous gully characteristics. Parameters we measured include apparent source depth and distribution, vertical and horizontal dimensions, slopes, orientations, and present-day characteristics that affect local ground temperatures. We find that the number of gully systems normalized to the number of MOC images steadily declines as one moves poleward of 30° S, reaches a minimum value between 60°–63° S, and then again rises poleward of 63° S. All gully alcove heads occur within the upper one-third of the slope encompassing the gully and the alcove bases occur within the upper two-thirds of the slope. Also, the gully alcove heads occur typically within the first 200 meters of the overlying ridge with the exception of gullies equatorward of 40° S where some alcove heads reach a maximum depth of 1000 meters. While gullies exhibit complex slope orientation trends, gullies are found on all slope orientations at all the latitudes studied. Assuming thermal conductivities derived from TES measurements as well as modeled surface temperatures, we find that 79% of the gully alcove bases lie at depths where subsurface temperatures are greater than 273 K and 21% of the alcove bases lie within the solid water regime. Most of the gully alcoves lie outside the temperature–pressure phase stability of liquid CO2. Based on a comparison of measured gully features with predictions from the various models of gully formation, we find that models involving carbon dioxide, melting ground ice in the upper few meters of the soil, dry landslide, and surface snowmelt are the least likely to describe the formation of the martian gullies. Although some discrepancies still exist between prediction and observation, the shallow and deep aquifer models remain as the most plausible theories. Interior processes involving subsurface fluid sources are generally favored over exogenic processes such as wind and snowfall for explaining the origin of the martian gullies.
The large Martian channels, especially Kasei, Ares, Tiu, Simud, and Mangala Valles, show morphologic features strikingly similar to those of the Channeled Scabland of eastern Washington, produced by the catastrophic breakout floods of Pleistocene Lake Missoula. Features in the overall pattern include the great size, regional anastomosis, and low sinuosity of the channels. Erosional features are streamlined hills, longitudinal grooves, inner channel cataracts, scour upstream of flow obstacles, and perhaps marginal cataracts and butte and basin topography. Depositional features are bar complexes in expanding reaches and perhaps pendant bars and alcove bars. Scabland erosion takes place in exceedingly deep, swift floodwater acting on closely jointed bedrock as a hydrodynamic consequence of secondary flow phenomena, including various forms of macroturbulent votices and flow separations. If the analogy to the Channeled Scabland is correct, floods involving water discharges of millions of cubic meters per second and peak flow velocities of tens of meters per second, but perhaps lasting no more than a few days, have occurred on Mars.
Early observations of Mars conducted by means of telescopes are considered. Secchi introduced the Italian word 'canale' ('channel') in 1869 to describe apparent lines on the planet's surface. Between 1877 and 1888 Schiaparelli mapped a profusion of 'canali'. Schiaparelli's work led to famous controversies about Mars. This book attempts to investigate the puzzle posed by the Martian channels, taking into account also the results of the studies conducted with the aid of the two orbiting Viking spacecraft which have produced a total number of nearly 60,000 pictures. The channel types are discussed along with questions regarding the distribution, the ages, and the proposed origins of the channels. Attention is given to the geomorphology of Mars, the patterns and networks of Martian valleys, ice and the Martian surface, the outflow channels, catastrophic flood processes, questions of analogy between terrestrial and Martian geographic features, and Martian phenomena associated with water liquid or water ice.
Water on Mars The Channels of Mars, Univ
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