Columbus crater and other possible groundwater‐fed paleolakes
of Terra Sirenum, Mars
J. J. Wray,1 R. E. Milliken,2 C. M. Dundas,3 G. A. Swayze,4 J. C. Andrews‐Hanna,5
A. M. Baldridge,6 M. Chojnacki,7 J. L. Bishop,8 B. L. Ehlmann,9 S. L. Murchie,10
R. N. Clark,4 F. P. Seelos,10 L. L. Tornabene,11 and S. W. Squyres1
Received 12 July 2010; revised 15 October 2010; accepted 3 November 2010; published 5 January 2011.
[1] Columbus crater in the Terra Sirenum region of the Martian southern highlands
contains light‐toned layered deposits with interbedded sulfate and phyllosilicate minerals,
a rare occurrence on Mars. Here we investigate in detail the morphology, thermophysical
properties, mineralogy, and stratigraphy of these deposits; explore their regional
context; and interpret the crater’s aqueous history. Hydrated mineral‐bearing deposits
occupy a discrete ring around the walls of Columbus crater and are also exposed beneath
younger materials, possibly lava flows, on its floor. Widespread minerals identified in the
crater include gypsum, polyhydrated and monohydrated Mg/Fe‐sulfates, and kaolinite;
localized deposits consistent with montmorillonite, Fe/Mg‐phyllosilicates, jarosite, alunite,
and crystalline ferric oxide or hydroxide are also detected. Thermal emission spectra
suggest abundances of these minerals in the tens of percent range. Other craters in
northwest Terra Sirenum also contain layered deposits and Al/Fe/Mg‐phyllosilicates,
but sulfates have so far been found only in Columbus and Cross craters. The region’s
intercrater plains contain scattered exposures of Al‐phyllosilicates and one isolated mound
with opaline silica, in addition to more common Fe/Mg‐phyllosilicates with chlorides.
A Late Noachian age is estimated for the aqueous deposits in Columbus, coinciding with a
period of inferred groundwater upwelling and evaporation, which (according to model
results reported here) could have formed evaporites in Columbus and other craters in Terra
Sirenum. Hypotheses for the origin of these deposits include groundwater cementation
of crater‐filling sediments and/or direct precipitation from subaerial springs or in a
deep (∼900 m) paleolake. Especially under the deep lake scenario, which we prefer,
chemical gradients in Columbus crater may have created a habitable environment
at this location on early Mars.
Citation: Wray, J. J., et al. (2011), Columbus crater and other possible groundwater‐fed paleolakes of Terra Sirenum, Mars,
J. Geophys. Res., 116, E01001, doi:10.1029/2010JE003694.
1. Introduction
[2] The modern surface of Mars is frigid and desiccated at
low latitudes, but many observations suggest that liquid
water once played a substantial role in shaping the surface
geology. The presence of hydrous minerals attests to water‐
rock interactions during the Noachian and Hesperian Periods
[e.g., Squyres et al., 2004b; Bibring et al., 2006], a time that
coincides with the formation of valley networks that suggest
liquid water flowed across the surface [e.g., Baker, 1982;
Carr, 1995; Fassett and Head, 2008a]. Although in some
cases surface water may have been ephemeral [Segura et al.,
2002], evidence also exists for standing bodies of water that
may have persisted for hundreds to tens of thousands of years
or longer [e.g., Moore et al., 2003; Fassett and Head, 2005;
Grant et al., 2008].
1Department of Astronomy, Cornell University, Ithaca, New York,
USA.
2Department of Civil Engineering and Geological Sciences, University
of Notre Dame, Notre Dame, Indiana, USA.
3Lunar and Planetary Laboratory, University of Arizona, Tucson,
Arizona, USA.
4U.S. Geological Survey, Denver, Colorado, USA.
5Department of Geophysics, Colorado School of Mines, Golden,
Colorado, USA.
6Jet Propulsion Laboratory, California Institute of Technology,
Pasadena, California, USA.
7Department of Earth and Planetary Sciences, University of Tennessee,
Knoxville, Tennessee, USA.
8SETI Institute, Mountain View, California, USA.
9Institut d’Astrophysique Spatiale, Université Paris Sud, Orsay, France.
10Johns Hopkins University Applied Physics Laboratory, Laurel,
Maryland, USA.
11Center for Earth and Planetary Studies, National Air and Space
Museum, Smithsonian Institution, Washington, D. C., USA.
Copyright 2011 by the American Geophysical Union.
0148‐0227/11/2010JE003694
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 116, E01001, doi:10.1029/2010JE003694, 2011
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[3] Impact craters are the most common type of basin on
the Martian surface in which ancient water could have
ponded. Hundreds of candidate crater paleolakes have been
identified based on morphologic evidence such as inlet and/
or outlet valleys, fan‐shaped (possibly deltaic) deposits, and
putative shoreline features [e.g., Forsythe and Blackwelder,
1998; Cabrol and Grin, 1999; Fassett and Head, 2008b].
Because of their potential for habitability and preservation
of biosignatures in sediments deposited in a quiescent
environment, paleolakes are considered high‐priority targets
in the astrobiological exploration of Mars [e.g., Farmer and
Des Marais, 1999; Ehlmann et al., 2008a].
[4] Minerals formed in paleolakes record ancient envi-
ronmental conditions because evaporites and other pre-
cipitates can reflect both lake chemistry and the composition
of atmospheric or other volatile reservoirs with which the
lake water was in contact; for example, the relative partial
pressures of CO2 and SO2 in the Martian atmosphere and
their effects on surface water could have determined whether
evaporites were carbonate‐rich or sulfate‐rich [Bullock and
Moore, 2004]. The potential value of paleolake evaporites
has prompted many searches for them, but while sulfates and
chlorides have been identified in canyons, intercrater plains,
and some craters [e.g., Squyres et al., 2004b; Gendrin et al.,
2005; Osterloo et al., 2008], the mineralogic results for
classic morphologic paleolakes have been largely negative
[Ruff et al., 2001; Squyres et al., 2004a; Stockstill et al.,
2005, 2007]. Recent orbital detections of phyllosilicates in
a few paleolakes [Ehlmann et al., 2008a; Dehouck et al.,
2010; Milliken and Bish, 2010; Ansan et al., 2010] suggest
that evaporite salts might be found using similar techniques.
[5] A spectral survey covering much of the southern
highlands in search of new hydrated mineral exposures
[Wray et al., 2009a] identified a unique group of craters in
northwest Terra Sirenum that contain Al‐phyllosilicates
(first reported in Cross crater by Poulet et al. [2007]) and
hydrated sulfates in finely bedded deposits. The alteration
mineral assemblages in these craters are reminiscent of those
associated with terrestrial acid‐saline lakes and groundwaters
[Benison et al., 2007; Baldridge et al., 2009; Story et al.,
2010]. By analogy, the Terra Sirenum crater deposits may
be lacustrine evaporites; even if not, their mineralogic and
morphologic properties define a distinct class of aqueous
deposit on Mars [Murchie et al., 2009b]. Here we investigate
in detail the morphology, thermophysical properties, min-
eralogy, and stratigraphy of these deposits; we then examine
hypotheses for their origin to better determine their
implications for ancient Martian environments. We focus
first on Columbus crater (29°S, 166°W), where the greatest
diversity of hydrated minerals is observed, and then look at
nearby craters with similar deposits. Key data sets used in
this study include the Mars Reconnaissance Orbiter (MRO)’s
High Resolution Imaging Science Experiment (HiRISE)
[McEwen et al., 2007], Compact Reconnaissance Imaging
Spectrometer for Mars (CRISM) [Murchie et al., 2007], and
Context Camera (CTX) [Malin et al., 2007], as well as the
High Resolution Stereo Camera (HRSC) [Neukum and
Jaumann, 2004] on board Mars Express, the Thermal
Emission Imaging System (THEMIS) [Christensen et al.,
2004a] on Mars Odyssey, and the Mars Orbiter Laser
Altimeter (MOLA) [Smith et al., 2001] and Thermal Emis-
sion Spectrometer (TES) [Christensen et al., 2001a] on Mars
Global Surveyor.
2. Morphology of Columbus Crater
2.1. General Characteristics
[6] Columbus crater lies in northwest Terra Sirenum in
the southern highlands of Mars. Immediately surrounding
Columbus are highly cratered plains of the Npl1 unit [Scott
and Tanaka, 1986], dated to the Middle Noachian Epoch
[Tanaka, 1986]. Fluvial dissection is sparse here compared
to other regions of the Noachian southern highlands [Carr,
1995; Hynek et al., 2010], although this may be partly due to
Figure 1. Two views of Columbus crater (29°S, 166°W).
(a) HRSC nadir channel mosaic. Here and subsequently,
numbered outlines indicate locations of future figures; north
is up, unless indicated otherwise. (b) THEMIS daytime IR
band 9 mosaic, colorized with THEMIS‐derived thermal
inertia (scale bar units are tiu). Superposed contours are
MOLA elevations spaced 500 m apart, beginning at
+250 m. Note medium‐inertia (green) materials following
the 1750 m contour around the crater walls. Arrow indicates
small valleys on northeast wall, as described in the text
(sections 2 and 5). (c) Location of Columbus crater on
MOLA global topographic map.
WRAY ET AL.: COLUMBUS CRATER E01001E01001
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