The legacy of aqueous environments on soils of the McMurdo Dry Valleys: contexts for future exploration of martian soils

Abstract

Introduction The McMurdo Dry Valleys are the largest and one of the most southernly exposed terrestrial antarctic environments (Ugolini and Bockheim,2008) and have been a prominent analog environment for speculations about surface processes (Mahaney et al., 2001; Dickenson and Rosen, 2003; Marchant and Head, 2007) and potential biology (McKay, 1997; Wynn-Williams and Edwards, 2000) on Mars. The extremes in cold and aridity, the paucity of visually conspicuous life forms, and the undisturbed conditions of the McMurdo Dry Valleys make this region an obvious candidate for such comparisons. Recent discoveries of evidence demonstrating past and perhaps present availability of liquid water on the martian surface detected by the Mars Global Surveyor (Malin and Edgett, 2000; Baker, 2001) and the Spirit and Opportunity rovers (Squires et al., 2004a; Haskin et al., 2005) have extended the foundation of these comparisons beyond similarities in climate to surface geomorphology, geochemistry, and mineralogy (Chevrier et al., 2006; Marchant and Head, 2007; Amundson et al., 2008). Water is the primary limitation to geochemical weathering and biological activity in the McMurdo Dry Valleys of Antarctica and other cold desert ecosystems where availability and movement of liquid water is limited by low temperatures (Kennedy, 1993; Convey et al., 2003; Barrett et al., 2008). This limitation of liquid water results in slow weathering and highly constrained biological activity contributing to relatively stable geochemical conditions in surface environments. Thus, in the McMurdo Dry Valleys, the legacy of paleo-aquatic environments is preserved in contemporary patterns of soil geochemistry.