Abstract：
:We observed 20-200 m sized low-albedo seepage-like streaks and their annual change on defrosting polar dunes in the southern hemisphere of Mars, based on the Mars Orbiter Camera (MOC), High Resolution Stereo Camera (HRSC), and High Resolution Imaging Science Experiment (HiRISE) images. The structures originate from dark spots and can be described as elongated or flowlike and, at places, branching streaks. They frequently have another spotlike structure at their end. Their overall appearance and the correlation between their morphometric parameters suggest that some material is transported downward from the spots and accumulates at the bottom of the dune's slopes. Here, we present possible scenarios for the origin of such streaks, including dry avalanche, liquid CO(2), liquid H(2)O, and gas-phase CO(2). Based on their morphology and the currently known surface conditions of Mars, no model interprets the streaks satisfactorily. The best interpretation of only the morphology and morphometric characteristics is only given by the model that implies some liquid water. The latest HiRISE images are also promising and suggest liquid flow. We suggest, with better knowledge of sub-ice temperatures that result from extended polar solar insolation and the heat insulator capacity of water vapor and water ice, future models and measurements may show that ephemeral water could appear and flow under the surface ice layer on the dunes today.
journal_name
Astrobiologyjournal_title
Astrobiologyauthors
Horváth A,Kereszturi A,Bérczi S,Sik A,Pócs T,Gánti T,Szathmáry Edoi
10.1089/ast.2007.0212subject
Has Abstractpub_date
2009-01-01 00:00:00pages
90-103issue
1eissn
1531-1074issn
1557-8070pii
10.1089/ast.2007.0212journal_volume
9pub_type
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