A morphological view on potential niches for exobiology on Mars.

The discovery of microbiota in the Dry Valleys of Antarctica has encouraged the construction of new models of Martian ecosystems in order to determine if life could have once existed on Mars. The Antarctic cyanobacteria reside just below the surface of sandstone rocks where they are protected from the extreme cold and dry environment. Analogy with the Antarctic Dry Valleys supports speculation that hypothetical micro-organisms existed on Mars in the early history of the planet and could have migrated into suitable rocks as the availability of liquid water decreased. Although evidence for sandstone layers on Mars has not been substantiated, the palaeohydrology of Martian fluvial valleys (MFVs) reveals the evidence of lake bed sediment depositions which have formed consolidated sediments. As the MFVs formation may result from underground drainage processes, the sediment material would be expected to contain debris such as pumice washload, and pumilith of volcanic and meteoritic origin. These materials may have formed consolidated porous terrains similar to the Antarctic sandstone. Therefore, the endolithic model is consistent with the Martian liquid water habitat model of perenially ice-covered lakes.