A MORPHOLOGICAL VIEW ON POTENTIAL NICHES FOR EXOBIOLOGY ON MARS

The discovery of microbiota in the Dry Valleys of Antarctica has encou raged the construction of new models of Martian ecosystems in order to determine if life could have once existed on Mars. The Antarctic cyan obacteria 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 coul d have migrated into suitable rocks as the availability of liquid wate r decreased. Although evidence for sandstone layers on Mars has not be en substantiated, the palaeohydrology of Martian fluvial valleys (MFVs ) reveals the evidence of lake bed sediment depositions which have for med consolidated sediments. As the MFVs formation may result from unde rground 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 endolithi c model is consistent with the Martian liquid water habitat model of p erenially ice-covered lakes.