Yes it is!
So far we have found evidence for vast quantities of frozen water in the polar caps. The NASA Rovers Spirit and Opportunity just uncovered the first hard evidence that liquid water has been present on Mars at some time in its past, so this important ingredient for life was once present. That also means Mars definitely had a denser earth-like atmosphere, though its detailed composition may have been very different from Earth.
We are finding bacteria living under almost impossible physical conditions here on earth...buried in solid rock for millions of years...eating rock..swimming in acid..enjoying high temperatures near the boiling point of water. In comparison, the subsurface conditions on mars must be quite comfortable to new species of bacteria. Still...we have no proof either in living bacteria or fossils, that live existed on Mars. Not even the earlier claim for the discovery of nano-bacteria in a mars meteorite has remained undisputed.
Return toAsk the Astronomer