If these Mars Express findings are what they seem to be -- and with Mars, as we know, pretty much nothing is as it seems to be -- then the likelihood of subsurface biology on Mars increases substantially. Active surface biology may still be rare or generally absent, but we don't know that and have been unable to test for it since the Vikings of yore.

The argument is put in terms of "biology or volcanism"... but why not both? In other words, volcanism of the peculiarly Martian variety -- not necessarily what we would expect on Earth -- that serves as an energy source for subsurface biology?

But no one has seen evidence of current volcanism on Mars, right? No, no one has seen an eruption of one of the numerous large volcanoes, and there is yet to be any confirmation of possible smaller outgassing or eruptive events. Except for those "sand geysers" in the south polar region, widely accepted now as a real phenomenon (not an optical illusion) but driven by sunlight in a very cold environment, not driven by release of internal heat...

Yet "heat" is a relative thing, and maybe, in order to grasp hold of what may be going on on Mars, we need to dial down our expectations of volcanic heat. Maybe volcanics on Mars work at much lower temperatures than we would expect -- say ordinary room temperature -- and so we may have a hard time recognizing events we actually see, because our expectations aren't satisfied.

Nevertheless, the vagueness of the Mars Express findings are aggravating.

Cheers, BRFelix