In NASA Researchers Claim Evidence of Present Life on Mars, Space.com writer Brian Berger reports that two NASA scientists have evidence that life may exist on Mars. Which is true enough, though not in itself new, since uneven methane signatures in the Martian atmosphere (detected in 2004 by Mars Express) have already revealed the possibility of an underground biosphere.

What Carol Stoker and Larry Lemke of NASA’s Ames Research Center in Silicon Valley bring to the table are their findings in southwestern Spain, where the the acidic ecology of the Rio Tinto offers an environment somewhat similar to Mars. It’s telling that concentrations of the mineral salt jarosite have been identified both on Mars and in hot springs and bodies of water like the Rio Tinto. If life could exist in an underground microbial ecosystem under conditions not terribly dissimilar from Mars, it might also be found on Mars itself.

But proceed with caution. Stoker and Lemke won’t have their paper out until May; it is currently undergoing peer review at Nature. And the next Mars rover won’t fly until 2009. We’re building an interesting case but it’s still circumstantial and will be until we have better instrumentation on the scene.