UPDATE: see what our reporter at the conference makes of The latest from Mars

Mars rover Spirit has run over something interesting – quite literally run over. A damaged wheel on the rover has churned up the Martian surface so much that researchers have been able to see underneath to what may be evidence of hot springs or acid steam on the red planet.

What Spirit unearthed appears to be nearly pure silica, a substance that NASA thinks could have appeared in one of two ways. Either hot springs dissolved silica out of volcanic rock and then precipitated it out of solution when the water cooled, or acidic steam from cracks called fumaroles stripped everything bar the silica out of the soil (NASA press release).

“Whichever of those conditions produced it, this concentration of silica is probably the most significant discovery by Spirit for revealing a habitable niche that existed on Mars in the past,” says Steve Squyres, principal investigator for the rovers’ science payload. “The evidence is pointing most strongly toward fumarolic conditions, like you might see in Hawaii and in Iceland. Compared with deposits formed at hot springs, we know less about how well fumarolic deposits can preserve microbial fossils.”

The research surfaced at the current American Geophysical Union meeting (which Nature reporters are blogging). Squyres told the meeting “We’re really excited about this.” (BBC). One reason for this excitement is that both hot springs and fumaroles support extremeophile bacteria. The finding, says Squyres, “as implications for habitability” (SF Chronicle).

Spirit now needs somewhere to settle down for the Martian winter and the lack of sunlight it will receive. Yet again there are concerns that dust storms may have blocked its solar panels, endangering its survival (AP). “Team members are pulling out all the stops to get Spirit to a winter location where, based on solar power projections, the rover has a chance at survival,” says NASA (press release 2).

Image: NASA