The Martian rovers and orbiters have sent so much data back to Earth in the last few years that discoveries about Mars' wet and active past come left and right. Yesterday we covered the story that the stuck Spirit rover may have found evidence of recent water right under its tracks. And another study this week, out in Nature Geoscience, pinpoints a spot by a Mars volcano that could contain evidence of a watery system more than 3 billion years old—and perhaps even life, too. The finding came after the Mars Reconnaissance Orbiter observed a mineral called hydrated silica sitting on the flank of the extinct Syrtis Major volcano.
The mineral is transported and then concentrated by hot water or steam, suggesting the deposits were laid down in what was once a hydrothermal environment. Groundwater may have been heated by magma from the erupting volcano and vented to the surface as steam, says John Mustard of Brown University in Rhode Island, a member of the team that identified the mineral. [New Scientist]
The trouble with evidence like silica is that it's hard to be sure about its origin, especially after billions of years. But the team argues that the case for volcanic activity helping to deposit the silica there is strong. For one thing, Ars Technica notes
, sediment doesn't erode upward—the deposits are high on the slope, so that's probably where they originated. And secondly, the alternative explanations have weaknesses.
Other options for forming silicates include an acidic fog derived from volcanic activity, but this should have had a widespread impact; instead, the deposits appear to be tightly clustered. A second option, hot ground water, is also unlikely, since there wouldn't be much groundwater near the peak of a volcano. [Ars Technica]
Because of the nature of the silica material, and because it has apparently stayed in one place for so long, Mustard's team raises the possibility that if life lived here way back when, the evidence could still exist.
According to Mustard, traces of any organisms that existed could still be found in the silica, which is non-porous and ideal for preserving fossil remains from the ravages of time and weather. Even after 3.7 billion years, any degradation would come only from silica-penetrating cosmic rays. Those break down biological compounds, but would still leave telltale residues of carbon. [Wired.com]
So Syrtis Major is one more must-see when future rovers visit the Red Planet. Related Content: DISCOVER: Did NASA's Phoenix Find Liquid Water on Mars?
Image: NASA/JPL-Caltech/MSSS/JHU-APL/Brown Univ