Thanks to the work of NASA’s Mars Reconnaissance Orbiter (MRO), there is now additional evidence that water might have (and may still) flow on the surface.
The MRO captured images of a hilly landscape consisting of bands of light and dark rock in Candor Chasma, part of the Mars rift valley Valles Marineris. These bands are very similar to band found on earth where there is a cycle of water. In addition, researchers from the University of Arizona described numerous “halos” of bleached rock were cracks (the official term is joints) in the surface where the surface rock clearly reacted some kind of fluid. This fluid, whether it be water or liquid carbon dioxide probably came from underground reservoirs.
Like with story a couple months of very recent erosion on a crater (within a few year), it’s uncertain whether this was caused water or liquid carbon dioxide. Nevertheless, this story is still very significant because these halos would be a good place to look for evidence of life. These haloes were once underground, but have been exposed due to erosion. Back in the day, the overlying rock would have been a great shield from the harsh Martian atmosphere while life was supported below by underground reservoirs.
For some pictures of the Candor Chasma check out the BBC article on this story. They have three pictures from the original research article published journal Science that you can enlarge for a better look.
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Posted by Tim Roth, author of the political blog Think Anew and Act Anew