These gullies have been involved in an ongoing debate over the past few years. Now with higher resolution images from MRO, it is becoming almost certain that some of these were formed by recent liquid water:
http://www.space.com/scienceastronomy/090302-mm-mars-gullies.html
And that such water on Mars is cyclic in nature- and will return again in the (geologically speaking) near future.
A connected picture is emerging where Mars's huge axis tilt variation causes liquid water regions (and habitable zones) to form on Mars every few 100k years- kind of the opposite of ice-ages on Earth; we get ice-ages every few 10k years, whereas Mars gets water-ages every few 100k years!
Phoenix results are also showing similar evidence of more watery past for some of the stuff found in the north-polar region. Along with the recently cofirmed localized yearly release of Methane on Mars, this bodes well for finding some biological hotspots in the next few years.
Monday, March 02, 2009
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