New evidence of (transient) liquid water on Mars!
Source: Phil Plait, Astronomy, Pretty Pictures, Science
Excerpt: Does liquid water still flow on Mars? We know that in the distant past — like, a billion years ago — liquid water was abundant on Mars. We also know that water currently exists on Mars in the form of ice, .... But can there still be liquid water flowing on Mars, even if only for a very, very short time? Maybe. ... HiRISE image shows a small region of a Martian crater named Russel… There are a lot of sand dunes in it, and … many gullies as well.... Sometimes, these gullies can form due to the presence of dry ice: … the dry ice turns into a gas, dislodging material and letting it roll downhill. …But these Russell Crater gullies are different. …The gullies do widen where two tributaries meet, which is exactly as you’d expect from flowing material.
http://blogs.discovermagazine.com/badastronomy/2010/04/12/new-evidence-of-transient-liquid-water-on-mars/
http://blogs.discovermagazine.com/badastronomy/2010/04/12/new-evidence-of-transient-liquid-water-on-mars/