Bad news for life on Mars? Red Planet's wet epoch may have been shorter than we thought

At left, an illustration of a spacecraft in orbit around Mars. At right, a spacecraft photo of icy gullies on Mars.

Mars may be dry and barren today, but multiple lines of evidence show that water flowed across the Red Planet billions of years ago. 

Now, new research has suggested that this water may have existed at the surface of Mars for less time than previously thought. That's because gullies observed on Mars by spacecraft like NASA's Mars Reconnaissance Orbiter (MRO), which had previously been thought to have been carved out by the flow of water, could have instead been created by explosively evaporating carbon dioxide ice.