Check out these before and after snaps of a Martian crater and you'll see something that wasn't there before — and that something is a brand new gully, marked above with the arrow. But anyone hoping that this is even further evidence of flowing water on Mars may be disappointed.
The pictures were taken along the inner slope of a crater in Mars' Terra Sirenum region with the ultra-high resolution HiRISE camera currently orbiting the planet. The shots, taken three years apart, confirm that a gully has indeed formed, but , although it looks similar to the gullies carved out on Earth by water, the explanation is little more unusual than that.
When scientists at JPL captured the images earlier this month of what appeared to be flowing water on Mars, one of the things that clued them in was the greater movement of the flows during the Martian summer.
The gully, however, seemed to be following the exact opposite pattern, forming in the Martian winter as the weather was getting colder not warmer. So what's creating the gullies? It's not water, it's seasonal carbon-dioxide frosts, or, as its commonly called here on Earth, dry ice.
Image: NASA/JPL - Caltech/Univ. of Arizona