Melting Snow and the Gullies of Mars . ... Credit Copyright: P. Christensen (ASU), THEMIS , Mars Odyssey , NASA Explanation: Tantalizing images of gullies on Mars have offered striking evidence for recent flows of liquid water. ... Melting snow, running underneath the snow pack and down the crater walls would be protected from the extreme surface conditions, remaining liquid and eroding the gullies over time. Could life exist in a liquid water environment beneath the Martian snow? ...