Marks on Martian Dunes May Reveal Tracks of Dry Ice Sleds

NASA research indicates hunks of frozen carbon dioxide -- dry ice -- may glide down some Martian sand dunes on cushions of gas similar to miniature hovercraft, plowing furrows as they go.

via NASA Breaking News

http://www.nasa.gov/home/hqnews/2013/jun/HQ_13-180_Mars_Dry_Ice_Gullies.html