Channel Surfing: Are Dry Ice Sleds Carvi

July 13 [Sat], 2013, 14:54

Some things are uniquely Martian. And dry ice hovercraft may be one of them.

For 10 years, scientists have been trying to understand what causes linear gullies on Marslong, thin canals carved into sandy slopes and crater walls. Flowing water doesnt quite work as an explanation. Water should carry rocks and dirt downstream, dumping it in a fan-shaped apron at the bottom. But these gullies dont have debris deposits. They abruptly stop.

New gullies appearand old ones growevery spring as the winter ice thaws. And some researchers noticed that the sinuous, leveed ditches looked like trails carved by blocks sliding down the hills. That led astronomers to consider an intriguing possibility for the gullies origin: chunks of dry icefrozen carbon dioxideplowing through the sand while riding cushions of gas. But the idea had never been tested.

Researchers at NASAs Jet Propulsion Laboratory (JPL) spent a couple of days in Coral Pink Sand Dunes State Park in Utah to see if ice, on its own, could carve out a furrow on the shallow slopes. Water icethe same stuff you put in your lemonadedidnt do much. Mostly, it just melted. The dry ice, however, came alive. The dry ice behaved dramatically different, says JPL systems engineer Serina Diniega, lead author on a paper in Icarus. The water ice blocks didnt move at all, but the dry ice just took off! After a small nudge, the dry ice glided down the dune, blowing away sand as it did. When the block stopped, the sand beneath it writhed as jets of carbon dioxide escaped from under the ice. We were surprised, she adds.