The mysterious thin grooves visible on the surface of Mars might have been caused by chunks of frozen carbon dioxide - dry ice, according to a NASA research report.
The dry ice might have glided down the Martian sand dunes on cushions of gas similar to small hovercraft, plowing furrows as they go.
The findings based on examining images from NASA's Mars Reconnaissance Orbiter (MRO) were published in the journal Icarus.
"I have always dreamed of going to Mars," said Serina Diniega, a planetary scientist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif., and lead author of the report. "Now I dream of snowboarding down a Martian sand dune on a block of dry ice."
According to the research, the linear gullies or hillside grooves have a constant width of a few meters, with raised banks or levees along the sides.
Unlike gullies caused by water flows on Earth and possibly on Mars, they do not have aprons of debris at the downhill end of the gully. Instead, many have pits at the downhill end.
"In debris flows, you have water carrying sediment downhill, and the material eroded from the top is carried to the bottom and deposited as a fan-shaped apron," said Diniega. "In the linear gullies, you're not transporting material. You're carving out a groove, pushing material to the sides."
The images captured from MRO's show sand dunes with linear gullies covered by carbon dioxide frost during the Martian winter. Researchers have compared the images from different season and determined that the gullies are formed during early spring.
There appears to be bright objects in gullies in some images. Researchers believe that the bright objects are pieces of dry ice that have broken away from points higher on the slope. Based on the new hypothesis, the pits could result from the blocks of dry ice completely sublimating away into carbon-dioxide gas after they have stopped traveling.
"Linear gullies don't look like gullies on Earth or other gullies on Mars, and this process wouldn't happen on Earth," said Diniega. "You don't get blocks of dry ice on Earth unless you go buy them."