Sliding Dry Ice Resulted in Mysterious Gullies on Martian Dunes

The mysterious furrows that are visible on Martian dunes are a result of sliding blocks of frozen carbon dioxide, otherwise known as dry ice, according to the latest NASA report.

The researchers assume that this process could explain one class of gullies that is visible on the Martian sand dunes by examining images from NASA's Mars Reconnaissance Orbiter (MRO), as well as conducting experiments on the sand dunes in Utah and California.
The researchers state that the linear gullies have a constant width of a few yards, with elevated banks by the side.

The difference in the gullies that are formed on Earth by the flow of water and that of Mars is that they lack debris at the bottom of the lower edge and are instead filled with pits at the downhill end. Gullies on Earth, on the other hand, have a lot of debris.

"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 Serina Diniega, scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., and lead author of the report. "In the linear gullies, you're not transporting material. You're carving out a groove, pushing material to the sides."

To know more about these gullies, researchers looked at images provided by MRO's High Resolution Imaging Science Experiment (HiRISE) camera. The images showed sand dunes with linear gullies blanketed by dry ice during the Martian winter. The linear gullies are located on dunes that spend the Martian winter covered by dry ice. Even during the experiments conducted on the sand dunes of Utah and California, researchers noticed that the frozen carbon dioxide slid down the dunes, to what the scientists refer as a 'cushion on gas that is similar to the miniature hovercraft'. Grooves are mostly formed during the early spring. In some images, the scientists have captured bright objects in the gullies, which they believe are pieces of dry ice that are broken from higher areas of dunes.

Based on the new hypothesis, the pits could be from the blocks of frozen carbon dioxide that have sublimated into carbon dioxide gas

"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."