Dry Ice Block May Explain Marks on Martian Sand Dunes
Blocks of dry ice sliding down slopes might be behind the unusual marks on Martian sand dunes, said NASA.
According to a study published under the auspices of the National Aerodynamics and Space Agency, the blocks of dry ice slide down some sand dunes on pillows of gas, creating downhill flows as they go.
NASA scientists claim that this is process which has given rise to one mysterious type of gullies seen on Mars sand dunes. These gullies have been observed in pictures taken by NASA's Mars Reconnaissance Orbiter and several tests were performed on similar sand dunes in Utah in California.
"Whether you're a snowboarder or a hovercraft enthusiast, Mars has something for everybody," said Serina Diniega, a planetary scientist at the space agency's JPL, and lead author of the study. "This finding should help adventure seekers dream of snowboarding on the Martian surface using a block of frozen carbon dioxide."
The linear gullies, according to the study, reveal somewhat constant width with raised banks along the sides. Unlike gullies resulting from water flows on Earth, the Martian gullies do not have smocks of debris at the downhill end of the gully. Instead, quite a few of them have pits at the downhill end.
"Usually," Diniega said, "water moves sediment downhill, forcing material from the top to the bottom of the gully where it is deposited in a fan-shaped smock. No material is transported or carried in a linear gully. Instead, the material is pushed to the side."
Images from the MRO's High Resolution Imaging Science Experiment camera show sand dunes with numerous linear gullies overlaid by carbon-dioxide frost during the winter on Mars. The linear gullies are found on dunes that wait out the Martian winter concealed by carbon-dioxide frost.
NASA researchers examined before-and-after pictures from varying seasons on Mars, and they concluded that the grooves were created during early spring.
According to NASA, many images have also revealed bright objects in the linear gullies.
Scientists now think that the bright objects are chunks of dry ice that have separated from points higher on the Martian dunes.
"The blocks of frozen carbon dioxide sublimate away into CO2 gas after they have ceased sliding, which could explain the pits at the downhill end of the linear gullies," said Candice Hansen of Planetary Science Institute and co-author of the study.