NASA's Mars rovers are not the only space devices making Martian discoveries nowadays.
NASA's Jet Propulsion Laboratory (JPL) researchers published a paper on gullies seen in sand dunes via the Mars Reconnaissance Orbiter (MRO). According to a public release by NASA, the paper indicated the grooves in the sand were made by blocks of frozen carbon dioxide (dry ice) sliding down the dune on a cushion of vapor - like a hovercraft.
The grooves are called linear gullies and they are all a few yards wide, meaning the dry ice would have to have been that wide. Similar to gullies caused by water flow on Earth, the dry ice gullies left raised banks on the sides. Unlike water flow gullies; there were no aprons of debris at the bottom. Instead, there were pits from where the dry ice sat and evaporated.
"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," Serina Diniega, NASA JPL planetary scientist and lead author of the study, said in the release. "In the linear gullies, you're not transporting material. You're carving out a groove, pushing material to the sides."
The researchers determined that the gullies were formed in spring and, during winter, were coated in a carbon dioxide frost. Some images even show bright and shiny objects in the dunes.
Click here to see more images of the Martian dunes.
"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."
That is what Diniega and co-author Candice Hansen, of the Planetary Science Institute in Tucson, Az., and their team did. In the deserts of California and Utah, they tried to first slide a block of water ice down a dune. It went nowhere. Next they tried a block of wood and it went nowhere. When they tried a block of dry ice, it slid smoothly all the way down and stopped only when it hit some bushes.
"MRO is showing that Mars is a very active planet," Hansen said. "Some of the processes we see on Mars are like processes on Earth, but this one is in the category of uniquely Martian."
Hansen also said that this dry ice theory should not apply to all gullies found on the red planet.
"There are a variety of different types of features on Mars that sometimes get lumped together as 'gullies,' but they are formed by different processes," she said. "Just because this dry-ice hypothesis looks like a good explanation for one type doesn't mean it applies to others."
Whatever the outcome, it gives researchers and scientists another angle to understand the mysterious planet.
"I have always dreamed of going to Mars," Diniega said. "Now I dream of snowboarding down a Martian sand dune on a block of dry ice."
