Today’s cool image is an update on a previous cool image published in April 2020 about how scientists believe the grooves seen on the slope of a giant dune in Russell Crater on Mars are believed to be formed by frozen blocks of carbon dioxide sliding down the slope when spring arrives. The photo to the right, taken on March 3, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and rotated and cropped to post here, shows these grooves. As I wrote then,
Because the block is sublimating away, the gas acts as a lubricant so that it can slide down the hill. If large enough, the dry ice block will stop at the base of the hill to disappear in a small pit. If small enough, it actually might completely vaporize as it slides, explaining the grooves that appear to gradually fade away.
The scientists actually did a test on Earth, buying a dry ice block at a grocery store and releasing it at the top of a desert dune. Go to my April 2020 link above to see the very cool video.
Several planetary scientists did further combing through many MRO photos of this dune and now think they have spotted examples where the camera actually captured a block as it was sliding downhill.
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