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Cracking the Mysteries of Martian Dust Avalanches That Reshape the Planet

NASA’s Odyssey orbiter has been circling Mars for more than two decades, mapping the surface of the Red Planet. The spacecraft also carries something called THEMIS, a temperature-sensitive camera that offers scientists a unique view of our dusty, red neighbor.
Dust avalanches in an area of Mars called Acheron Fossae 6 photos
Photo: NASA/JPL-Caltech/UArizona
Martian surface frost appears blueish-whiteDark streaks cause by Martian dust avalanchesDark streaks cause by Martian dust avalanchesDark streaks cause by Martian dust avalanchesDark streaks cause by Martian dust avalanches
Odyssey can observe visible and infrared reflections from the Martian surface thanks to THEMIS. Last year, scientists were intrigued by some images taken by the orbiter around dawn. They could see some faint streaks of morning frost (essentially dry ice which forms overnight) when they looked at the surface with visible light.

But using THEMIS was a different story. What seemed to be invisible to the naked eye appeared more widely in some areas in the infrared images. In an article published in the Journal of Geophysical Research: Planets, researchers proposed a theory that might also explain how dust avalanches form after dawn.

Since the Red Planet has a thin atmosphere made up of mostly CO2, the sunlight rapidly melts the frost that has formed overnight, vaporizing it in just a few minutes. Scientists suggest that the dry ice mixed with dust was only visible in the infrared images.

They also found out that this dirty frost might be responsible for some of the black streaks that can be seen stretching for miles down slopes in many images sent by the orbiter. In their paper, the authors note that these dark streaks are occurring where morning frost has formed.

The streaks, according to the researchers, were the result of vaporizing ice which causes just enough pressure to release the dust particles accumulated, creating an avalanche.

It’s also important to note that these dark streaks are not the same as the recurring slope lineae, which are caused by dry sand or dust flows that take place in the same spots every year for extended periods of time.

“Every time we send a mission to Mars, we discover exotic new processes,” said Chris Edwards, a paper co-author at Northern Arizona University in Flagstaff. “We don’t have anything exactly like a slope streak on Earth. You have to think beyond your experiences on Earth to understand Mars.”
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About the author: Florina Spînu
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Florina taught herself how to drive in a Daewoo Tico (a rebadged Suzuki Alto kei car) but her first "real car" was a VW Golf. When she’s not writing about cars, drones or aircraft, Florina likes to read anything related to space exploration and take pictures in the middle of nature.
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