The Mars Reconnaissance Orbiter (MRO) captured for the first time ever an avalanche in progress on another world!
These images were taken with the Hi Resolution Imaging Experiment (HiRISE) flying on the MRO. This image was taken at 34° latitude and 235.8° longitude, which is in Mars’ north polar region. The geology of this region is that of a layered dome of material, and this cliff is located at the edge of it. The cliff is about one half of a mile high! (70 m = 2300 ft) and is incredibly steep with slopes as great as 60°. The cloud of dust is about 590 feet across and extends about 625 feet from the base of the cliff.
This image was taken on February 18, 2008 at 1:05pm Martian local time. In the northern hemisphere of Mars, spring began on December 10, 2007, and the Carbon Dioxide ice (seen in the left side of the image at the top of the cliff) is beginning to thaw in the spring “heat”. The Carbon Dioxide ice does not melt, instead it sublimes (turning from a solid to a gas). As it does sediments and ice in these steep cliffs give way to avalanches.
The scientists have been watching these particular locations with the hope of catching one in action. They have succeeded!
Here you can compare before (PSP_007140_2640) and after (PSP_007338_2640) photos.
While much of Mars looks like the deserts of Utah, the Martian South Polar regions have revealed some surprising geology unlike anything we have here on Earth.
At the 2007 American Geophysical Union Fall Meeting in San Francisco, Chris Okubo, Candace Hansen, and Timothy Titus who work with the Mars Reconnaissance Orbiter’s High Resolution Imaging Camera presented research suggesting that these intriguing structures are caused by explosions of subliming carbon dioxide.
The theory is that there is a layer of translucent Carbon Dioxide ice and when the surface is heated during the summer months, the ground beneath the ice heats up vaporizing the Carbon Dioxide gas. This gas flows uphill and bursts out of weak spots in the ice. This results in geysers which spew Carbon Dioxide gas and Martian dust into the atmosphere. The gas refreezes and snows out forming the white material along the spider-shaped network of tunnels blown out by the subliming Carbon Dioxide.
This same process is believed to be responsible for similar more extensive landscapes called lacework and lizard skin. It would be fascinating to see these from the ground.