Saturn's ice moon lapetus hosts landslides and avalanches more frequently than any other Solar System body, discovered scientists.
NASA's Cassini spacecraft revealed 30 massive avalanches on Iapetus - 17 along crater walls and 13 along the giant equatorial ridge.
According to U.S. planetary scientist Kelsi Singer, from Washington University at St Louis, who studied the Cassini images taken by NASA's Cassini spacecraft when orbiting Saturn in September 2007 and December 2004, the icy landslides are "something we never expected to see on Iapetus." She says, "We see landslides everywhere in the solar system, but Saturn's icy moon Iapetus has more giant landslides than any body other than Mars."
Lapetus, the walnut-shaped moon, has 12-mile high mountains- double the height of Mount Everest. Falling from such heights, the lapetus landslide becomes similar to long-runout landslides on Earth, what we know as sturzstroms, say the scientists. Unlike the normal landslides, which typically travel only twice the height they fall from, sturzstroms can travel a distance of 20 to 30 times.
However, after measuring the ratio of the landslide's vertical to horizontal motion, scientists have discovered that the faster-moving ice has far lower "coefficient of friction" on Iapetus than the usual seen for ice in Earth-bound laboratories. As a result of friction drop, ice starts flowing instead of tumbling and then travels many miles before it finally comes to rest after dissipating the energy of fall.
Singer believes that "the landslides on Iapetus are a planet-scale experiment that we cannot do in a laboratory or observe on Earth."
"They give us examples of giant landslides in ice, instead of rock, with a different gravity, and no atmosphere. So any theory of long-runout landslides on Earth must also work for avalanches on Iapetus."
Professor William McKinnon, also from Washington University, said: "You might think friction is trivial, but it's not. And that goes for friction between ices and friction between rocks. It's really important not just for landslides, but also for earthquakes and even for the stability of the land. And that's why these observations on an ice moon are interesting and thought-provoking."
The report has been published in Nature Geoscience.
