Giant avalanches on an icy moon of Saturn may provide clues about devastating landslides on Earth, say scientists.
Thirty huge ice falls on Iapetus, a walnut-shaped moon girdled by steep 12-mile high mountains, were spotted in images from the American space agency Nasa's Cassini spacecraft.
In 17 cases, the avalanches plunged down crater walls while another 13 swept down the sides of the equatorial mountain range.
Scientists identified a strange feature of the avalanches. At high speeds, the falling ice began to behave like a liquid, travelling many miles before finally coming to rest.
Professor William McKinnon, from Washington University in St Louis , explained: "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."
Experts are still trying to explain a similar phenomenon seen in landslides and earthquakes on Earth.
"Long runout" rock landslides sometimes travel 20 or 30 times further than they fall, covering long distances horizontally or even surging uphill.
In the same way as the Iapetus avalanches, they appear to spill like a fluid rather than tumble.
Laboratory tests suggest that "flash heating" caused by friction may make rocks, or cold ice, slippery. Very cold ice, as occurs on Iapetus, behaves like beach sand.
The research is published in the journal Nature Geoscience .
