Saturn moon Iapetus' huge landslides stir intrigue
Published: 29th Jul 2012 22:01:48
Saturn's moon Iapetus frequently plays host to a huge type of landslide or avalanche that is rare elsewhere in the Solar System, scientists report.
Sturzstroms or "long-runout landslides" move faster and farther than geological models predict they should.
They have been seen on Earth and Mars, but there is debate about their causes.
Now, images from the Cassini space mission, reported in Nature Geoscience, suggest that heating of icy surfaces helps the landslides keep going.
On Earth, landslides typically travel a horizontal distance that is less than twice the distance that the material has fallen.
Long-runout landslides, by contrast, can travel as much as 30 times the vertical falling distance.
A great many mechanisms have been proposed to explain this phenomenon, ranging from simple sliding on ice to the sound waves from the slide making rock and debris behave more like a fluid.
But there is little consensus on which of these theories, if any, is correct.
Now, Kelsi Singer of Washington University in St Louis, US, and colleagues report that the geography of Iapetus is a unique setting to test these theories.
"The landslides on Iapetus are a planet-scale experiment that we cannot do in a laboratory or observe on Earth," Ms Singer said.
"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."
Iapetus is a geologically interesting place to look; it is a squashed sphere, fatter at its equator than its poles, and is mostly encircled by a ridge that reaches peaks some 20km high.
It also has a number of giant impact craters reaching depths of 25km.
The icy satellite has more giant landslides than any Solar System body other than Mars. The reason, says Prof William McKinnon, also from Washington University, is Iapetus' spectacular topography.
"Not only is the moon out-of-round, but the giant impact basins are very deep, and there's this great mountain ridge that's 20km (12 miles) high, far higher than Mount Everest," he explained.
"So there's a lot of topography and it's just sitting around, and then, from time to time, it gives way."
Ms Singer was looking for stress fractures in the moon's ice, but instead found evidence of 30 massive landslides - 17 along crater walls and 13 along the giant equatorial ridge.
Analysis of the images from these events suggests that the "coefficient of friction" - a measure of how much the slip-sliding of material in a landslide tends to slow it down - on Iapetus is far lower than expected for ice.
It appears that this faster-moving ice seen on Iapetus has a lower friction coefficient than that of slow-moving ice measured in Earth-bound laboratories.
The team suggests that the tiny contact points between bits of ice debris in such a landslide may heat up considerably, melting it and forming a more fluid - and thus less friction-limited - mass of material.
They suggest that physicists here on Earth test the idea in the laboratory, giving insight not only into what is happening on Iapetus, but closer to home as well.
Harvard CitationBBC News, 2012. Saturn moon Iapetus' huge landslides stir intrigue. [Online] (Updated 29 Jul 2012)
Available at: http://www.manchesterwired.co.uk/news.php/1443362-Saturn-moon-Iapetus-huge-landslides-stir-intrigue [Accessed 18th May 2013]
At 20:28:08 in OtherThe extradition of one of Britain's most wanted fugitives has been delayed by an investigation into separate charges by Spanish police....
At 19:01:15 in OtherA conman dubbed the "King of Marbella" and his three accomplices have been jailed over a £675,000 bank fraud....
At 18:27:17 in OtherFriends of a violin teacher found dead at home after giving evidence against a couple who sexually abused her are playing a concert in her h...
At 17:48:13 in OtherA 46-year-old man has been jailed for life for the murder of a fellow Ukrainian at a Salford flat on New Year's Day....
At 14:35:14 in OtherCoronation Street actor Michael Le Vell has pleaded not guilty to 19 sexual offences against a child....
At 13:29:31 in OtherAn engineer from Greater Manchester was unlawfully killed by his kidnappers in Nigeria minutes after a UK-led rescue operation stormed in, a...
At 12:34:54 in OtherA man has been rescued by neighbours from a Manchester flat after becoming so "engrossed" in a crossword he failed to notice a chi...
At 11:16:53 in OtherA council has been called "ludicrous" for considering spending nearly £800,000 on leasing a drive-through coffee shop....
At 11:07:08 in OtherA company director is one of eight people charged with drug dealing by officers investigating a £3.8m internet-based drugs ring....
At 10:54:32 in OtherA man who admitted stabbing a British soldier outside a Cyprus nightclub has been jailed for eight years....
News In Other Categories
With the doors to its brand new £1million training centre officially open, one of the UK's leading apprentice training providers, Bristol ba...
Computers and smartphones have become a "digital dummy" used by parents to pacify their children, says a head teachers' leade...
The education secretary is like a "fanatical personal trainer" who urges schools to jump higher and run faster, a head teachers...
Legendary Indian batsman Rahul Dravid has spoken of his anguish after three players from the team he captains in the Indian Premier league w...
The Swedish city of Malmo is gearing up to host the Eurovision Song Contest final with 26 countries set to perform for millions of TV viewer...
A lorry driver from County Tyrone has been jailed for 14 years in Greece after being convicted for his part in smuggling herbal cannabis wor...