Feeds

Boffins puzzled over impossibly fast ice avalanches on Saturn's moon

Is all that rubbing making ice rubble hot?

Securing Web Applications Made Simple and Scalable

Planetary boffins have spotted that Saturn's other moon, the walnut-shaped Iapetus, is home to spectacular ice avalanches that flow across the surface of the rock.

A ridge around Iapetus' equator makes it look like a walnut

The walnut in the sky. Credit:NASA/JPL/SSI

The ridge of 20km-high mountains, twice the height of Mount Everest, that circle the equator of the moon and give it its walnutesque appearance are the starting point for the ice-slides. The mountainous heights and the deep giant impact basins make for good conditions to get up a bit of speed when the ice gives way. What's strange is that at some point, the coefficient of friction drops and the slide flows instead of tumbling, allowing the ice to go much further.

Earth and Mars both have a similar phenomenon in so-called long-runout landslides or sturzstrom. Instead of travelling the typical horizontal distance of something less than twice what they've fallen, the rocks flow on for 20 or 30 times farther than the first fall, sometimes even managing to surge uphill.

What should be happening is that the rockslide tumbles until the friction between the debris and the ground uses up all the energy the rocks got from falling, stopping the slide in its tracks. Instead, the sturzstrom flow across the ground like a fluid river, something boffins have trouble explaining.

Scientists have posited some sort cushion of air, water or even powdered rock under the slide that helps lubricate it into a flow.

"The landslides on Iapetus are a planet-scale experiment that we cannot do in a laboratory or observe on Earth," Kelsi Singer, a graduate student in earth and planetary sciences at Washington University in St Louis, 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."

Singer spotted the icy avalanches by studying images from the Cassini spacecraft, but the pictures don't give much clues about what's causing the massive slides.

The researchers think that it may be sheer speed that cuts the friction for the ice, in the same way that major faults can slip off each other during an earthquake – resulting in "localized frictional heating in [the] ice rubble".

"If you had some kind of quick movement, whether it was a landslide or the slip along a fault, the same kind of thing could happen," Singer says. ®

The paper was published in Nature Geoscience yesterday.

HP ProLiant Gen8: Integrated lifecycle automation

More from The Register

next story
ALIEN BODY FOUND ON MARS: Curiosity rover snaps extraterrestrial
And NASA kept evidence to itself for over a month
Malaysian Airlines flight MH17 claimed lives of HIV/AIDS cure scientists
Researchers, advocates, health workers among those on shot-down plane
Mwa-ha-ha-ha! Eccentric billionaire Musk gets his PRIVATE SPACEPORT
In the Lone Star State, perhaps appropriately enough
Diary note: Pluto's close-up is a year from … now!
New Horizons is less than a year from the dwarf planet
Forty-five years ago: FOOTPRINTS are FOUND ON MOON
NASA won't be back any time soon, though
NASA: ALIENS and NEW EARTHS will be ours inside 20 years
ETs, habitable planets will soon pop up with our new 'scopes
prev story

Whitepapers

Top three mobile application threats
Prevent sensitive data leakage over insecure channels or stolen mobile devices.
The Essential Guide to IT Transformation
ServiceNow discusses three IT transformations that can help CIO's automate IT services to transform IT and the enterprise.
Mobile application security vulnerability report
The alarming realities regarding the sheer number of applications vulnerable to attack, and the most common and easily addressable vulnerability errors.
How modern custom applications can spur business growth
Learn how to create, deploy and manage custom applications without consuming or expanding the need for scarce, expensive IT resources.
Consolidation: the foundation for IT and business transformation
In this whitepaper learn how effective consolidation of IT and business resources can enable multiple, meaningful business benefits.