Rolling stones could mean Mars still rocks

Lisa Grossman

Rocks sometimes fall down slopes on Mars - but why? (Image: NASA/JPL/U of Arizona)

Mars's surface may shake with powerful quakes today, a new study suggests. If so, the planet may still be geologically active, which could be a boon to life.

Conventional wisdom holds that the Red Planet ceased all its internal rumblings and volcanic activity many millions of years ago. That's because at about half the size of the Earth, Mars would have radiated away its internal heat much more quickly than our own restless planet.

But a region called Cerberus Fossae, a system of faults and channels that cuts across relatively young lava flows, has gotten geologists excited that the planet's rock-n-roll days may not be behind it.

Images of the region from NASA's sharp-eyed HiRISE camera on the Mars Reconnaissance Orbiter spacecraft show boulders between 2 and 20 metres wide scattered within the faults' valley-like chasms, suggesting they rolled down there from the surface.

The boulders, plus earlier evidence that the faults are giving off heat that could be related to volcanic activity, made Gerald Roberts of the University of London and colleagues wonder if the region is still active and quaking. But Mars's boulders can also move when ice vaporises.

To tell the two scenarios apart, Roberts and colleagues compared the distribution of boulders on Mars to the way boulders fell after the 2009 earthquake in moutainous L'Aquila, Italy. In that quake, large boulders stayed close to the epicentre, while some smaller boulders rolled farther away. Vaporising ice, by contrast, should show no special distribution according to boulder size, the researchers say.

They found that the size and number of boulders decreased with distance from Cerberus Fossae. "This is consistent with the hypothesis that boulders had been mobilised by ground-shaking, and that the severity of the ground-shaking decreased away from the epicentres of marsquakes," Roberts said in a statement.

Because the lava fields the faults cross are just 2 million years old, the researchers think the quakes must be no older than that. Better still, the boulders left trails in the Martian dust that had not yet been swept away by wind. Tracks from the Mars rovers are known to be covered up within a few years, so the displaced rocks could have been shaken up even more recently.

If the faults are indeed active (hints of recent faults have been seen elsewhere on Mars), they might be driven by the subsurface movement of magma related to the nearby volcano Elysium Mons. That could be good news for the search for Martian life, since the energy from all that moving magma could melt ice, providing wet, life-friendly habitats, the researchers note.

Source: http://feeds.newscientist.com/c/749/f/10897/s/1cd45a40/l/0L0Snewscientist0N0Cblogs0Cshortsharpscience0C20A120C0A20Crolling0Estones0Ecould0Emean0Emars0Bhtml0DDCMP0FOTC0Erss0Gnsref0Fonline0Enews/story01.htm

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