Thursday, February 23, 2012

Recent geological activity on the Moon and Mars

Marsquakes on the red planet and crustal make bigger on the Moon show that planet Earth is not the only geographically dynamic body in our local Solar System neighbourhood.

New images from NASA’s Lunar Reconnaissance Orbiter (LRO) suggest that the Moon’s crust was being stretched as recently as 50 million years ago. Tiny valleys many times longer than they are wide were formed as the crust pulled apart, dropping down between two bounding fault lines. Known by geologists as graben, these features have been identified in a number of locations across the Moon, but the finding contradicts the signs of global contraction identified by LRO in 2010. By examining scarps – lobe-shaped cliffs – planetary scientists then estimated that the Moon had shrunk by about 100 metres since it formed over 4.5 billion years ago (read our story The Moon is shrinking, here).

“We think the Moon is in a general state of global contraction because of cooling of a still hot interior,” says Thomas Watters of the Center for Earth and Planetary Studies at the Smithsonian’s National Air and Space Museum in Washington. “The graben tell us forces acting to shrink the Moon were overcome in places by forces acting to pull it apart. This means the contractional forces shrinking the Moon cannot be large, or the small graben might never form.”

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