A handful of linear valleys called graben are being formed as the moon's crust stretches, breaks and drops down along two bounding faults, NASA reported Monday.
A handful of the graben systems have been found across the lunar surface, the agency said.
"We think the moon is in a general state of global contraction because of cooling of a still hot interior," Thomas Watters of the Center for Earth and Planetary Studies at the Smithsonian's National Air and Space Museum in Washington, said. "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."
Scientists say they believe this geologic activity occurred less than 50 million years ago, considered relatively recent compared to the moon's age of more than 4.5 billion years.
"This pulling apart tells us the moon is still active," said Richard Vondrak, LRO Project Scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. "LRO gives us a detailed look at that process."
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