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Seismic Activity May Mean Moon Is Not Dead Yet

Shallow graben that may have been formed in the past 50 million years.
Shallow graben that may have been formed in the past 50 million years.

The Lunar Reconnaissance Orbiter is casting doubts on the belief that the moon is a lifeless piece of rock.

New observations from the LRO show that tectonic activity may still be going on in the moon. That means that the core of the moon may still be cooling causing it to contract, which in turn causes wrinkles on the moon's surface. Previously, scientists believed the moon had cooled entirely and thought the last seismic activity happened about 1 billion years ago. But scientists estimate the graben — narrow, trench-like features — found by the LRO could have resulted from tectonic activity that happened 50 million years ago.

Discovery News reportsscientists telegraphed the news in a new paper in Nature Geoscience. They spoke to one of the lead authors:

"The graben the scientists detected, which reach up to about 1,640 feet (500 meters) wide and 1.1 miles (1.8 kilometers) long, appear relatively pristine. This suggests they formed recently — otherwise, they would be marred more often by craters from meteor impacts over time.

"'We think they're less than 50 million years old, but they could be 10 million years old, could be 1 million years old, could have happened 40 years ago,' [said study lead author Thomas Watters, a planetary scientist at the Smithsonian Institution in Washington.] 'The intriguing picture that's emerging of the moon is that there is recent geological activity going on.'"

"Moonquakes detected by seismic sensors installed during the Apollo missions support the notion of recent activity on the moon, researchers added. All in all, the moon's interior may still be hot."

Wired reports the reason scientists hadn't noticed seismic activity before is because major activity is long over. But recent images from the LRO "revealed smaller features that had escaped earlier notice."

In its press release, the scientists say the contractions of the moon may also be a clue that the moon did not form the way other planets did. That suggests that the moon did not completely melt in the early stages of its formation, instead, "observations support an alternative view that only the moon's exterior initially melted forming an ocean of molten rock."

NASA, by the way, put together this video of the kind of information the LRO will provide. It also provides some cool images of the moon:

Copyright 2021 NPR. To see more, visit https://www.npr.org.

Eyder Peralta
Eyder Peralta is NPR's East Africa correspondent based in Nairobi, Kenya.