The shrinking has occurred as the interior of the moon has cooled, NASA said in a Monday press release. It's become about 150 feet skinnier over the past several hundred million years.
The shrinking has caused the crust to form "thrust faults" on the moon's surface, which resemble stair-step-shaped cliffs.
NASA tweeted a video that shows fault lines on the moon's surface.
You've heard of earthquakes. But what about moonquakes? Like a wrinkled grape drying out to a raisin, the Moon is shrinking as its interior cools causing wrinkles or faults to form on its brittle surface. When enough stress builds, it releases the quakes: https://t.co/H3ixgywT1p pic.twitter.com/OxNrVveAQk
— NASA (@NASA) May 13, 2019
“Our analysis gives the first evidence that these faults are still active and likely producing moonquakes today as the moon continues to gradually cool and shrink,” said NASA scientist Thomas Watters. “Some of these quakes can be fairly strong, around 5 on the Richter scale.”
Scientists were able to draw this conclusion based on data from four seismometers placed on the moon’s surface during the Apollo missions, NASA said. Other evidence came from photos of the moon’s surface taken by NASA’s Lunar Reconnaissance Orbiter spacecraft.
“It’s really remarkable to see how data from nearly 50 years ago and from the LRO (Lunar Reconnaissance Orbiter) mission has been combined to advance our understanding of the Moon while suggesting where future missions intent on studying the moon’s interior processes should go,” said NASA scientist John Keller.
The findings were published in the journal Nature Geoscience.
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