The moon is shrinking — and may be generating "moonquakes" as a result

The interior of the moon has been cooling and as a result, has gotten about 150 feet "skinnier " over the past several hundred million years — leading to a phenomenon known as "moonquakes," NASA data suggests.

Similar to a grape's skin when it shrinks into a raisin, the moon wrinkles as it gets smaller.  And as it gets "skinner," the moon actively generates moonquakes along the faults. When the moon's fragile crust breaks, it creates visible stair-step-like cliffs as parts of the crusts are pushed up and over one another. These faults, which are "high and extending for a few miles" on the surface, remain active and moving in response to the gradual reduction in size that the moon is undergoing.

"Some of these quakes can be fairly strong, around five on the Richter scale," said Thomas Watters, a senior scientist at the Smithsonian's National Air and Space Museum in Washington. The data reported was recorded by the seismometer that was placed on the moon during five Apollo missions, and NASA's Lunar Reconnaissance Orbiter captured 3,500 images.

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