According to NASA, the moon is shrinking.
It might not sound like much, but research shows the moon has gotten "about 150 feet skinnier over the last several hundred million years," according to a news release from the National Aeronautics and Space Administration.
Just as a grape wrinkles at it shrinks down to a raisin, the moon is wrinkling as it shrinks, NASA said.
Bob Bonadurer, director of the Daniel M. Soref Planetarium at the Milwaukee Public Museum, found the findings fascinating.
But he cautioned the shrinkage won't be visible to humans.
"We're talking 1 inch for 1 million years," Bonadurer said, laughing.
"But it's a cool discovery to know the moon, and to know there's something going on there," he added.
Because the moon's surface is hard and brittle, faults are formed as it shrinks.
That's leading to seismic activity that NASA has dubbed "moonquakes."
“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 Thomas Watters, senior scientist in the Center for Earth and Planetary Studies at the Smithsonian’s National Air and Space Museum in Washington.
“Some of these quakes can be fairly strong, around 5 on the Richter scale," Watters added.
Watters led a study that analyzed data from four seismometers previously placed on the moon by Apollo astronauts.
"I think it's very exciting that scientists are still looking at the moon and still using some of the instruments the astronauts left there." — Bob Bonadurer, director of the Daniel M. Soref Planetarium
Researchers calculated the pinpoint locations for previously detected quakes and found that eight of the 28 shallow moonquakes recorded between 1969 and 1977 "were within 30 kilometers (18.6 miles) of faults visible in lunar images."
"This is close enough to tentatively attribute the quakes to the faults, since modeling by the team shows that this is the distance over which strong shaking is expected to occur, given the size of these fault scarps," NASA researchers concluded.
"I think it's very exciting that scientists are still looking at the moon and still using some of the instruments the astronauts left there," Bonadurer said.
The moon isn’t the only thing in the solar system that's shrinking as it ages.
Mercury has very large thrust faults — up to about 600 miles long and more than a mile high, which indicate it shrank much more than the moon.
