Lee Lincoln Scarp at the Apollo 17 landing site
The moon is shrinking — much like the way a grape shrivels into a raisin — and that may be causing it to have “moonquakes,” according to NASA.
“The moon is shrinking as its interior cools, getting more than about 150 feet (50 meters) skinnier over the last several hundred million years,” a May 13 NASA news release says. “Just as a grape wrinkles as it shrinks down to a raisin, the moon gets wrinkles as it shrinks.
“Unlike the flexible skin on a grape, the moon’s surface crust is brittle, so it breaks as the moon shrinks, forming ‘thrust faults’ where one section of crust is pushed up over a neighboring part,” NASA continued.
NASA just got the evidence that confirms “these faults are still active and likely producing moonquakes today as the Moon continues to gradually cool and shrink,” said senior scientist Thomas Watters, with the Center for Earth and Planetary Studies at the Smithsonian’s National Air and Space Museum, according to the release.
Watters said some of the quakes “can be fairly strong” — as high as a 5 on the Richter scale.
For comparison, a 2.5 to 5.5 magnitude earthquake is “often felt, but only causes minor damage,” according to the UPSeis program with Michigan Technological University. A 5.5 to 6.0 magnitude quake can cause “slight damage to buildings and other structures.”
The quakes on the moon were recorded after astronauts placed seismometers — the instruments that measure quakes — during the Apollo 11, 12, 14, 15, and 16 missions, NASA said.
“The Apollo 11 seismometer operated only for three weeks, but the four remaining recorded 28 shallow moonquakes – the type expected to be produced by these faults – from 1969 to 1977,” the release says.
Those “moonquakes” ranged from a magnitude to 2 to 5, according to NASA.
“It’s really remarkable to see how data from nearly 50 years ago and from the LRO 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 Lunar Reconnaissance Orbiter (LRO) Project Scientist John Keller.
The Lunar Reconnaissance Orbiter first helped NASA learn that the moon was shrinking in 2010, the agency reported at the time.
“Newly discovered cliffs in the lunar crust indicate the moon shrank globally in the geologically recent past and might still be shrinking today, according to a team analyzing new images from LRO spacecraft,” NASA said at the time. ”The results provide important clues to the moon’s recent geologic and tectonic evolution.”
NASA says the moon isn’t the only part of our solar system that is “shrinking with age,” as planet Mercury has shrank more than the moon has.