Earth’s moon is shrinking and quaking, study says

The moon is slowly shrinking over time, which is causing wrinkles in its crust and moonquakes, according to photos captured by NASA's Lunar Reconnaissance Orbiter.

"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", Thomas Watters, a senior scientist from the Center for Earth and Planetary Studies said.

Lunar tectonic activity likely arises because the moon is continuing to shrivel like a raisin as its interior cools and shrinks, the researchers said. Unlike the flexible skin on a grape, however, the moon's crust is brittle, causing it to break as the interior shrinks.

The ultra-HD image is 9000px by 9000px.

This results in faults on the surface where one section of crust is pushed up over an adjacent section.

The scarps tend to be around 10yds high and a few miles long - making them resemble a giant stairway on the lunar surface.

In 1972, Apollo 17 astronauts Eugene Cernan and Harrison Schmitt had to ascend one of these cliffs, the Lee-Lincoln fault scarp, by zig-zagging the lunar rover over it.

"We think it's very likely that these eight quakes were produced by faults slipping as stress built up when the lunar crust was compressed by global contraction and tidal forces, indicating that the Apollo seismometers recorded the shrinking Moon and the Moon is still tectonically active", Watters explained.

"We found that a number of the quakes recorded in the Apollo data happened very close to the faults seen in the [NASA's Apollo and Lunar Reconnaissance Orbiter missions] LRO imagery", Nicholas Schmerr, an assistant professor of geology at the University of Maryland, said in a statement.

A total of five seismometers were placed on the Moon's surface by crewmembers of Apollo 11, 12, 14, 15 and 16.

From the data analysed and algorithms used, researchers were able to determine eight of the 28 shallow quakes recorded were within 30 kilometres of faults and were visible in lunar images. Some of these shallow quakes might in theory result from activity on lunar faults, but the locations and depths of the sources of these quakes were uncertain.

For the study, scientists studied 28 moonquakes from 1969 to 1977, and hypothesized that eight of these moonquakes derived from "true tectonic activity - the movement of crustal plates", instead of rumblings inside the celestial satellite or asteroid impacts, Fox News reported.

This means that the Apollo seismometers recorded the moon shrinking, the researchers said.

These incredible findings were published today (May 13) in the journal Nature Geosciences.

"It's really remarkable to see how data from almost 50 years ago and from the [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 John Keller in a statement, study author and Lunar Reconnaissance Orbiter project scientist at NASA's Goddard Space Flight Center. Seven quakes within about 37 miles (60 km) of these faults happened when the moon was at the farthest point in its orbit from Earth and certain parts of the moon are experiencing the greatest amount of stress from Earth's gravitational pull.

The research also sheds some light on the moon's internal composition. For example, bright patches of ground have been observed near faults, which appear to be patches of lunar regolith that have yet to be darkened by weathering and radiation.

"It is truly unbelievable that the datasets collected by the astronauts so many years ago are still yielding new scientific findings about our moon", Schmerr said.