The Moon may be shrinking as it experiences lunar quakes, known as "moonquakes," according to an analysis of imagery captured by NASA’s Lunar Reconnaissance Orbiter (LRO) published Monday. It is also causing wrinkling on its surface. Researchers analyzed 28 moonquakes from 1969 to 1977 and came up with the startling revelation that moon Moon doesn’t have tectonic plates. Instead, its tectonic activity occurs as it slowly loses heat from when it was formed 4.5 billion years ago.
A survey of more than 12,000 images revealed that lunar basin Mare Frigoris near the Moon’s north pole—one of the many vast basins long assumed to be dead sites from a geological point of view—has been cracking and shifting. Since the moon’s crust is brittle, these forces cause its surface to break as the interior shrinks, resulting in so-called thrust faults, where one section of crust is pushed up over an adjacent section.
As a result, the Moon has become about 150 feet (50 metres) “skinnier” over the past several hundred million years.
“It’s quite likely that the faults are still active today,” said Nicholas Schmerr, an assistant professor of geology at the University of Maryland who co-authored the study.
“You don’t often get to see active tectonics anywhere but Earth, so it’s very exciting to think these faults may still be producing moonquakes."
The moonquakes were recorded by five seismometers that were placed on the Moon's surface during the Apollo 11, 12, 14, 15 and 16 missions. If they had been on Earth, the quakes would have registered between a 2 and a 5 on the Moment Magnitude scale, according to the researchers.
“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,” said Thomas Watters, lead author of the research paper, in the statement.