It withers, like a raisin.
Our satellite cooled a long time ago and now, like a giant fossil, it is shrinking. This is the conclusion of the analysis of a series of images taken in 2010 by NASA’s Lunar Reconnaissance Probe (LRO), according to a study published yesterday in the journal Nature Geoscience .
Specifically, these images reveal thousands of cliffs, called thrust faults, on the Moon’s surface, which today may be causing a series of earthquakes, causing it to shake, and shrinking in size.
The Moon shakes from tectonic activity, not from asteroids
A team of researchers, including Nicholas Schmerr, an assistant professor of geology at the University of Maryland, designed a new algorithm to re-analyze seismic data from NASA’s Apollo missions in the 1960s and 1970s. Their analysis provided more accurate data on the rent of the epicenter of 28 moonquakes recorded from 1969 to 1977.
The team then overlaid this data on the LRO images of the thrust faults. Based on the proximity of the earthquakes to the thrust faults, the researchers found that at least eight of the earthquakes had occurred as a result of tectonic activity, the movement of the crustal plates, and not by asteroid impacts, such as it was believed until now.
Although Apollo’s instruments recorded its last earthquake in 1977, the researchers suggest that the moon is likely still experiencing earthquakes today.
“We realized that a series of earthquakes recorded in the Apollo mission data occurred very close to what the LRO images indicate,” according to Schmerr, noting that the LRO images also show physical evidence of geologically recent movements, such as landslides, falls and boulders. “It is very likely still active today. You don’t often see active tectonics anywhere other than Earth, so it ‘s very exciting to think that these faults can still produce lunar earthquakes . “
The Apollo mission, in search of lunar earthquakes
Astronauts placed five seismometers on the Moon during the Apollo 11, 12, 14, 15, and 16 missions. The remaining instruments recorded 28 shallow lunar earthquakes from 1969 to 1977. On Earth, the tremors would have been about 2 a magnitude. 5.
Using the revised location estimates from their new algorithms, the researchers found 28 shallow tremors were within 30 kilometers of the faults visible in the LRO images, close enough for the team to conclude that they caused the earthquakes. Schmerr led the effort to produce model-derived “shock maps” that predict where the strongest shock should occur, given the size of the thrust faults.
The researchers also found that six of the eight earthquakes occurred at the point where the Moon was farthest from Earth. This is where the additional stresses of Earth’s gravity place total stress on the lunar crust, making slippage along thrust faults more likely.
The moon wrinkles like a raisin
Just as a grape wrinkles when it becomes a raisin, the Moon also wrinkles when its interior cools, and it shrinks. Unlike our supple skin, the Moon is fragile, causing it to break inside. This breakage results in thrust failures, where a section of the crust is pushed onto an adjacent section. These faults resemble small stair-shaped cliffs, when viewed from the lunar surface.
The LRO has detected more than 3,500 faults on the moon since it began operating in 2009. Some of these images show landslides or rocks at the bottom of relatively bright patches on the slopes of the field. Due to the fact that they are slowly changing on the surface of the Earth, they are clearly exposed to an event such as a Moon earthquake.
Other images of LRO faults show fresh rocks tumbling down the slopes of their cliffs. Such tracks would be relatively fast, in geological terms, due to the constant shower of micrometeoroid impacts on the Moon. With nearly a decade of LRO images available, the team would like to see images of specific fault regions from different times to recent evidence of recent moonquakes.
“For me, these findings indicate that we have to go back to the Moon,” says Schmerr.
