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The moon shrinks and shakes, says Nasa

The moon shrinks – and shakes as it is, according to new NASA data.

Over the past decade, scientists have found that while the inside of the moon cooled, it shrunk like a raisin. That left it reefing with cliffs called "thrust errors", marked all over the surface.

Now a new analysis, using data from NASA missions, suggests that the Moon can still shrink today. As it is, it experiences lunar quakes along those thrust errors, with the planet shaking past those cliffs.

Scientists compare the process with the way a grape gradually wrinkles, and adds lines as it cools and shrinks. But unlike the skin of a grape, the crust around the moon cannot stretch and is instead brittle, causing it to break when shrinking occurs.

The errors occur when the crust moves and part of the crust is pushed up over another. They form unusual-looking rocks that can be seen from the surface, long and miles long.

The new research was made possible by the creation of an algorithm that processed seismic data taken in the 1960s and 1970s. It helped shed new light on those moonquakes, including allowing a better understanding of where they actually come from.

Once that location data was generated, it could be superimposed on the images of the jolting errors made in a 2010 study with images from NASA's Lunar Reconnaissance Orbiter.

They compared the two and found that at least eight of the rumblings stemmed from movements of plates below the surface of the moon, not from asteroid effects or other explanations. That helped confirm that the Moon is still experiencing real tectonic activity, according to the new article published in Nature Geoscience.

The instruments that Apollo astronauts left behind in the past ended their work in 1977. But scientists think that shaking and shrinking continues to this day, with images appearing to be evidence of recent movements, such as boulders and landslides that recently seem to have fallen. about.

One of the thousands of errors found on the moon nasa & # 39; s Lunar Reconnaissance Orbiter (LROC NAC frame M190844037LR; NASA /GSFC/ Arizona State University / Smithsonian)

"We discovered that some of the earthquakes in the Apollo data were very close to the errors in the LRO images," said Nicholas Schmerr, assistant professor of geology at the University of Maryland, in a statement.

"It is quite likely that the errors are still active, you will not often see active tectonics everywhere except the Earth, so it is very exciting to think that these errors can still produce moonquakes."

The seismic data comes from instruments that astronauts dropped on the surface during Apollo missions. The only one who left Apollo 11 died after a few weeks – but the rest kept measuring, and eventually recorded 28 different, shallow moonquakes between 1969 and 1977.

Of those earthquakes, eight were picked up in the vicinity of the errors seen in images of the moon's surface. That led them to the conclusion that the two were connected.

What's more, most shakes took place when the moon was farthest from the earth at the point of its orbit. That happens because the stress of the earth's gravity disturbs the crust.

"We think it is very likely that these eight quakes were caused by errors slipping when the tension was built up when the lunar bottom was compressed by global contraction and tidal forces, indicating that the Apollo seismometers registered the shrinking moon and the moon still is always tectonically active, "said Thomas Watters, lead author of the research paper and senior scientist at the Smithsonian Institution's Center for Earth and Planetary Studies in Washington.

Scientists now hope to return to the moon and learn more about what happens to the moon. The Trump government has ordered Nasa to return as soon as possible and hopes to get astronauts back on the surface within five years.

"For me, these findings emphasize that we have to go back to the moon," Schmerr said. "We have learned a lot from the Apollo missions, but they really only scratched the surface. With a larger network of modern seismometers, we were able to make enormous progress in our understanding of the geology of the moon.

"This yields a number of promising, low-hanging fruits for science about a future mission to the moon."

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