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The Moon is cooling, shrinking and has moonquakes, Nasa finds

14 May 2019

Similar to how a grape shrivels up as it shrinks into a raisin, the moon obtains wrinkles as it decreases in size. This shrinking is causing wrinkles in the crust of the moon, and it is, in turn, resulting in the rise of seismic activities. When portions of the crust split they move over neighbouring sections of the surface, triggering earthquakes, or rather, moonquakes.

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. Each of the magnitudes of the 28 moonquakes would register as somewhere between two and five on the Richter scale if they had been carried out on Earth.

This work was supported by NASA's Lunar Reconnaissance Orbiter Project and the Natural Sciences and Engineering Research Council of Canada.

There are now thousands of cliffs scattered across the moon's surface, averaging a few miles long and tens of yards high.

USA astronauts placed seismometers on the lunar surface during the Apollo 11, 12, 14, 15 and 16 missions, recording 28 shallow quakes up to nearly 5 magnitude, which is moderate strength.

It is measured on a machine called a seismograph.

There have been a range of theories about what causes quakes, including meteorite collisions or gravitational forces exerted by the Earth and sun.

"It's really remarkable to see how data from almost 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.

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.

The researchers found a less than four percent chance the tremors erupted near the faults as a pure coincidence. 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 instruments placed by NASA's Apollo missions in the 1960s and '70s.

NASA posted a video on Twitter showing fault lines on the moon's surface. Researchers suggested these faults were evidence of lunar tectonics, although it was unclear how recent this activity was.

The moon is not the solar system's only object shrinking with age.

The LRO has imaged more than 3,500 fault scarps on the moon since it began operation in 2009. Since rocky worlds expand when they heat up and contract as they cool, Mercury's large faults reveal that is was likely hot enough to be completely molten after its formation.

NASA will send the first woman, and next man, to the Moon by 2024. They were first discovered more than 50 years ago by the Apollo astronauts. "We learned a lot from the Apollo missions, but they really only scratched the surface".

The Moon is cooling, shrinking and has moonquakes, Nasa finds