Like a Raisin: Study Finds Earth’s Shrinking Moon is Causing Quakes

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Washington-The Moon is steadily shrinking, causing wrinkling on its surface and quakes, according to an analysis of imagery captured by NASA's Lunar Reconnaissance Orbiter (LRO) published Monday.

The study appears in the journal Nature Geoscience.

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.

The budget increase is on top of the initial $US21 billion ($30.19 billion) budget request from NASA to accelerate the return to the lunar surface.

"Just as a grape wrinkles as it shrinks down to a raisin, the Moon gets wrinkles as it shrinks", say the team of NASA scientists. Another $1 billion will be used to build human lunar landing systems "three years earlier than previously envisioned to bring humans to the Moon's surface by 2024", the budget amendment stated. Meteor strikes, like those that caused the Moon's most distinctive features, still rain down today, so astronomers couldn't be sure whether the Moon was shaking itself, or being shaken by external forces.

These faults are also "likely producing moonquakes" that can be as strong as a magnitude-5 quake on the Richter scale, NASA cited Thomas Watters, a senior scientist at the Smithsonian's National Air and Space Museum, as saying.

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The New York Times' Robin George Andrews reports that there were explanations for numerous shakes. Meteorite collisions caused some, others were attributed to Earth's gravitational pull and others were caused by huge 500-degree temperature changes on the moon when night turns to day.

These faults push one part of the lunar crust up and over the adjoining part, said University of Maryland geologist and study co-author Nicholas Schmerr.

"And if we look at the history of moon landings, it was test pilots from the 1960s and 1970s, fighter pilots, and there were no opportunities for women back then". This point, which is called apogee, is also the period during which Earth's gravity inflicts the most stress, or tidal pressure, on the Moon's structure. Scientists believe that due to this, the Moon has shrunk about 150 feet during the last millions years. The valley was explored in 1972 by the Apollo 17 mission astronauts Eugene Cernan and Harrison Schmitt. Boulder fields, patches of relatively high bright soil or regolith, are found on the scarp face and back scarp terrain (high side of the scarp, right-pointing arrows).

The relative proximity of the quakes to the faults suggest that they were triggered by geological activity rather than asteroid impacts or tremors from much deeper within the rocky body.

NASA has flip-flopped between the moon and Mars, a victim of changing presidential administrations. “The connection between the location and timing of shallow moonquakes and known young faults is further evidence that our moon is a dynamic world.”.

This illustration shows NASA's Space Launch System (SLS) in the Block 1 cargo configuration.