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Earthquakes shrink the moon like a raisin

Washington. The moon can still be tectically active today. This is indicated by a new evaluation of moonquakes from the era of "Apollo" missions. Eight of the 28 registered earthquakes have occurred near geologically young fracture zones, the team of analysts reported to Thomas Watters of the Smithsonian Institution in Washington in the journal Nature Geoscience.

When the moon has cooled after its formation, it is contracted like a raisin, forming from a dehydrating grape. The surface of the moon, which is not as elastic as the skin of the berry, has been broken several times and has formed thousands of cliffs. About ten years ago, the Lunar Reconnaissance Orbiter (LRO) probe of the American space agency Nasa discovered geologically relatively young such fractures. However, it was unclear how young this very tectonic activity is.

Still active today

The astronauts of the manned "Apollo" missions 12, 14, 15 and 16 had left four seismometers on the moon to record the activity. In the years 1969 to 1977, the instruments registered 28 moonquakes, which could be caused by asteroid effects, among other things. The data has now been re-evaluated.

The epicenter of eight quakes was therefore no more than 30 kilometers away from young fracture zones. Researchers think it is highly likely that they were caused by fractures that slipped after the tension in the lunar floor had increased due to worldwide contraction and tidal forces. Although the seismometers have been switched off since 1977. However, geologically this is not a significant time. It is likely that the fault zones are still active today.

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