13 May 2019
Cracks in the lunar surface suggest the moon is still tectonically active NASA/GSFC/Arizona State University/SmithsonianBy Kelly OakesThe first humans to settle on the moon might need quake-proof housing. Moonquakes recorded during the Apollo missions have been linked to specific cracks on the lunar surface, suggesting that the moon is still tectonically active today.
Thomas Watters of the Smithsonian Institution in Washington DC and his colleagues re-examined data collected between 1969 and 1977 from seismometers placed by astronauts at four Apollo landing sites.
The Apollo sensors measured 28 shallow moonquakes, with some reaching magnitude 5.5, which on Earth is enough to cause slight damage to buildings. Previous efforts to pin down their epicentres were only rough estimates, potentially out by as much as 90 kilometres.
Using a new algorithm designed to make sense of the limited seismic data, Watters and his colleagues were able to do much better. When they compared their epicentres to pictures of the moon’s surface taken by NASA’s Lunar Reconnaissance Orbiter, they found that eight of the epicentres fell within 30km of geological features known as lobate scarps.
These cliff-like features are typically tens of metres tall and form along thrust faults, where the moon’s crust has broken as it has contracted, and one side has been pushed up over the other.
They are the best way to search for recent activity on the moon, says Amanda Nahm of the Arctic Planetary Science Institute, because they’re believed to be at most 50 million years old – relatively young, geologically speaking.
The researchers also saw disturbances in the lunar soil and boulder movements in these areas. All of this “strongly argues for a recently – as in present day – tectonically active moon,” says Nahm.
The findings mean future astronauts should take moonquakes seriously. “We know that there are thousands of these young faults on the moon,” says Watters. “If we’re correct and these are active faults, they are something that we need to be aware of when we go back to the moon.”
Journal reference: Nature Geoscience, DOI: 10.1038/s41561-019-0362-2
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