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The moon slowly shrinks over time, causing crustal wrinkles and moon tremors, according to photos taken by NASA's Lunar Reconnaissance Orbiter.
Unlike the Earth, the moon does not have tectonic plates. Instead, while the moon 's interior has cooled over the past few hundred million years, the surface has become wrinkled as it shrinks. Unlike the supple skin of a grape that is reduced to grapes, the fragile crust of the moon breaks. This creates steep cliffs called thrust faults when part of the crust is pushed up and over another part close to the crust.
There are now thousands of cliffs scattered on the surface of the moon, a few miles long on average and several dozen meters high. Since 2009, the orbiter has photographed more than 3,500 of them. In 1972, Apollo 17 astronauts, Eugene Cernan and Harrison Schmitt, had to climb one of these cliffs, the Lee-Lincoln Fault, zigzagging against the lunar vehicle.
Today, the moon is "finer" at 50 meters because of this process. And as it narrows, the moon is actively producing moonshells along the faults. The researchers reanalyzed the seismic data they had obtained from the moon to compare them to images collected by the orbiter.
Data from seismometers placed on the moon during Apollo 11, 12, 14, 15 and 16 missions revealed 28 moonquakes recorded between 1969 and 1977. The researchers compared the location of the epicentres of these earthquakes with imaging. orbital faults. At least eight earthquakes are due to activity along the faults. This excludes the possibility of impacts of asteroids or rumblings from inside the moon.
This means that the Apollo seismometers recorded the narrowing of the moon, the researchers said. The study of Apollo seismic data and the analysis of more than 12,000 photos of the orbiter were published Monday in the newspaper Nature Geoscience.
"It's really remarkable to see how the data of almost 50 years and the [orbiter] The mission was combined to advance our understanding of the Moon while suggesting where should future missions go to study the inner processes of the Moon, "said John Keller in a statement, author of the study and researcher Lunar Reconnaissance Orbiter project at NASA's Goddard Space Flight Center.
Researchers believe that earthquakes still occur on the moon, which means it is actively changing.
"Our analysis shows for the first time that these flaws are still active and are likely to produce moon shifts today, as the Moon continues to cool and shrink gradually," said Thomas Watters, Senior Scientist. at the Smithsonian's Ground and Planetary Studies Center, National Air and Space. Museum in Washington. "Some of these earthquakes can be quite strong, around five on the Richter scale."
Some of the earthquakes also occurred at a location in the moon's orbit, farthest from the Earth, indicating that tidal stress caused by the gravity of the Earth could have contributed to the earthquake. degradation of the crust of the moon.
"We do not often see active tectonics elsewhere than on Earth, so it's very exciting to think that these faults can still produce moonshares," said Nicholas Schmerr in an article, author and professor, and assistant geologist at the University of Maryland. Schmerr designed the algorithm that analyzed the Apollo data again.
The researchers noted further evidence on landslide and boulder photos at the bottom of the bright plates, signaling recent activity. Over time, the lunar surface darkens due to inclement weather and radiation. The bright spots are therefore areas where recent activity has exposed areas on the lunar surface.
"For me, these results underscore the need to return to the moon," Schmerr said. "We learned a lot from the Apollo missions, but they only scratch the surface, and with a larger network of modern seismometers we could make tremendous progress in our understanding of the moon's geology." provides very promising results for science on a future mission on the moon ".
"The establishment of a new network of seismometers on the lunar surface should be a priority for the human exploration of the moon, both to learn more about the interior of the Moon and to determine the magnitude of the moonquakes on the hazards, "said Renee Weber, co-author of the study. and planetary seismologist at NASA's Marshall Space Flight Center, in a statement.
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