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The moon is not only still tectonically active, but is shrinking, according to NASA, generating "moon tremors" as it slowly contracts. The new discoveries combine data from several Moon missions that took place nearly five decades ago with the LRO mission, the Lunar Reconnaissance Orbiter, which is currently mapping the surface of the Earth's satellite.
Four missions were placed on the Moon by the Apollo Missions 11, 12, 14, 15 and 16, the instruments working collectively between 1969 and 1977. Although the data were collected for less than ten years, it was sufficient to: record what NASA describes as 28 "shallow moonquakes" over the period. These earthquakes lasted from 2 to 5 on the Richter scale.
Although we know the active tectonics behind the formation of new lands on Earth, like the Krakatoa Archipelago, in the case of the Moon, it is a contraction, not a Expansion at stake. While its interior continues to cook, the Moon has shrunk more than 30 meters in diameter over the past one hundred million million years, NASA announced. This has a noticeable impact on its surface.
The fragile crust of the Moon contracts and breaks, forming what is called "flaws pushed" on the surface. Resembling small stair-shaped cliffs, these are parts of the rock where overlaps have been created. According to NASA, they usually measure several tens of meters but can extend for several kilometers.
Seismometer data have been stored for decades, but their combination with LRO mission mapping is new. Thomas Watters, Senior Researcher at the Center for Earth and Planetary Studies at the Smithsonian National Museum of Air and Space in Washington, DC, led a study of Apollo discoveries with a new algorithm to better understand identify the epicenter of each earthquake. He then compared these data with high-resolution images of the Moon from the orbiting spacecraft.
"We believe that it is very likely that these eight earthquakes were caused by faults that slipped under the effect of stress accumulation when the lunar crust was squeezed by contraction. tidal forces, "says Watters. always active on the tectonic plane. The team was able to isolate the specific seismic signatures of the moonquakes from other incidents causing earthquakes, such as the impact of meteorites.
The photos of LRO have added to this trust. With the help of images of more than 3,500 of these stair-shaped cliffs, called fault scarves, researchers were able to identify landslides or boulders nearby. Different levels of obscuration – due to the alteration of solar and space radiation – confirmed the relative age of each section.
"Other images of the LROC fault show traces of falling rocks, which would be predictable if the fault slipped and the resulting earthquake sent rocks down the slope of the cliff," suggests NASA. "These tracks are evidence of a recent earthquake because they should be erased fairly quickly, at geologic time scales, by the constant rain of micrometeoroid impacts on the moon. Traces of blocks near faults in the Schrödinger Basin have been attributed to recent block falls caused by earthquakes. "
The hope is now that new seismic measurements can be taken to strengthen the understanding of what is happening beneath the surface of the moon. A new human mission is expected to take place by 2024, with sustainable missions expected to begin in 2028. These experiences will help shape NASA's future human missions on Mars.
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