Earth rises above the lunar horizon in this image from NASA’s Apollo 17 spacecraft while in orbit during the Apollo program’s final lunar landing mission.
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A new study shows that spacecraft left by American astronauts on the moon can cause small tremors known as moonquakes.
Researchers have revealed a previously unknown form of seismic activity on the Moon for the first time by analyzing Apollo-era data using modern algorithms.
The report indicates that the huge temperature fluctuations that occur on the Moon could cause human-made structures to expand and contract in a way that produces these vibrations. The moon’s surface is an extreme environment, fluctuating between -208 degrees Fahrenheit (minus 133 degrees Celsius) in the dark and 250 degrees Fahrenheit (121 degrees Celsius) in direct sun, according to a press release about the study.
In fact, the entire surface of the Moon expands and contracts in cold and heat, as indicated by the study published September 5 in the journal Journal of Geophysical Research: Planets. However, scientists were able to use a form of artificial intelligence To get an accurate understanding of the Apollo-era data so they could identify light tremors emanating from the Apollo 17 lunar lander that was sitting a few hundred meters from the lunar seismic recording instruments, one of the researchers said. summary For the study conducted by researchers from institutions including the California Institute of Technology and NASA. (NASA provided funding for the study.)
The analysis provides new insights into how the Moon responds to its surroundings and what could affect its seismic activities. The tremors were not dangerous and would likely have been imperceptible to humans standing on the moon’s surface.
Understanding lunar quakes could be essential for future exploration if NASA and its partners build a permanent site on the moon — a goal, experts said. Artemis, the agency’s lunar exploration program.
“How strong do we need to build our structures, and what other risks do we need to mitigate?” Dr. Angela Marusiak, assistant research professor at the University of Arizona’s Lunar and Planetary Laboratory, said about the questions this type of data analysis can help answer. Marusiak was not directly involved in the study, although she was in contact with the authors as a fellow expert in lunar seismology.
Marusiak noted that every Apollo mission carried instruments to detect lunar earthquakes. But no Apollo 17 missionThat probe, launched in 1972, was noteworthy because it left behind an array of seismometers capable of detecting thermal lunarquakes — or tremors caused by the intense heating and cooling of the moon’s surface.
“Thousands of these signals were recorded during an 8-month period from 1976 to 1977 on four seismometers deployed during the Apollo 17 Lunar Seismic Characterization Experiment, but poor data quality makes analysis difficult,” the researchers wrote. “We have developed algorithms to precisely time the arrival of waves, measure the strength of the seismic signal, and find the direction of the source of the lunar earthquake.”
Scientists revisited the data for the first time in decades. The new analysis allowed the research team to conclude that a particular type of lunar earthquake — called an impulsive thermal earthquake — came not from natural sources, but from the heating and cooling of the nearby spacecraft.
“Every lunar morning, when the sun hits the lander, it begins to appear,” study co-author Allen Husker, a research professor of geophysics at Caltech, said in a statement. “Every five to six minutes (there was) another one, over the course of five to seven Earth hours. They were incredibly regular and frequent.”
These tremors They differ from another type of moonquake, called thermonuclear moonquake, which is likely caused by the Earth’s natural reaction to exposure to sunlight, according to the study.
The researchers said they hope future lunar missions will provide a more comprehensive picture of this phenomenon.
Aside from thermal earthquakes, moonquakes are also known to have occurred Deep and shallow tremors As well as activity believed to be caused by meteorite strikes.
It is important to note the main difference between the Moon and the Earth: on the surface of the Moon, there is no shift Tectonic plates Which could cause catastrophic events. But the Moon has an active inner life, and — like Earth — certain types of seismic events can occur at any time or place on the Moon’s surface, Marusiak said.
Marusiak was keen on India’s lunar lander, Chandrayaan-3, which included a seismometer. Indeed, the Indian Space Research Organisation He confirmed it The instrument was able to detect a lunar earthquake. (ISRO researchers have not yet released comprehensive data on the recording or proposed a proposed cause for the event.)
The Chandrayaan-3 instrument, which recorded activity near the moon’s south pole for the first time, was shut down in early September. Researchers will try to wake the spacecraft to collect more data on September 22, when the Chandrayaan landing site enters sunlight again.
“I hope that through the Artemis program, seismometers will continue to be included because they are really essential to understanding what is happening, not just at the surface, but even deeper in the regolith,” Marusiak said.
But scientists are excited that digging into Apollo-era data using modern technology could yield surprising new results.
“It’s important that we know as much as we can about the existing data so that we can design experiments and missions to answer the right questions,” Hosker said. “The Moon is the only planetary body other than the Earth that has more than one seismometer at the same time. It gives us the only opportunity to study another body accurately.
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