According to a new research study, the Moon may be shrinking as it experiences lunar quakes, known as "moonquakes".
On Earth, tectonic activity, such as earthquakes and volcanism, results from shuffling of the crust's tectonic plates driven by the churning of the planet's molten interior.
John Keller of NASA's Goddard Space Flight Center said: "It's really remarkable to see how data from almost 50 years ago and from the LRO mission has been combined to advance our understanding of the Moon while suggesting where future missions intent on studying the Moon's interior processes should go". The scarps form when one section of the moon's crust (left-pointing arrows) is pushed up over an adjacent section (right-pointing arrows) as the moon's interior cools and shrinks.
"We found that a number of the quakes recorded in the Apollo data happened very close to the faults seen in the [NASA's Apollo and Lunar Reconnaissance Orbiter missions] LRO imagery", Nicholas Schmerr, an assistant professor of geology at the University of Maryland, said in a statement. "It's quite likely that the faults are still active today".
"Our analysis gives the first evidence that these faults are still active and likely producing moonquakes today as the Moon continues to gradually cool and shrink", Thomas Watters, senior scientist in the Center for Earth and Planetary Studies at the Smithsonian's National Air and Space Museum in Washington, said in the press release.
NASA said the Moon's scarps resemble "small stair-step shaped cliffs", which extend for up to a few miles at a times. Tectonic activity makes moonquakes a regular occurrence, according to a paper in Nature Geoscience. For example, the Apollo missions detected about 11,000 moonquakes happening about 500 to 680 miles (800 to 1100 kilometers) beneath the lunar surface.
The Apollo missions also detected about one moonquake per day resulting from space rocks hitting the lunar surface. Those missions even saw artificial moonquakes from the impacts of the spacecraft used to bring astronauts to the moon, Schmerr added.
Earth and the moon might be similar in the geological department: A new study suggests that the moon is shrinking and has active faults responsible for moonquakes on the lunar surface. To do so, the scientists relied on analytical techniques developed to interpret data from sparse networks of seismometers on Earth.
The researchers believe the quakes are still occurring on the moon. Some of these images show landslides or boulders at the bottom of relatively bright patches on the slopes of fault scarps or nearby terrain. This point, which is called apogee, is also the period during which Earth's gravity inflicts the most stress, or tidal pressure, on the Moon's structure.
"It's really remarkable to see how data from almost 50 years ago and from the LRO mission has been combined to advance our understanding of the moon while suggesting where future missions intent on studying the moon's interior processes should go", said Lunar Reconnaissance Orbiter (LRO) Project Scientist John Keller.
Far from being the serene world that we may imagine when we look up at the night sky, the moon is restless.
As the moon cools and gets smaller, its crust becomes brittle and breaks up: a bit like what happens to a grape as it dries out to become a raisin.
"For me, these findings emphasize that we need to go back to the moon". "It is also a testament to how much can be gained by human spaceflight to the surface of other worlds and underlines the incredible potential for future missions back to the moon and, hopefully someday, Mars".