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Better watch out, future lunar colonists. There are quakes up there

Apollo 17 landed in the middle of the Taurus-Littrow Valley. The astronauts drove their lunar rover up and over the cliff face of the Lee-Lincoln fault scarp that cuts across the valley.
Apollo 17 landed in the middle of the Taurus-Littrow Valley. The astronauts drove their lunar rover up and over the cliff face of the Lee-Lincoln fault scarp that cuts across the valley.(NASA/GSFC/Arizona State University)

In the future, someone on a moon base may look up from a computer screen and feel the rumblings of a moonquake. New research released this week may ensure that those rumblings are distant and faint, and the astronaut can get back to work.

A team of scientists, including a geology professor from Wheaton College, has found that the moon, rather than just being a dead rock, may be geologically alive.

“The moon is our closest neighbor,” professor Geoffrey Collins said on the Wheaton College news site. “It’s one of the places in the universe that we thought we understood the best, and part of what we thought we understood about the surface of the moon was that nothing has been happening there for a long time. That appears not to be true.”

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The research was published Monday in Nature Geoscience.

“Our analysis gives the first evidence that [faults on the moon] are still active and likely producing moonquakes today as the Moon continues to gradually cool and shrink,” said Thomas Watters, senior scientist at the Center for Earth and Planetary Studies at the Smithsonian’s National Air and Space Museum in Washington.

“Some of these quakes can be fairly strong, around five on the Richter scale,” Watters, lead author of the paper, said in a statement from NASA.

The fault scarp or cliff is like a stairstep in the lunar landscape
The fault scarp or cliff is like a stairstep in the lunar landscape(NASA/GSFC/Arizona State University/Smithsonian)

The research could help planners to keep future moon bases away from moonquake trouble, Collins said in a telephone interview.

“While these moonquakes that were detected were maybe small by California standards, they were still big enough that you’d have to worry about them if you were to build a lunar base next to one of those faults,” he said.

Scientists studied readings from seismometers placed on the moon’s surface during the Apollo 12, 14, 15, and 16 missions. They recorded 28 shallow moonquakes from 1969 to 1977, ranging from around 2 to 5 on the Richter scale, NASA said.

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They used a new algorithm designed to determine quake locations from a sparse seismic network and developed moonquake location estimates, NASA said.

“We have much better algorithms now than they did in the 1970s for determining where a quake occurs, even if you only have a few stations recording it,” Collins said on the Wheaton news site. “Advances in computing have made it possible to locate much more precisely where these shallow moonquakes were happening.”

The scientists found that eight of the 28 quakes were within 18.6 miles of “thrust faults” visible in lunar images, which, NASA said, was “close enough to attribute the quakes to the faults.”

The thrust faults are formed when one section of crust is pushed up over a neighboring part, as the moon shrinks, NASA said.

The analysis also found that six of the eight quakes happened when the moon was at or near its apogee, its farthest point from Earth in orbit. That would cause tidal stress from gravity, making fault slippage more likely.

Watters said a combination of the two forces was thus probably at play.

“We think it’s very likely that these eight quakes were produced by faults slipping as stress built up when the lunar crust was compressed by global contraction and tidal forces,” Watters said.

Collins did research on tidal forces on the moons of giant planets, such as Jupiter, and how they cause the buildup of geological stresses. His computer models showed the correlation between the time and location of the moonquakes and the gravitational influence of the Earth on the moon.

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Collins said one of the moons he studies is Jupiter’s Europa, which has a big ocean under an icy surface that is affected by the gravitational pull of a giant planet. “It’s just a more obvious process” there, he said.

On our moon, where there is no water, it’s “more subtle,” he said in the interview.

“It took us going out to look at the moons of Jupiter and Saturn to realize how important some of these tidal forces are,” Collins said. “Now we realize, after looking at other moons, that our own moon is undergoing the same forces.”

NASA noted that highly detailed images of the moon by the Lunar Reconnaissance Orbiter spacecraft showed landslides or boulders at the bottom of relatively bright patches on fault scarps, suggesting a recent moonquake had sent materials sliding down a cliff. Other images showed tracks from boulder falls, suggesting boulders had rolled down a cliff.

Anna Horleston, a planetary seismologist and member of the InSight mission on Mars — which recently detected its first marsquake — told The New York Times the study’s data look solid, but “it would be awesome to get more seismometers on the moon and to test this out properly.”

The new study comes as NASA plans to land the first man and the first woman at the south pole of the moon by 2024, in what it’s dubbed the Artemis project. Artemis was Apollo’s sister in Greek mythology.

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Material from Globe wire services was used in this report.