Space

Shrinking Moon may be experiencing powerful quakes to this day

Shrinking Moon may be experien...
Earth and the Moon as shot by Expedition 10 crewmembers aboard the International Space Station in 2017
Earth and the Moon as shot by Expedition 10 crewmembers aboard the International Space Station in 2017
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Artist's impression of NASA's Lunar Reconnaissance Orbiter observing Earth's moon
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Artist's impression of NASA's Lunar Reconnaissance Orbiter observing Earth's moon
An enormous mosaic of the Moon stitched together from 15,000 Wide Angle Camera images taken by the Lunar Reconnaissance Orbiter
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An enormous mosaic of the Moon stitched together from 15,000 Wide Angle Camera images taken by the Lunar Reconnaissance Orbiter
LRO image displaying a prominent thrust fault
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LRO image displaying a prominent thrust fault
Earth and the Moon as shot by Expedition 10 crewmembers aboard the International Space Station in 2017
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Earth and the Moon as shot by Expedition 10 crewmembers aboard the International Space Station in 2017

Earth's closest natural satellite could be producing powerful moonquakes as it cools and shrinks, according to a newly-published study. The scientists behind the research analyzed data from instruments placed by astronauts who visited the Moon's surface in the Apollo-era, as well as more recent data collected by NASA's Lunar Reconnaissance Orbiter (LRO).

A total of five seismometers were placed on the Moon's surface by crewmembers of Apollo 11, 12, 14, 15 and 16. The instruments successfully detected 28 moonquakes that were likely caused by friction at tectonic faults before they were decommissioned in 1977.

The moonquakes detected in the 1960s and 70s shook the lunar surface with power the equivalent to magnitude two to five quakes back on Earth.

The team of scientists behind the new paper developed an algorithm that allowed them to accurately pinpoint the epicenters of these moonquakes. The refined Apollo-era location data was then overlaid on LRO imagery.

Eight moonquakes were discovered to have epicenters within 19 miles (31 km) of geological formations called thrust faults. These dramatic features, which are similar in appearance to cliffs found on Earth, can be miles long and tens of feet high.

Thrust faults are created when the Moon's interior cools, forcing the barren world to shrink. As it contracts, the fragile crust breaks, and parts of it are forced up and over neighboring sections. Some 3,500 such faults have been discovered by the LRO to date.

LRO image displaying a prominent thrust fault
LRO image displaying a prominent thrust fault

The relative proximity of the quakes to the faults suggest that they were triggered by geological activity rather than asteroid impacts or tremors from much deeper within the rocky body.

Of the eight moonquakes that occurred close to visible thrust faults in the LRO data, six took place when the Moon was at its most distant orbital point relative to the Earth. 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.

"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, indicating that the Apollo seismometers recorded the shrinking moon and the moon is still tectonically active," comments Thomas Watters, lead author of the new paper, and senior scientist in the Center for Earth and Planetary Studies at the Smithsonian Institution in Washington.

The LRO images also revealed surface features that support the theory that the Moon continues to be active. For example, bright patches of ground have been observed near faults, which appear to be patches of lunar regolith that have yet to be darkened by weathering and radiation.

Similarly, tracks are apparent on slopes where boulders have been dislodged from perches on higher ground. This again suggests recent activity, as these trails would be quickly erased by micrometeoroid impacts.

"For me, these findings emphasize that we need to go back to the Moon," said Nicholas Schmerr, an assistant professor of geology at the University of Maryland and co-author of the paper. "We learned a lot from the Apollo missions, but they really only scratched the surface. With a larger network of modern seismometers, we could make huge strides in our understanding of the Moon's geology. This provides some very promising low-hanging fruit for science on a future mission to the Moon."

The study has been published in the journal Nature Geoscience.

Source: University of Maryland

5 comments
Nobody
Since the same side of the moon always faces the earth I would think that the force of gravity would be stronger when it is at perigee rather than apogee. The pull of the sun could also add to the tidal effect.
Bob Stuart
Interesting, but the space weenies have used up more than their share of resources already, and particularly trashed the ozone with the solid rockets on the shuttle. Care for Earth first.
Wolf0579
"Space Weenies" are going to be the Human Race's salvation, as humans refuse to control their own numbers and start choking in their own waste products and waste heat. Don't even give me the mother earth crap... there is no way we pitiful humans could ever have serious lasting effects on the planet... it's continually recycling it's surface under the mantle at the subduction zones and belching out new stuff at the mid ocean ridges and else where. It's the biosphere that we're mucking up... the bit we need to live with. Either "space weenies" will deliver the wealth of the asteroids to us, or they will give us the escape hatch from the ruined biosphere of earth. Perhaps one will enable the other. One thing is certain, Mr. Bob Stuart, if you have offspring, they or their offspring will benefit greatly from the existence of the "space weenies".
EZ
Maybe all the powerful forces on earth can have their war on another planet. That could be one benefit of travelling to another rock. Designate that planet as the "Battle Field" rock. At least in that way, earth might have a chance to be saved.
ProfessorWhat
... . . . but the moon isn't a satellite, it's a binary planet system with the earth exactly because it orbits around the moon as well, so.