Moon's Shrinking May Be Causing Moonquakes

This was presumably a result of the ground shaking, because they are also seen close to fault scarps - and have rolled or bounced down a slope.

As the moon's interior cools, it shrinks, which causes its hard surface to crack and form fault lines, according to research sponsored by NASA. Detectors laid down by Apollo astronauts revealed small shakes on the moon, but their causes weren't well understood. A paper describing the work, co-authored by Schmerr, was published in the journal Nature Geoscience on May 13, 2019.

By layering the seismic data over the LRO's map of thrust faults, the researchers found the quakes were likely the result of activity in the Moon's crust, rather than tremors caused by external forces such as asteroid impacts, or deep interior rumblings.

Astronauts have placed seismometers on the moon over a series of past missions. On Earth, the quakes would have ranged in magnitude from about 2 to 5.

The team discovered that of the 28 detected shallow quakes, eight are close to (within 30km of) fault scarps, suggesting these faults may indeed be active. "Such a young age raises the intriguing possibility that these thrust faults are now active", says Watters and colleagues in their paper.

What's more, most of the Moonquakes occurred during times of the month when the tidal stresses between the Moon and Earth were at their greatest, which would make those faults more likely to slip and thus cause a quake. This shrinkage creates "wrinkles" on the Moon's skin, except the rock isn't flexible.

The cliffs that form are called thrust faults. And it is going to take far more than $1.6 billion to develop and/or manufacture everything needed for the mission.

Analysis shows that these faults are relatively young, not older than about 50m years. Instead, any ongoing lunar geological resurfacing would be produced by the slow dissipation of heat from the Moon's core and the tidal stresses that Earth puts on Luna as it orbits. These faults are part of a vast, global network revealed in high resolution images collected by the LRO and have been estimated to be less than 50 million years old.

Earth's moon developed vast basins called "mare" billions of years ago, and for a long time, scientists have thought that these basins were dead. With almost a decade of LRO imagery already available and more on the way in the coming years, the team would like to compare pictures of specific fault regions from different times to look for fresh evidence of recent moonquakes. "This provides some very promising low-hanging fruit for science on a future mission to the moon".

Jim Bridenstine (left, facing camera), and NASA Johnson Space Center Director Mark Geyer (right, facing camera), participate in a media roundtable in front of the Orion test crew capsule at NASA's Johnson Space Center in Houston. A team of researchers have now reanalyzed the data along with detailed images captured by the Lunar Reconnaissance Orbiter, which was launched in 2009. The content of this article does not necessarily reflect the views of these organizations.

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