The Moon Is Shrinking, Wrinkling, Shaking And Cooling

Rodiano Bonacci
Dicembre 1, 2019

But a new analysis of Apollo-era data suggests these conclusions are inaccurate.

The mission of Beresheet, the first private lunar lander, came to a sudden end on April 11 during its descent to the lunar surface. While these seismometers have long since gone silent, they returned up to eight years of data while active. Although data was collected for less than a decade, it was enough to record what NASA describes as 28 "shallow moonquakes" over the period.

Of the 28 moonquakes measured, the team found at least eight were caused by true tectonic activity, with an equivalent quake magnitude of about 2 to 5. 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.

A new paper in Nature Geoscience discusses these findings, which could collectively demonstrate that the Moon is not, in fact, a geologically dead world. From an analysis of the timing of these eight events, we found that six occurred when the Moon was less than 15,000km from the apogee distance. "It's quite likely that the faults are still active today". And as it shrinks, the moon actively produces moonquakes along the faults. It isn't volcanic like Io or Venus (Venus is not known to be volcanically active at present, but the planet contains more volcanoes than any other location in the solar system). This won't be the only budget increase NASA proposes in the years ahead, as it only addresses the immediate need for new cash in 2020, but if Trump wants to go to the Moon he should know that it's going to cost taxpayers a pretty penny.

Beresheet hit the surface at a low angle of approach (8.4 degrees relative to the surface) and with a relatively low velocity and light mass compared to a typical meteoroid (space rock) that slams into the moon's surface, NASA officials noted.

"Our goal here is to build a program that gets us to the moon as soon as possible", Bridenstine told reporters on a telephone conference call late on Monday.

As a result, the moon has become about 150 feet (50 meters) "skinnier" over the past several hundred million years. Unlike the flexible skin on a grape, however, the moon's crust is brittle, causing it to break as the interior shrinks. Because the moon doesn't have plate tectonics like Earth, moonquakes are believed to be caused by the cooling of the lunar interior, as well as Earth's gravity.

Watters says that the quakes can be strong, around a five on the Richter scale, according to the NASA statement.

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.

"It's really remarkable to see how data from almost 50 years ago and from the [orbiter] 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 John Keller in a statement, study author and Lunar Reconnaissance Orbiter project scientist at NASA's Goddard Space Flight Center.

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