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  • Gloria Hoffner

How to 'feel' a Moonquake

Science for Seniors FREE Tuesday activity - Space theme for the upcoming Moon Landing 50th anniversary. Did you know the moon experiences Moonquakes? This report published in USA Today 5/13/19 by journalist Doyle Rice:

Scientists Monday gave us the unsettling news that our favorite natural satellite is shrinking, according to a new study. The shrinking is also causing "moonquakes," which have only recently been detected.

But it's no cause for concern, said study co-author Nicholas Schmerr, a University of Maryland geologist, in an email to USA TODAY.

"As the moon cools, its overall size has contracted or decreased by about 100 meters over the past 4.5 billion years, which is why we say it is shrinking," he said. "This puts the crust under compression.

"If there's enough compressive stress, the crust can fail, producing earthquakes – or in this case moonquakes," he said.

Fortunately, the moon's mass isn’t changing, "and the radius change is small, so the effect on Earth is minuscule, and it won’t affect tides or make the moon disappear," Schmerr said.

To detect the quakes, researchers reviewed data gathered by Apollo astronauts back in the late 1960s and early 1970s, along with new information from NASA's Lunar Reconnaissance Orbiter (LRO). The LRO is an unmanned probe in orbit around the moon.

Experiment: How to 'feel' a moon quake.

Materials: Flat table, 5 pound weight and two resident volunteers.

Process: Have volunteers sit at opposite ends of the table and close their eyes. Drop the weight in the center of the table. Then at each end nearest a resident. Observe and let residents describe what they felt when the weight hit the table.

Result: The place where the weight strikes the table is simulating the epicenter of a Moonquake, the location on the surface of the moon above where a seismic event has happened in the Moon's crust. Usually this is the location of the strongest movement, as felt by volunteers in this experiment, and then as the shock wave from the impact moves through the crust the impact strength diminishes. This is similar to when you drop a pebble in the center of a pond and the ripples decrease as the shock reaches the shoreline. However, scientists have recently discovered some shock waves even several miles from the epicenter are stronger than at the epicenter.

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