It is well-known the Moon’s gravity is responsible for the tides we see on Earth’s ocean and lakes. What most people don’t know is that Earth has the same effect on the Moon.
While astronomers have known about the opposing effect for some time now, using observations that were recorded by the NASA Lunar Reconnaissance Orbiter (LRO), researchers are now able to confirm the pull on the Moon’s surface from Earth’s gravity can open faults on the surface of the Moon.
“We know the close relationship between the Earth and the Moon goes back to their origins, but what a surprise [it was] to find the Earth is still helping to shape the Moon.”
Over the last six years, around 3000 cracks have been discovered with most being less than 6.2 miles (10 km) long. As the moon’s liquid core is cooling and slowly solidifying, these cracks will appear naturally.
Researchers expected a random distribution of these cracks, but what they found was Earth was influencing them.
“There is a pattern in the orientations of the thousands of faults, and it suggests something else is influencing their formation, something that’s also acting on a global scale, and that something is the Earth’s gravitational pull,” Watters said in a press release.
As Earth moves toward and then away from the Moon, it creates “fault scarps” on the surface of the Moon in recognizable patterns. Earth’s gravitation pull creates stresses on the Moon’s surface similar to how the Moon affects Earth’s tide. It has taken five years to have enough data to see the pattern emerge.
“The discovery of so many previously undetected tectonic features as our LROC high-resolution image coverage continues to grow is truly remarkable,” Mark Robinson, co-author and principal investigator of LROC, said in a statement.
“Early on in the mission, we suspected that tidal forces played a role in the formation of tectonic features, but we just did not have enough coverage to make any conclusive statements,” Robinson added.
Watters believes the faults are young and still forming, and suggests — if the faults are active — shallow “moon-quakes” could be occurring along them. The moon-quakes would occur mainly when the Moon is furthest away from the Earth.
Next time you find yourself gazing up at the Moon, think about how our green and blue planet is moving the rocks on the Moon.