The gravitational relationship between Earth and the Moon is so strong that it regularly creates deformities in both bodies. Scientists have known about this for ages, but for the first time ever, NASA satellites have observed this phenomena firsthand.
In the illustration above, you can see how the gravitational pull creates a bulge on the lunar surface (right), otherwise known as a lunar body tide; it’s almost as if the moon got punched and swelled up.
For folks who live near the beach, seeing the effects of this gravitational tension in the form of tides happens everyday. The resulting gravity has a powerful effect because water moves so freely; but, the moon has no surface water, which results in a more visible distortion. The resulting distortion isn’t really all that big—about 20-inches—but it actually affects both the near side as well as the far side.
“The deformation of the moon due to Earth’s pull is very challenging to measure, but learning more about it gives us clues about the interior of the moon,” said Erwan Mazarico, a scientist working at NASA’s Goddard Space Flight Center.
NASA was able to witness this effect using its Lunar Reconnaissance Orbiter satellite, which is being used to more deeply study the moon, by measuring thousands of locations. Scientists then compared the height of each spot, giving them enough data to track the lunar tide. While the findings merely corroborate calculations researchers have made from the ground, they further our understanding about the moon’s interior.
As researchers have said before, the moon’s interior might be more complex than initially thought.