How Did the Moon Get Its Shape?

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Source:  By , EOS—publication of AGU

Excerpts: Scientists find a solution to a 200-year-old problem: syncing the prominent bulges on the Moon with our natural satellite's origins. Scientists have known for hundreds of years that the Moon’s rotational and tidal bulges are much larger than expected. The deformation is thought to be a remnant from when the Moon orbited much closer to Earth than it does today. The problem is, the bulges we see require an unusual eccentric orbit—one that scientists do not think the Moon ever had. Keane and Matsuyama solved this problem by discovering a new component to the Moon’s global figure.
The Moon is not perfectly spherical because strong forces pull it in different directions. There are two main forces: bulging at the equator due to lunar rotation and bulging on the nearside and farside due to tidal forces between the Earth and the Moon. The observed lunar deformation is much larger than scientists would expect, given the Moon’s current orbit and rotation rate. Scientists believe that this extra deformation arises because the Moon “froze” its shape billions of years ago when it orbited closer to Earth and thus had much larger forces pulling on it.

https://eos.org/research-spotlights/how-did-the-moon-get-its-shape

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