A paper published in the July 30 issue of Nature by Ian Garrick-Bethell – an assistant professor of Earth and planetary sciences at University of California Santa Cruz – examines the shape of the Moon as it would be had not millions of meteorite collisions knocked chunks off it, and ponders how it got that way.
“If you imagine spinning a water balloon, it will start to flatten at the poles and bulge at the equator,” Garrick-Bethell said. “On top of that you have tides due to the gravitational pull of the Earth, and that creates sort of a lemon shape with the long axis of the lemon pointing at the Earth.”
The Moon formed about four billion years ago and was initially much closer to Earth, and spinning rather more than it does today. As the Moon cooled and hardened, the effects of tidal forces exerted by Earth froze the surface into a slightly elongated shape with a bulge pointing towards Earth and a corresponding bump on the other side.
I think she’s just as rotational and spherical as she was at two billion.
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