“The pressure to compete, the fear somebody else will make the splash first, creates a frenzied environment in which a blizzard of information is presented and serious questions may not be raised.” -Carl Bernstein
Why is our Moon so unlike every other moon in the Solar System? No other moon is such a large percent of its parent planet’s mass or size; no other moon rotates so far afield of its planet’s rotational axis; no other moon orbits so far out of the planet-Sun plane. Yet our Moon does it all. The giant impact hypothesis might explain why the Moon is made of the same material as Earth, but wouldn’t explain these features.
The layers of the Moon, consistent with an origin that is identical to the Earth’s interior. Image credit: Wikimedia Commons user Kelvinsong.
Unless, that is, the giant impact occurred with a very large velocity out of the plane of proto-Earth’s orbit. Unless, again, the Earth weren’t rotating at 23.5º prior to the impact. This new tweak on the impact hypothesis, put forth by a team of authors earlier this week in the journal Nature, might explain the unique history of the Earth-Moon system, including some features we don’t normally think about as being puzzling.
The Earth and Moon, along with some of their more important orbital and rotational properties. Image credit: NASA.