Lecture #18: Formation of Moons


I. Our Moon
-- our Moon has a high rock content, similar to Earth's mantle
-- seems likely it broke off from the Earth's mantle as the Earth was forming, probably due to a collision with something that had about the mass of Mars
-- since then, the Moon has gradually spiralled away from the Earth (see tidal effects)
II. Moons of gas giants
-- the gas giants are like mini solar systems, and formed with their own disks
-- those disks would have then formed moons, much like the planets formed from the Sun's disk
III. Captured moons
-- some moons probably did not form with their planet, as they are not anywhere near the equatorial plane of the planet's rotation
-- they may have formed somewhere else and been captured by the planet, in a three-body interaction or collision