Earth May Once Have Had Multiple Moons

fyc writes "A new study from NASA's Ames Research Center has suggested that the collision of Earth and a Mars-sized object that created the Moon may also have resulted in the creation of tiny moonlets on Earth's Lagrangian points. 'Once captured, the Trojan satellites likely remained in their orbits for up to 100 million years, Lissauer and co-author John Chambers of the Carnegie Institution of Washington say. Then, gravitational tugs from the planets would have triggered changes in the Earth's orbit, ultimately causing the moons to become unmoored and drift away or crash into the Moon or Earth.'" The longest-lasting of such Trojans could have persisted for a billion years. They would have been a few tens of kilometers in diameter and would have appeared in the sky like bright stars.

Perhaps the asteroid that did for the dinosaurs..

[Viol8]

... was one of those old moonlets paying its last visit to earth. If it had left a Langraigian point it could still have orbited very near earth for a long long time until one small nudge put it on the trajectory for that fateful day.

Not far fetched.

[Auckerman]

Doesn't sound too far fetched since Earth has Cruithne [wikipedia.org] sharing it's orbit, which in it's own way is a "second moon". On a functional level, not that different from what they are suggesting. I would even take it step futher, there's no reason to even believe any specific natural satellite of Earth originated from our planet or it's creation.

Re:The Moon (ridiculous liberal myth) is receding

[Anonymous Coward]

Maybe it was the moon that killed the dinosaurs!

Re:Not far fetched.

[4D6963]

Earth has Cruithne sharing it's orbit, which in it's own way is a "second moon"

If it's not permanently orbiting within the Earth's Hill sphere [wikipedia.org], it's no moon.

On a side not, since these moons were originally at Lagrangian points, it makes me wonder whether or not some of them could evolve into having a horseshoe orbit with the Earth. Actually a mission to one of these asteroids when they get about 1.5 Gm from Earth would be interesting and pretty easy as they would be close to Earth and moving pretty slowly. I guess you could look them up closer to find out if they share material in common with the Moon or anything.

Re:Moons? Nomeclature?

[mdwh2]

Let me see if I have this straight - Pluto is NOT a planet, because it falls beneath some arbitrary threshold for 'planet', but ANY object orbiting a planet is automagically a moon?

Apparentely so - the 63 Moons of Jupiter [wikipedia.org] include the 1 km in diameter 2003 J 9 [wikipedia.org].

I find it odd that people can't cope with there being hundreds of planets, and need some arbitrary distinction between "planet" and "natural satellite of the Sun", but 240 moons in the solar system is considered fine.

It's also strange that a body orbiting a dwarf planet is still considered a moon, and not a "dwarf moon"...