Did Multiple Moons Once Orbit Earth?

The history of planet Earth is a fascinating story, involving catastrophic collisions with other small planets and a veritable plethora of asteroid impacts. The prevailing theory about the formation of the moon is called the giant impact hypothesis: the theory goes that a Mars-sized object, known as Theia, crashed in to the young Earth. What was left was Earth, and its moon.

A new computer model suggests, however, that the Moon may not have been the only reminder of that big collision. Jack J. Lissauera of the Space Science and Astrobiology Division, NASA Ames Research Center, and John E. Chambers of the Department of Terrestrial Magnetism, Carnegie Institution of Washington, have suggested that moonlets called Trojans may have been left behind in the collision.

"The giant impact that likely led to the formation of the Moon launched a lot of material into Earth orbit, and some could well have been caught in the Langrangian points," -points in space where the gravity between two objects cancels the other out, said says study team member Lissauer. Their theory places small moonlets, or Trojans, in Earth’s orbit, for up to 100 million years.

Over time, gravitational tugs from other planets would have eventually altered Earth’s orbit, even if it was only slightly. Thus, the Langrangian points would have altered, leaving the Trojans once again susceptible to gravity. From there, they could be anywhere by now, or destroyed entirely. (Source: Daily Galaxy) (Opinion: In 'lucid dreams' of Mars ... Mars was in orbit of another planet. Could Mars have been in orbit or closer to Earth in the distant past?)