Giant impact hypothesis

Impact
In astronomical terms, the impact would have been of moderate velocity. Theia is thought to have struck the Earth at an oblique angle when the planet was nearly fully formed. Computer simulations of this "late-impact" scenario suggest an impact angle of about 45° and an initial impactor velocity below 4 km/s.[11] Theia's iron core sank into the young Earth's core, as most of Theia's mantle and a significant portion of the Earth's mantle and crust were ejected into orbit around the Earth. This material quickly coalesced into the Moon (possibly within less than a month, but in no more than a century). Estimates based on computer simulations of such an event suggest that some two percent of the original mass of Theia ended up as an orbiting ring of debris, and about half of this matter coalesced into the Moon. The Earth would have gained significant amounts of angular momentum and mass from such a collision. Regardless of the rotation and inclination the Earth had before the impact, it would have had a day some five hours long after the impact, and the Earth's equator would have shifted closer to the plane of the Moon's orbit.[citation needed]

It has been suggested that other significant objects may have been created by the impact, which could have remained in orbit between the Earth and Moon, stuck in Lagrangian points. Such objects may have stayed within the Earth-Moon system for up to 100 million years, until the gravitational tugs of other planets destabilized the system enough to free the objects.[12]