Most theories claim the Moon formed out of the debris of a collision between the Earth and an object about the size of Mars, called Theia, coalescing in orbit over months or years. A new simulation ...

MFM simulation of the canonical Moon-Forming giant impact. Here different colors trace different components of Gaia and Theia. The lower mantle of Gaia, denoted by the dashed circle with a radius of 0 ...

There may be chunks of an ancient planet trapped in Earth’s mantle. The prevailing theory of the moon’s formation is called the giant impact hypothesis, in which a Mars-sized object called Theia ...