New data from NASA's Lunar Prospector spacecraft add weight to the theory that the moon was formed when the Earth collided with an object the size of Mars. Similarities in the mineral composition of the Earth and the moon indicate that they share a common origin, but the two bodies have very different cores, according to the new data.
The Earth's makes up 30 per cent of its mass while the Moon's makes up only 4 per cent. If they had formed together from a shared cloud of rocks and dust the core proportions would have been closer, NASA scientists speculated.
The collision, they added, probably occurred after the Earth's iron core formed, with the impact throwing off iron-poor material from the plant's outer shell into orbit.
