Violent Collisions Creating Moons are Rare Events

Nadya Gorlova and her team from the University of Florida have been looking for dust which would show evidence of a violent collision taking place as a moon is formed, and have found relatively little.

The Earth’s moon is thought to have been created when a body the size of Mars hit the Earth and broke off a piece of the Earth’s mantle. Some of the debris fell into orbit around the Earth, and eventually joined together to form the Moon. Reasoning that if this happened in other planetary systems, they would become full of dust, Gorlova and her team studied about 400 stars the same age our Sun was when the moon was formed – around 30 million years old. They found only one solar system enveloped in dust.

Based on these findings, the team have calculated that the probability of a solar system creating a moon like Earth’s to be only five to ten per cent.

Moons can form in other ways. For example, space rocks can be captured by the gravity of a planet and become locked in its orbit, or dust can clump together around a new planet and form a moon.