Scientists think the Moon was formed when the Solar System was very young and an object about the size of Mars collided with the young Earth. They think the Moon is debris from the collision, pulled together in Earth’s orbit by gravity.
The giant-impact hypothesis, sometimes called the Big Splash, or the Theia Impact suggests that the Moon formed out of the debris left over from a collision between Earth and an astronomical body the size of Mars, approximately 4.5 billion years ago, in the Hadean eon; about 20 to 100 million years after the Solar System coalesced. The colliding body is sometimes called Theia, from the name of the mythical Greek Titan who was the mother of Selene, the goddess of the Moon. Analysis of lunar rocks, published in a 2016 report, suggests that the impact may have been a direct hit, causing a thorough mixing of both parent bodies.
The giant-impact hypothesis is currently the favoured scientific hypothesis for the formation of the Moon. Supporting evidence includes:
- Earth’s spin and the Moon’s orbit have similar orientations.
- Moon samples indicate that the Moon’s surface was once molten.
- The Moon has a relatively small iron core.
- The Moon has a lower density than Earth.
- There is evidence in other star systems of similar collisions, resulting in debris disks.
- Giant collisions are consistent with the leading theories of the formation of the Solar System.
- The stable-isotope ratios of lunar and terrestrial rock are identical, implying a common origin.
Picture Credit : Google