Giant impact hypothesis

Definition

The giant impact hypothesis suggests that the Moon formed from the debris ejected when a Mars-sized body collided with the early Earth. This collision is believed to have occurred around 4.5 billion years ago, shortly after the formation of the solar system.

5 Must Know Facts For Your Next Test

1. The Mars-sized body involved in the collision is often referred to as Theia.
2. Evidence supporting this hypothesis includes similarities in isotopic compositions between Earth's mantle and lunar rocks.
3. Computer simulations of planetary collisions support the feasibility of this hypothesis.
4. The giant impact would have melted part of the Earth's crust, leading to the formation of a magma ocean on both Earth and the Moon.
5. The hypothesis explains why the Moon has a small iron core compared to Earth.

Review Questions

• What is the name of the hypothetical Mars-sized body that collided with Earth according to the giant impact hypothesis?
• How does isotopic evidence support the giant impact hypothesis?
• Why does the giant impact hypothesis explain differences between Earth's and Moon's iron cores?

Related terms

Theia:

Hypothetical Mars-sized protoplanet that collided with early Earth, leading to debris formation and eventually forming the Moon.

Isotopic Composition:

The relative abundances of isotopes in a substance, used as evidence for common origins between Earth and lunar materials.

Magma Ocean: A global layer of molten rock that formed on early Earth and Moon due to heat from large impacts.