1. Formation Theories

2. Theory 1 – The Capture Theory
This proposes that when the solar system was forming, a large object came too close to the Earth and was trapped in the Earth’s gravitational pull and formed the Moon
Problems – the object would have had to slow down and the Moon and Earth are made of similar elements

3. Theory 2 – The Simultaneous Formation Theory
This proposes that the Earth and Moon were formed at the same time in the same general area
Positives – would show why the Earth and Moon are made of the same general elements and the object would not have had to slow down
Problem – does not account for different amounts of iron
Moon is generally iron deficient

4. Theory 3 – The Impact Theory
Most commonly accepted
Computer models indicate that Earth was hit by a Mars-sized object about 4.5 billion years ago
Because of this collision, materials from that large object and from Earth’s outer layers were ejected into space, forming the Moon
Positives – this accounts for similar composition, heat from the collision would have evaporated any water that could have been on the Moon