Giant impact hypothesis
The Earth's relatively large natural satellite, the Moon, is unique. During the Apollo program, rocks from the Moon's surface were brought to Earth. Radiometric dating of these rocks has shown the Moon to be 4527 ±10 million years old, about 30 to 55 million years younger than other bodies in the Solar System. New evidence suggests the Moon formed even later, 4.48 ±0.02 Ga (billion years ago), or 70–110 Ma (million years ago) after the start of the Solar System.