History of the Earth
The Earth's relatively large natural satellite is the Moon.  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 mya after the start of the Solar System. Another notable feature is the relatively low density of the Moon, which must mean it does not have a large metallic core, like all other terrestrial bodies in the solar system.