How did water arrive on Earth?

Asteroids and comets are debris left over from the formation of our solar system and are rich in water.

These small bodies are time capsules that contain tantalizing clues about what our solar system was like 4.5 billion years ago.

Most asteroids orbit the Sun between the planets Mars and Jupiter, but many swing nearer to Earth and even cross our orbit. Comets are found in the outer reaches of our solar system, either in the Kuiper Belt just beyond the orbit of Pluto, or in the vast, mysterious Oort Cloud that may extend halfway to the nearest star.