How did Earth get its water? Moon rocks suggest it might have been here all along.

The water that Earth has may have been here since the planet formed, and not delivered later by collisions with icy comets, a new study finds.

The research analyzed moon rocks brought to Earth by the Apollo program and may shed light on our planet’s earliest days. Although more than 70% of Earth’s surface is covered in water, overall our planet is actually relatively poor in water and other volatile molecules compared with most other bodies in the solar system, study lead author Lars Borg, a planetary scientist at Lawrence Livermore National Laboratory in Livermore, California, told