Water inside moon mostly from asteroids, study suggests

Hydrogen in lunar samples reveals water could have been delivered by asteroids crashing into the moon's vast magma ocean billions of years ago

Water inside the moon mostly came from asteroids that smashed into the lunar body more than four billion years ago, with comets adding less than previously thought, scientists say.

Composed of material ejected when a large, Mars-sized body ploughed into Earth around 4.5 billion years ago, the moon was long thought to be bone-dry. But research has shown that traces of water exist both on the surface and inside.