Did Earth And The Moon Get Their Water From The Same Place?

Since a suite of spacecraft confirmed abundant water on the moon in the past few years, scientists have wondered how it got there. Could it have come from comets, dusty snowballs making their way toward the sun and melting? Could it have come from meteorites, collecting tiny amounts of water over time? Or maybe even the sun, donating hydrogen particles from its blustery wind that combined with lunar oxygen? Now there’s a new theory: It came from Earth.

Most moon-formation theories hold that the moon came from the Earth, and was sheared off when a Mars-sized object walloped our planet in its youth. And just a couple months ago, scientists reported that the moon probably has had water its entire life. A new study that examines lunar water evidence could explain this: Earth had water when this happened, and that somehow, it survived the collision and wound up on the moon.

Alberto Saal, associate professor of Geological Sciences at Brown University, and colleagues examined some Apollo moon rocks, specifically looking for a phenomenon called melt inclusions. These are small pockets of volcanic glass, usually trapped inside a mineral called olivine.