That proto-Earth (called Gaia) clashed severely with another early planet, Theia, while tracing its orbit around the sun. Due to Gaia’s large size, it dominated the collision and began to form the shape of Earth as we know it today. Meanwhile, much of the debris from the collision ...
Here we assess the composition of Theia, and we constrain the type of collision that led to the formation of the Moon. For the first time, we bring D/H data of lunar samples (Robinson et al., 2016) to bear on these questions. We show that the Moon incorporated very low-D/H (δD...