New isotope analysis suggests Theia formed closer to sun than Earth

Four and a half billion years ago, a planetary body called Theia collided with the young Earth in a cataclysm that gave birth to the moon — and now, through the patient reading of isotopic fingerprints in Earth and lunar rocks, scientists are beginning to reconstruct the identity of that long-vanished world. A team from the Max Planck Institute and the University of Chicago has determined that Theia was not a distant wanderer from the outer solar system, but a neighbor, formed in the same inner region as Earth itself, perhaps even closer to the sun. The finding invites us to reconsider the ear