Two-stage process formed moon, simulations suggest

Chemicals missing from lunar rocks may be hiding under crust

illustration of planets colliding

ONE-TWO PUNCH  A two-stage moon formation, following a collision between Earth and a smaller planet (illustrated), might explain the absence of certain elements in lunar rocks.

JPL-Caltech/NASA

OXON HILL, Md. — Rocks on Earth and the moon are nearly identical — except when they’re not.