The Moon, our planet's constant companion for some 4.5 billion years, may have been forged by a rash of smaller bodies smashing into an embryonic Earth, researchers said Monday.
Such a bombardment birth would explain a major inconsistency in the prevailing hypothesis that the Moon splintered off in a single, giant impact between Earth and a Mars-sized celestial body.
In such a scenario, scientists expect that about a fifth of the Moon's material would have come from Earth and the rest from the impacting body.
Yet, the makeup of the Earth and the Moon are near identical-an improbability that has long perplexed backers of the single-impact hypothesis.
"The multiple impact scenario is a more 'natural' way of explaining the formation of the Moon," said Raluca Rufu of the Weizmann Institute of Science in Rehovot, who co-authored the new study published in the journal Nature Geoscience.
Such multiple hits would have excavated more Earth material than a single one, which means the moonlets would more closely resemble our planet's composition, said the study authors. Rufu and a team created nearly a thousand computer simulations of collisions between a proto-Earth and embryonic planets called planetesimals, smaller than Mars.