In DepthPlanetary Science

Moon-forming impact left scars in distant asteroids

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Science  17 Apr 2015:
Vol. 348, Issue 6232, pp. 271
DOI: 10.1126/science.348.6232.271

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Summary

Not too long after the planets began forming, a Mars-sized object slammed into Earth, creating the debris that would coalesce into the moon. But some of the debris escaped all the way out to the asteroid belt. Collisions there left shock-heating signatures that can still be detected billions of years later in meteorites that have fallen to Earth. Planetary scientists have found that a significant number of these altered meteorites have ages clustering at 105 million years after the solar system's birth—the true age of the moon-forming impact, they say. The result is an independent check on different estimates for the moon's age, and it suggests that the asteroid belt could be witness to other ancient disruptions in the inner solar system.