Retracing origins of massive moon crater.

PositionOrientale Basin

The extreme collision that created one of the moon's largest craters 3,800,000,000 years ago has been reconstructed by an international team of scientists. Jeffrey Taylor, a professor in the School of Ocean and Earth Science and Technology at the University of Hawaii, Manoa, was among the scientists who retraced the moon's dramatic response in the first hours following the massive impact, and identified the processes by which large, multiring basins can form in the aftermath of such events.

The findings, published in Science, may shed light on how giant impacts shaped the evolution of the moon, and even life on Earth, shortly after the planets formed.

The team's results pertain to the Orientale basin, an expansive, bull's eye-shaped depression on the southwestern edge of the moon, just barely visible from Earth. The basin is surrounded by three concentric rings of rock, the largest one stretching 580 miles across. Until now, it has been unclear how massive impacts produced the complex structures displayed by multiring basins.

Probes on NASA's Gravity Recovery and Interior Laboratory (GRAIL) spacecraft took measurements of the basin's gravity field at high spatial resolution, providing scientists with a precise map of the moon's interior mass distribution that enabled the researchers to make revealing geophysical observations and develop a computer model to re-create the impact and its effects.

Maria Zuber, professor of geophysics at the Massachusetts Institute of Technology, Cambridge, Mass., and her colleagues analyzed GRAILs gravity field measurements and were able to solve a key mystery: the size and location of the basin's transient crater, which is the initial depression created when an asteroid blasts material out from the lunar surface.

The researchers determined that the basin was created by a huge impactor that punched an initial, transient crater into the lunar surface, measuring up to 285 miles in diameter. This impact, the researchers calculated, sent at least 816,000 cubic miles of pulverized lunar crust flying out from...

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