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Tech & Science
A massive, layered asteroid struck the moon at a shallow angle over 4 billion years ago, creating its largest crater and scattering deep lunar material near a planned NASA landing site.
A colossal asteroid collision more than 4 billion years ago carved the largest scar on the moon's surface. New research suggests this ancient impact may have scattered a geological treasure precisely where NASA intends to send its astronauts.
The South Pole-Aitken basin, spanning over 1,200 miles (2,000 km) on the moon's far side, was likely formed by a differentiated asteroid—one with a dense iron core and a rocky outer layer—that struck at a very shallow angle, according to a study published May 7 in Science Advances. This finding could answer major scientific questions about the basin's formation and carries significant implications for future lunar exploration.
A research team led by Shigeru Wakata from Purdue University used high-resolution 3D computer simulations. They discovered that the basin's distinctive oval shape is best explained by the impact of an asteroid 160 miles (260 km) wide, which had already developed a separate iron core, much like a miniature planet.
The asteroid hit the moon traveling from north to south at roughly eight miles per second (13 km per second), striking at a shallow angle of just 30 degrees. This shallow trajectory is the key: the asteroid's "head" was effectively severed, with its upper layers separating while the dense iron core continued forward, creating the basin's elongated shape. A simpler, non-differentiated asteroid would have produced a more circular basin.
Critically, the team found that this violent impact ejected rocky debris from deep within the moon's mantle—the layer beneath the crust—toward the lunar south pole. According to the study, NASA astronauts landing near the south pole on the Artemis mission may find deposits containing material from depths exceeding 56 miles (90 km) inside the moon.
If the simulations are correct, samples returned to Earth by these astronauts could help scientists precisely date the South Pole-Aitken basin and reveal the composition of the deep lunar interior. This would offer valuable clues about how the moon evolved shortly after its formation over 4 billion years ago.
