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Scientists discover how Moon’s Bull’s-Eye crater came into existence
The origin of Orientale Basin on the Moon, a 580 miles wide Bull’s-Eye crater surrounded by three concentric rings, has long been perplexing scientists. But, a new study has apparently solved that mystery.
Using data collected by NASA’s Gravity Recovery and Interior Laboratory (GRAIL) space probe, a team of scientists peered beneath the Moon’s surface and pieced together information about the crater’s origin.
Lead author Brandon Johnson wrote, “Big impacts like the one that formed Orientale were the most important drivers of change on planetary crusts in the early solar system. Thanks to the tremendous data supplied by GRAIL, we have a much better idea of how these basins form, and we can apply that knowledge to big basins on other planets and moons.”
The scientists concluded that giant crater was formed by a forty-mile-wide object traveling at a speed of more than 9 miles per second. The transient crater on the Moon flung massive volumes of material outward, and the weak material from its mantle moved upward. Some cliffs of the material created by the impact got preserved as the outer two rings.
The findings about the giant crater were detailed in a pair of articles published in the most recent edition of journal Science.
The findings could help scientists better understand how multi-ringed impact basins formed on the Moon as well as other planets during a critical time in the evolution of the solar system, said Katarina Miljkovic of Curtin University, who was a co-author on both studies.
"We've shown how the rings form, not just the rings of Orientale, but the exact mechanism for ring formation on the moon, and in general that should work on any other body as well," Miljkovic said.
The data, published in the first study, revealed that while the outermost of the crater's three rings has a diameter of more than 930 kilometers (578 miles), there was also a smaller transient crater that is not visible today.
Computer modelling in the second study indicated a crater that matched the GRAIL data would have been formed when a 40-mile-wide asteroid slammed into the moon.
"Big impacts like the one that formed Orientale were the most important drivers of change on planetary crusts in the early solar system," Johnson said in a statement. "Thanks to the tremendous data supplied by GRAIL, we have a much better idea of how these basins form, and we can apply that knowledge to big basins on other planets and moons."
"Warm material at depth collapses inward more easily than the material above it, and that pulls in the brittle crust along with that inflowing mantle material, causing the crust to kind of break into mega blocks that then give you these large fault scarps," or circular cracks in the surface, Johnson said.
"We use gravity to map the interior of a planet in ways somewhat analogous to an X-ray," said Maria Zuber, a geophysicist at the Massachusetts Institute of Technology who led the gravity field study.
"The process is so violent a larger portion of the surface feels this pressure going out of excavation, and then the other rings which are beyond this inner depression start faulting," Miljkovic said.