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Asteroid's Birthplace Traced to Specific Crater on the Moon

Many asteroids can be traced back to their parent body - the planet or moon they broke off from. But now, for the first time, scientists claim to have traced the origins of an asteroid back to the specific crater it was birthed from.

The lunar crater Giordano Bruno
The lunar crater Giordano Bruno | Credit: NASA/Goddard/Arizona State University

Scientists can often tell which parent body any given asteroid originated from, by analyzing the rocks’ composition, reflectiveness, and other signatures. But they usually can’t figure out exactly where on those worlds they came from - until now.

Measuring about 58m (190 ft) wide, Kamo’oalewa is an asteroid that was discovered in 2016 as a “quasi-satellite” of Earth. That means this strange little space rock technically orbits the Sun, but Earth’s gravity has enough of an influence on it that it never gets too far away from us. In 2021, a follow-up study found that it’s probably a piece of the Moon, based on its reflectivity and orbit.

Now, an international team of scientists has tracked its home even more precisely. Impact and dynamical modelling revealed that to launch a chunk of rock the size of Kamo’oalewa away from the Moon, it would take an impact from an asteroid of at least 1 km (0.6 miles) wide. That in turn would leave a crater larger than 20 km (12.4 miles) in diameter. It also would have had to have been relatively recent – meaning the last few million years – for Kamo’oalewa to still be hanging around.

The team scanned the thousands of craters littering the lunar surface, and found only one that matches the age and size - Giordano Bruno. Named after a 16th-century Italian intellectual whose cosmological views were so ahead of his time that he was burned at the stake for heresy. This crater is located on the far side of the Moon, measures 22 km (14 miles) wide, and has been dated to just 4 million years old. Making it an exact fit for Kamo’oalewa.


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