Scientists discover origins of Earth's estranged 'second moon'

An asteroid discovered in 2016 has been something of a mystery since it was found but now astronomers believe it may be a chunk of the Moon.

In new analysis led by astronomer Yifei Jiao of Tsinghua University in China, the asteroid called Kamo'oalewa has been linked back to the Giordano Bruno crater on the far side of the Moon.

"We have explored the processes for impact-induced lunar fragments migrating into Earth co-orbital space and presented support for Kamo'oalewa's possible origin from the formation of the Giordano Bruno crater a few million years ago," the researchers write in their paper.

"This would directly link a specific asteroid in space to its source crater on the Moon and suggests the existence of more small asteroids composed of lunar material yet to be discovered in near-Earth space."

From Earth, it is difficult to see things in space, meaning we struggle to see the 'minions' near our planet.

Kamo'oalewa has been sharing Earth's orbital proximity with the Sun for centuries, and eventually scientists identified that the asteroid was once part of the Moon.

This was discovered due to the way Kamo'oalewa reflects light, as well as its colour, which are very similar to the lunar surface.

Jiao and his team have taken the analysis one step further to find out its origin. They used physical and orbital properties of the asteroid as well as models of lunar impacts.

They discovered that Kamo'oalewa has to be younger than 100 million years. This is because near-Earth asteroids don't usually remain near earth for longer than than this time.

Further, there aren't many craters on the Moon that fit the size requirement and are younger than 100 million years old. While there are some candidates, the Giordano Bruno crater fits the best.

"It is clear that the largest, youngest craters are more probable sources, as they produce more escaping fragments that still remain in space or the Earth co-orbital region," they write.

"And indeed, Giordano Bruno is the only possible source crater satisfying the criterion."

While the evidence isn't conclusive, the Chinese National Space Administration has plans to launch an asteroid sampling mission that will explore Kamo'oalewa, retrieve a sample, and bring it back to Earth for studying.

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