'Second moon': Origin of mysterious near-Earth asteroid revealed

Scientists have discovered that Earth's 'second moon' is actually a piece of rock that they say comes from the original Moon.

It's called Kamo'oalewa and, despite its nickname, isn't really a moon at all. It's a near-Earth asteroid, given the title of 'second moon' as it appears to orbit the Earth but is actually orbiting the Sun at the same time as Earth.

Research published in Nature Astronomy found that Kamo'oalewa likely came from a lunar crater on the far side of the Moon.

Scientists think that Kamo'oalewa became dislodged when an asteroid hit the Moon at some point between 1 million to 10 million years ago, leaving the crater behind.

Kamo`oalewa is a Hawaiian word that roughly means 'the oscillating celestial fragment' - much nicer than its technical name of asteroid 2016 HO3!

Scientists estimate that it's 40m to 100m wide - around the size of the Statue of Liberty.

In 2021, scientists at the University of Arizona looked at telescope images and found that it the asteroid was similar to lunar rock brought back by the 1970s Apollo missions, making them think that it might come from the Moon.

The new research that gives more evidence for Kamo`oalewa's Moon origins was done with lots of maths, using simulations to model which lunar crater might have once had the rock lodged inside it.

They found that the Giordano Bruno crater would be the most likely source, as its size and shape matches the models.

This theory will be tested out by the upcoming Tianwen-2 Chinese space mission, which is aiming to visit the asteroid to collect samples for further study.