A so-called "mini moon" that has been floating round Earth for two months will soon disappear.
The harmless space rock, which scientists say could be a boulder that was blasted off the actual moon, was first spotted in August.
Known as 2024 PT5, the rock began to partially circle Earth in a horseshoe-shaped path in September, but NASA has clarified that it never fully entered orbit.
Astrophysicist brothers, Raul and Carlos de la Fuente Marcos, from Complutense University of Madrid, first identified the asteroid's "mini moon behaviour".
It is expected to peel away from the Earth on Monday as it is overcome by the stronger pull of the sun's gravity.
It will not reappear again until 2055.
Data suggests that during its next visit in around 30 years, the sun-circling asteroid will once again make a temporary and partial lap around Earth.
On its return, it will be moving more than double its current speed, Mr Marcos said.
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Currently more than two million miles (3.5 million km) away, the rock is too small and faint to see without a powerful telescope.
The Marcos brothers have used telescopes in the Canary Islands to observe the asteroid hundreds of times.
NASA said it would track the asteroid for more than a week in January - when it is expected to make a brief reappearance - using the Goldstone solar system radar antenna in California's Mojave Desert, part of the Deep Space Network.
(c) Sky News 2024: Earth's 'mini moon' to disappear for 30 years
