Scientists say ‘city-killer’ asteroid on potential collision course with Moon

A “city-killer” asteroid previously thought to be on a collision course with the Earth could smash into the Moon instead, new data suggests.

Asteroid 2024 YR4 caused global concern after its discovery last year as the space rock’s trajectory indicated a 3 per cent chance of it crashing into the Earth in December 2032. Estimates suggested the collision could shatter structures as far as 80km from the impact zone.

Subsequent observations of the rock reduced the threat to virtually zero.

But new direct observations of the asteroid by Nasa’s James Webb Space Telescope suggest a nearly 4 per cent chance of the rock smashing into the Moon.

Scientists say that even a 1 per cent chance of a rock this big hitting the Earth may warrant the development of deflection missions. “At this writing, a 2032 impact with the Moon has not been ruled out,” astronomers, including Andy Rivkin from Johns Hopkins University, write in a new study.

“After 2025 May, 2024 YR4 will next enter JWST observing window in the first part of 2026 as a challenging target, which may be worth pursuing to determine whether a lunar impact will occur,” the study, published in the journal RNAAS, notes.

There is still over 96 per cent chance that the asteroid will miss the Moon entirely, Nasa said in a statement on Thursday.

The latest observations also revise the space rock’s size from 40-90m to 53-67m, about the size of a 15-storey structure.

“While we are confident that 2024 YR4 will not hit the Earth in 2032, there is still great value in making these observations and analysing the results,” Dr Rivkin says.

“We expect more possible impactors to be found in coming years as more sensitive asteroid search programmes begin operation.”

Many scientists hope for the asteroid to impact the Moon as it could provide more data to prepare for future planetary defence operations.

“The possibility of getting a chance for an observation of a sizable Moon impact is indeed an interesting scenario from a scientific point of view," Richard Moissl, head of the European Space Agency's planetary defence office, says, adding the collision could be "valuable for planetary defense purposes".