Nasa feared giant asteroid had 20pc chance of hitting Earth

Telegraph

25-02-2025

Nasa feared the chances of a deadly asteroid hitting Earth could rise past 20 per cent, but now believe it is more likely to collide with the Moon.
The '2024 YR4' space rock, which is thought to be up to 90 metres in diameter – almost the length of a football pitch – was spotted on Christmas Day by a telescope in Chile, and its risk of impact rose steadily through January.
Last week, Nasa increased the impact odds of the space rock to 3.1 per cent – or a one-in-32 chance of striking Earth in December 2032.
But a statistical analysis seen by The Telegraph showed that the US space agency had warned that in a 'worst-case scenario' the chance of collision could climb past 20 per cent by April.
The UN-endorsed space mission planning advisory group warns that 'terrestrial preparedness planning' should begin if the probability of impact is greater than 10 per cent within the next 20 years.
The Nasa projections, submitted during a meeting of the International Asteroid Warning Network (IAWN) in Vienna, reveal just how seriously the agency was taking the threat.
Latest observations show that 2024 YR4 is no longer a threat to Earth. However, the chance of it hitting the Moon has now risen to one in 55 (1.8 per cent), with the risk expected to increase in the coming weeks.
A spokesman for Nasa said: 'There still remains a very small chance for asteroid 2024 YR4 to impact the Moon.
'When first discovered, asteroid 2024 YR4 had a very small, but notable chance of impacting our planet in 2032.
'As observations of the asteroid continued to be submitted…experts at Nasa Jet Propulsion Laboratory's centre for near-earth object studies were able to calculate more precise models of the asteroid's trajectory and now have found there is no significant potential for this asteroid to impact our planet for the next century.'
An asteroid of similar size to 2024 YR4 collides with Earth every few thousand years and would be of sufficient size and speed to cause loss of life and severe damage to property.
Astronomers had rated the threat of the new asteroid as being a level three on the Torino impact hazard scale and 'capable of causing localised destruction'.
Nasa said the scare had provided an 'invaluable opportunity' to test planetary defence and notification processes.
The agency said it will continue to observe 2024 YR4 and the James Webb space telescope will also study the rock throughout March to gain more insights.
The asteroid will swing past Earth again in 2028, when final observations can be made ahead of the 2032 pass.
The odds of a collision with Earth currently stand at one in 37,000 (0.0027 per cent) – but its new calculated trajectory means the chance of it hitting the Moon is rising.
'No longer a major impact threat'
Dr Vishnu Reddy, IAWN manager, said: 'The object is no longer a major impact threat. So we are good. Based on what I have seen in the past, it is unlikely to go up higher once it is trending down towards nought per cent.
'The Moon impact probability is up now and will go higher for a few weeks before that comes down as well.'
In recent years the threat from asteroids led Nasa and the European Space Agency (Esa) to crash a spacecraft into an asteroid in the first ever test to see if a space rock could be moved in orbit. Data showed that the mission did change the trajectory.
Esa said that it expected the threat to the Moon to rise in the coming months, before falling.
A spokesman said: 'We do not calculate the impact probability (IP) for the Moon in the same rigorous manner, as for the Earth. However, indeed we still see an upward trend of the Moon IP, which is currently around 1.8 per cent
'The situation is similar as it was when Earth was still well within the uncertainty region.
'The most likely outcome is that also the Moon IP will peak at some point and then start to drop quickly.
'Whether this will happen during the current visibility period, or whether we will have to wait for the next measurement opportunities in 2028, remains to be seen.'