An asteroid that was briefly feared to be on a collision course with Earth is now more likely to strike the Moon in 2032, according to updated calculations by Nasa.
Astronomers have refined the orbit of asteroid 2024 YR4 using data collected by the James Webb Space Telescope, revealing a slightly higher probability that the space rock could crash into the Moon’s surface.
The asteroid, about 80 metres wide, was discovered in late 2024 and initially appeared on Nasa’s risk list for colliding with the Earth.
More observations, however, have ruled out a direct hit. Latest calculations show that there is a 4.3 per cent chance the asteroid will strike the Moon on December 22, 2032.
“While asteroid 2024 YR4 is currently too distant to detect with telescopes from Earth, Nasa’s James Webb Space Telescope collected one more observation of the asteroid before it escaped from view in its orbit around the Sun,” the agency said.
Even if the asteroid were to collide with the Moon, it would have no effect on its orbit or stability, Nasa said.
'Unprecedented opportunity'
Dr Dimitra Atri, principal investigator at New York University Abu Dhabi’s Space Exploration Laboratory, said the probability of impact was “relatively low”, but a collision would give researchers “an unprecedented scientific opportunity”.
“For the first time, we could observe the formation of a major lunar crater in real time using modern orbital instruments,” he said.
“Such an event would open possibilities for follow-up exploration. Rovers or astronauts could investigate the fresh impact site, yielding invaluable data about how impacts have shaped not only the Moon, but planetary surfaces throughout the solar system.”
The Moon’s heavily cratered surface is largely the result of asteroid and meteorite impacts over billions of years, but all those collisions happened before the age of space flight.
A new impact, and one that can be observed and studied from start to finish, could reveal how craters evolve, how subsurface materials are exposed and help scientists test planetary defence strategies.
A complex orbital path
Jonathan Ward, a fellow of the UK’s Royal Astronomical Society, said the orbital path of 2024 YR4 was still not fully understood due to factors such as the Yarkovsky effect, a force caused by the way an asteroid absorbs sunlight and radiates heat, altering its trajectory over time.
“We won’t know anything better about its potential for an impact in 2032 until it comes back by the Earth in 2028,” Mr Ward said.
Researchers were using the JWST to track the asteroid because it uses infrared wavelengths to detect heat signatures.
But now telescopes have lost sight of the space rock as it moves behind the Sun.
Mr Ward said the 2028 fly-by will be a critical opportunity to track the asteroid’s position with greater precision and determine if any further course changes are likely.
Could a deflection mission be possible?
While there is no threat to Earth, the asteroid has renewed discussions about planetary defence, particularly following the success of Nasa’s Dart mission in 2022, which intentionally slammed a spacecraft into an asteroid to chance its trajectory.
“A mission like Dart takes three to five years to prepare and launch,” Mr Ward said.
“If it ever became necessary, that gives us some time to act after the 2028 observations.
“But we still don’t know the full make-up of this asteroid. It’s likely a stony object, unlike Dimorphos, which was more of a rubble pile. That affects how it might respond to an impact.”
Looking ahead to 2028
Nasa confirmed that no additional observations of the asteroid are expected until 2028, when it returns closer towards Earth.
The asteroid is expected to pass at a safe distance, giving astronomers the best chance yet to determine whether a Moon impact in 2032 is possible.
