Why asteroid 2024 YR4 has reached a record level on ‘impact hazard' scale

Yahoo

20-02-2025

The inventor of the Torino Impact Hazard Scale has explained how scientists are working to 'pin down' the position of asteroid YR24.
Professor Richard Binzel tells Yahoo News that it is 'perfectly natural' that the odds of impact will 'bounce around' at this point.
The asteroid 2024 YR4 is ranked at three on the Torino Impact Hazard Scale, higher than any previous asteroid bar Apophis which briefly achieved four in 2004.
The risk of a huge asteroid hitting Earth has dropped after Nasa reported its highest-ever impact probability for an object of its size.
Space rock 2024 YR4, estimated to be 130 to 300 feet wide (40 to 100 metres), now has a 1.5% chance of colliding with Earth in December 2032, the agency said.
On Tuesday, Nasa had put the impact probability at 3.1%, the highest ever recorded for an object of its size.
The Torino Impact Hazard Scale was adopted in 1999 to offer a way to communicate asteroid impact danger to the public.
Used to describe potential impacts within the next 100 years, it ranges from zero ('No Hazard', classified as white) to 10, red (A collision is certain, capable of causing global climatic catastrophe that may threaten the future of civilization as we know it'.
Asteroid 2024 YR4 is ranked three (green): Nasa describes level 3 asteroids as a "close encounter, meriting attention by astronomers. Current calculations give a 1% or greater chance of collision capable of localised destruction."
The time of closest approach to Earth (when it could potentially impact) is 22 December 2032.
The inventor of the Torino Impact Hazard Sale, Richard Binzel, Professor of Planetary Science at Massachusetts Institute of Technology, tells Yahoo News it was proposed in 1997, and adopted at a conference in Torino (Turin) Italy in 1999, by the International Astronomical Union (IAU).
It was proposed at the same time as a rise in the number of surveys of near-Earth objects (NEO) meant that knowledge of potential impacts would rise, Binzel says.
Astronomers are targeting telescopes at 2024 YR4 to get better readings of its position.
The asteroid is currently heading away from Earth and astronomers will use increasingly large telescopes until May, when it will pass out of view.
Binzel says 'It is perfectly natural that the impact chances for asteroid 2024 YR4 will bounce around a bit.
'The way it works is that the uncertainty for where the asteroid will be in the future stretches out into a long thin shape like a fettuccine or spaghetti noodle that spans all the way across the orbit of the Moon around the Earth. Earth just happens to lay underneath that noodle, and the fraction that the Earth occupies is the probability of impact.
More tracking data will allow astronomers to 'shrink the noodle', Binzel explains.
He says, 'As the noodle shrinks, but still happens to include the Earth, it can make the calculated probability go up.
'The good news is that eventually we will pin down the asteroid's position to that of a single grain. Most likely that grain will not be on top of the Earth. It could be even farther than the Moon.'
It is too soon to know where it might land if it did hit Earth.
However, the UK is not within the current predicted 'impact risk corridor', which is the area where the asteroid could land, according to the International Asteroid Warning Network (IAWN).
This corridor stretches across the eastern Pacific Ocean, northern South America, the Atlantic Ocean, Africa, the Arabian Sea, and South Asia, the IAWN said.
If the asteroid hits it could cause 'severe blast damage' as far as 50 km (31 miles) from the impact site, scientists say.
There is a 0.8% chance the asteroid will impact the moon, Nasa said.
It is difficult to accurately predict any potential damage. NASA says that a 100-metre asteroid has 10 times the destructive force of the 2021 Tonga volcanic eruption, which caused a large explosion and tsunamis in several countries.
The damage caused by such an explosion would vary depending on where the asteroid hit.
"An asteroid this size impacts Earth on average every few thousand years and could cause severe damage to a local region," the ESA has said. NASA says that the impact could kill up to a million people, "averaged over all possible impact locations".
"These deaths could result from a direct hit or by tsunami (tidal wave) in the event of an ocean strike," it adds.
An asteroid thought to have been around 18m across 'blew up' over the Russian town of Chelyabinsk in 2013.
During the 2013 Chelyabinsk event, 1,500 people were injured and 7,300 buildings were damaged by the intense overpressure generated by the shockwave at the Earth's surface.