NASA has increased the chances of the 'city-killing' asteroid smashing into Earth in eight years.
The space agency revealed Tuesday the risk now sit at 3.1 percent, a five percent increase from the previous prediction, or 1 in 32 odds of impact on December 22, 2032.
Astronomers estimate Asteroid 2024 YR4's size to be between 130 and 300 feet wide, based on its brightness.
Analysis of its light signatures suggests it has a fairly typical composition, rather than being a rare metal-rich asteroid.
Astronomers have speculated that if it does enter Earth's atmosphere, the asteroid will likely explode midair with a force of approximately eight megatons of TNT - more than 500 times the power of the Hiroshima bomb.
Unlike the six-mile-wide asteroid that wiped out the dinosaurs 66 million years ago, 2024 YR4 is classified as a 'city killer. That means it is not a global catastrophe, but still capable of causing significant destruction.
Richard Moissl, head of the European Space Agency's planetary defense office, said this is a 'very, very rare event.'
'This is not a crisis at this point in time. This is not the dinosaur killer. This is not the planet killer. This is at most dangerous for a city,' he added.
NASA's announcement makes the asteroid the most threatening space rock ever recorded by modern forecasting.
The last time an asteroid of greater than 98 feet in size posed such a significant risk was Apophis in 2004, when it briefly had a 2.7 percent chance of striking Earth in 2029 - a possibility later ruled out by additional observations.
2024 YR4 was first detected on December 27, 2024 by the El Sauce Observatory in Chile.
Astronomers predicted a 1.2 percent chance of impact at the time, but that was enough to place the asteroid immediately at the top of NASA's automated Sentry risk list, which ranks known Near Earth Objects (NEOs) on how likely they are to collide with our planet.
Retired Canadian astronaut Chris Hadfield said that if it slams into Earth's surface in one piece rather than breaking up after entering Earth's atmosphere
The blast would send fragments of rock shooting outward at more than 10 miles per second, which is faster than the speed of the International Space Station hurtling around the Earth, Hadfield said.
The force of the blast was equivalent to detonating 50 million tons of TNT. It flattened an estimated 80 million trees over 830 square miles of forest and reportedly killed three people.
The potential impact corridor of 2024 YR4 spans the eastern Pacific, northern South America, the Atlantic, Africa, the Arabian Peninsula, and South Asia -- though Moissl emphasized it is far too early for people to consider drastic decisions like relocation.
Alternatively, 2024 YR4 may enter Earth's atmosphere but explode in mid air in what's known as an 'air burst,' like the Tunguska asteroid did in 1908.
Though this scenario would prevent it from slamming into the surface, it could be just as destructive. The Tunguska asteroid caused the most explosive impact in recorded history when it blew up over Siberia.
However, Bruce Betts, chief scientist for the nonprofit Planetary Society, said he is not panicking.
'Naturally when you see the percentages go up, it doesn't make you feel warm and fuzzy and good,' he added, but explained that as astronomers gather more data, the probability will likely edge up before rapidly dropping to zero.'
NASA revealed last week that it plans to send its James Webb Space Telescope (JWST) to investigate the space rock.
'Webb is able to see things that are very, very dim,' said Betts.
The the asteroid's orbit is currently taking it out towards Jupiter, and its next close approach will not be until 2028.
If the risk rises over 10 percent, the International Asteroid Warning Network (IAWN) would issue a formal warning, leading to a 'recommendation for all UN members who have territories in potentially threatened areas to start terrestrial preparedness,' explained Moissl.
