The odds of asteroid YR4 hitting Earth have climbed. Should we be worried?

Remember 2024 YR4, the asteroid NASA revealed last week, that has a one-in-83 chance of smashing into our home planet in 2032?

Well, there’s good news and bad news.

First, the bad news: Experts at NASA, this week, have bumped up the odds of an impact to a one-in-43 chance.

The good news, however, is scientists still say it’s not keeping them up at night and no one should panic, despite not being able to rule out the possibility of an impact.

Last week, the European Space Agency (ESA) gave the asteroid a 1.3 per cent chance of hitting the Earth on Dec. 22, 2032. NASA’s Center for Near Earth Object Studies (CNEOS) said Thursday that the likelihood of impact has now reached 2.3 per cent.

NASA’s Asteroid Terrestrial-impact Last Alert System (ATLAS) in Chile first detected 2024 YR4 in late December while hunting for near-Earth objects.

ATLAS reported the sighting on Dec. 27, 2024, to the Minor Planet Centre, the official group for observing and reporting new asteroids, small bodies and comets in the solar system.

The asteroid measures between 40 and 90 metres wide (130 and 300 feet) based on estimates from its reflected light.

“An asteroid this size impacts Earth on average every few thousand years and could cause severe damage to a local region,” the ESA said in a space safety briefing. “As a result, the object rose to the top of ESA’s asteroid risk list.”

At this point, it’s hard to say where the unlikely collision would happen. A warning published last week by the International Asteroid Warning Network (IAWN) says the impact risk corridor extends “across the eastern Pacific Ocean, northern South America, the Atlantic Ocean, Africa, the Arabian Sea, and South Asia.”

If it did strike Earth, 2024 YR4 would cause “severe blast damage,” according to IAWN, spanning as far as 50 kilometres from the impact site.

For now, YR4 has been given a Level 3 rating out of 10 on the Torino Impact Hazard Scale, meaning a close encounter with the asteroid is “meriting attention by astronomers,” according to CNEOS. A collision with Earth is only certain when an object reaches an 8, 9 or 10 rating, with higher ratings indicating more damage likely to be caused.

That said, YR4’s rating is way out in front of any other asteroid being monitored at the moment.

Dr. Shyam Balaji, a researcher in astroparticle physics and cosmology at King’s College London, told Forbes that context is key in understanding YR4.

“More than 33,000 near-Earth asteroids have been discovered and tracked since 1990 — so asteroid 2024 Y24 is one of many being observed,” he told the outlet. “At present, the public should not be overly concerned, though the asteroid warrants continued monitoring.”

CNEOS says that while there’s a possibility the asteroid could make potential impacts on Earth six times between 2032 and 2071, the probability drops with each subsequent pass.

Asteroids that are initially calculated to have a small chance of slamming into Earth are usually downgraded to have a lower probability of doing so over an extended observation period.

“It is moving away from the Sun, getting farther and farther and fainter and fainter,” Paul Chodas, the director of CNEOS, told Gizmodo. “The key thing is that it’s fading. It requires larger and larger telescopes to detect, and by April we think it’ll be too faint to observe with the largest telescopes.”

The asteroid follows an elliptical, four-year orbit, swinging through the inner planets before passing Mars and heading out toward Jupiter.

For now, it’s heading away from Earth and its next close pass won’t come until 2028.

In the unlikely event that YR4 were to be on a collision course with our planet, one option would be to change the trajectory of the asteroid by slamming a robotic spacecraft into it, similar to the successful DART test mission by NASA in 2022, which changed the course of an asteroid that was of no threat to Earth.

Alternatively, a nuclear deflection could be used to deflect the asteroid, or a gravity tractor, a spacecraft designed to tug the asteroid off course with its own gravitational pull, could be called in to help.