Editor’s Update (2/20/25): Shortly after this story was released, NASA declared updated information collected overnight has decreased the likelihood of asteroid 2024 YR4 hitting Earth from an unprecedented 3.1 percent to 1.5 percent. This figure will likely continue to decrease until it reaches zero, but as long as the chance of an Earth strike remains above 1 percent, 2024 YR4 will still be closely monitored.

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The asteroid known as 2024 YR4, first observed last December as it passed alarmingly close to Earth, now has a revised 3.1 percent chance of impacting our planet during its next approach in late 2032, according to recent announcements by space scientists. This marks the highest impact probability ever calculated for such a large asteroid, though the likelihood of an actual collision remains low, at about one in 32.

“This is the highest impact probability we have noted for an asteroid of this size or larger,” stated Davide Farnocchia, a specialist in impact hazards at NASA’s Center for Near Earth Object Studies at the Jet Propulsion Laboratory (JPL). However, Farnocchia also mentioned that this status might change quickly. “The impact probability could shift by the time this report is published,” he remarked.

2024 YR4 was initially detected by a dedicated asteroid-detection telescope in Chile on December 27 last year. It wasn’t until a month later, however, that the asteroid became a significant concern when preliminary orbit calculations indicated it had more than a 1 percent chance of colliding with Earth on December 22, 2032. The area at risk stretches from the eastern Pacific Ocean to South Asia, including vast uninhabited regions of ocean and desert as well as densely populated cities such as Bogotá, Lagos, and Mumbai. There’s also a very slight chance the asteroid could hit the moon.

Should the asteroid strike Earth, the immediate effects could be similar to a hydrogen bomb explosion, causing enough localized destruction to obliterate any unfortunate city in its path.

Thus, the periodic increases in 2024 YR4’s estimated impact probability have understandably alarmed astronomers and puzzled the public. Many wonder how predictions about the asteroid’s trajectory can remain uncertain, why scientists appear unconcerned about the increasing chances of a collision, and why it’s taking so long to determine the real level of threat.

The simple explanation is that calculating an asteroid’s orbit becomes more accurate the longer it is observed, and there hasn’t been enough time to track 2024 YR4 extensively. Currently, the asteroid is moving away from Earth and has dimmed beyond the detection capability of most telescopes. Nevertheless, it continues to be monitored by major observatories. In the upcoming months, astronomers plan to use NASA’s James Webb Space Telescope to refine their measurements of the asteroid’s size and path.

The inconsistency in risk assessments, which just yesterday suggested a 2.6 percent chance of impact, results from limited observational opportunities and new data. For instance, the full moon in February obscured precise observations for about a week, followed by fresh data from observatories in New Mexico and Spain. These observations are independently processed at three different facilities globally, all of which currently agree on a low but slowly increasing probability of an impact.

“For now, I would not be concerned,” advised Detlef Koschny, a planetary scientist at the Technical University of Munich and chair of the United Nations–affiliated Space Mission Planning Advisory Group (SMPAG). He explained that as uncertainty decreases, the probability of the asteroid crossing Earth’s path may initially increase, only to potentially confirm that it won’t hit our planet at all.

This was the case with Apophis, a previously identified potentially hazardous asteroid. Despite early predictions of a possible Earth impact in 2029, continued observations led to its impact probability dropping to zero. It’s likely that 2024 YR4’s increasing impact probability will similarly turn out to be a false alarm.

According to Timothy Spahr, an astronomer managing the International Asteroid Warning Network, the orbit of 2024 YR4 is already well-understood enough that daily changes are not a major concern. “Yes, the impact probability can shift, but we need more days of observation to refine the estimates,” he explained. By later this year, astronomers will have a clearer picture of how concerned everyone should be.

If the threat level of 2024 YR4 remains significant as it approaches again in 2028, contingency plans for 2032 might need to be considered, ranging from evacuating risk areas to potentially launching missions to alter the asteroid’s course or destroy it. However, “given that continued observations are likely to rule out an impact, discussing deflection strategies is still premature,” concluded Farnocchia.

Additional reporting by Meghan Bartels.