Global planetary defense organizations are closely observing asteroid 2024 YR4, which carries a very small chance of colliding with Earth.
The European Space Agency (ESA) has stated that there is an almost 99% likelihood that the asteroid will pass safely by Earth on December 22, 2032. However, experts caution that a potential impact “cannot yet be entirely ruled out.” The current probability of collision is estimated at 1.3%.
Dr. Robert Massey of the Royal Astronomical Society expressed confidence that the risk remains minimal. “I’m not panicking or losing sleep over it,” he said. “There is no need for alarm. The thing about this kind of event is that historically they tend to go away when the calculations are refined.”
At the same time, Massey emphasized the importance of continued vigilance. “We need to be aware, alert, and we need to give astronomers the resources they need to track these kinds of threats so that we can take action as soon as possible.”
Discovery and Potential Impact
Asteroid 2024 YR4 was first identified on December 27, 2024. Initial calculations suggest it measures between 40 and 90 meters across. Were it to collide with Earth, it could unleash energy equivalent to a nuclear explosion, causing extensive destruction if the impact were to occur in a populated region.
Despite this, scientists believe it is far more likely that YR4 would land in an ocean or an uninhabited part of the planet if an impact were to occur. Given its current distance from Earth and existing uncertainties, pinpointing a potential impact location remains impossible at this stage.
Since early January, astronomers have been conducting further observations using telescopes to refine their calculations of the asteroid’s size and trajectory. Currently, YR4 has been classified as a level 3 threat on the Torino Impact Hazard Scale, which ranges from 0 to 10. This rating signifies “a close encounter that warrants attention from astronomers and the public.” In contrast, a collision is considered certain only if the rating reaches levels 8, 9, or 10, which correspond to increasing levels of expected damage.
Past Cases of Overestimated Risk
Astronomers stress that when asteroids are first assessed as having a small probability of striking Earth, the likelihood of impact usually drops to zero as further data is collected. A similar situation arose in 2004 when scientists initially calculated that an asteroid named Apophis had a 2.7% chance of colliding with Earth in 2029. Later observations, however, ruled out that possibility.
Under planetary defense protocols, any object with a diameter exceeding 50 meters and a greater than 1% chance of impacting Earth automatically triggers precautionary measures. These protocols ensure that even minor risks are closely observed, allowing authorities to take action if necessary.
Monitoring by International Agencies
The first step in such cases involves activating two key UN-backed asteroid monitoring organizations: the International Asteroid Warning Network (IAWN), which is chaired by NASA, and the Space Mission Planning Advisory Group (SMPAG), overseen by ESA.
SMPAG is currently holding discussions to determine the best course of action. The group has already concluded that it is too early to take immediate measures but affirmed that it would “monitor the evolution of impact threat and possible knowledge about the size closely.”
Another meeting to decide on future actions is scheduled for late April or early May. However, if new data suggests an increased threat, an earlier meeting may be convened.
If YR4’s probability of impact remains above the 1% threshold, SMPAG will provide recommendations to the United Nations and may begin evaluating possible intervention strategies.
Potential Deflection Strategies
In the unlikely scenario that asteroid 2024 YR4 is determined to be on a collision course with Earth, one viable option would be to divert its path using a robotic spacecraft. This method was successfully demonstrated in 2022 through NASA’s Double Asteroid Redirection Test (DART) mission, which altered the trajectory of an asteroid that was not on a collision course with Earth.
Dr. Massey pointed to the success of that mission as evidence that humanity has the capability to prevent such impacts—provided that threats are identified with sufficient lead time. “NASA’s DART mission showed that we have the means to divert an asteroid, but only if we spot it early enough,” he said.
Challenges in Tracking YR4’s Path
At present, asteroid YR4 is moving away from Earth in an almost linear trajectory, which makes it difficult to determine its exact orbit with precision. Scientists expect the asteroid to fade from view in the coming months, after which it will be monitored through both ground-based and space telescopes.
ESA has acknowledged the possibility that YR4 could become unobservable before scientists can definitively rule out the risk of impact in 2032. “It is possible that asteroid 2024 YR4 will fade from view before we are able to entirely rule out any chance of impact in 2032,” the agency stated. “In this case, the asteroid will likely remain on ESA’s risk list until it becomes observable again in 2028.”
For now, experts emphasize that while the situation warrants attention, there is no cause for immediate concern. As additional observations refine the asteroid’s trajectory, scientists expect the probability of an impact to decrease even further.