Astronomers have raced to observe asteroid 2024 YR4
NASA/Magdalena Ridge 2.4m telescope/New Mexico Institute of Technology/Ryan
The recent findings from the world’s space agencies have significantly reduced the likelihood of asteroid 2024 YR4 colliding with Earth to less than 1 per cent. This positive development indicates that a potentially catastrophic impact is now unlikely. Despite this, the asteroid is still projected to pass very close to our planet, offering astronomers a rare opportunity to study an asteroid in close proximity.
Richard Moissl from the European Space Agency (ESA) stated, “We are currently not anticipating the impact probability to exceed 1 per cent during the close approach to Earth in 2032. The probability is more likely to decrease further, possibly even reaching 0.”
The concerns regarding asteroid 2024 YR4 first emerged in December of the previous year when astronomers identified a possible collision course with Earth in 2032. With an estimated size ranging between 40 and 90 meters, a potential impact could result in significant damage if it were to strike a populated area. Over the following weeks, various telescopes and space agencies closely monitored the asteroid’s trajectory, refining its projected path with greater accuracy. The peak impact risk was recorded on 17 February, with a 1-in-32 chance, but subsequent observations reduced this risk to 1-in-67, equivalent to a 1.5 per cent probability.
By 20 February, updated observations led to a substantial decrease in the impact risk, with NASA calculating a 0.27 per cent chance of impact (1-in-360) and ESA even lower at 0.16 per cent (1-in-625). These revised assessments place asteroid 2024 YR4 at a level 1 on the Torino scale, indicating it is now classified as one of the numerous low-risk asteroids discovered annually that ultimately avoid colliding with Earth.
Gareth Collins from Imperial College London acknowledged the positive development but emphasized the significance of the asteroid’s close approach for testing planetary defense systems and advancing scientific knowledge. “Despite the reduced risk of impact, this close approach will still provide a unique opportunity for observation. The fact that the impact risk was previously high suggests that the asteroid will pass remarkably close to our planet,” Collins explained.
Continued planning by NASA, ESA, and space organizations on potential strategies to deflect the asteroid is expected, according to Niklas Voigt from OHB, a German space company. Voigt mentioned ongoing discussions about a mission to alter 2024 YR4’s trajectory, emphasizing the importance of preparedness despite the decreased risk. “While the risk has diminished, we are continuing our work on this topic for now,” Voigt stated.
The upcoming close approach presents an opportunity to validate asteroid deflection capabilities, Voigt added, citing NASA’s successful DART mission, which altered the course of the 160-meter-wide asteroid Dimorphos in 2022. Another possibility is deploying a satellite to rendezvous with 2024 YR4, similar to ESA’s Ramses satellite intended for observing the asteroid Apophis during its close approach to Earth in 2029.
A final decision on how to address the potential threat posed by 2024 YR4 is anticipated following planned observations in March utilizing the James Webb Space Telescope. These observations will provide crucial data on the asteroid’s trajectory, size, and composition, which will be crucial for determining the best course of action. The United Nations-backed Space Mission Planning Advisory Group is expected to evaluate this data and make a decision by the end of April. Collins emphasized the importance of these exercises in facilitating informed decision-making with sufficient time to implement effective measures.
Although the risk of an Earth impact has significantly decreased, the likelihood of 2024 YR4 colliding with the moon has risen to 1.2 per cent, prompting further evaluation of the potential consequences. Moissl highlighted the need for additional assessment to determine the exact effects of an impact on the moon by an object of this size.
Collins noted that the response to asteroid 2024 YR4 has served as a valuable rehearsal for addressing future asteroid threats. “It is crucial to avoid complacency and ensure that the public remains vigilant about potential threats from space,” Collins emphasized.
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