NASA has significantly lowered the risk of near-Earth asteroid 2024 YR4 as an impact threat to Earth for the foreseeable future. When first discovered, asteroid 2024 YR4 had a very small, but notable chance of impacting our planet in 2032. As observations of the asteroid continued to be submitted to the Minor Planet Center, experts at NASA Jet Propulsion Laboratory’s (JPL’s) Center for Near-Earth Object Studies were able to calculate more precise models of the asteroid’s trajectory and now have updated its impact probability on Dec. 22, 2032 to only 0.004% and found there is no significant potential for this asteroid to impact our planet for the next century. The latest observations have further reduced the uncertainty of its future trajectory, and the range of possible locations the asteroid could be on Dec. 22, 2032, has moved farther away from the Earth.
Animation of 2024 YR4’s Earth impact probability over time (credit: NASA/JPL Center for Near-Earth Object Studies)
There still remains a very small chance for asteroid 2024 YR4 to impact the Moon on Dec. 22, 2032. That probability is currently 1.7%.
NASA will continue to observe asteroid 2024 YR4 with observatories funded by its Planetary Defense Coordination Office, and NASA’s James Webb Space Telescope will observe the asteroid in March to further gain insights about its size for scientific purposes.
While this asteroid no longer poses a significant impact hazard to Earth, 2024 YR4 provided an invaluable opportunity for experts at NASA and its partner institutions to test planetary defense science and notification processes. The latest data on all known near-Earth asteroids that could pose an impact hazard to Earth will continue to be available at NASA’s automated Sentry page.
Observations made overnight on Feb. 19 – 20 of asteroid 2024 YR4 have further decreased its chance of Earth impact on Dec. 22, 2032, to 0.28%. NASA’s planetary defense teams will continue to monitor the asteroid to improve our predictions of the asteroid’s trajectory. With this new data, the chance of an impact with the Moon increased slightly to 1%. The latest data will continue to be available at NASA JPL’s automated Sentry page.
Now that skies are darker after a week of limited visibility around full moon, astronomers have resumed observations of asteroid 2024 YR4. Ground-based telescopes require dark skies to observe asteroids, which are often very faint. Around the time of a full moon, the sky becomes too bright to detect these faint points of light.
NASA’s Center for Near-Earth Object Studies at the agency’s Jet Propulsion Laboratory in Southern California has incorporated the new observations reported to the Minor Planet Center and on Feb. 18, updated the impact probability of asteroid 2024 YR4 in 2032 to 3.1%. This is the highest impact probability NASA has ever recorded for an object of this size or larger. However, on Wednesday, Feb. 19, new data collected overnight reduced the impact probability to 1.5%.
Graphic of the possible locations of 2024 YR4 on Dec. 22, 2032 as of Jan. 27, 2025. Earth is close to the center of the white circle, which represents the Moon’s orbital path. Credit: NASA JPL/CNEOSGraphic of the possible locations of 2024 YR4 on Dec. 22, 2032 as of Feb. 19, 2025. Earth is close to the center of the white circle, which represents the Moon’s orbital path. The range of possibilities has decreased from the previous image because of the additional data gathered. Credit: NASA JPL/CNEOSCredit: NASA JPL/CNEOS
Each additional night of observations improves our understanding of where the asteroid could be on Dec. 22, 2032 and underlines the importance of gathering enough data so that our planetary defense experts can determine future risk to the Earth. NASA expects the impact probability to continue to evolve as new observations of asteroid 2024 YR4 are made over the coming days and weeks.
These recent observations have further constrained the uncertainty around the asteroid’s trajectory, and the yellow dots in the above graphics represent possible locations of the asteroid on Dec. 22, 2032. As we continue to observe the asteroid’s motion over time, the region of possible locations will shrink even further. For the impact probability to drop to zero, the Earth would need to fall outside of the range of potential locations of asteroid 2024 YR4 on Dec. 22, 2032.
Additionally, there is also a – much lower — chance this asteroid could impact the Moon. Current calculations estimate this impact probability to be 0.8%.
NASA’s Near-Earth Object Surveyor mission, set to launch no earlier than Sept. 2027, will accelerate NASA’s ability to discover unknown asteroids by hunting for them in the infrared. While dark in visible light, asteroids and comets glow in the infrared as they’re heated by sunlight. In addition, NEO Surveyor will add an in-space vantage point that complements ground-based observatories.
While still an extremely low possibility, additional observations and analysis of asteroid 2024 YR4 indicate that its impact probability with Earth has increased to a 2.3% chance on Dec. 22, 2032. Ongoing observations from ground-based telescopes involved with the International Asteroid Warning Network will continue while the asteroid is still visible through April, after which it will be too faint to observe until around June 2028.
NASA’s James Webb Space Telescope will also observe the asteroid in March 2025 to better assess the asteroid’s size. Currently the asteroid is estimated to be 130-300 feet across.
As more observations of the asteroid’s orbit are obtained, its impact probability will become better known. It is possible that asteroid 2024 YR4 will be ruled out as an impact hazard, as has happened with many other objects that have previously appeared on NASA’s asteroid risk list, maintained by NASA’s Center for Near-Earth Object Studies. It is also possible its impact probability will continue to rise. The latest data will continue to be made available via NASA’s automated Sentry page.
NASA analysis of a near-Earth asteroid, designated 2024 YR4, indicates it has a more than 1% chance of impacting Earth on Dec. 22, 2032 – which also means there is about a 99% chance this asteroid will not impact. Such initial analysis will change over time as more observations are gathered.
Currently, no other known large asteroids have an impact probability above 1%.
Asteroid 2024 YR4 was first reported on Dec. 27, 2024, to the Minor Planet Center– the international clearing house for small-body positional measurements – by the NASA-funded Asteroid Terrestrial-impact Last Alert System station in Chile. The asteroid, which is estimated to be about 130 to 300 feet wide, caught astronomers’ attention when it rose on the NASA automated Sentry risk list on Dec. 31, 2024. The Sentry list includes any known near-Earth asteroids that have a non-zero probability of impacting Earth in the future.
There have been several objects in the past that have risen on the risk list and eventually dropped off as more data have come in. New observations may result in reassignment of this asteroid to 0 as more data come in.
More information about asteroids, near-Earth objects, and planetary defense at NASA can be found at:
The small near-Earth asteroid 2024 PT5 was first observed on Aug. 7, 2024, by the Sutherland, South Africa telescope of the University of Hawai’i’s Asteroid Terrestrial-impact Last Alert System (ATLAS), which is funded by NASA. Estimated to be about 33 feet (10 meters) wide, the asteroid does not pose a hazard to Earth.
Because 2024 PT5 has a similar motion to Earth’s around the Sun, the asteroid will linger as a distant companion of our planet for a few months at a distance of about nine times farther away from Earth than the Moon. During this time, the object will never be captured by Earth’s gravity. So while it’s not quite a “mini-moon,” 2024 PT5 is an interesting object and NASA has plans to track it with planetary radar.
Part of NASA’s Deep Space Network, the Goldstone Solar System Radar, near Barstow in California, will track the object during its next close pass of our planet, in January 2025, which will still be five times as far from Earth as the Moon. The asteroid will then leave the vicinity of Earth as it continues its orbit around the Sun.
Given the similarity between asteroid 2024 PT5’s motion and that of our planet’s, scientists at NASA’s Center for Near Earth Object Studies (CNEOS) suspect that the object could be a large chunk of rock ejected from the Moon’s surface after an asteroid impact long ago. Rocket bodies from historical launches can also be found in such Earth-like orbits, but after analysis of this object’s motion, it has been determined that 2024 PT5 is more likely of natural origin.
Based at NASA’s Jet Propulsion Laboratory in Southern California, CNEOS precisely characterizes the orbits of all known near-Earth objects, predicts their close approaches with Earth, and makes comprehensive impact hazard assessments in support of the agency’s Planetary Defense Coordination Office (PDCO) at NASA Headquarters in Washington.
ATLAS and the Goldstone Solar System Radar are supported by NASA’s Near-Earth Object Observations Program within PDCO. Managed by JPL, the Deep Space Network receives programmatic oversight from the Space Communications and Navigation program office within the Space Operations Mission Directorate at NASA Headquarters.
Left: Matt Daniels, Assistant Director of the White House Office of Science and Technology Policy (OSTP) for Space Security & Special Projects, briefs PDC participants on the newly released 2023 NEO Strategy and Action Plan for Planetary Defense; Center: NASA Planetary Defense Officer, Lindley Johnson, provides an update on the status of projects in NASA’s Planetary Defense program; Right: Kelly Fast, NASA’s NEO Object Observations Program Manager and Coordinating Officer for the International Asteroid Warning Network speaks to the importance of international collaboration.
In a world where many global challenges exist, finding ways to respond to an as yet undiscovered asteroid that might one day impact Earth could seem like a lesser priority. While it is true there are currently no known asteroids of significant size on a collision trajectory with Earth, an asteroid impact with our planet has potential for catastrophic damage and could change the course of civilization as we know it. Equipped with this understanding, Planetary Defense experts around the globe convened last week in Vienna, Austria, for the 8th IAA Planetary Defense Conference (PDC) to discuss ongoing efforts focused on addressing the asteroid impact hazard.
During the conference, which occurred from April 3 – 7 and was hosted by the United Nations Office of Outer Space Affairs (UN-OOSA), scientists, engineers, global thought leaders, policymakers, government officials, and other Planetary Defense experts discussed what their respective stakeholders were doing to better understand how humanity might respond if an asteroid or comet, any near-Earth object (NEO), headed our way were ever discovered. Additionally, the PDC provided the Planetary Defense community the unique opportunity to engage directly with national policy makers to discuss the latest advancements in humanity’s capability to find, track, and deflect potentially hazardous NEOs. Through bringing the world’s Planetary Defenders together, the PDC also allowed attendees to share their respective knowledge and expertise with one another to help encourage coordination among global asteroid impact mitigation. This knowledge sharing occurred through a series of panels and sessions, each with their own respective objectives and focus.
One such panel, which focused on disaster preparedness, allowed PDC attendees to hear directly from the Deputy Administrator of the Federal Emergency Management Agency (FEMA) on how they work with local and national government to coordinate response to emergency events and what information would be needed from the Planetary Defense community about an impending asteroid impact. Through these conversations, nations can learn best practices from one another and work toward creating a global strategy to respond to an actual impact threat if ever necessary. During the PDC, the White House Office of Science and Technology Policy (OSTP) also released the updated National Preparedness Strategy and Action Plan for Near-Earth Objects and Planetary Defense, which establishes six key US Government goals for the next ten years to ensure the Nation is well better equipped to mitigate potentially hazardous NEO impacts. NASA is planning to soon release its own complementary PD strategy to ensure the agency is working toward its goals in Planetary Defense for the next decade.
NASA Program Scientist Michael Kelley briefs PDC members on lessons learned from an international campaign to observe near-Earth asteroid Apophis during its 2021 close approach with Earth.
Conference attendees also had the opportunity to participate in a brief asteroid impact tabletop exercise to simulate how information would unfold in the years and months leading to an actual asteroid impact event. The exercise included representatives from two collaborative bodies recommended in 2014 by the United Nations and now very active within the Planetary Defense community: The International Asteroid Warning Network (IAWN) and the Space Mission Planning Advisory Group (SMPAG). NEO impacts are a global hazard that require global cooperation and international collaboration through IAWN and SMPAG, and events like the PDC are key to fostering that cooperation.
Ultimately, preventing an asteroid impact with Earth and avoiding a catastrophic natural disaster poses a complex problem that requires a multidisciplinary approach. Additionally, if a NEO were headed toward Earth, its devastation would not recognize national borders or politics. International coordination is at the heart of Planetary Defense, and conferences like the PDC provide an invaluable opportunity for experts around the world to come together, share their knowledge, and unite as one under the common goal of safeguarding Earth from asteroid impacts for generations to come.
Group photo of some of the in-person attendees of the 8th International Academy of Astronautics Planetary Defense Conference. Credit: Max Alexander
Asteroid “Chelyabinsk 2013” explodes over the city of Chelyabinsk, Russia on February 15, 2013. Credit: The Planetary Society/YouTube.
On Feb. 15, 2013, the people of Chelyabinsk, Russia, experienced a shocking event, and yet it was a small fraction of the devastation an asteroid on a collision course with Earth could yield. As NASA’s Planetary Defense experts reflect on the Chelyabinsk impact 10 years ago, they also look forward to the future and all that the agency has since accomplished in the field of Planetary Defense.
Harmless meteoroids, and sometimes small asteroids, impact our planet’s atmosphere daily. When they do, they disintegrate and create meteors or “shooting stars” and sometimes bright fireballs or bolides. Such was the case on Feb. 12 when a very small asteroid impacted Earth’s atmosphere over Northern France soon after discovery, resulting in a spectacular light show for local onlookers. Much more rarely, a larger asteroid that is still too small to reach the ground intact, yet large enough to release considerable energy when it disintegrates, can do significant damage to the ground. On Feb. 15, 2013, one such bolide event garnered international attention when a house-sized asteroid impacted Earth’s atmosphere over Chelyabinsk, Russia, at a speed of eleven miles per second and exploded 14 miles above the ground. The explosion was equivalent to 440,000 tons of TNT, and the resulting air blast blew out windows over 200 square miles, damaged buildings, and injured over 1,600 people – mostly due to broken glass. Due to the asteroid’s approach from the daytime sky, it was not detected prior to impact, serving as a reminder that while there are no known asteroid threats to Earth for the next century, an Earth impact by an unknown asteroid could occur at any time.
Coincidentally, negotiations sponsored by the United Nations were finalizing formal recommendations for the establishment of Planetary Defense-related international collaborations – the International Asteroid Warning Network (IAWN) and the Space Missions Planning Advisory Group (SMPAG) – when the Chelyabinsk impact occurred. Since then, NASA established the agency’s Planetary Defense Coordination Office (PDCO) in 2016 to oversee and coordinate the agency’s ongoing mission of Planetary Defense. This includes acting as a national representative at international Planetary Defense-related caucuses and forums, such as IAWN and SMPAG, and playing a leading role in coordinating U.S. government planning for response to an actual asteroid impact threat if one were ever discovered. The PDCO also funds observatories around the world through NASA’s Near-Earth Object (NEO) Observations Program to find and characterize NEOs – asteroids and comets that come within 30 million miles of Earth – with a particular focus on finding asteroids 460 feet (140 meters) and larger that represent the most severe impact risks to Earth. To help accelerate its ability to find potentially hazardous NEOs, NASA is also actively developing the agency’s NEO Surveyor mission, which is designed to finish discovery of 90 percent of asteroids 140 meters in size or larger that can come near Earth within a decade of being launched.
In 2022, working together with the Italian Space Agency, NASA’s Double Asteroid Redirection Test (DART) mission successfully demonstrated the world’s first-ever test for deflecting an asteroid’s orbit. Launched in 2021, DART successfully collided with a known asteroid – which posed no impact threat to Earth – demonstrating one method of asteroid deflection technology using a kinetic impactor spacecraft. Since DART’s impact, Planetary Defense experts have been continuing to analyze data returned from the mission to better understand its demonstrated effects on the asteroid, which contributes to the understanding of how a kinetic impactor spacecraft could be used to address an asteroid impact threat in the future if the need ever arose.
The Chelyabinsk impact was a spark that ignited global conversation in Planetary Defense, and much progress in the field has occurred since then. However, there is still more work to be done, and NASA is actively at the forefront. In addition to building NASA’s NEO Surveyor to find the rest of the population of asteroids that could pose a hazard to Earth, the agency is considering a “rapid response reconnaissance” capability to be able to quickly obtain a more detailed characterization of a hazardous asteroid once it is discovered. NASA is also considering sending out a reconnaissance spacecraft to study an asteroid making a close approach to Earth in 2029.
“A collision of a NEO with Earth is the only natural disaster we now know how humanity could completely prevent” said NASA Planetary Defense Officer Lindley Johnson. “We must keep searching for what we know is still out there, and we must continue to research and test Planetary Defense technologies and capabilities that could one day protect our planet’s inhabitants from a devastating event.”
