Asteroid 2024 YR4 – chance of impacting Earth
2024 YR4 is an asteroid that is classified as an Apollo-type (Earth-crossing) near-Earth object, with an estimated diameter of 40 to 90 metres.
Calculations using the observation arc of 55 days as of 18 February 2025, it has a rating of 3 on the Torino scale, with a 1-in-32 (3.1%) chance of impacting Earth on 22 December 2032 around 14:02 UT, and a rating of −0.18 on the Palermo scale, corresponding to an impact hazard 66.1% of the background level. 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%. The uncertainty region for the path of its potential impact in 2032 is 1.1 million km wide. The nominal closest approach to Earth is on the 22nd at 10:02 UT (with an uncertainty in the closest approach time of about 8 hours and being 4 hours earlier than virtual impactor) at a distance of 198,000 kilometres (0.52 lunar distances), with a 3-sigma uncertainty of 356,000 kilometres (0.926 lunar distances). The nominal closest approach to Moon is seven hours later at 16:25 UT. Due to 2024 YR4’s size and greater-than-1% impact probability, it is rated at Torino scale level 3, which has prompted the International Asteroid Warning Network to issue a notice on 29 January 2025. This is the second-highest Torino scale rating an asteroid has ever reached, behind 99942 Apophis which briefly ranked Torino scale level 4 in late 2004. NASA gives a Palermo scale rating of −0.18 for 2024 YR4, which corresponds to an impact hazard of 66.1% of the background hazard level. The European Space Agency gives a Palermo scale rating of −0.20 with an impact probability of 2.81%, while NEODyS gives −0.21 with an impact probability of 2.27%.
The asteroid was discovered by the Chilean station of the Asteroid Terrestrial-impact Last Alert System (ATLAS) on 27 December 2024. The discovery triggered the first step in planetary-defense responses, prompting several major telescopes to gather data about the asteroid and leading United Nations–endorsed space agencies to begin planning asteroid threat mitigation. The asteroid made a close approach to Earth at a distance of 828,800 kilometres (2.156 lunar distances) on 25 December 2024, two days before its discovery, and is now moving away. Its next close approach will take place on 17 December 2028. From early April 2025 to June 2028, the asteroid is expected to be too distant for ground-based telescopes to observe. However, space-based infrared telescopes could continue monitoring it during some of this period; for example, the James Webb Space Telescope is scheduled to observe it between March and May 2025. Preliminary analysis of spectral and photometric time series suggests that 2024 YR4 is a stony S-type (most likely), L-type or K-type asteroid, with a rotation period of approximately 19.5 minutes. A number of known asteroids, including other virtual impactors, follow orbits somewhat consistent with that of 2024 YR4. As of 23 February 2025 NASA gives Palermo scale rating of −3.45 for 2024 YR4, which corresponds to an impact hazard of 0.08% of the background hazard level. NEODyS gives −4.38 with an impact probability of 0.000444%, while the European Space Agency gives a Palermo scale rating of −3.55 with an impact probability of 0.00162%.
Using observations through 26 March 2025, 2024 YR4 has around a 4% chance of impacting a 70% waning gibbous moon on 22 December 2032 around 15:17 to 15:21 UTC. The nominal approach to the Moon is near the impact scenario at around 15:18 UTC ± 1.5 hours at a distance of 3,100 km (0.0081 LD) from the center of the Moon, or about 1,400 km above the 1,737 km radius of the Moon, with a 3-sigma uncertainty of 83,000 km. The impact could create an impact crater with a diameter of 500 to 2,000 metres wide on the lunar surface, releasing about 5.2 megatonnes of TNT (21.8 petajoules) of energy if it were to impact the Moon at an estimated velocity of 13.9 km/s, an explosion about 340 times more powerful than the Hiroshima bomb. The impact corridor is a line that extends through the southern parts of Mare Humorum and Mare Nubium. Michael Busch of the SETI Institute notes that an explosion on the Moon “would be very obvious to any spacecraft observing from lunar orbit” but may not be as visible to the unaided eye from Earth due to the Moon’s brightness. However, other astronomers believe the impact could be visible from Earth. Gareth Collins suggested that “the impact flash of vaporized rock would be visible from Earth, even in the daytime”, while Daniel Bamberger of the Northolt Branch Observatories in London stated that the impact “could be brighter than the full moon” making it clearly visible to the naked eye.
ESA actively monitoring near-Earth asteroid 2024 YR4
NASA Shares Observations of Recently-Identified Near Earth Asteroid
2024 YR4 – International Asteroid Warning Network
2024 YR4 – Earth Impact Risk Summary
Dark Skies Bring New Observations of Asteroid 2024 YR4, Lower Impact Probability