The impact hazard assessment for near-Earth asteroid 2024 YR4

Discovered by the ATLAS survey on December 27, 2024, asteroid 2024 YR4 represented one of the most significant impact risks ever detected. Roughly 60 m in size, this asteroid reached a 3% probability of impacting the Earth on December 22, 2032. We discuss the orbit and impact analyses carried by the three impact monitoring systems Sentry, Aegis, and NEODyS. The orbit solution proved to be remarkably stable and the impact probability behaved according to expectations as the uncertainty decreased thanks to additional observations, i.e., the impact probability initially increased as the Earth remained within the core of the uncertainty region and then dropped as the Earth moved towards the tail and eventually outside of the uncertainty region. Although the risk of an Earth impact has been ruled out, there remains a 4% probability of a lunar impact on December 22, 2032. To confirm or more likely rule out that possibility, we need to wait until new astrometric data become available, e.g., during the 2028 apparition.