Apollo-type asteroid Apollo-type asteroid 2024 YR4 triggers global planetary defence procedures for the first time and rises to the top of the Palermo Technical Impact Hazard Scale after recent observations confirmed it has a 1-in-77 (1.3%) chance of impacting Earth on 22 December 2032. Follow up observations in 2028 will provide a more refined estimation of the likelihood of impact in 2032. Sources: The Guardian