"Nuclear to Protect the Moon?"—The Ultimate Planetary Defense Proposed by 2024 YR4: Is Nuclear Allowed in Space?

The asteroid "2024 YR4," discovered in December 2024, initially had a maximum 3.1% probability of colliding with Earth in 2032. However, subsequent observations have ruled out an Earth collision. Instead, the probability of a lunar impact is estimated at about 4%. If a lunar collision occurs, it could result in small debris entering Earth's low orbit, potentially increasing the risk of satellite damage by up to 1,000 times over a few days. A new study released on September 15 (pre-peer review) suggests that deflection is unrealistic and proposes strong impacts or nuclear "robust fragmentation" as practical solutions. The proposed launch windows are from late 2029 to the end of 2031 (nuclear) and from April 2030 to April 2032 (non-nuclear). Despite significant challenges posed by treaty constraints (PTBT, Outer Space Treaty) and the difficulty of international consensus, it is urgent to conduct reconnaissance in 2028 to determine the asteroid's mass and internal structure, thereby ensuring decision-making flexibility. [Sources: Live Science, arXiv, NASA/IAWN].