Observation Timeline for the Potential Lunar Impact of Asteroid 2024 YR 4

Abstract The near-Earth asteroid 2024 YR 4 —a ∼60 m rocky object that was once considered a potential Earth impactor—has since been ruled out for Earth but retains a ∼4.3% probability of striking the Moon in 2032. Such an impact, with equivalent kinetic energy of ∼6.5 Mt TNT, would be expected to produce a ∼1 km crater on the Moon and would be the most energetic lunar impact event ever recorded in human history. Despite the associated risk, this scenario offers a rare and valuable scientific opportunity. Using a hybrid framework, combining Monte Carlo orbital propagation, smoothed particle hydrodynamics impact modeling, and N -body ejecta dynamics, we evaluate the physical outcomes and propose an observation timeline for this rare event. Our results predict an optical flash of visual magnitude from −2.5 to −3, lasting for several minutes directly after the impact, followed by hours of infrared afterglow, from ∼2000 K molten rock cooling to a few hundreds of Kelvins. The associated seismic energy release would lead to a global-scale lunar reverberation (seismic magnitude ∼5.0) that would be detectable by any modern seismometer. Furthermore, the impact would throw out ∼10 8 kg debris, to escape lunar gravity, with a small fraction reaching Earth, to produce a lunar meteor outburst within 100 yr. Finally, we integrate these results into a coordinated observation timeline, identifying the best detection windows for ground-based telescopes, lunar orbiters, and surface stations.