2024 YR4 briefly carried ~3% Earth‑impact odds before being ruled out; lunar impact risk rises as JWST sizes the 60±7 m object

Near‑Earth asteroid 2024 YR4, discovered 27 December 2024, briefly carried a ~3% probability of impacting Earth in December 2032 before additional observations ruled out an Earth strike on 23 February 2025. Subsequent data shifted the risk toward a possible lunar impact (~4% by May 2025); JWST measured its diameter at 60±7 m.

Discovered 2025-09-19T04:51:53.540298-07:00 | 2025-09-19T04:51:53.540298-07:00

Briefing

What Hype is tracking

Initial impact probabilities moved rapidly: Earth impact odds peaked near ~3% (18 Feb 2025) then were ruled out (23 Feb 2025), while lunar‑impact probability climbed to about ~4% by the end of the apparition in May 2025; JWST sizing gives a diameter of 60±7 m, a key input for mitigation planning. See the growing global focus on monitoring ahead of Apophis 2029 (https://hype.aero/?story=795c48f8-3183-4ddd-851a-b653ee6f2f84).
The episode highlights the operational value of space‑based characterization (JWST) for narrowing impact uncertainties and informing response options; it reinforces momentum behind coordinated reconnaissance and rapid‑response mission concepts like the ESA–JAXA Rapid Apophis flyby (https://hype.aero/?story=bb651471-cdae-4494-bc6a-dd0bcbb366dd).
Rapid swings in risk estimates underline the need for internationally coordinated mitigation decision‑frameworks and pathfinder reconnaissance capabilities, echoing proposals for short‑notice flybys and pathfinder missions (https://hype.aero/?story=2c482437-be13-4410-bced-b80965d27268).

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