Case study: 2024 YR4

2024 YR4 was discovered on 27 December 2024. During January and February 2025 its Earth impact probability for 22 December 2032 rose as observations accumulated, peaking around 3% (Torino 3) on both agencies' lists in mid-February — the highest ever published for an object of its size (~40–90 m). Within days, new observations brought it down to near zero.

What the archive shows — and what it misses

The history before Two Skies started is reconstructed from Internet Archive captures. ESA's risk page was captured roughly weekly, and 2024 YR4 sat at the top of it, so the archive shows the climb step by step: 0.1% in early January, Torino 3 by early February, 2.9% on 19 February, then the collapse to ~0.002% a week later.

NASA's Sentry API was captured only a handful of times a year, so the whole rise and fall happened between two NASA captures. The archive records only the residual probability afterwards. Comparing the agencies during the peak is impossible from archives alone.

This is exactly why Two Skies snapshots both lists every day: the next 2024 YR4 will be recorded day by day, on both lists, including the moments the agencies' numbers diverge or converge.

See the object page for the full record.