Moon Could Have Formed in Five Hours

A new simulation study (University of Arizona / Southwest Research Institute; Astrophysical Journal Letters, 2026) that includes the material strength of planetary rock finds a scenario where a Theia–Earth impact can produce an almost‑complete Moon within roughly five hours, with the remnant shedding mass for about a day. The result depends on moderately high surface temperatures (~3,140 °F) at impact so that parts of the bodies behave near but below melting, altering whether Theia is largely absorbed or leaves a large satellite. — If robust, the finding shifts scientific narratives about how quickly major planetary satellites can assemble and constrains early Earth–Theia conditions, with knock‑on implications for interpreting lunar samples and models of early Solar System dynamics.