Rapid heating rates define the volatile emission and regolith composition of (3200) Phaethon.

Asteroid (3200) Phaethon experiences extreme solar radiant heating ( ~ 750 °C) during perihelion (0.14 au), leading to comet-like activity. The regolith composition and mechanism of volatile emission are unknown but key to understanding JAXA's DESTINY mission data (fly-by in 2029) and the fate of near-Sun asteroids more generally.