Icy Beginnings: How Growing Planetesimals Warmed, Melted, and Evolved

Kimura et al. model how icy planetesimals heat, melt, and chemically evolve as they grow, showing that final size, growth timing, and accretion rate strongly control whether they stay cold, experience aqueous alteration, or even melt metal. Their results explain how Ryugu’s parent body remained cool while other bodies formed iron meteorites, and they outline conditions that could produce Enceladus-like interiors.