Iceworlds

Iceworlds are planetary bodies whose surfaces are dominated by ice, usually water ice or volatile ices such as carbon dioxide, and that maintain mean temperatures well below freezing. The term appears in planetary science and science fiction to describe worlds with persistent or global ice cover, whether they are icy moons, dwarf planets, or cold exoplanets.

Many iceworlds feature high reflectivity and rugged terrains carved by ice. Surface temperatures, ice thickness, and activity vary: some lie in stable icy shells, others experience dynamic processes such as cracking, cryovolcanism, or plume activity. Subsurface oceans may exist beneath an ice crust, kept liquid by tidal heating or radiogenic energy.

Geologically, ice shells can deform by brittle fracture or ductile flow, creating features like ridges and grooves. Cryovolcanic eruptions can bring liquid water, ammonia, or methane to the surface, forming transient plumes or resurfacing events.

Habitability prospects are generally limited by surface conditions, but internal oceans or chemical energy could support life in subsurface environments. Atmospheres range from tenuous to absent; some iceworlds retain modest atmospheres through sublimation or outgassing, while others are airless.

In our solar system, Europa and Enceladus exemplify icy worlds with suspected global or regional oceans beneath ice. Pluto and its moons show extensive volatile ices on the surface. Triton exhibits cryovolcanism. In fiction, iceworlds are common settings for exploration and colonization, often presenting logistical and survival challenges.

Studying iceworlds involves radar sounding, spectroscopy, and asteroid/comet analogs, with missions planned or proposed to assess ice thickness, ocean depth, composition, and potential habitats.