Ceres, the only dwarf planet in the asteroid belt, has a thin water vapor atmosphere. The vapor could have been produced by ice volcanoes or by sublimating ice from the surface. The presence of water on Ceres had led to speculation about its current and past habitability. Although the dwarf planet might not have living things today, there could be signs it harbored life in the past.

Jupiter was computed by Carl Sagan and others in the 1960s and 1970s considering conditions for hypothetical microorganisms living in its atmosphere. The intense radiation and other conditions, however, do not appear to permit encapsulation and molecular biochemistry, so life there is thought unlikely. In contrast, some of Jupiter’s moons may have habitats capable of sustaining life.

Saturn’s Titan has an atmosphere that is considered similar to that of the early Earth, although somewhat thicker. The surface is characterized by hydrocarbon lakes, cryovolcanos, and methane rain and snow. Like Earth, Titan is shielded from the solar wind by a magnetosphere, in this case, generated by its parent planet for most of its orbit. The shield’s influence on Titan’s atmosphere is considered sufficient to facilitate the creation of complex organic molecules. The remote possibility of an exotic methane-based biochemistry life has been hypothesized.

Saturn’s Dione has been suggested to have an internal water ocean under 100 kilometers of crust. Based on data gathered and simulations, the tens of kilometers deep ocean would likely be in contact with the moon’s rocky core, making it suitable for microbial life in the aspect of available nutrients. This ocean has probably existed for the moon’s entire history, meaning there has potentially been plenty of time for life to take root and evolve beneath Dione’s battered, icy shell.

Models of heat retention and heating via radioactive decay in smaller icy Salar System bodies suggest that Rhea, Titania, Oberon, Triton, Pluto, Eris, Sedna, and Orcus may have oceans underneath solid icy crusts approximately 100 km thick. Of particular interest in these cases is the fact that the models indicate that liquid layers are in direct contact with the rocky cores, which allows efficient mixing of minerals and salts into the water. This configuration contrasts with the oceans that may be inside larger icy satellites like Ganymede, Callisto, or Titan, where layers of high-pressure phases of ice are thought to underlie the liquid water layer.