Ocean Worlds in the Outer Regions of the Solar System (Review)

Abstract

There is an astonishing variety of celestial bodies in the outer regions of the Solar System: Europa, with its bizarre surface features, Enceladus, small but geologically active, Titan, the only moon with a significant atmosphere, Pluto, with its nitrogen glaciers, and many others. Over the past 25 years, measurements from spacecraft have shown that many of these celestial bodies are ocean worlds with large volumes of liquid water trapped under icy surfaces. This new group of celestial bodies, ocean worlds, is important for research for several reasons, but the most convincing and at the same time the simplest reason is that they can be potential habitats. Life, as we know it, requires liquid water in addition to energy, nutrients, and a sustainable environment. All these requirements can be met for some of these celestial bodies. The moons of the giant planets on which the presence of the subsurface ocean is established (Europa, Ganymede, Titan, and Enceladus) and their astrobiological potential are discussed.