
A moon of Jupiter with a subsurface ocean, used as a benchmark for habitable conditions in this study.Europa is the fourth-largest moon of Jupiter and one of the most promising candidates for hosting habitable environments beyond Earth. Its icy surface hides a global subsurface ocean of liquid water, kept warm by tidal heating from Jupiter's gravity. This makes Europa a benchmark for studying the conditions necessary for life and a target for future space missions.
The idea of a subsurface ocean on Europa was proposed in the 1970s based on Voyager images showing a young, cracked surface, and strongly supported by Galileo spacecraft measurements of its magnetic field in the 1990s.
Europa's interior is heated by tidal flexing: as it orbits Jupiter, the planet's gravity stretches and relaxes the moon, generating friction that melts the ice below the crust. This heat maintains a liquid water ocean beneath a shell of ice, and the ocean is in contact with a rocky seafloor, providing chemical energy sources that could support microbial life.
Europa is the target of NASA's Europa Clipper mission, which will study its ice shell and ocean to assess its habitability and prepare for future landers.
Europa's ocean may contain more than twice the volume of all Earth's oceans combined, despite the moon being only a quarter of Earth's size.



























