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Which moons of Jupiter may contain oceans beneath icy surfaces?

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Habitable zone The habitable zones (green) for stars that are like the Sun (middle), hotter than the Sun (top), and cooler than the Sun (bottom). The red areas are those in which liquid surface water would be lost as a result of a runaway greenhouse effect, and the blue areas are those in which liquid surface water would be completely frozen.

Within the context of astrobiology and the search for life, several of Jupiter's moons are considered candidates for harboring liquid water oceans beneath their icy surfaces.

Europa: This moon is the most prominent candidate. Data from the Galileo spacecraft and other observations strongly suggest that a global saltwater ocean exists beneath its icy crust, potentially warmed by tidal energy.12
Ganymede and Callisto: These moons are also believed to potentially possess layers of water ice beneath their surfaces, though they are less frequently highlighted as primary candidates for habitable oceans compared to Europa.2

While Io is a major moon of Jupiter, it is characterized by extreme volcanic activity rather than icy surface features and is not considered a candidate for a subsurface water ocean. The presence of these subsurface reservoirs is significant because, even outside a star's traditional habitable zone, internal heat sources like tidal heating can maintain liquid water, which is considered essential for life.234