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How can tidal heating keep an ocean warm beneath Europa’s ice?

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Planet TOI 700e — extraterrestrial life An illustration of the Earth-size planet TOI 700e orbiting within the habitable zone of its star. The habitable zone is the area around a star where liquid water, and thus possibly life, can survive on a planet's surface. Its Earth-size sibling, TOI 700d, can be seen in the distance.

Europa’s potential subsurface ocean is maintained by the immense gravitational influence of Jupiter, which generates tidal energy within the moon's interior.12

As Europa orbits Jupiter, the planet's powerful gravitational pull creates tidal forces that stretch and flex the moon's crust and interior. This process, known as tidal heating, acts as a continuous source of internal energy—a milder version of the same mechanism that powers the intense volcanic activity on the neighboring moon Io. This energy is sufficient to partially melt the ice or maintain a liquid layer, potentially keeping a saltwater ocean warm beneath the moon's icy crust.312

The presence of this heat source, combined with the inferred liquid water, is a primary reason scientists consider Europa a leading candidate in the search for extraterrestrial life, as it could provide the necessary conditions for biological processes to occur in the absence of sunlight.23