Europa is located outside the Sun's habitable zone and yet may be habitable. How can this be?

Question

Quizplus · Accepted Answer

Europa is not in the Sun's habitable zone, which is the region where the temperature is just right for liquid water to exist on the surface of a planet. However, its subsurface ocean of liquid water is believed to exist due to tidal heating caused by its proximity to Jupiter. The gravitational pull of Jupiter causes friction and generates heat in Europa's interior, keeping the water beneath its icy surface liquid. This makes Europa a potentially habitable world, even though it is outside the Sun's habitable zone.

Europa Is Located Outside the Sun's Habitable Zone and Yet