Roche limit is the distance within which a celestial body, held together only by its own gravity, will disintegrate due to a second celestial body's tidal forces exceeding the first body’s gravitational self-attraction. Inside the Roche limit, orbiting material will tend to disperse and form rings, while outside the limit, material will tend to coalesce. The term is named after Édouard Roche, the french astronomer who first calculated this limit in 1848

Roche limit r

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Examples of Roche limits

(THE ROCHE LIMIT…) Generally …large natural bodies orbit beyond their Roche Limit; exceptions have other adhesive forces binding the object (e.g. human-made, low-orbit satellites around Earth!) The (major) rings of Saturn, Jupiter, Neptune and Uranus are all within their Roche limit  particles from crushed up former satellites?

Energy generated by tidal movements  dissipated as heat Io (Jupiter’s innermost moon) – tidal forces  internal heat  powers extreme volcanic activity Europa (also Jupiter’s) – tidal heat  substantial sub- surface ocean  dark biospheres?

..also cryo-volcanism! e.g. ice volcanoes on Saturn’s moon Enceladus!