Roche limitis 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 frenchastronomer who first calculated this limit in 1848

Roche limit

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Roche limit

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Roche limit

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Examples of Roche limits

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!