17
The Roche Limit
When can tides tear a moon apart?
•As a planetary body get close to another object, tidal forces distort the body more and more.
–Remember, Earth raises tides on the Moon
just like it raises tides on the Earth
–
•If the distortion gets large enough, the moon will be pulled apart
–Happens at “Roche Limit” when moon is
~2.44 ´ radius of planet away
–At that point, tidal force pulling up on surface of moon is greater than moon’s gravity pulling down
–
•Only matters for objects held together by gravity
–Astronaut in orbit will not be pulled apart
•Is held together by much stronger chemical forces
–Astronaut standing on the outside of the shuttle, hoping the shuttle’s gravity would hold her there, will be pulled away from the shuttle
From Worlds Apart by Consolmagno and Schaefer