small), except for the two classes of tidally decelerated bodies. In most cases, however, the effect is small enough that even after billions of years most satellites will not actually be lost. The effect is probably most pronounced for Mars's second moon Deimos, which may become an Earth-crossing asteroid after it leaks out of Mars's grip. The effect also arises between different components in a binary star. Tidal deceleration This comes in two varieties: Mercury and Venus are believed to have no satellites chiefly because any hypothetical satellite would have suffered deceleration long ago and crashed into the planets due to the very slow rotation speeds of both planets; in addition, Venus also has retrograde rotation. See also Tidal locking Tidal force Tides Tidal heating References External links The Recession of the Moon and the Age of the Earth-Moon System Tidal Heating as Described by University of Washington Professor Toby Smith Acceleration Geodesy Orbits Orbit of the Moon