Double planet the four, small, outer satellites of Pluto. A now-abandoned hypothesis for the origin of the Moon was actually called the "double-planet hypothesis"; the idea was that the Earth and the Moon formed in the same region of the solar system's proto-planetary disk, forming a system under gravitational interaction. This idea, too, is a problematic condition for defining two bodies as "double planets" because planets can "capture" moons through gravitational interaction. For example, the moons of Mars (Phobos and Deimos) are thought to be asteroids captured long ago by Mars. Such a weak definition would also deem Neptune-Triton a double planet,
Red Planet Mars Red Planet Mars Red Planet Mars is a 1952 American science fiction film released by United Artists starring Peter Graves and Andrea King. It is based on a 1932 play "Red Planet" written by John L. Balderston and John Hoare and was directed by art director Harry Horner in his directorial debut. An American astronomer obtains images of Mars suggesting large-scale environmental changes are occurring at a pace that can only be accomplished by intelligent beings with advanced technology. At the same time a colleague claims to have been contacting Mars by radio, using technology stolen from the Nazis after