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,
The Angry Red Planet CineMagic process: "Our set for the planet Mars cost us a couple of hundred dollars instead of the thousands we had estimated". Pink also estimates in that interview that the movie "will be made at half the original cost", confirming that "Invasion of Mars" (the film's working title before its release) was a low-budget project. The "meager" $200,000 production budget cited for "The Angry Red Planet" may therefore be a credible ballpark figure. Filming for "The Angry Red Planet" began on September 9, 1959 at Hal Roach Studios in Culver City, California, only a month after Melchior and Pink completed