Martian colony administrator threatens a Martian child. The Martians demand that the humans leave Mars, but a human doctor convinces them to reconsider. In Heinlein's 1956 novel "Double Star", humans have colonized the solar system, and a politician on Mars faces the civil rights issue of granting a native Martian species (who are second-class citizens) the right to vote. In Philip K. Dick's novel "Martian Time-Slip" (1964), a human colony on Mars is trying to cope with arduous environmental conditions. They treat an aboriginal race, whom they call "Bleekmen", with casual racism. In "The Three Stigmata of Palmer Eldritch" (1965), Mars
Five-planet Nice model Planet Nine is Nice planet #5" Five-planet Nice model The five-planet Nice model is a recent variation of the Nice model that begins with five giant planets, the current four plus an additional ice giant, in a chain of mean-motion resonances. After the resonance chain is broken, the five giant planets undergo a period of planetesimal-driven migration, followed by a gravitational instability similar to that in the original Nice model. During the instability the additional giant planet is scattered inward onto a Jupiter-crossing orbit and is ejected from the Solar System following an encounter with Jupiter. An early Solar System