Martian Earth, but faced a process of devolution as conditions on the planet worsened. "Quatermass and the Pit" (1958–59) is a British television serial in which a crashed spacecraft is discovered in London. The wreck evidences that the human population of Earth resulted from the experiments of a Martian civilisation, now long dead. A film remake was released in 1967. "Ghosts of Mars" (2001) human invaders war with Martians in an attempt to conquer Mars. In the "Invader Zim" episode "Battle of the Planets" (2001), Zim discovers that a Martian race died off after converting Mars into a giant spacecraft. In
Planet Nine some combinations of semi-major axis and mass) and that its gravity dominates the outer edge of the Solar System, which is sufficient to make it a planet by current definitions. Jean-Luc Margot has also stated that Planet Nine satisfies his criteria and would qualify as a planet if and when it is detected. Brown speculates that the predicted planet is most probably an ejected ice giant, similar in composition to Uranus and Neptune: a mixture of rock and ice with a small envelope of gas. In fact, if it once orbited the region of the gas/ice giants, the planet probably