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starship-design: Fwd: Interstellar Planets Could Support Life

A weird new relm for SF stories.  Or deep space exploration. 


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                             Interstellar Planets Could Support Life

Published: 1999 July 3  
am ET (1353 UT)
      Earth-sized planets ejected early in the
      history of solar systems could support life
      even in the cold depths of interstellar
      space, a Caltech scientist has found.

        In a paper published in the July 1 issue of the journal
      Nature, David Stevenson of Caltech found that such
      "interstellar planets" could retain enough heat to support
      conditions conducive to the formation of life.

        Simulations of the formation of the solar system show that
      up to ten planets the size of the Earth could have formed, but
      either collided with Jupiter or were ejected from the solar
      system during close approaches to the giant planet.

        These planets would normally cool as they moved far
      away from the Sun or any other star, but a dense hydrogen
      atmosphere retained from their formation could act as an
      insulating blanket, retaining the heat generated by the
      radioactive decay of elements in the interior of the planet.

        This could create Earth-like temperatures on the surface of
      the planet, even in the absence of an outside heat source.
      The planet could have liquid water oceans, but would have a
      surface pressure similar to that at the bottom of the Earth's

        If these planets have geothermal-like heat sources, the
      energy could be enough to allow the formation of some small,
      simple life forms. How complex the life could be is an open
      question, Stevenson believes. "I don't think anyone knows
      what is required to drive biological evolution from simple to
      very complex systems."

        However, other research, including that by Caltech
      colleagues Eric Gaidos and Joseph Kirschvink, suggests that
      geothermal energy sources may not be sufficient to generate
      anything more than the simplest life forms.

        Efforts to locate these planets, which may be
      commonplace if other solar systems formed like our own,
      would require advanced detection techniques, because of
      the limited amount of light they emit. Steven suggested
      looking for occultations, when the light from a background
      star is temporarily dimmed by the passage of one of these

        "I'm not saying that these objects have life," Stevenson
      said. "All I'm saying is that, among the places you might want
      to consider for sustainable life, you might eventually want to
      look at these objects. They could be the most common
      location for life in the universe."
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