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Earth As an Extrasolar Planet

Posted by timothy on from the how-else-to-test dept.

sciencehabit writes "Astronomers have a theory that they can detect whether a planet light years away will be habitable by just looking at how its sun is reflected in its atmosphere. To test the idea, they pretended that they were observing Earth from a distant object — in this case, the moon. And sure enough, they picked up critical components for life in Earth's atmosphere: ozone, oxygen, sodium, and nitrogen."

5 of 83 comments (clear)

  1. Re:Proving What by MichaelSmith · · Score: 3, Informative

    It looks like they focused on only measuring certain atmospheric things, but this proves nothing as far as extrasolar planets go.

    Free oxygen on any planet tells you that something is making oxygen. In our case it is the plants which we treat so badly: turning them into newspapers, etc. Oxygen is so reactive that its presence tells you something must be going on. Mars used to have free oxygen but it combined with iron in the soil, turning it red: Iron Oxide.

    --
    http://michaelsmith.id.au
  2. The Galileo probe already did this by De_Boswachter · · Score: 4, Informative

    "A search for life on Earth from the Galileo spacecraft", Nature, 1993 C. Sagan et al., http://www.nature.com/nature/journal/v365/n6448/abs/365715a0.html

    1. Re:The Galileo probe already did this by interactive_civilian · · Score: 4, Informative

      For those without access to Nature, a Google Scholar search turns up a freely downloadable PDF of the full article.

      PDF Link

      I remember reading about this in Sagan's "The Pale Blue Dot", and thought it was such an awesome idea. I'm looking forward to reading the original paper. :)

      --
      "Empathise with stupidity, and you're halfway to thinking like an idiot." - Iain M. Banks
  3. Re:Proving What by murdocj · · Score: 3, Informative

    The Slashdot summary was really, really bad. They didn't pretend to be observing the earth from the moon, they analyzed the spectra of light passing through the earth's atmosphere and reflected off of the moon. The idea is that this is similar to analyzing the light passing through a planet's atmosphere as it transits in front of a star. So it's not as crazy as it sounds.

  4. RTFA by pigeon768 · · Score: 3, Informative

    So, now to apply this to an extrasolar planet, we have to have the planet reflect the light of its sun back at the Earth, which means that their sun is already between them and us (counting "between" as being able to project the vector from here to their sun upon the vector from here to the extrasolar planet, and result in a vector of lesser magnitude than the vector from here to the extrasolar planet). And we're supposed to be able to isolate any of the light from that planet apart from its sun?

    You misunderstand the experiment. For this idea to work, the planet has to be between us and the star. Exactly between - as in, the planet is eclipsing its sun, from our point of view. They're not detecting light that's been reflected off a planet, they're detecting light that's been filtered through a planet's atmosphere.

    This is something we've already done with large gas giant planets. The 'new' thing is that we did it with a planet the size of earth, with its significantly thinner atmosphere.