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Space Science

Earth As an Extrasolar Planet 83

Posted by timothy
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."
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Earth As an Extrasolar Planet

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  • Why not point Cassini back at us and take some readings.. that should also give some good results.
    • Re: (Score:3, Insightful)

      by Tablizer (95088)

      Cassini is probably not designed to be sensitive to those signatures. It's built for Saturn and co. It cost a lot to add & launch extra's outside of mission objective.

    • by pigeon768 (589860) on Saturday July 24, 2010 @04:27AM (#33012058)

      This technique only works on light that passes through the planet's atmosphere. In this case, during a lunar eclipse, they pointing a telescope at the part of the moon that was reflecting the light that had traveled through the Earth's atmosphere. They found that the moon had absorption lines resulting from interactions with Earth's atmosphere.

      The technique would work if the Earth occulted the Sun from Cassini's viewpoint, but such occultations are rare.

      • Re: (Score:1, Flamebait)

        by snowgirl (978879)

        This technique only works on light that passes through the planet's atmosphere. In this case, during a lunar eclipse, they pointing a telescope at the part of the moon that was reflecting the light that had traveled through the Earth's atmosphere. They found that the moon had absorption lines resulting from interactions with Earth's atmosphere.

        The technique would work if the Earth occulted the Sun from Cassini's viewpoint, but such occultations are rare.

        So... the light went through the Earth's atmosphere, into a reflector on the moon, which reflected it back... to the Earth's surface? Like... THROUGH the atmosphere that they were trying to detect anyways?

        If it simply needed to pass through the atmosphere, I could do that in my back yard, why reflect it off the moon? Why involve anything other than a sensor on the Earth's surface? If "zomg, we have to be all mythbusters sciencey on this", then why not just a LEO satellite... each one, I'm sure receives m

        • Re: (Score:2, Insightful)

          by pigeon768 (589860)

          So... the light went through the Earth's atmosphere, into a reflector on the moon, which reflected it back... to the Earth's surface? Like... THROUGH the atmosphere that they were trying to detect anyways?

          Yes. Part of calibrating a spectroscope involves adjusting for the fact that every result you'll ever get ever will have passed through Earth's atmosphere, and will demonstrate roughly the same absorption lines as a result. This is mitigated partially by the fact that spectroscopic analysis is usually performed somewhere at an observatory on the top of a mountain in some dry region with relatively stable weather, but considerations must still be made. Otherwise, every single star in the sky demonstrates mol

          • Re: (Score:1, Informative)

            by Anonymous Coward

            We're finding a few planets like that with the kepler mission. I'm sure we'll have some spectroscopy results published this decade.

        • Re: (Score:1, Informative)

          by Anonymous Coward

          You miss the point, most sensors we have for detecting extrasolar planets are still placed within the atmosphere. What they simulated was detecting an earth-like planet placed two moon-distances away from earth trough the earth atmosphere.
          Except for the distance beeing way too short by at least a factor of 10^10 this is something that could be useable.

          • by snowgirl (978879)

            The technology and science necessary to make the equivalent observation of an extrasolar planet that we made of the Earth necessary requires a knowledge level that would circumscribe this technology.

            In other words, "by the time we can actually make the detections necessary for the extrasolar case, we necessarily would have all the knowledge necessary to produce this test."

            Which is kind of a retarded way of saying "we're going to have this technology first."

            But having plenty of time left before it's even use

      • by BudAaron (1231468)
        More importantly it only applies to carbon based life I would assume. How about silicon based life - as an example?
        • by Jarik C-Bol (894741) on Saturday July 24, 2010 @11:09AM (#33013542)
          yes of course, lets worry deeply about detecting (from light years upon light years away) a form of life that has only be theorized to be possible, and if exists is most likely in an environment that is totally incompatible with ours, thus making any contact with such life forms extremely difficult at best..

          or you know, we could figure out how to detect life forms similar to our own, then try and branch out from that knowledge base once we accomplish that.
        • Re: (Score:3, Interesting)

          by gstoddart (321705)

          More importantly it only applies to carbon based life I would assume. How about silicon based life - as an example?

          You know, someone asks this in almost every thread where the search for extra terrestrial life comes up.

          The reality of it is, we don't know anything about what a hypothetical silicon-based life-form would look like, or what kind of environment it would need.

          Since we know nothing about this life-form, how do you propose we look for this? The simple answer is, we can't because we don't know what

    • by De_Boswachter (905895) on Saturday July 24, 2010 @07:13AM (#33012546) Homepage
      "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 [nature.com]
  • by Anonymous Coward

    http://en.wikipedia.org/wiki/Jupiter#Possibility_of_life
    http://www.youtube.com/watch?v=uakLB7Eni2E
    http://www.thelivingmoon.com/41pegasus/02files/Critters_Carl_Sagans_Cosmos_Life_on_Jupiter.html

    Besides extremophiles, there may entirely new systems of life.

  • by gmuslera (3436) on Saturday July 24, 2010 @03:27AM (#33011908) Homepage Journal
    NASA has finally proved that planet Earth is (still, at least) habitable! We knew that all that investment will bring us new knowledge some day.
    • Not NASA (Score:2, Insightful)

      by pigeon768 (589860)

      Astrophysicist Alfred Vidal-Madjar and colleagues at the Institut d'Astrophysique de Paris decided to test the idea...

      Granted, NASA does have the firepower and crack soldiering skills necessary to invade and occupy Paris, but they haven't done it. (yet)

      • Astrophysicist Alfred Vidal-Madjar and colleagues at the Institut d'Astrophysique de Paris decided to test the idea...

        Granted, NASA does have the firepower and crack soldiering skills necessary to invade and occupy Paris, but they haven't done it. (yet)

        I am happy to know that NASA has soldiering skills. That means we will be able to fend off any alien invasion for sure!

    • by youn (1516637)

      Oh don't worry, we're working on it... we've been delayed by those green people... not the martians of course, the martians did a good job at turning their planet into a big desert :)... I wish they were still around so we could speed up the process :)... sheesh, saving the planet... what are they thinking?

    • by Arancaytar (966377) <arancaytar.ilyaran@gmail.com> on Saturday July 24, 2010 @05:57AM (#33012338) Homepage

      Well, they needed a control experiment to compare their findings to when they prove otherwise in 20 years.

    • by Kvasio (127200)

      NASA has finally proved that planet Earth is (still, at least) habitable! We knew that all that investment will bring us new knowledge some day.

      now, if only we had means to find out if there is intelligent life.
      Personally I doubt that.

  • From the moon, you have a pretty good view of earth. You can make out oceans and continents, and even manmade features if you have a good telescope. It looks like they focused on only measuring certain atmospheric things, but this proves nothing as far as extrasolar planets go. The distances involved make the earth-moon distance a piss-poor analogy for drawing any conclusions from this about anything light years away.
    • Re:Proving What (Score:4, Informative)

      by MichaelSmith (789609) on Saturday July 24, 2010 @04:23AM (#33012040) Homepage Journal

      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.

      • by Yvan256 (722131)

        Mars used to have free oxygen but it combined with iron in the soil, turning it red: Iron Oxide.

        So life originated on Mars, we screwed things up, were able to move to earth and now we're screwing things up again. Great.

      • Re: (Score:3, Interesting)

        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.

        The issue is burning down large areas of rain forest to get more short-term farmland, which uses up oxygen as well as permanently destroys the source for oxygen. The newspaper is not so relevant, since it is partially recycled and partially grown for the purpose.

    • They are testing techniques for detecting elements that may signal the existence of life as we know it. You have to learn to walk before you learn to run.

      If everyone had your attitude we'd still be living in caves and worshiping the spirits all around us.

      • Re: (Score:3, Insightful)

        by snowgirl (978879)

        You have to learn to walk before you learn to run.

        Right, but learning to walk is not the first steps towards crossing an ocean.

        This test is trivial at best, because the data present themselves so readily. We can't even isolate extrasolar planets from their sun. Could we even detect this stuff from a more reasonable distance away. If this detects elements in the atmosphere, then we can use it on Venus, too, right? Which would be a lot more meaningful since it is relatively faint from the Earth surface, and LEO.

        Not like much of this really means jack any

        • by maxume (22995)

          As we speak, an optimistic slug is oozing his way towards a nice canoe-sized tree.

        • RTFA (Score:4, Informative)

          by pigeon768 (589860) on Saturday July 24, 2010 @09:13AM (#33012892)

          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 [wikipedia.org] 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.

          • by snowgirl (978879)

            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 [wikipedia.org] 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.

            At twice the distance of the Earth and moon, I don't think the observable difference in thickness of the atmosphere is particularly significant. (I haven't done the math, but it strikes me as so.)

            Even if there were a significant difference in the measurement required, then what? We've managed to prove that technology has gotten more precise at taking measurements? Whoopdidoo! Slow news day news!

    • Re: (Score:1, Interesting)

      by Anonymous Coward

      uh, you do realize they were looking at the light reflected off the moon that was "coming" from earth ( light comes from sun to earth, bounces off, hits moon, and then they measured it, simulating a large distance since the moon is not super reflective (and neither is the earth)).

    • Re:Proving What (Score:4, Informative)

      by murdocj (543661) on Saturday July 24, 2010 @08:24AM (#33012708)

      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.

  • They could have just given me a few hundred thousand and I'd confirm for them that the Earth is hospitable for humans!
    • Re: (Score:2, Funny)

      by Tablizer (95088)

      They could have just given me a few hundred thousand and I'd confirm for them that the Earth is hospitable for humans!

      Until the point that American Idol and Fox News is detected ;-)
             

  • by Anonymous Coward

    wHo says that life needs oxygen? Even on our planet are living beings who do not need oxygen at all. Black smoker bacterias for example.

    Life develops according to outer circumstances. Darwin. Read it.

    it's just plain stupid to believe extra-terrestial life can only develop on Earth 2.

    • Re: (Score:3, Insightful)

      by MichaelSmith (789609)

      People are chucking around the idea of life on Titan, with Hydrogen taking the place of Oxygen. The thing you have to look for is an environment out of balance. Plant life on Earth turns sunlight and carbon dioxide into oxygen. Our free oxygen gives the game away and would be obvious to a good telescope many light years away. I think we would look first for free oxygen, but other combinations would raise alarm bells too.

    • by cheesecake23 (1110663) on Saturday July 24, 2010 @04:44AM (#33012108)

      wHo says that life needs oxygen? Even on our planet are living beings who do not need oxygen at all. Black smoker bacterias for example. Life develops according to outer circumstances. Darwin. Read it. it's just plain stupid to believe extra-terrestial life can only develop on Earth 2.

      Thank God we have enlightened ACs teaching scientists how to do things! I'm sure they never considered the points you raised.

      To address your point: they do NOT assume that life needs oxygen. However, the presence of significant amounts of oxygen in a planetary atmosphere is a strong indicator of life. This is because the gas is so reactive that it gets removed from the atmosphere very quickly. The only reason we have oxygen in our air is because it is continuously put there by photosynthesis.

      • Re: (Score:3, Funny)

        by deusx (8442)

        And besides, finding life that uses oxygen means we're more likely to find life similar to ours, so we can have sex with it.

        • by Tablizer (95088)

          And besides, finding life that uses oxygen means we're more likely to find life similar to ours, so we can have sex with it.

          But some days I'll settle for anything with suction cups.
             

    • Re: (Score:3, Insightful)

      they're not saying life can only develop this way. but if they find an earth-like planet, there's a pretty good chance it might have life. by the way, they're looking for habitable planets, not life.
      the science of a class of systems "X" is always hard when you have just one example; there's no need to call them stupid.

    • by Vahokif (1292866)
      Do you know any other characteristics we can look for?
      • Do you know any other characteristics we can look for?

        Porn? That's a dead give away that some hanky panky is going on . . . and where there is hanky panky . . . there is life.

        So NASA should build some, um, probes, that detect porn on extrasolar planets. Then we'll know if there is really life there.

        Probably . . .

        • That's an easy problem to solve, just need to get a few of the investigators at the FTC to transfer over to NASA and we're set!
  • sodium (Score:2, Funny)

    by Anonymous Coward

    It's natrium, you insensitive clod!

    • by Tablizer (95088)

      My buddy and I nicknamed it "Nadium" in chem class to better match the periodic table symbols. One day one of us slipped and put it on a pop-quiz. It came back with triple red question marks.

  • So they take Earth, which has life, and use that to train up an algorithm to detect if other planets have life. Then they test this algorithm against... earth.

    This is not how you're supposed to train systems. You need to keep your training and test data separate. Couldn't we have at least thrown one of those self-sustaining fish-globes up into space, and test that for life?

    • The researchers formulated a hypothesis based on first principles ("training data"), then tested that hypothesis by applying it to earth ("test data"). So, they didn't mix training and test data.

  • WTF? (Score:5, Funny)

    by mcneely.mike (927221) on Saturday July 24, 2010 @08:00AM (#33012662)
    I for one welcome our new Earth overl-...... wait a second.....HEY, that's me!
  • Not new at all (Score:3, Interesting)

    by chebucto (992517) on Saturday July 24, 2010 @08:07AM (#33012676) Homepage

    This is spectroscopy. They've been doing it for years, and it is the reason we know the chemical composition of everything from stars to planets to gas clouds. It's a fundamental tool of astronomy. The only novelty re: extrasolar planets is the resolution required, but even that isn't new, afaik.

    The article quotes the boffin as saying

    "The surprise was that we succeeded with extremely sparse observations under relatively bad weather conditions," Vidal-Madjar says. "But seeing how easily oxygen was seen strongly argues in favor of high-spectral-resolution searches [of Earthlike extrasolar planets]."

    So it seems that the news here is that it's easier than expected to measure oxygen.

  • Hmmm.

    Sodium (Na) a necessity in the atmosphere of a planet in order to make life (in a form similar to the one we know) possible?
    If so, what about the minimal content of Tungsten (again, in a planet's atmosphere)? Barium, anyone's guess?

    Just wondering...

  • Earth is heaven... (Score:2, Interesting)

    by nulled (1169845)

    Now if only people, including Scientists of all fields, would realize that Heaven already exists and anyone that is alive is living in it. It is called planet EARTH.

    No other place in the known universe has such a perfectly tuned atmosphere, able to support intelligent life. Let alone any type of life. Below is a list of traits the Earth has, which are rare, yet essential for life to spawn and be sustained.

    1) A large moon to make stable the earths rotation (seasons), make oceans slosh which is said to have h

    • by SheeEttin (899897)
      We evolved to make use of our environment. What makes you think life on other planets can't be, say, sulfur-based instead of carbon-based? (Yeah, something about carbon bonds with other elements, I know. It's an example.)
      And why need an atmosphere at all? Burrow around in the crust, you'll do just fine. You just won't be respiring. Or swim in the ocean, and respire something other than oxygen. Say, hydrogen.

      Sure, Earth is a paradise--but only if your concept of "life" is limited to what's on Earth.
      • Silicon forms many of the same types of bonds with other elements as carbon, you were probably thinking of that instead of sulfur. :)
    • Re: (Score:1, Informative)

      by Anonymous Coward

      1- We don't know how rare if at all for a planet like earth is to have a large moon, based in our solar system that may be the norm and Venus being the rarity.
      2- Again, not true, mercury has one, earth has one, Mars had one, same with the non rocky planets, Venus being the exception.
      3- by the actual sample of extrasolar planets it looks as if the goldie locks zone it is a good orbit for planets to form and as yourself mention our own solar system has two in that orbit
      4-by the latest data it also looks as i

      • by nulled (1169845)

        I am not saying that another Earth is not possible.

        In fact, I know there is one. The universe is infinitely huge, so the math says so.

        What I am trying to say is that so far it is the ONLY planet we know of. We will not be traveling to any planets anytime soon. It takes light years to get to the nearest star. And the nearest star may not have planets.

        Planet Earth may not be rare but it is very far to the next one. And no, Worm holes are not proven to exist. And if worm holes do exist there is no way to trave

    • Most likely, life started in/around hydrothermal vents via a process known as chemosynthesis. Life in the universe might not be so uncommon so long as you have liquid water, geothermal energy, and necessary elements.

  • I think it was Maturana and Varela, but I can't for the life of me figure out where I left that book, who had the hypothesis that life has a tendency to modify its surroundings, so that the surroundings are subsequently more suitable for that life to exist.
    Think about worms; they eat the earth, but in the process they make the earth more aerated and more suitable for worms to live in, as anyone with a compost heap can attest.
    I think this ties in nicely with the idea of Ilya Prigogine that life is a proc
    • by nulled (1169845)

      What you are trying to say is this...

      Every one of us, (Humans, plants and animals) are connected. If one group dies, the rest will die as well.

      • by fritsd (924429)
        No.. not really what I meant.. more that, if everything would die, the composition and spectrum of our planet's atmosphere would become more boring, more like most planets, as it quickly goes to chemical equilibrium.
        What you're saying, that we are all connected, is a bit more in line with James Lovelock's Gaia theory. I don't really know what to think of that. I think there is some ecological idea about "keystone" species [wikipedia.org] of ecosystems, maybe we're one of them.

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