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Space Science

Comets Probably Seeded Earth's Nitrogen Atmosphere 110

Posted by samzenpus
from the in-the-beginning dept.
KentuckyFC writes "One of the biggest puzzles of astrobiology is the origin of the Earth's oceans and atmosphere. One favored theory is that our water is the leftovers from a bombardment of comets early in Earth's history. But the ratio of hydrogen and deuterium in the oceans doesn't match the ratio in the four comets measured so far (Halley's, Hyakutake, Hale-Bopp and C/2002 T7 LINEAR). Now a new analysis of the ratio of nitrogen-14 and 15 isotopes in these comets and on Earth places new limits on how much of our environment could have come from comets. On the one hand, the astronomers who did the work say that no more than a few percent of Earth's water could have come from comets. But on the other, they say that the ratio of nitrogen isotopes in these comets almost exactly matches the ratio in Earth's atmosphere. That suggests that while Earth's oceans must have come from somewhere else, Earth's early atmosphere was probably seeded by comets."
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Comets Probably Seeded Earth's Nitrogen Atmosphere

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  • Obvious? (Score:1, Informative)

    by muphin (842524) on Thursday July 02, 2009 @12:41AM (#28553945) Homepage
    Although comets may have initiated seeding of life and the foundry of everything from water to minerals .. there has been proof that water is abundant in space and maybe have just been absorbed into the atmosphere on earth and generated that way, over time rain would have brought the water molecules to the surface.
    http://www.space.com/scienceastronomy/astronomy/milkyway_water_010412.html [space.com]
  • by khayman80 (824400) on Thursday July 02, 2009 @01:04AM (#28554029) Homepage Journal

    ... it'd take a while but is it really so far fetched to think that ultimately all our water and atmosphere are extra-terrestrial?

    The point is that the isotope abundances of the oceans don't match the only four comets that have been observed precisely enough. H20 and HDO are easily distinguished from each other, and deuterium (the "D" in HDO) is quite stable so the isotope abundances shouldn't have changed. We've only measured 4 comets, though, so perhaps other comets more closely resemble our oceans.

    Coincidentally, I attended Dr. Goldblatt's fascinating talk at the Fall 2008 AGU conference where he showed that the faint young sun paradox [dumbscientist.com] could be mitigated by a higher nitrogen pressure in the primordial atmosphere. Someone in the crowd (a Slashdot user, perhaps?) answered my question about experimental constraints on this pressure by saying that current research involving "raindrops" might produce a constraint soon.

    This paper seems like it should be relevant, but I've yet to see a direct connection. If anything, the disparities in the isotope abundances between 15N/14N and D/H seem to imply their origins are (at best) only loosely connected. But unfortunately the guy who shouted "raindrops" didn't have a microphone and he was across a crowded lecture hall, so I don't have the foggiest idea what he meant. Maybe "raindrops" was a brief reference to the "enstatite chondrites" on page 7 of this new paper (the context seems similar, at least). However, Javoy's paper was published in 1986 and my mysterious benefactor definitely said the research was currently underway. Plus, the topic at the time was the total pressure of nitrogen, not the isotope abundance...

    Anyone who knows about this subject, please enlighten me!

  • Re:Wood to Gold (Score:2, Informative)

    by Schmorgluck (1293264) on Thursday July 02, 2009 @07:38AM (#28555883)
    Gold? That would be from a supernova.
  • by ceoyoyo (59147) on Thursday July 02, 2009 @09:06AM (#28556537)

    Carefully note the words "probably" and "suggests."

    In other words, nobody has claimed anything is "true." They noted an interesting pattern and thought about what it could mean. Now they'll try to devise experiments to test that hypothesis.

    Contrast this with theological reasoning: "the bible says so, therefore it is true. End of discussion."

  • by radtea (464814) on Thursday July 02, 2009 @09:20AM (#28556671)

    Faith in what? Have you read the paper behind this idea? It's full of assumptions and caveats that are explicitly laid out by the authors, pointing out that one can follow a particular thread of plausible but unproven argument, and suggesting ways of empirically testing it.

    Ideas are tested by experiment and systematic, often quantitative, observation. That is the core of science.

    Ideas are believed without question. That is the core of faith.

    See the difference?

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