Rosetta finds carbon molecules in comet dust

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The Rosetta science team has announced that they have detected very complex carbon molecules in solid dust particles that were released from Comet 67P/C-G.

“Our analysis reveals carbon in a far more complex form than expected,” remarked Hervé Cottin, one of the authors of the paper reporting the result that is published in Nature today. “It is so complex, we can’t give it a proper formula or a name!” The organic signatures of seven particles are presented in the paper, which the COSIMA team say are representative of the two hundred plus grains analysed so far.

The carbon is found to be mixed with other previously reported elements such as sodium, magnesium, aluminium, silicon, calcium and iron. It is bound in very large macromolecular compounds similar to the insoluble organic matter found in carbonaceous chondrite meteorites that have fallen to Earth, but with a major difference: there is much more hydrogen found in the comet’s samples than in meteorites.

But as this kind of meteorite is associated with reasonably well-processed parent bodies such as asteroids, it is reasonable to assume that they lost their hydrogen due to heating. By contrast, comets must have avoided such significant heating to retain their hydrogen, and therefore must contain more primitive material.

Because of the use of the term organics here for these carbon-based molecules, expect a lot of news reports to misreport this discovery and incorrectly announce with great excitement that Rosetta has “discovered life” on Comet 67P/C-G! Among scientists, any carbon molecule is referred to as organic, even if it is entirely inanimate. In this case these molecules are not the result of life, but of carbon’s atomic structure, allowing it to form an infinite variety of molecules with almost any other element.


  • Localfluff

    Carbon is the third or fourth most common element in the Universe and the Solar System. If they had NOT found carbon, it would’ve been a notable news. Stars which end by producing, and explodingly distribute, more carbon than oxygen create CO and organically rich environments. Stars which (for fusion physical reasons in their cores) produce more oxygen than carbon, cause water ice rich regions and Solar Systems.

  • Edward

    Localfluff wrote: “Stars which (for fusion physical reasons in their cores) produce more oxygen than carbon, cause water ice rich regions and Solar Systems.”

    During college, I did a summer internship for a company that made spectrometers to measure the content of the solar wind, but during my first week, the guy I worked for was on vacation, so they had me do research in the department’s library. The most astonishing thing that I learned was the unexpectedly high content of oxygen in the solar wind (unexpected by me, anyway). I did not know the reason for it, but now I learn from Localfluff that it is due to the physics of fusion in the sun’s core.

    Thanks, Localfluff. One more mystery solved.

  • wayne

    (I should know better, than to challenge either one of you on science-factoids!)

    I will have to check on this in depth, but… I was not aware the Sun was busily producing elemental oxygen and spewing it into the solar system.
    –the Sun does produce elemental oxygen, but that doesn’t wind up in the atmosphere or on the surface of the Earth. I’m no chemist but elemental oxygen is highly reactive if I recall that correctly.(?)
    There is oxygen in open space, just not very much of it.

    Now I’m intrigued…and I’ll do some actual digging.

    (‘Fluff is totally correct that stars that explode, spew out every Element in the periodic table. )

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