The organic dust of Comet 67P/C-G

My annual birthday-month fund-raising drive for Behind the Black is now on-going. Not only do your donations help pay my bills, they give me the freedom to speak honestly about science and culture, instead of being forced to write it as others demand.


Please consider donating by giving either a one-time contribution or a regular subscription, as outlined in the tip jar below.


Regular readers can support Behind The Black with a contribution via paypal:

Or with a subscription with regular donations from your Paypal or credit card account:

If Paypal doesn't work for you, you can support Behind The Black directly by sending your donation by check, payable to Robert Zimmerman, to
Behind The Black
c/o Robert Zimmerman
P.O.Box 1262
Cortaro, AZ 85652


You can also support me by buying one of my books, as noted in the boxes interspersed throughout the webpage. And if you buy the books through the ebookit links, I get a larger cut and I get it sooner.

A study of the dust released by Comet 67P/C-G and captured by Rosetta shows that carbon molecules appear to comprise the comet’s largest component, and that this material is found in the form of very large macromolecules.

As the study shows, organic molecules are among those ingredients at the top of the list. These account for about 45 percent of the weight of the solid cometary material. “Rosetta’s comet thus belongs to the most carbon-rich bodies we know in the solar system,” says MPS scientist and COSIMA team member Dr. Oliver Stenzel. The other part of the total weight, about 55 percent, is provided by mineral substances, mainly silicates. It is striking that they are almost exclusively non-hydrated minerals i.e. missing water compounds. “Of course, Rosetta’s comet contains water like any other comet, too,” says Hilchenbach. “But because comets have spent most of their time at the icy rim of the solar system, it has almost always been frozen and could not react with the minerals.” The researchers therefore regard the lack of hydrated minerals in the comet’s dust as an indication that 67P contains very pristine material.

…The current findings also touch on our ideas of how life on Earth came about. In a previous publication, the COSIMA team was able to show that the carbon found in Rosetta’s comet is mainly in the form of large, organic macromolecules. Together with the current study, it becomes clear that these compounds make up a large part of the cometary material. Thus, if comets indeed supplied the early Earth with organic matter, as many researchers assume, it would probably have been mainly in the form of such macromolecules.

Organic here does not mean life, but is instead used as chemists use it, to mean the molecule includes the element carbon. The results do suggest however that the early solar system had a lot of carbon available, and that much of it was in a relatively pure form available to interact with other elements.



  • steve freedman

    Hi. Very interesting. I’m reading just your encapsulation above. If you want me to go to the original paper, send me the link if there is one. There are two things here: 1. the nature of the carbon macromolecules and, 2. the reason why the minerals (mainly silicates) are not hydrated. With regard to the macromolecules, I can only guess that it is graphite. Think about the hoopla if they find diamonds in the mix!
    Regarding 2., I will look into the the nature of silicates and hydrated minerals in general and try to find – or fathom – a basis for non-hydration. You are right to characterize them as pristine (pure) but the question is whether this is an anomaly relative to what we find here on Earth. They suggest that it is in fact anomalous.
    I’ll check.

    I’m starting a new semester in a few days so please bear with me in terms of getting answers to the above.

    All the best for a Happy New Year,

  • steve freedman: I am confused. Didn’t we have an email exchange about this, and didn’t I email you the link to the paper (which is also available at the story above)?

  • Localfluff

    If this thing has drifted for billions of years between the stars, isn’t it expected that its surface has not been hydrated by the photons of Solar winds, like a Solar System bound object would be? And I guess that the spectra taken of this object are pretty inconclusive for mostly everything, other than that it is deep reddish. Like blood…

Leave a Reply

Your email address will not be published. Required fields are marked *