Organic Macromolecules on Comet P67

Comet Churyumov–Gerasimenko (67P)You may remember back in November, I went a little crazy about the Rosetta mission to comet Churyumov-Gerasimenko (67P). And I was especially crazy about the lander, Philae, because I thought that through it, the science team would be able to test for organic compounds. This is my main interest in comets: the idea that the building blocks of life (or life itself) could have been seeded onto earth. So when Philae did its big bounce and got jammed up against a cliff wall, my hopes were dashed. But I was mistaken. It turns out that Rosetta can do a whole lot more from a distance from the comet than I had realized.

Last week, Science Magazine put out a special issue on new research from the Rosetta mission. Joseph Stromberg over at Vox provided a good overview, The Rosetta Probe Discovered That Comet 67P/C-G Is Light as a Cork. As the title indicates, 67P has a very low density: roughly that of a cork. It’s porosity is more than 70%. Associated with that, I think, is the fact that the comet has very little water. I assume that the comet once had water, which it outgassed, leaving behind all these pores. So that’s interesting. Also of note is the fact that the water that is on the comet is much “heavier” than earth water — as a percentage, there is three times as much deuterium (“heavy hydrogen” or hydrogen with a neutron).

But the big news is a paper by F Capaccioni and 77 colleagues, The Organic-Rich Surface of Comet 67P/Churyumov-Gerasimenko as Seen by VIRTIS/Rosetta. The satellite has a spectrometer that looks at visible and infrared light. And looking at the light that bounces off the surface of the comet, they can tell what bandwidths are absorbed and thus determine which chemicals are on the surface. Based upon this, they found very little water and lots of organic compounds. Well, what they say is very much what we expect from scientists: their results are “compatible with opaque minerals associated with nonvolatile organic macromolecular materials.” I have to wonder if creatures had evolved and were building high rises, would they be willing to say much more than that the buildings were compatible with the existence of higher life forms?

Unfortunately, we don’t know what the organic chemicals are. All the spectral data can tell us is that they are “a complex mixture of various types of carbon-hydrogen and/or oxygen-hydrogen chemical groups, with little contribution of nitrogen-hydrogen groups.” DNA and RNA consist of carbon, hydrogen, oxygen, nitrogen, and phosphorus. But long carbon compounds are primarily concerned with carbon, hydrogen, and oxygen. The fact that the data indicate macromolecular materials, that would have to be what we are talking about.

This is all very exciting. And this is just what scientists managed to discover so far. In fact, this article isn’t even based on the results of Rosetta while orbiting it. The paper was submitted to Science Magazine back in the middle of October. The main thing to remember is that it is this kind of science that the Rosetta mission is all about. Here in the United States, we tend to focus on the technology side of it, “Hooray! We got a spaceship to orbit a comet! We landed on a comet!” But that’s just the means of doing something much greater. The objective of the mission is to better understand the origins of the solar system. And that work will be going on for years to come. It’s great stuff — the best of what we are.

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