Love the fact that you guys are putting up the "fresh" data! Reminds me of the Voyager flyby (when both Dr. Porco and I were at Caltech) and the JPL folks had a near live feed of the images coming in piped on to the big screen in Beckman Auditorium. In contrast, the folks running the Dawn mission are being pretty stingy with the data. Maybe you could send them a message about how it _should_ be done.
Just for context, the abundance of CO2 in the Earth's atmosphere -an essential fuel for photosynthesis- is only 0.04%, so 0.1% is not so bad. Also, large creatures did not emerge on Earth till Oxygen levels had risen substantially and there has been speculation that those are related, that big creatures need rich concentrations of energy whereas microbial life can eke out a living with less. Partly for this reason, though I'm hoping for microbes (being a microbiologist myself), I would bet against Titanian Kraken swimming the depths of Kraken Mare, the Methane Sea near Titan's North Pole.
Just as an aside, I came to this list through an odd route. A physicist-songwriter friend of mine goaded me into promising to write a song back in February. As an old chem major, I'd been interested in Titan for a long time, and had been following the news about the proposed Titan Mare Explorer mission to "sail" one of the moon's methane seas. Lacking any other ideas, I decided to write a sea-chanty set on Titan. After I finished it, I thought maybe some real Titan-ologists would get a kick out of it, so I sent it to Carolyn Porco, who wrote back to say she enjoyed it and put me on the ciclops mailing list (which I hadn't known about). In the process of finding her contact information, I looked up her published papers, and from the author list realized that when I was an undergrad studying chemistry at Caltech, she was a grad student modeling planetary rings and her thesis advisor was the RA for my student house! (I remember him talking about the work, but did not remember the name of the grad student doing it). Small world. (Just in case anyone is interested, the song is "The Shoals of Kraken Mare" and is up on YouTube: http://www.youtube.com/watch?v=AaWg7Wm-IwM ) But back to my first comment: many thanks to Drs. McKay and Porco for doing this and please keep it up!
One of the (many) things that makes Titan so interesting for pre-biotic chemistry is that it is so heterogeneous in terms of chemical environments, where lots of interesting molecules can arise. There will be non-thermal photochemistry at the top of the atmosphere (to a first approximation temperature-independent), high-temperature aqueous-phase chemistry deep underground (assuming theories about subsurface liquid water are correct), and mineral-catalyzed reactions at the base of methane lakes and pools undergoing repeated cycles of flooding and drying (and that's just a start!). As long as there is even a little mixing between these environments (and a lot of time) there will be a lot of opportunity for very complex molecules to arise. Since we only have an N of 1 (life on Earth) we just don't really know how hard it is to get from there to the autocatalytic "hypercycles" of molecules where selection can start to work and climb the complexity ladder up toward life, but Titan will be a good test case. One further interesting twist is that if there are water/ammonia cryovolcanoes (as has been hypothesized), the environment in an around them may be well within the temperature, pressure, and chemical composition where some Earth extremophiles could live -sort of a Titanian twist on the deep vents of Earth's oceans.
Putting on my biochemist's hat, I think sobrien60 is missing the point McKay is making. _Un-catalyzed_ reaction rates drop with temperature, but that says nothing about what enzyme-catalyzed reaction rates might be. This is limited only by how far they might be able to lower the free energy of the transition states. The lower than predicted levels of acetylene and _maybe_ hydrogen _might_ imply that something is catalyzing an energy-producing reaction between them. Also, one shouldn't discount the potential for kinds of chemistry that is _too_ reactive for Earth biology but might work in colder climes: boron chemistry, fluorine chemistry, free-radicals, etc. Finally, there is photochemistry at the top of the atmosphere and thermal chemistry deep under the surface that will gradually mix into the surface chemistry. The point of the hypothesis (as far as I understand it) was exactly that anomalous patterns that wouldn't make sense in terms of ordinary chemical thermodynamics might actually be a clue indicating the presence of biological chemistry in the way that Sagan proposed that simultaneous presence of Methane and Oxygen in an atmosphere would be a telltale sign of life.
Thanks for the article. Great stuff. As a scientist, I find most news articles frustratingly vague (or wrong!) about what the data really are and what they mean. Especially appreciate the citations. As an old organic chem major, I've been interested in Titan chemistry for a long time. Quick question: Aside from Methane itself, the one organic molecule I've seen cited as present in much _higher_ than expected abundances on Titan is benzene. Might this be another biomarker, since methane organisms could not get energy by reducing it with H2 (since it is so stable from resonance effects)? That is, in a methane ecology would there be an excess of carbon atoms that eventually end up in a benzene dead-end? (As an aside, I think aromatic compounds will be very interesting on Titan with antiaromatic-transition-state-preferring photochemistry at the top of the atmosphere, aromatic-transition-state-preferring thermal chemistry deep underground, and slow cycling of carbon atoms between them.)