I’ve been meaning to say something about these chemistry results from the ongoing Rosetta comet mission, and my plans to attend this astronomy get-together this weekend have brought them to mind again. (Here are the papers from the Rosetta team themselves). Note the variety of small organic molecules that this (ordinary) comet contains, and consider the masses of organic chemistry found in samples like the Murchison meteorite. The universe is swimming in this stuff.
Many people probably don’t realize that. The common picture of outer space probably leans more towards forbidding airless rocks, partly because that’s a reasonable description of the only extraterrestrial landscape humans have ever walked on. And while there’s plenty of that sort of thing out there (Mercury’s landscape does not look particularly inviting), one of the realizations of the last 30 years or so is that there’s a lot more going on under the surface. The outer moons of the solar system, in particular, had gone in the imagination from the sites of 1930s-style “planetary romance” science fiction stories (breathable atmosphere, tree ferns, strange natives) to a dull collection of cratered rock balls. I think that the first Mariner flyby of Mars in 1965 really hammered people’s expectations – no one was seriously expecting a Ray Bradbury landscape, but the ancient craters that showed up were even more forbidding than most had anticipated. (As it happens, those first shots were of some of the least interesting parts of the whole planet, as fate would have it – some eroded canyonlands would have gone done much better! And what interesting features it had a chance to see were lost in the poor resolution of the camera systems of the time.)
So for a while, the feeling was that the rest of the solar system was probably as bad or worse. The Voyager missions helped, though, with closeups of the Jupiter and Saturn system showing volcanos, ice flows and cracked ice rafts. Further missions (Galileo, Cassini, etc.) have established that even the initially less-exciting moons appear to have gigantic oceans of liquid water under their ancient Luna-like landscapes, and now even Pluto has been found to have an actively remodeled surface. You could have won some serious money betting on that years ago.
All that is in the realm of geology and inorganic chemistry, although just showing that there’s so much interest and variety on those levels represents a real reversal. But I think that we’re due for the same rethinking of outer space, in the popular imagination, in the area of organic chemistry. There have been way too many cheap movie plots where aliens travel all the way to Earth from distant star systems in search of. . .water, of all things. But water is everywhere. Huge piles of ice, gigantic underground oceans with more volume than all of Earth’s, a million comets full of the stuff. (Even Mercury has some). Our moon is a desert, but most of the rest of the solar system isn’t. And it’s not just water – spectroscopy (and some “ground truth” as the geologists say) shows that the kinds of results seen in the Rosetta mission are quite common. Planetary systems are not only soaking in water, they’re covered with organic gunk.
I’ve found, in talking with people outside of chemistry or outside of science in general, that there’s an assumption that other planets or star systems must have totally different chemistry, even totally different physics. You have to blame a lot of special effects in movies and TV shows for that, I suppose, even as the landing parties in almost every Star Trek episode beamed down with no protective equipment whatsoever, not even bothering to sniff the air before getting the plot moving. (Surely every planet with a breathable atmosphere also has a smell or two?) It comes as a surprise to some that no matter where we look, we see the same basic physical and chemical behavior, though (fundamental principle of the physical sciences though that is). And not only that, but the chemistry is (in many cases) that of familiar molecules – ethanol, ammonia, acetylene, cyanide, carbon dioxide. Even the less famous molecules are the sorts of things you can buy in rail car lots (acetamide, propanediol, acetone, ethylamine).An aspect of this that might surprise people is the thought that so many of these distant, pristine landscapes, safely removed from the hand of man, are dripping with mixtures of industrial chemicals. Looking across thousands of light years and finding the sorts of stuff you can order from any supply house seems somehow less exotic than many might expect, but building blocks are building blocks, the universe over.
All this brings up the next level of speculation: biochemistry. Origin-of-life studies are a mess, no doubt about it, but as time goes on, one thing seems clear to me. If life (as we know it, or off in some other nearby, but chemically plausible directions) is at all feasible, it must be all over the place. Unless there are some really low-probability bottlenecks that we don’t have enough data to recognize just yet, I don’t see how it can’t be. There are just so many piles of small organic molecules everywhere you look, with light all up and down the spectrum shining on it, being stirred and warmed in huge oceans, poured over rocks and zapped by lightning bolts. Abiogenesis is being given every chance, all the time, everywhere. I realize that there’s a case to be made against this point of view, but for now, this is where I land.