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The Solvent-Soaked Universe

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.

29 comments on “The Solvent-Soaked Universe”

  1. SP says:

    Food babe will freak out when she hears that the rest of the universe is so polluted with all those _chemicals_!

  2. Kelvin says:

    To be even more profound, there are theories with a lot of evidence to suggest that the universe itself is “alive” – in the sense that it can reproduce via black holes. Essentially, all the laws of physics (and thus chemistry) seem finely tuned to spawn as many black holes (and thus new universes) as possible.

  3. sansnom says:

    Moar posts on space chemistry, please!

    May I suggest the topic of interstellar chemistry as explored by Herschel IR telescope?

  4. imaging guy says:

    Have you seen the paper is today issue of Science about producing opiates from recombinant yeast cells genetically modified with 21 genes from plants, rat and bacteria?

  5. Mack says:

    Derek, you really need to enable a “Like” button on these comments. I sprayed my coffee all over the computer screen when I read @SP’s comment! I’d like to to be able to recognize readers for their good points or coffee-spray-inducing comments!

  6. Anon says:

    @imaging guy: Now that’s a scary thought! The brewing industry will never be the same again.

  7. SP says:

    Thanks for the compliment, but be sure to tell your IT department I’m not paying for the damage.

  8. Ash (Wavefunction) says:

    Freeman Dyson who I am meeting next month has proposed that comets are far better sources for the origin of life than any planets because of their very high concentrations of potential origin of life compounds and their widespread abundance in the universe. For knowing more about his ideas on the topic, take a look at the Wikipedia entry titled “Colonization of trans-Neptunian objects.”

  9. Kyle says:

    I’ve been wondering lately about the weirdest biochemistry that might actually exist out there in the universe. Some of it seems pretty hard to get away from just because of chemistry and the distribution of elements. Like, cellular life (and probably all other life, if it can exist) needs some sort of solvent, obviously, and water, the universal solvent, is present anywhere oxygen is plentiful, since hydrogen is an inescapable element. So to find the weirdest biochemistry that might actually exist, a good place to look is where the oxygen *isn’t*.

    Our planet type is technically an oxide planet. The rocks are silicon oxides or titanium oxides or other metal oxides. The oceans are hydrogen oxide. The air is carbon oxides and oxygen oxides, and also nitrogen, because given a few million years to react, it all goes to elemental nitrogen.

    But that’s not the only terrestrial planet type that can exist. Carbonaceous planets have a relative scarcity of oxygen, and a relative abundance of carbon. So the rocks are stuff like silicon carbide, when they aren’t just graphite or diamond. Oceans would presumably be of light hydrocarbons and alcohols (the oxygen would be scarce but still present). The atmosphere might be methane, ethane and carbon dioxide, plus nitrogen, of course.

    That seemed to me like a place where completely weird biochemistry might actually happen. I spent a while trying to figure out the basic energy cycle but I’m not good enough at chemistry to figure it all out – I had some weird thing involving ammonia and cyanide that I’m pretty sure wouldn’t actually work. Any actual chemists want to take a stab at fundamental biochemistry in an environment where oxygen can be considered a trace element?

  10. Rhodium says:

    Speaking of cyanide and building blocks, adenine, one of the four DNA bases, is just five hydrogen cyanides jammed together. Alien “DNA” may not have phosphodiester backbones, but purines and pyrimidines seem hard to avoid.

  11. m says:

    The first “really low-probability bottleneck” is probably the mitochondrion’s function.

  12. Question says:

    Just wondering: Is there any chemical that can catalyze its own synthesis from simpler available building blocks?

    Could that be considered as the most basic form of “life”?

  13. Cookie says:

    I follow Carl Sagan’s view on this. With millions of galaxies, and billion and billions of stars in each one, if a fraction of those stars have planets and a fraction of those planets have the right elements for life, then it is almost certain that there are other, mostly likely intelligent, life forms elsewhere in the universe.

    With the results that have been coming in over recent years from the planet hunting studies, it appears that many stars have planets orbiting them and there is at least one, to my knowledge, that has an Earth like planet. Also, our conceptions of what is “habitual conditions” were shaken up by the discovery in the 1970’s/80’s of life around the thermal vents found in the tectonically active deep ocean trenches (life powered by sulfur based energy cycles, not oxygen – photosynthesis based) and the range of bacterial life found in the hydrothermal springs in Yellow Stone park which reach “cooking” temperatures. Life can survive under some extreme conditions.

    Factor in the amounts and diversity of organic chemicals that have now been found, Carl Sagan’s view appears to be a gross underestimate of the possibility of life out there. In fact it wouldn’t be that surprising if there is life on other bodies in our own solar system.

    I agree with Derek’s point about the 1930’s “planetary romance” view in science fiction stories. Life will be very alien. However, I would expect to see similar biochemical processes occurring, like photosynthesis. But I expect that those planets have arrived at a different solution to the same problem.

    There is one aspect of the science fiction stories that I don’t believe. Intelligent aliens are regularly visiting Earth (e.g. America) and abducting people for “probing sessions”. That is science fiction!

  14. Noni Mausa says:

    Cookie: “Life will be very alien…”

    Heck, life here is sometimes pretty alien. But back to the topic: I think we’d better pray the life we come across is chemically incompatible with our planet. Otherwise, their biota landing here, and ours landing there, would be likely to wipe out local forms faster than you can say “Bunnies in Australia!”

  15. Noni Mausa says:

    PS sorry to mention this, but “science fiction” does not mean “fantastical and impossible.” Just sayin’.

    But I rather agree that the UFO people-sampling business is probably fantastical. Not so sure about impossible.

  16. Archaic says:

    Great post Derek. This touches me as Ive had the pleasure of meeting Stanley Miller and Carl Woese. Carl is among the most underappreciated scientists-particularly during his key work. To me, these questions are the most interesting in all of science. Likely much less lucrative than drug discovery but the science evolving nicely.

  17. I ask questions, I don't do chemistry says:

    “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”

    Derek, I think the book you link to argues that microbial life is common but intelligent life is rare, so it is not against abiogenesis.

    And to cookie, who said “it appears that many stars have planets orbiting them” … I did the edX course on exoplanets and I believe the result of the Kepler survey is that almost all stars have planets. Earth-like planets in the habitable zone are much rarer, but most stars have planets and the easiest to spot are hot Jupiters: large planets close to their star. It will take time to spot planets with the right density in the habitable zone….

  18. Brett says:

    The potential limiter is timing. If these environments friendly to abiogenesis are relatively stable and “hospitable” for hundreds of millions of years (or billions), then I can certainly imagine life evolving there. For example, if Enceladus’s and Europa’s under-oceans have been liquid with access to the building blocks of life from their rocky parts for billions of years, then I definitely think there’s a great chance of life being there.

    There’s four places I’d really love to go looking for life:

    1. Under-Sea of Europa
    2. Under-Sea of Enceladus
    3. Atmosphere/clouds of Venus
    4. Three kilometers down or more beneath the surface of Mars.

    The first two are obvious. Venus may have something in its clouds, where the temperatures are more hospitable – the atmosphere is supposedly out of equilibrium already. And going down deep in Mars gets you to places where you might have warmth and water.

    @ I ask questions, I don’t do chemistry

    It will take time to spot planets with the right density in the habitable zone….

    Yep, it is quite literally time and our instruments needing to be just a bit more accurate. We need to be able to spot the transits of Earth-sized planets in habitable orbits around F, G, and K-class main sequence stars. Then we need to directly image them so we can figure out what they’ve got in their atmospheres.

  19. Ziggy Stardust says:

    I already found spiders living on Mars.

  20. steve says:

    I point once again (as I did in an earlier thread) to the Horta, intelligent, silicon-based life forms that evolved on Janus VI. They would be difficult to discover since it uses they their powerful acid secretions to move through rocks; there would therefore be little to discover looking at the planet surface. Every 50,000 years, the entire race dies except for one that keeps care of the eggs that give rise to a new generation. I really don’t understand this generation of exobiologists that seem to have totally forgotten the lessons of Star Trek.

  21. John Schilling says:

    “Abiogenesis is being given every chance, all the time, everywhere”

    How many chances does it need? Given one cubic centimeter of generic primordial soup, simmering at 300 K with 1 kW/m2^2 of visible and 100 W/m^2 UV flux for any interesting photochemistry, what is the probability per second of a viable living organism being abiogenically produced? 1E-30? 1E-40? 1E-50?

    Back of the envelope, those guesstimates give life everywhere, life every few solar systems, and life every few galaxies. But I made up those numbers off the top of my head.

    And near as I can tell, so does everyone else. Does anybody have a number they would care to defend, with any sort of rigor, to within even ten orders of magnitude?

  22. gippgig says:

    The requirement for life is the ability to form complex systems capable of interacting with the environment. There is no reason such systems must be chemical. One obvious possibility is life based on the electrical properties of silicon.
    It is also worth noting that a hobbyist has created an abstract mathematical pattern called a cellular automaton that is capable of nontrivial self-replication and therefore by one definition is a life form (in the aptly named Game of Life)!

  23. Shion Arita says:

    @John Schilling:

    Here’s one way to estimate the number: I read somewhere that Earth developed life about 500 million years after it was able to do so. So let’s make the rough assumption that the probability of getting life after that long given Earth’s amount of appropriate environment is 1/2.

    using your methods, what probability of mL/second would give 1/2 for 500 million years and Earth’s amount of appropriate environment?

    1. Shion Arita says:

      p.s. With moderate confidence, I’d defend that number, of p=.5 for 500 million years with an Earth’s worth of material to within 10 orders of magnitude.

  24. Morten G says:

    @Shion Arita:
    I was sure it was “the oldest fossils are from 500 mio years after the planet cooled enough for life”. To me that said that life showed up almost as soon possible. Multicellular life however appears to have been dependent on a considerable amount of oxygen in the atmosphere. And “intelligent” life took a long while to come around after multicellularity.

  25. Paul D. says:

    The argument “life started early, therefore it’s probably not too hard” assumes that the chance of starting life is constant over time. Alternately, it’s possible that if life is going to start, it will do so when a planet is young, or it won’t start at all.

    Another possibility is that panspermia is possible, but only in dense stellar birth clusters. The Sun formed in a cluster of about 10,000 stars packed into a volume of about 1 cubic light year. It could be that most stellar systems with life will be seeded in such clusters, in which case the odds would be heavily biased toward early origination. This also suggests SETI searches focus on “solar siblings”, which by now are smeared in an arc around the galaxy. The correlation of the history of those systems with our own could evade the Fermi argument.

    Myself, I hope origin of life, and if not that evolution of intelligent life, are extremely low probability events, or else as Bostrom points out we are doomed.

  26. John Schilling says:

    “Life started early therefore it is not that hard” also overlooks the fact that the question, at present, can only be asked on planets where life evolved at all.

    If the probability of abiogenesis is 1E-20 per habitable planet per eon, such that there are only ~fity life-bearing planets in the observable universe, and if we assume that life will inevitably evolve intelligence given sufficient time, then there will be ~fifty groups of scientist-philosophers asking the question, and ten percent of those will observe that life evolved in the first half-billion years of the ~five-billion-year window for a typical habitable planet.

    And if the probability of abiogenesis is 1E-15 per planet per eon, or 1E-25 and there at least 1E5 universes similar to our own, approximately 10% of scientist-philosophers will observe that life evolved within the first five hundred million years. Given the inherently biased set of observers, this observation is not terribly useful for pinning down the probability of abiogenesis from a single data point.

  27. Nile says:

    The big surprise is the complexity of the chemistry.

    Basic knowledge of stellar physics will tell you to expect Carbon, Nitrogen. and Oxygen; and, as almost everything in the universe is Hydrogen, you’d expect to see the hydrogen compounds of CNO…

    …And not much else, bar the odd lumps of nickel-iron.

    The tarry red crap that turns up on the surface of CNO-rich objects is formed, we hear, by the effects of solar UV radiation. But I ‘d expect that, and evaporation loss to vacuum, to be a destructive process that left very boring chemistry.

    Instead, we get the unexpected, which means that there are significant scientific discoveries to be made.

    Some very, very interesting things are going on in our solar system

  28. sepisp says:

    This is an extremely interesting result for an organic chemist, since it seems much of the discussion is dominated by walk-in-the-clouds types, boring physicists and astronomers or clueless biologists.

    First of all, the mix is obviously very toxic. It has methyl isocyanate, which we remember from Bhopal, but you can’t ignore isocyanic acid, hydrogen cyanide, ammonia, methylamine, and even ethylene glycol. But, the presence of these compounds almost guarantees there are compounds like ureas and carbamates. It’s a shame we got only a whiff, since if there was a comprehensive chemical analysis, someone could do a modern-day Miller-Urey experiment to attempt to replicate early Earth, this time with actual cometary contents.

    This stuff is not by any means uncommon except here in the inner solar system, which is basically mostly a desert. Whereas, you need to go only to Jupiter distance to find worlds like Callisto, Titan, Triton and Pluto that are covered in organic material. The same material also rained on Earth during its formation, and provided all necessary chemical starting materials for life.

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