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Two papers released last week detailing oddities found on Titan have blown the top off the ‘jumping to conclusions’ meter, and following media reports of NASA finding alien life on Saturn’s hazy moon, scientists are now trying to put a little reality back into the news. “Everyone: Calm down!” said Cassini imaging team leader Carolyn Porco on Twitter over the weekend. “It is by NO means certain that microbes are eating hydrogen on Titan. Non-bio explanations are still possible.” Porco also put out a statement on Monday saying such reports were “the unfortunate result of a knee-jerk rush to sensationalize an exciting but rather complex, nuanced and emotionally-charged issue.”
Astrobiologist Chris McKay told Universe Today that life on Titan is “certainly the most exciting, but it’s not the simplest explanation for all the data we’re seeing.”
McKay suggests everyone needs to take the Occam’s Razor approach, where the simplest theory that fits the facts of a problem is the one that should be selected.
The two papers suggest that hydrogen and acetylene are being depleted at the surface of Titan. The first paper by Darrell Strobel shows hydrogen molecules flowing down through Titan’s atmosphere and disappearing at the surface. This is a disparity between the hydrogen densities that flow down to the surface at a rate of about 10,000 trillion trillion hydrogen molecules per second, but none showing up at the surface.
“It’s as if you have a hose and you’re squirting hydrogen onto the ground, but it’s disappearing,” Strobel said. “I didn’t expect this result, because molecular hydrogen is extremely chemically inert in the atmosphere, very light and buoyant. It should ‘float’ to the top of the atmosphere and escape.”
The other paper (link not yet available) led by Roger Clark, a Cassini team scientist, maps hydrocarbons on Titan’s surface and finds a surprising lack of acetylene. Models of Titan’s upper atmosphere suggest a high level of acetylene in Titan’s lakes, as high as 1 percent by volume. But this study, using the Visual and Infrared Mapping Spectrometer (VIMS) aboard Cassini, found very little acetylene on Titan’s surface.
Of course, one explanation for both discoveries is that something on Titan is consuming the hydrogen and acetylene.
Even though both findings are important, McKay feels the crux of any possible life on Titan hinges on verifying Strobel’s discovery about the lack of hydrogen.
“To me, the whole thing hovers on this determination of whether there is this flux of hydrogen is real,” McKay said via phone. “The acetylene has been missing and the ethane has been missing, but that certainly doesn’t generate a lot of excitement, because how much is supposed to be there depends on how much is being made. There are a lot of uncertainties.”
McKay stressed both results are still preliminary and the hydrogen loss in particular is the result of a computer calculation, and not a direct measurement. “It is the result of a computer simulation designed to fit measurements of the hydrogen concentration in the lower and upper atmosphere in a self-consistent way,” he said in a statement he put out over the weekend. “It is not presently clear from Strobel’s results how dependent his conclusion of a hydrogen flux into the surface is on the way the computer simulation is constructed or on how accurately it simulates the Titan chemistry.”
However, the findings are interesting for astrobiology, and would require the actual existence of methane-based life, a theory McKay himself proposed five years ago, which he described today as an “odd idea.”
In 2005, McKay and Heather Smith (McKay and Smith, 2005) suggested that methane-based life (rather than water-based) called methanogens on Titan could consume hydrogen, acetylene, and ethane. The key conclusion of that paper was “The results of the recent Huygens probe could indicate the presence of such life by anomalous depletions of acetylene and ethane as well as hydrogen at the surface.”
Even though the two new papers seem to show evidence for all three of these on Titan, McKay said this is a still a long way from “evidence of life”. However, it is extremely interesting.
But what does McKay really think?
“Unfortunately, if I was betting, the most likely explanation is that Darrel’s (Strobel) results are wrong and that further analysis will show there is another explanation for the data he is trying to fit, besides the strong flux of hydrogen into the surface. I would be very happy if we did confirm all that data, but we do have to take it in steps.”
McKay provided four possibilities for the recently reported findings, listed in order of their likely reality:
1. The determination that there is a strong flux of hydrogen into the surface is mistaken. “It will be interesting to see if other researchers, in trying to duplicate Strobel’s results, reach the same conclusion,” McKay said.
2. There is a physical process that is transporting H2 from the upper atmosphere into the lower atmosphere. One possibility is adsorption onto the solid organic atmospheric haze particles which eventually fall to the ground. However this would be a flux of H2, and not a net loss of H2.
3. If the loss of hydrogen at the surface is correct, the non-biological explanation requires that there be some sort of surface catalyst, presently unknown, that can mediate the hydrogenation reaction at 95 K, the temperature of the Titan surface. “That would be quite interesting and a startling find although not as startling as the presence of life,” McKay said.
4. The depletion of hydrogen, acetylene, and ethane, is due to a new type of liquid-methane based life form as predicted (Benner et al. 2004, McKay and Smith 2005, and Schulze-Makuch and Grinspoon 2005 (Astrobiology, vol. 5, no. 4., p. 560-567.).
McKay said if further analysis shows that a strong flux of hydrogen into the surface really is happening, “then my first two explanations are no longer options and we are then left with two really quite remarkable alternatives, either there is some mysterious metalysis going on, which at 95 k is really hard to imagine, and would have enormous implications for things like chemical engineering. And the second alternative is that there is life, which is even more amazing.”
“So to make process on this,” McKay continued, “we have to confirm Darrel’s result that there is hydrogen being fluxed onto the surface of Titan, that is really way unexpected, and unfortunately, it constitutes extraordinary claims that need extraordinary evidence. Darrel’s paper is just a first step in that.”
What does McKay think about the rash of media reports claiming life on Titan?
“Well, I think it reflects our human fascination and desire to find life out there,” he said. “We want it to be true. When we’re given a set of facts, if they are consistent with biology we jump to that explanation first. The most biologically interesting explanation is the first one we look to. We ought to give that a name — something like ‘Carl Sagan’s Razor’ as opposed to ‘Occam’s Razor,’ which would say that ‘The most exciting explanation is assumed to be true until it is proven false.'”
You can read all of McKay’s written response on the CICLOPS website, which Porco said will be “the first installment in a new feature on the CICLOPS website, called ‘Making Sense of the News’, where from time to time, scientists, both involved in Cassini and not, will be invited to comment on new developments that bear on the exploration of the solar system and the study of planetary systems, including our own.”
All of that could happen. Since IIRC there is a substantial flow of presumed fullerenes to ground they could theoretically trap and transport hydrogen ‘invisibly’, for example.
But if not and it stands up, the chemical imbalance in itself is a much more interesting observation than methane on Mars, as I just noted.
Also, I’m not sure that “extraordinary claim” is a correct description of life. It happened easy enough here on Earth. It may well be that the 95 K catalyst is the more unlikely phenomena.
[OTOH, that was what we once thought about high-temperature superconductors too…]
Pretty fantastic to even imagine cryogenic lifeforms! But since I love surprises, why not? Superconducting neurons and all…
Short story subject: An extraterrestrial race comes into our solar system after having detected possible life on Titan. They land there and begin to study those primitive organisms as those lifeforms closely resemble their own metabolisms. Inadvertently one of the crew, while scanning radio frequency wavelengths for anomalous energy in the system, stumbles across radio transmissions from Earth. He presents his findings to his captain who promptly berates him for his seemingly absurd suggestion. “Our science has found that NOTHING can live at those temperatures!” he reminds. The crewman returns humbled to his studies….
Didn’t Carl Sagan use that razor to successfully cut up all of Immanuel Velokovski’s theories?
I would love to see a rover on that moon. Maybe power it with hydrogen? 😉
Thinking further, McKay claims several possible imbalances. Three in fact: ethane which is an old observation, acetylene which is a multiple observation, and hydrogen.
In his model for metabolism they are combined. But that doesn’t really change the situation; we should consider the combined unlikeliness of having multiple imbalances.
If they stand up, that is. Having multiple errors on the table at the same time is nothing new.
I love the concept of “Carl Sagan’s Razor”. I think that should catch on.
What it does show, however, is that science does not have all the answers – and whatever our pre-conceived notions of life might be (using Earth as the only model) we really haven’t got a clue about the rest of the solar system or indeed the Universe. Just because it’s a bit too hot or a bit too cold, that only changes the rules – the game is still the same.
Best way is to go there and find out. Can’t wait.
@StockportJambo
If science DID know all answers then t would be the end of science since it became obsolete.
All of this could indeed be the case, where there is some form of life which operates on chemical reduction instead of oxidation. There are of course a range of question which need to be addressed if one were to even theoretically justify this. I am not sure how DNA would behave in such cryogenic temperatures. Molecules at low temperatures don’t bend or flex well and the physical properties of DNA might be remarkably different. At least with the Europa conjecture you have DNA in water, which would preclude some of these problems — maybe. DNA under these conditions might be utterly brittle without water at these low temperatures. Some classical thermal chemistry at these temperatures needs to be done in the sort of environment envisioned.
To be honest this strikes me as something similar to what once was said about particle physics. If you have lost your keys in the dark near a street light one at least first does a search near the light. In a similar manner this seems to be a manner of trying to interpret data within the “street light” of there being life. The strategy might work, so why not? — this seems to be in line with the Carl Sagan rule idea being bandied about here.
LC
I never liked the Occam’s Razor only method.
If Einstein would have followed Occam’s Razor, then we would probably still using Newtons laws.
Or in the case of particle physics, quantum mechanics would be put in the garbage can because it was not a simple solution.
At least try some second or third hand possibilities to check if you really have the simplest solution.
Olaf:
Me neither — I prefer to use a Philishave. 😉
True, one should extract and test as much predictions as possible out of alternatives before using “beauty” measures such as parsimony. That is why I rather discuss likelihoods until there _are_ testable predictions at hand.
I can see what McKay is going for, but the reverse analogy is both mistaken (since the most exciting explanation may well be the most predictive, as here; catalysts being simpler than a set of metabolic enzymes, hell _life_ is more complex than a single chemical) and non-pedagogical as it suggests “Razor only”.
He did alright before then though.
Not simple but parsimonious. 😮 Parsimony can be applied in many ways, and there is no good and general definition that I know of.
The simplest [sic!] and best definition is the way it is applied in, say cosmology. Lambda-CDM is parsimonious over a set of parameters; it is the simplest model, it has least entities (variables). That is, GR without the dark energy cosmic constant is simpler, but it can not predict observations.
In that sense QM is the simplest possible theory. The wave function is one entity that sums up all what you need to make observational predictions. Further, QM does not permit hidden variables to sneak out of that.
There is also a rather nice axiomatization in an arxiv paper, where one express classical (CM) and quantum mechanics (QM) in the form of respective probabilities. The CM probability is the usual, and one have the usual transformation from one a priori state to one a posteriori. The QM formulation has to use three dimensions but still permits a simple transformation.
However, it turns out that CM mechanics is the discrete case (discrete state to discrete state) while QM is the continuous physics (continuous transformation over state space)! This is what is observed too, apparently one can take systems in and back out of decoherence again in this seamless fashion, while in CM a collision, say, is a collision – no take backsies.
Since CM is the discrete physics it is not so simple all else equal, in a math sense discrete structures are iffier to work with. To sum up “parsimony” here, in principle in CM there are more parameters needed than in QM (for the discrete structures), so likely more variables for “the same physics”; but less dimensions.
[And of course, actual QM means using Hilbert spaces which are infinite dimensional, so we already knew that.]
Dimensions is not something to go and measure “parsimony” over.
Seriously, Olaf has a point; according to Wikipedia’s article on Occam’s razor — Science and the scientific method:
Also, since I’m summing up my thoughts on parsimony here, I would add that another definition used is wrong: having “parsimony” mean the least number of assumptions.
It is true that parsimony is observed to go on theories, not results.
I.e. if the theory is simple, the application likely isn’t. (Compare newtonian gravity expression with a ballistic trajectory expression.) The reasons are legion: theories are observed to often be simplest; parsimony means having less reversals in the end if the theory keeps being wrong (by starting with less parameters); it is good research strategy to set up minimum of needed tests and having less likelihood to mess up predictions; and so on.
But in a testability sense, assumptions are predictions of the theory. All we need to test if the theory is both applicable and correct is that we can make implications out of it. And assumptions are such testable implications of having the theory. For example, newtonian gravity assumes a mass. No mass, gravity was wrong.
Since assumptions goes towards answer testability, one can not also use them as part of a “beauty” measure. (At least not without making things messier than they should be.)
@ IVAN3MAN:
Seriously? That is a philosophical article, not science.
Personally I don’t think one can take a “philosophy of science” seriously. “There is little empirical evidence that the world is actually simple or that simple accounts are more likely than complex ones to be true.[20]” Yeah, right. See cosmology above for one.
Note also that no one, and I mean _no one_, can mistake a beauty measure for greedy parsimony. Again, see cosmology above.
Except some philosophers, see the article: “a criterion for selecting among published models”. No, ultimately testability is that criterion. “future data often supports more complex theories than existing data”, Yes, again better predictivity is the ultimate criterion.
Note that they never define “simplicity” in that part. Or if they do, as in the article start, they are inconsistent as applied to science as I just shown.
Wrong too, as they use the faulty “fewest assumptions”, which mess with testability as I just noted. Or when they say “it is entirely a metaphysical assumption” though they admit that it is entirely methodological, used because it works as a heuristic.
Moreover, in a wider sense this is a clash between quasiinductionism and testability. “A single instance of Occam’s razor picking a wrong theory falsifies the razor as a general principle[7].” Only an inductionist can use such induction instead of testing as a criteria, in an article where testing is claimed to be the criteria.
(To spell it out, testing is based on uncertainty. How much weight should a single observation have, in say an actual 3 sigma binomial test of parsimony? Not much, because it would be a bad test.)
Since inductionism fails by its own measure, single instances can wreck the whole methodology as per their own example, and testing can be tested to work, there should be no argument. But inductionism is a popular “feature creep” among wide audiences, ever since it was found to be a useful tool for theology at the time evolution started to bother them.
An inductionist can always push his gods, or bad philosophical ideas for that matter, into inductionist gaps. No such luck with testing “beyond reasonable doubt”. Religious explanations, and bad philosophy, becomes unreasonable at the outset.
But even taking all those misunderstandings and all that sociology under consideration in this rant, it is a problem to use philosophy in science. All philosophy can do is arbitrate over consistency.
That is why the authors claim “axioms” of science instead of “tested methods”, which they must do to be consistent with those same axioms (“objectively falsified”). It has no empirical value as long as it isn’t using testing. In which case it becomes science, probably.
I’m all for the science of science though.
Oops, I forgot: yes, Olaf has a point, that is what triggered my comments in the first place.
‘quasi-inductionism’. Nice post(s) Torbjorn.
Life on Titan, well its a testable model. Lets un-quasifi it.
If it is a biology consuming Hydrogen and Acetylene, Methane is the most likely by-product. of such biology.
However its concentrations in the atmosphere are low 1.4% , compared to Oxygen on Earth; 20.95%. If it is life, its unlikely to be as ‘ubiquitous’ as i it is here on Terra.
The fact that Methane is there at all remains a Mystery however. (wikipedia)
Damian
As above – “We know practically nothing about organic chemistry at those temperatures…” THAT statement really says it all. From our relatively ‘warm’ biological enclave, we’ve made the assumption that all life would resemble our own… how naive is that? Then we found extremophiles and a wholly new biology right under our feet which has made all previously held assumptions questionable at best.
Cryogenic chrystalline lattices may function in a similar fashion as DNA for all we know… and probably does somewhere(?) due in part to the fact that in our vast universe anything you can imagine, in all the probabilities, does exist!
It’s there I tell ya! Primitive life exists on Titan and many of the icy planetoids in the outer solar system. We know practically nothing about organic chemistry at those temperatures, but, knowing organic chemistry, I’m very optimistic about life out there. Titan is my #1 suspect.
btw – there can be no oxidation without a corresponding reduction. They are oxidation-reduction (or redox) reactions. You cannot have one without the other. Even on earth.
@ Torbjörn Larsson OM,
Hey, chill out, dude! I only said “seriously” at the introduction of my last post in order to differentiate it from my previous tongue-in-cheek post, but your comment got in between them.
If we assume that DNA is the “life coding system,” then there are a number of properties of DNA which match those with water. Nucleotides have charged residues which interact with water, a polar molecule, at around STP. So if we adjust temperatures down and pressures up, say conditions we might find within the interior of Europa, this interaction between DNA and liquid water is vital in maintaining DNA in a dynamic state. Let us compare DNA in a liquefied state of light organics, such as ethane. These are nonpolar molecules and really only interact with DNA by simply banging into it. The thermal state of DNA would be entirely different.
LC
@ damian:
Thanks. The originator of the term is IIRC David Deutsch though, see his “The Fabric of Reality”.
Btw, nice comparison. Putative life on Titan may be methane bottle-necked, while modern life on Earth is bottle-necked by the requirement that it doesn’t start to set off self-combustion. (I.e. in practice: set off global scale wood fires.)
@ neoguru:
I confess that these discoveries, which I had missed, has made my belated move to such a position as well. Titan FTW!
@ IVAN3MAN_AT_LARGE:
I’m usually chilled in between rants and dancing (or visiting the gym); they are both great stress reliefs, and it so happened I had an important meeting a few hours later and no dance floor handy. 😀
Philosophy, and especially philosophy of science and quasi-inductionism, are pet peeves of mine. If you hadn’t guessed. :-~
As for the series of posts and attribution: ouch dude, my bad! Never assume the worst case scenario. But I didn’t scroll back up to see your previous comment, mine filled the screen. Talk about falling on your own grip (busy fingers?).