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Earth DNA deposited on Titan by Huygens?
Please excuse this naive query: How is it possible to know that we have not just deposited some "earth DNA" on Titan, via a single (or multiple) viral or bacterial hitchhiker? I realize that clean rooms are used for vehicle and instrument fabrication, that heat of atmospheric entry, the 7 year transit time and the radiological environment of interplanetary space all mitigate against this possibility, but... One compromised bacterium? One (or a dozen, or a few hundred) virus/viruses? And could someone point me to a discussion of this? (Fresher than the period of manned lunar exploration.) And is this now considered a trivial concern in the world of planetary exploration? Many thanks... |
#2
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In article .com,
Smith wrote: How is it possible to know that we have not just deposited some "earth DNA" on Titan, via a single (or multiple) viral or bacterial hitchhiker? I would presume the opposite. Huygens was not sterilized. From NASA Huygens Probe FAQ http://saturn.jpl.nasa.gov/faq/huygens.cfm: The Committee on Space Research (COSPAR), an interdisciplinary committee of the International Council for Science, maintains a consensus international planetary protection policy to be followed by spacefaring nations. In 1988, the U.S. National Research Council's Space Studies Board, working under COSPAR guidelines, determined that the Cassini-Huygens mission fit into "Category II" as follows: "Category II missions comprise all types of missions to those target bodies where there is significant interest relative to the process of chemical evolution and the origin of life, but where there is only a remote chance that contamination carried by a spacecraft could jeopardize future exploration. The requirements are for simple documentation only. Preparation of a short planetary protection plan is required for these flight projects primarily to outline intended or potential impact targets, brief pre? and post-launch analyses detailing impact strategies, and a post-encounter and End-of-Mission Report which will provide the location of impact if such an event occurs. Solar system bodies considered to be classified as Category II are listed in the Appendix to this document." For original documents, see http://www.cosparhq.org/scistr/PPPPolicy.htm. As a Category II mission, the Huygens Probe was not sterilized. For more information on this, see this European Space Agency web page on planetary protection: http://www.esa.int/export/esaCP/ESAUB676K3D_Life_2.html For information on NASA's planetary protection policies and procedures, see http://planetaryprotection.nasa.gov/pp/index.htm. -- Hud Nordin Silicon Valley |
#3
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Smith wrote:
Please excuse this naive query: How is it possible to know that we have not just deposited some "earth DNA" on Titan, via a single (or multiple) viral or bacterial hitchhiker? How is it possible to care? I mean, nothing terrestrial is going to *grow* there, so what the hell are you worrying about? Paul |
#4
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Smith wrote: How is it possible to know that we have not just deposited some "earth DNA" on Titan, via a single (or multiple) viral or bacterial hitchhiker? I think it's a fairly good chance. AFAIK, Huygens didn't get an extensive sterilization. But, I might be wrong. In any case, I say, "More power to any little bugger that can survive on Titan." If an Earth critter can prosper in cryogenic temperature, a reducing atmosphere, and in a lack of sunlight, good for it. Mike Miller, Materials Engineer |
#5
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In article .com,
Smith wrote: How is it possible to know that we have not just deposited some "earth DNA" on Titan, via a single (or multiple) viral or bacterial hitchhiker? Well, it's not, because Huygens wasn't sterilized. There *have* been sterilized spacecraft -- notably, the two Viking landers -- but it's a difficult thing to do and it runs up the cost badly. Heat sterilization is about the only fully effective method, and it's hard on electronics. Modern practice is to sterilize only if (a) there are life-detection experiments on board (which obviously might be confused by hitchhikers), or (b) the destination environment is a place where Earth life might have some chance of growing and spreading. Almost certainly there *were* bacteria on Huygens at launch, and some of them may even have still been technically viable on arrival. Titan, interesting though it is, is *way way* too cold for Earth life. (Temperatures not much colder than that are used for long-term pristine *storage* of biological samples.) There is no realistic prospect of hitchhiking organisms proliferating on Titan. -- "Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | |
#6
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Many thanks for your help (and patience) with my child-like query.
I proved my ignorance with the comments: "One compromised bacterium? One (or a dozen, or a few hundred) virus/viruses?" It seems the standards (even for Mars) run into the 10s if not 100s of thousands of micro-organisms as acceptable loads. But, to also answer my own initial query, following the links provided I eventually found http://www.astrobiology.com/protection.html a site friendly (simple) enough to have probably precluded it in the first place. Thanks. I do find it curious though that the general response here seems that as any earth organism would be unable to live/reproduce/thrive in such an environment, consideration of their dispersal is rendered uninteresting. I suppose lurking in my uninformed thought was a notion of "earth DNA" as potent information, even if not mechanically active. I understand it is considered in the realm of possibility that bacterial spores may possess integrity measured in "geologic" stretches... "On the basis of such laboratory experiments, it has been proposed that with proper shielding, bacterial spores might survive UV irradiation for very long periods, perhaps millions of years." from "Biological Contamination of Mars" Space Studies Board / National Academy of Science http://www7.nationalacademies.org/ssb/bcmarsch4.html But I certainly don't mean to take up serious time here with what are likely commonplace and perhaps adolescent wonderings. And I really have no cranky axe to grind concerning this. And if the last few decades might mark some potential exflorescence of the terrestrial habit to the near and middle bodies of our solar system, this hardly looms so very large in the wider view of things... Thanks again. |
#7
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Smith wrote:
Please excuse this naive query: How is it possible to know that we have not just deposited some "earth DNA" on Titan, via a single (or multiple) viral or bacterial hitchhiker? [...] I realize that clean rooms are used for vehicle and instrument fabrication, that heat of atmospheric entry, the 7 year transit time and the radiological environment of interplanetary space all mitigate against this possibility, but... One compromised bacterium? One (or a dozen, or a few hundred) virus/viruses? How sure do you want to be before you think you "know"? Lots of Greetings! Volker |
#8
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Smith wrote:
I do find it curious though that the general response here seems that as any earth organism would be unable to live/reproduce/thrive in such an environment, consideration of their dispersal is rendered uninteresting. I suppose lurking in my uninformed thought was a notion of "earth DNA" as potent information, even if not mechanically active. I understand it is considered in the realm of possibility that bacterial spores may possess integrity measured in "geologic" stretches... "On the basis of such laboratory experiments, it has been proposed that with proper shielding, bacterial spores might survive UV irradiation for very long periods, perhaps millions of years." I've always felt that the two possible answers to the question of is there life in the rest of the universe is either "yes" or "not yet". If we can't find it, then at some point we should start spreading it. Take a big blob of primordial hydrocarbon feasting ooze and put it into an armored bunker-buster casing and drop it on Titan in a probe that would survive an impact and burrow into the surface. And just let it do it's thing. |
#9
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[[ This message was both posted and mailed: see
the "To," "Cc," and "Newsgroups" headers for details. ]] Henry, My concern here is what happens when you dump RNA and DNA into a reducing soup containing amino acids at whatever temperature. Sometimes, or so I understand, the RNA and DNA replicate even without an enclosing cell. This could actually make a global change to the chemistry of Titan, if it could occur under those conditions. Proteins can sometimes self-replicate, too. This could cause a sort of molecular evolution to begin there. Not life-as-we-know-it, certainly, but it would be very interesting should it happen... -Ben Burch In article , Henry Spencer wrote: Titan, interesting though it is, is *way way* too cold for Earth life. (Temperatures not much colder than that are used for long-term pristine *storage* of biological samples.) There is no realistic prospect of hitchhiking organisms proliferating on Titan. |
#10
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In article ,
Ben Burch wrote: My concern here is what happens when you dump RNA and DNA into a reducing soup containing amino acids at whatever temperature. Sometimes, or so I understand, the RNA and DNA replicate even without an enclosing cell... DNA needs a complex set of supporting machinery to replicate. RNA can replicate by itself, although somewhat imperfectly, given a supply of bases. (Those are not amino acids; amino acids are what make up *proteins*, not nucleic acids like RNA.) However, RNA can and does appear spontaneously given a supply of bases. If there are substantial supplies of suitable raw materials sloshing around on Titan, then there will already be RNA present... and it will be evolved to suit conditions (yes, RNA can evolve, in simple ways) much better than any random Earth RNA would be. This could actually make a global change to the chemistry of Titan, if it could occur under those conditions. Proteins can sometimes self-replicate, too. This could cause a sort of molecular evolution to begin there... Again, if suitable conditions exist, then almost certainly they have existed for long enough for such a development to start spontaneously. -- "Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | |
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