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  • March 20, 2019, 8:10 p.m.

    Love Astrobiology. I worked in population genetics and know a few astrobiology people. (I was in physics before that). It is super cool.

    There are really 4 main points I want to make, where sci fi gets it really wrong. And SFIA gets it a lot more correct.

    1. If there is life on other planets and star systems then it is either panspermia or so utterly different from life as we know it. It will not be compatible with us in anyway. Basically you can't eat alien fruit. That is it won't have DNA.. it will probably have possible DNA analogue, but probably not specifically DNA. IT wont' be 20-22 amino acids. etc. It will almost definitively be carbon based however. Other base atoms just don't work. At ALL.

    2. Simple bacteria is NOT simple. It has more organisation and complexity that an entire vertical manufacturing facility and then some. Simple life could be really common, but by simple something much much simpler than a bacteria. Self replication is what life really is. And you don't need to be as complicated as bacteria if your not competing against bacteria.

    3. If there is life there then it would be trivial to detect. The whole "but would you recognise life" is a bad star trek trope up there with "beings of pure energy" and silicon based life. Once something can self replicate, even very slowly. It totally dominates the local chemistry of everything. Evolution will happen and then in just millions/billions of years then it is everywhere as well. Gray goo IS life. Really really. a single e-coli cell left to replicate unchecked would be the mass of earth in just a few days. We are a grey goo disaster!

    4. Even with panspermia sorting out earth contamination vers native life in something like mars is trivial so trivial it is kinda weird how nasa is with the contamination protocols. It is up there with moon astronauts decontamination.

    So my belief on the resolution of the Fermi Paradox is at least one great filter and a lot of major filters such that a civilisation in galaxy is very rare. What those filters are is best for perhaps another thread. like specifically on filters. Or just on the relevant SFIA episode since it is covered well.

    Also no FLT. Just the universe we live in.

  • Moderator
    March 21, 2019, 1:15 a.m.

    You have a good idea of the subject delt0r, but I respectfully disagree with the following points:

    While I totally agree with you that the biochemistries of exoplanets and Earth will be 90% of the time incompatible, I don't think that each planet with life will on it will have radically different, exotic biology. Certainly, on average, each planet may have life inhabiting different biomes, utilize different forms of bioenergetics, have differing trophic levels and so forth, but parallels will appear as examples of convergent evolution. Wings, hair, scales, eyes, exoskeletons, endoskelatons and other basic traits all have evolutionary uses independent of chemical composition. So what if an alien's eye is made out of tiny indium needle-like hairs that sense pressure and heat instead of visual light in a cold, high-pressure atmosphere - the point is that the biological imperative for sensing one's environment is there. The real differences occur when natural selection interferes and gradually alters the appearance or even use of that trait, sometimes removing it or adding something new to it.

    Given the sheer variety of possible biological pathways that only carbon-based, H2O-solvet organics ALONE can take alone, it would be a safe bet to maker that innumerable parallels of Earth-life could arise on a planet, with even more dissimilar, yet carbonaceous life based on similar chemical processes spawning - all via abiogenesis. I understand that you feel as though each example of abiogenesis will create radically-different life-forms per each environment, but considering that there are predicted to be billions of Earth-like worlds in the universe, statistically Earth-parallels will be present. This ignores for the moment other habitats that can make extremely different life-forms. In the universe at large, abiogenesis would be the most likely way for life to get started, perhaps even multiple times on a single planet. Panspermia could be possible in small, tightly-packed solar-systems like TRAPPIST-1 (which probably doesn't have detectable life in it, but that is beside the point), but aside from that the hurdles involved with getting a single organic cell from one planet to another are extremely challenging.

    This is incorrect. Grey-goo and other forms of nanotechnology do not strictly meet the scientific definition of life, biological or otherwise. They can be likened to viruses, which are also not 'alive' in the academic sense. This is somewhat controversial, since defining 'life' is tricky, but nevertheless grey-goo technology cannot be consider alive in most cases. See en.wikipedia.org/wiki/Life#Definitions .

    Furthermore, it is impossible for a replicating swarm to self-assemble so fast that they can overwhelm the surface of a planet in days and/or consume it entirely. The energy requirements for them to do so would be huge, and the heat created by them doing that at such a rate would produce so much infrared waste heat that they would vaporize themselves while replicating. This is a sci-fi trope, which is ironically something you condemn in your post. If the nanobot/bacteria can diffuse the produced waste heat in any-way, they then gain mass added by those facilities - exponentially slowing their replicatory process and growth rate.

    I'm not entirely sure what you are saying here. If you are pointing out that it is an unnecessary for NASA to decontaminate their rovers because Earth-life was originally from MArs anyway, then this is fallacious thinking because enough time has elapsed in dividing the biology of the two planets to make an addition of different organisms inimical to the native life. Plus, outgoing Earth-probes are sterilized to prevent cross-contamination. If NASA one-day finds life on Mars, it would be seriously disappointing if was just a colony of UV-resistant bacterium that hitched a ride on a early rover landing and proliferated in the following years.

  • March 22, 2019, 4:46 a.m.

    I'm not talking macroscopic things. I'm talking chemistry. Litterly DNA. You can store information in a LOT of different carbon based molecules. I mean litterly just about an infinite variety. We don't think DNA is the only thing. In fact if we found DNA in any extraterrestrial life even with different bases (ie extras over AGCT or not AGTC at all) it would be a very very strong case for panspermia.

    Even with billions of earths, There are Trillions apon trillions of possibilities here. Finding something the same chemically in the entire Observable universe is very improbable.

    Not really sure of what point your trying to make here. Gray goo disasters are a sci fi trope. The math basically means they don't and can't happen. There have been some papers put out about it. Self Replication no matter how (technically life or not) is all you need for "grey goo". AKA life is a observable case of grey goo.

    Mars is so hilariously more harsh than just UV. Oh and there isn't any such thing as UV resistance. You can't have DNA for that! We use UV to sterilise labs and equipement as a standard procedure. It kills everything.

    But working out that is earth bacteria is again so cheap and easy. Its a simple DNA sequencing test.

  • Moderator
    March 22, 2019, 8:47 a.m.

    I was referring to both the macroscopic organics and the microscopic processes that contributed to their evolution. While different organics and biochemistries are indeed possible, and DNA as a biological information-carrier has many alternatives like anhydrohexitol nucleic acid or HNA, this alone is not stable ground for proclaiming that DNA is utterly unique in its specific molecular configuration. Analogs will be present. Further, there are limitations to the amount of possible configurations organic matter can develop within natural laws. Biophysics follows certain rules which in turn curtail biological configuration. While there are certainly many thousands of possible ways carbon organics alone can manifest, and indeed finding a close analog to Earthly life may be improbable on a chemical level - there is not an infinite amount.

    The point I am making is that you cannot simply call a chemical/mechanical process 'life' because it self-replicates. Many natural processes on this planet self-replicate, and we do not consider them alive. Crystals, viruses, certain types of clay and even fire each have 'self-replicating' qualities, yet clearly these systems are not alive. Grey goo and other forms of nanotechnology, whether physically possible to engineer or not, do NOT fit the current definitions of life. Perhaps in the future we can broaden our understanding of life with newer, challenging discoveries. Until then, those processes and similar systems do not equate life.

    No, there are bacterium and OTHER life-forms, some more complex then others, that are UV-resistant. Not immune, but resistant. Furthermore, a surprising amount of bacterium have survived the disinfectant process on Earth. Obviously there is a limit to how much UV a biological system can withstand before too many chemical bonds are broken, but many species can be highly resistant to even ultraviolet-C radiation treatment (the kind they use for cleaning). According to NASA, almost 250000 members of 370 strains of bacterium survived their sterilization procedure on various rovers sent to Mars, specifically in this case Curiosity. Of course, a combination of freezing temperatures, low atmospheric pressure and intense radiation kills many organisms off once on Mars, but some especially hardy species can survive, especially if they can make it under the Martian topsoil. These trouble bacterium are mostly from the Bacillus genus, but a surprising amount come from other, less tough species. Research the Bacillus bacterium on Wikipedia, they are a natural marvel: en.wikipedia.org/wiki/Bacillus
    The Main report of bacterium contamination can be found HERE: sciencevibe.com/2018/01/10/nasa-admits-contaminating-mars-still-alive/

    Also, as a point of interest here, there are many ways organisms can resist UV and other types of ionizing radiation. Here are just a few examples that you can look into, and while they probably cannot survive on Mars, their evolution remains intriguing:

    The extremophilic bacterium Deinococcus radiodurans is the most UV resistant strain currently known. It, along with the other animals on this list, owes its radiation-resistance to hyperacceleratory cellular regeneration properties. Link: " en.wikipedia.org/wiki/Deinococcus_radiodurans

    Members of the Bdelloidea class of freshwater rotifers can withstand crazed amounts of ionized radiation via a mix of tough biology and hibernation precautions. Link: en.wikipedia.org/wiki/Bdelloidea

    Onto insects. A few members of the parasitoid wasp family of Braconidae can withstand up to 180000 rads of ionizing radiation at a time (1000 rads at once will condemn a healthy human to a slow, painful and certain death). Link: en.wikipedia.org/wiki/Braconidae

    Finally, the largest radiation-resistant organism on this list is the humble scorpion - who can survive up to 135000 rads of radiation. In addition to having a high cellular regeneration rate, they also possess a fluorescent pigment that reflects UV rays efficiently. While this alone is used mostly for navigation, they are extremely tough to kill by direct radiation exposure. Link: www.scorpionsetc.com/scorpions-what-is-truth-and-what-is-wrong.html

    In conclusion, it is entirely possible that certain organisms could hop over to Mars from Earth, or even vice versa if Mars has life and we unwittingly bring a sample back. Luckily for you, this is intriguing evidence for the possibility of panspermia occurring in solar-systems.

    Anyway, If you wish to continue this conversation, I would like to tentatively suggest that you improve your grammar in some way. Your writing is very difficult to understand. I mean no disrespect if English is not your first language, but I get the feeling like most of my quibbles are due to misunderstanding.