Abiogenisis and Panspermia:

Discussion in 'Astronomy, Exobiology, & Cosmology' started by paddoboy, Nov 28, 2017.

  1. paddoboy Valued Senior Member

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    https://arxiv.org/pdf/1703.00878.pdf

    Enhanced interplanetary panspermia in the TRAPPIST-1 system:


    I. INTRODUCTION
    The field of exoplanetary research has witnessed remarkable advances in the past two decades, with the total number of discovered exoplanets now numbering in the thousands [1]. This has been accompanied by a better understanding of the factors that make a planet habitable, i.e. capable of supporting life [2]. It is now wellknown that there exist ∼ 1010 habitable planets in the Milky-Way, many of which orbit M-dwarfs [3]. Planets in the habitable zone (HZ) - the region theoretically capable of supporting liquid water - of M-dwarfs have been extensively studied, as they are comparatively easier to detect and analyze [4]. The search for exoplanets around nearby low-mass stars has witnessed two remarkable advances over the past year, namely (i) the discovery of Proxima Centauri b, the nearest exoplanet to the Solar system [5], and (ii) the discovery of seven planets transiting the ultracool dwarf star TRAPPIST-1 [6]. The latter is all the more remarkable since three of the seven planets reside within the HZ, and each of them has a mass and radius that is nearly equal to that of the Earth [7]. Hence, the TRAPPIST-1 transiting system represents a unique opportunity for carrying out further observations to determine whether these planets possess atmospheres and, perhaps, even biosignatures [8]. If conditions favourable for the origin of life (abiogenesis) exist on one of the TRAPPIST-1 planets, this raises an immediate question with profound consequences: could life spread from one planet to another (panspermia) through the transfer of rocky material? Panspermia has been widely investigated in our own Solar system as a potential mechanism for transporting life to, or from, the Earth [9–13]. The planets in the HZ of the TRAPPIST-1 system are separated only by ∼ 0.01 AU, tens of times less than the distance between Earth and Mars. Thus, one would be inclined to hypothesize that panspermia would be enhanced in this system. Here, we explore this possibility by proposing a simple quantitative model for panspermia within the TRAPPIST-1 system. We show that the much higher probability of panspermia leads to a correspondingly significant increase in the probability of abiogenesis. We also draw upon models from theoretical ecology to support our findings, and extend our analysis to other planetary systems.


    I. DISCUSSION AND CONCLUSIONS
    In this paper, we addressed the important question of whether life can be transferred via rocks (lithopanspermia) in the TRAPPIST-1 system. By formulating a simple model for lithopanspermia, we demonstrated that its likelihood is orders of magnitude higher than the Earthto-Mars value because of the higher capture probability per impact event and the much shorter transit timescales involved. We explored the implications of panspermia for the origin of life in the TRAPPIST-1 system by drawing upon the quantitative approach proposed recently by Scharf and Cronin [24]. If panspermia (or pseudo-panspermia) is an effective mechanism, it leads to a significant boost in the probability of abiogenesis because each panspermia event can transfer a modest number of molecular ‘species’, and the cumulative probability scales exponentially in the best-case scenario. Thus, it seems reasonable to conclude that the chances for abiogenesis are higher in the TRAPPIST-1 system compared to the Solar system. We also benefited from the exhaustive field of theoretical ecology in substantiating our findings. By drawing upon the analogy with the theory of island biogeography, we argued that a large number of species could have ‘immigrated’ from one planet to another, thereby increasing the latter’s biodiversity. As known from studies on Earth, a higher biodiversity is correlated with greater stability [50], which bodes well for the multiple members of the TRAPPIST-1 system. We also utilized metapopulation ecology to conclude that the possibility of multiple planets being ‘occupied’ (i.e. bearing life) is higher than in the Solar system, given the considerably higher immigration rates. In order to observationally test the presence of life seeded by panspermia, we proposed a couple of general tests that can be undertaken in the future. We reasoned that a ‘smoking gun’ signature for panspermia may require the following criteria to be valid: the detection of (i) identical biosignature gases, (ii) the spectral “red edge” of vegetation occurring at the same wavelength, and (iii) distinctive homochirality. However, we predict that some of these observations may only fall within the capabilities of future telescopes, such as the Large UV/Optical/Infrared Surveyor (LUVOIR).2 Lastly, we extended our discussion beyond that of the TRAPPIST-1 system and presented other scenarios where panspermia, and hence abiogenesis, are more likely than in the Solar system. We identified exoplanetary systems orbiting lower-mass M-dwarfs (and perhaps brown dwarfs), and exomoons around Jovian-sized planets as potential candidates that favor panspermia. It seems likely that exoplanetary systems akin to TRAPPIST-1, with multiple exoplanets closely clustered in the habitable zone, will be discovered in the future. We anticipate that our work will be applicable to these exotic worlds, vis-à-vis the greater relative probability of panspermia and abiogenesis on them.
     
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  3. paddoboy Valued Senior Member

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    In essence, while Panspermia is still hypothetical, [as far as life on Earth is concerned] Abiogenesis while certainly lacking evidence at this time, is still the only scientific answer to how life arose...whether that be first on Earth or somewhere else, or a multiple of times.
     
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  5. Q-reeus Valued Senior Member

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    First, that 1010 is meant to be a 'staggering' 10^10 i.e. 10 billion. But such hubris. 'It is now well known'? How so exactly? In truth it is currently not known if there is even a single habitable planet outside our Earth. Which is not to say there aren't any, but nothing definite enough is known.
    That last bit about M-dwarfs too....Such are known to be far less stable than our own yellow star Sun. Prone to frequent and violent life-sterilizing flares etc.
    Not to mention inevitable tidal-lock of any 'habitable' planets within the relatively near-orbit 'habitable zone'. Unfortunately unbounded optimism often drowns out a more sober and comprehensive overview. Still - good that such folks keep looking. Who knows, one day an actual verified signature of exo-life may be discovered.
    Unlikely in our life time imo. Oh - I'm forgetting one of our members plans on living forever so that bit just may need a slight amendment. Ha ha.
     
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  7. paddoboy Valued Senior Member

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    Read the paper and article chum, and again if you see yourslef as really professional enough to debunk it, then do it professionally. I won't hold my breath though.
    You accept Abiogenisis I take it?
     
  8. paddoboy Valued Senior Member

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    • Please do not flame other members
    Your own lack of professionalism has lead you to misinterpret what was claimed..It obviously refers to planets that are "habitable' as in possible to support life, but certainly an unknown factor at this time. Understand?
    The rest of your so called criticism, rests on not taking into account many things such as atmosphere's magnetic fields etc.
    But again, hey, if you have a problem with it, and you believe you are professional enough, then take some professional action and submit a reply.
    You know, as with your past erroneous claims.

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  9. paddoboy Valued Senior Member

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    The interesting points in the paper though as I see it, are the discussion on Panspermia processes, and of course the well known fact that in reality Abiogenesis is the only scientific answer to how life got started in the first place.
     
  10. Q-reeus Valued Senior Member

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    Need reminding this is a forum? Not some peer review panel of a prestigious journal. That means being able to freely point out weaknesses in an article or post. Really.
    I know your memory is not great but surely not so bad as to have forgotten our long engagement in previous threads on that issue. As for your #5, nothing there worth responding to.
     
  11. paddoboy Valued Senior Member

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    Sure it is! And obviously open to any Tom, Dick or Harry, or any troubled agenda laden nut that is pushing that same agenda. And just as obviously is the reputable nature of the paper and the professional origin. Glad we can agree that people need reminding of that fact.
    My memory's OK for an old bugger, but obviously yours is somewhat troubled in suggesting the non scientific ID myth which is unscientific. Yes, Abiogenesis is the only scientific answer available. Us being here confirms that.
     
    Last edited: Nov 28, 2017
  12. Xelasnave.1947 Valued Senior Member

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    Hi Paddoboy.

    It is wonderful to find you have returned.

    I felt sorry that you felt that you had to leave as I imagined not having sciforums in your life would have been difficult for you.

    Hi Q-reeus it is nice to see you are still here and I hope you are happy and well.

    I thank you paddoboy for posting as I found the content interesting.

    I say however I find it difficult to accept the paper as what I consider science.

    The paper is as I said interesting and although well considered it would seem simply speculation.

    I could present a plan to hollow out a chamber below the surface of Mars and from there speculate how I could set up a community... Very speculative and let's say well planned referencing rules of engineering etc coming up with a model of how it could be...really would there be any benefit of making a model which is simply well thought out speculation.

    I don't see any difference between my speculation and theirs and certainly one could wonder if either is how science is done.

    Nevertheless thanks for taking your time to post this thread and all the others since you have come back.

    Q-reeus
    I apologise for not continuing my thread on gravity and thank you for participating.
    I will pose one question in that thread and hope you can offer input.

    Alex
     
  13. paddoboy Valued Senior Member

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    Thanks...Whether that return is permanent or not I havn't decided. I am part of another forum at this time, where I'm actually appreciated to some extent and the usual trolls and rif raf are generally quickly dispatched.

    Certainly it is speculative and while I believe as do most cosmologists that we most certainly are not alone, there is as yet, no evidence to support any ETL.
    But cosmologists are able to decypher through data and research which planets are capable of supporting life as we know it..
     
  14. Xelasnave.1947 Valued Senior Member

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    I can't speak for others but I can speak for myself and I say sincerely I appreciate your input here.

    You should not let others upset you.
    Freedom of speech extends to things we don't like to hear but that is no reason to restrict it...the folk you focus upon are no threat to anyone and dig their own graves..you don't even have to hand them the shovel.

    I really hope you can stay and not let anyone upset you.

    Alex
     
  15. Q-reeus Valued Senior Member

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    Hi Alex. It was big mystery as to reason behind your departure and lengthy outage but thankfully my worst fears obviously not well founded!

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    Yeah heading over to that other thread now....
     
  16. origin Trump is the best argument against a democracy. Valued Senior Member

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    Why do that, why do you continually attack? Can't you just discuss the things you bring up?
     
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  17. paddoboy Valued Senior Member

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    I give as good as I get even better.
    Your own reputation might be better if it wasn't tinged with some hypocrisy.
     

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