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Thread: Plausible? : Comets tranporting frozen live?

  1. #1 Plausible? : Comets tranporting frozen live? 
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    It is hypothesized that there are billions of comets around the solar system, in a hypothetical "Oort cloud", while the recurrent ones are supposedly in a closer ring somewhere outside Uranus orbit, the Kuiper belt. Somewhere I read (probably some informative wiki, where I appear to find more and more wisdom) that the total mass of all comets buzzing around the solar system may be 5 times that of Earth. Many of them never get close to the sun, and stay basically on very slow orbits that take millions of years around the sun, perhaps up to about 1/4 light year away. It's known that comets are basically huge dusty snowballs, containing a lot of water, but also methane and other substances, including solid materials just like asteroids. It is hypothesized that comets provided the water on Earth: When Earth first formed, it is assumed to have been way too hot to be able to keep water molecules stable. Comets come from areas that are far enough from the sun so that water can stay in stable molecular form. In fact, they loose some of it when they come closer to the sun, and that water gets split into hydrogen and OH because of the UV radiation. So if comets crashed into the young earth they may have provided all the water we have now, and eventually live may have formed spontaneously on earth. I think that's pretty much a widely accepted theory. But now I'm speculating: Is it also possible that some comets travel between different solar systems, and that they transport frozen live? This is not in contradiction to the idea of live forming under the proper conditions on planets similar to ours. But could it be that there is even exchange of live going on in the galaxy? (in the entire universe?) Just like non-recurrent comets come out of "nowhere" leaving their far out lonely course (perhaps because of some gravitational interaction between them and the outer planets) and come once close to the sun and disappear again, it may be possible that a comet gets tossed by the same mechanism out of the solar system, so fast that it never returns. If it has sufficient escape velocity it may just go to some other solar system. Of course, it will take many millions of years, but there is enough time. And if this happens around our solar system, it would also happen around other solar systems. So what about this: comets as the messengers that not only provide water for young planets, but also genetic information: encapsulated in ice under their crust of dirt?
    I'm pretty sure that this is not a new idea, but couldn't find anything.


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    As you suspect, it's not a new idea - the Greek philosopher Anaxagoras came up with the idea of 'Panspermia', namely that seeds of life pervade the cosmos.

    In scientific circles I think you'd be hard pressed to find anyone entertaining the idea of life being seeded across solar systems, simply for the travel time involved, the speed required to escape a solar system, and the chance of a comet coming across another solar system and then a planet capable of hosting life.

    That said, there has been some speculation that life originated on Mars, for example, and then was transported here. I do recall an article in Scientific American on the subject, but am not aware of the work it was based upon.


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    I'm not exactly discouraged by the time argument: The escape velocity from the solar system is only about 42km/sec, relative to the orbit of earth, overcoming sun's gravity. Let's say a comet speeds away from the sun and crosses the earth's orbit at 72 km/s. It would leave the solar system, and eventually it will slow down to about 30km/sec, which means that it takes 10,000 years to cover one light year, or 10 million years to travel 1000 light years. I grant it, if it was a billion years to get to another star, I would agree that the time of the universe would be too short for such an idea to have any merit at all. A comet traveling at 30 km/s in interstellar space, then hitting a planet that looks like earth just at the right time, I suppose it's bloody unlikely, but then if there are billions of comets near every solar system? It appears to be about as bloody unlikely as live itself is. Anyways, this was just an idea to ponder about, just along side the idea Mars or some other now icy planet being the original origin of live in the solar system.
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    Quote Originally Posted by rewtedesco
    I'm not exactly discouraged by the time argument: The escape velocity from the solar system is only about 42km/sec, relative to the orbit of earth, overcoming sun's gravity. Let's say a comet speeds away from the sun and crosses the earth's orbit at 72 km/s. It would leave the solar system, and eventually it will slow down to about 30km/sec, which means that it takes 10,000 years to cover one light year, or 10 million years to travel 1000 light years. I grant it, if it was a billion years to get to another star, I would agree that the time of the universe would be too short for such an idea to have any merit at all. A comet traveling at 30 km/s in interstellar space, then hitting a planet that looks like earth just at the right time, I suppose it's bloody unlikely, but then if there are billions of comets near every solar system? It appears to be about as bloody unlikely as live itself is. Anyways, this was just an idea to ponder about, just along side the idea Mars or some other now icy planet being the original origin of live in the solar system.
    If that were true, we should see lots of comets that have trajectories originating from outside the solar system. But as far as I know, all of the comets known so far can be traced back to the Edgeworth-Kuiper belt (short period comets) or the hypothesised Oort cloud.
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    Universal Mind John Galt's Avatar
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    Quote Originally Posted by tenderheart bear
    In scientific circles I think you'd be hard pressed to find anyone entertaining the idea of life being seeded across solar systems,
    I suppose that's true if we ignore the propositions of Orgel, and Crick, and Hoyle, and Wickramasinghe.
    I suppose you might reject Francis Crick's proposal as a tongue in cheek joke from a Nobel laureate. And we all know Hoyle was batty. Right?

    But you could consider this quote from Burchel in 2004 (International Journal of Astrobiology, vol. 3). "Panspermia is the idea that life migrates naturally through space. Although an old idea, there has been much recent theoretical and experimental work developing the idea in recent years."

    There is considerable interest in panspermia and while much of it is focused on the possibility of transfer of material within solar systems, researchers are also seriously considering longer distance and long time transfers.
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    I read a paper once which showed, using pretty simple math, that the possibility for life to travel between solar systems was negligibly small. But by the same token life traveling inside a solar system is plausible, assuming extremophiles can survive the trip through space. There's certainly evidence of chunks of Mars being thrown at Earth.
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    Quote Originally Posted by John Galt
    There is considerable interest in panspermia and while much of it is focused on the possibility of transfer of material within solar systems, researchers are also seriously considering longer distance and long time transfers.
    For functioning life, or material?

    When I consider, for example, the fragile nature of chemautotrophic ecosystems in hydrothermal vent settings, and associated hypotheses (e.g. whale carcasses acting as 'islands' for hopping bacteria), the idea of life surviving an extended, interstellar journey on a lithologic body with no energy source seems highly implausible.

    Lacking evidence of alien life with respect to something such as chirality or anomalous amino acids, I suspect that life on Earth originated on Earth.
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    Universal Mind John Galt's Avatar
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    Quote Originally Posted by tenderheart bear
    For functioning life, or material?
    Both, but very definitely for functioning - though quiescent - life.
    Quote Originally Posted by tenderheart bear
    the idea of life surviving an extended, interstellar journey on a lithologic body with no energy source seems highly implausible..
    I really don't like to get into discussion where I am debating a position that is an argument from incredulity. Check the literature. There is a small body of material that addresses the potential for preservation of lifeforms within aggregates of dust particles, or embedded in ice.

    Quote Originally Posted by tenderheart bear
    Lacking evidence of alien life with respect to something such as chirality or anomalous amino acids, I suspect that life on Earth originated on Earth.
    It's a reasonable assumption, but there is as little evidence supporting a local origin, as a more distant one. I wouldn't argue for panspermia, but I certainly wouldn't argue against it.
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    Quote Originally Posted by John Galt
    I really don't like to get into discussion where I am debating a position that is an argument from incredulity.
    And I've never been fond of debating, "a lack of evidence is not evidence". If there is a fancy and imposing term for that approach, I'll let the resident philosophers apply it.

    Check the literature. There is a small body of material that addresses the potential for preservation of lifeforms within aggregates of dust particles, or embedded in ice.
    Is there, in fact, literature? I wonder what they have to say about the effects of chemical kinetics on a cell, over the amount of time required to transfer life from one solar system to another.

    Quote Originally Posted by tenderheart bear
    It's a reasonable assumption, but there is as little evidence supporting a local origin, as a more distant one. I wouldn't argue for panspermia, but I certainly wouldn't argue against it.
    I would, as I prefer to go with what is simple, and therefore most likely:

    1) Abiogenesis occurring in another solar system and travelling light years to reach our own, or
    2) Abiogenesis occuring on Earth, requiring no extended intervals of transport

    It's pretty slam dunk to me, but I guess we'll just have to wait and see.
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    There's a third option, slightly less tenable from a scientific standpoint: life is a fundamental property of matter that has always existed for as long as matter has existed. This view is not one I would hold, but it is held by some proponents of panspermia.

    Also, life appears on Earth pretty soon after it's creation. If we assume that life developed on Earth, that means that it's probable, from our limited experience, that life is easy to develop. If life were seeded from somewhere else, though, that means life had a much larger probability space to develop in (multiple planets instead of just one), and that means life doesn't have to be as easy to develop. So while Occam's razor has us assume that life developed on Earth, if it didn't it would have an effect on how we approach abiogenesis.

    A possible scenario, in my mind, is that Eukaryotes were seeded from another planet. The development of Eukaryotes was a rather large leap in evolution, with multiple improvements being developed at almost the same time, geologically speaking. I don't think it's an invalid hypothesis to consider that early Eukaryotes were seeded from somewhere else.
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