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Thread: Galactic Panspermia?

  1. #1
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    Galactic Panspermia?

    Many years passed before “panspermia” even reached escape velocity; it was stuck on Earth, if you will. Then, evidences amassed and “lithopanspermia” was accepted as plausible, if not probable, but “interstellar” was most doubtful. Now however, it seems panspermia isn’t necessarily restricted to our solar system:

    Galactic Panspermia

    Abstract:
    We present an analytic model to estimate the total number of rocky or icy objects that could be captured by planetary systems within the Milky Way galaxy and result in panspermia should they harbor life. We estimate the capture rate of objects ejected from planetary systems over the entire phase space as well as time. Our final expression for the capture rate depends upon the velocity dispersion as well as the characteristic biological survival time and the size of the captured object. We further take into account the number of stars that an interstellar object traverses, as well as the scale height and length of the Milky Way’s disk. The likelihood of Galactic panspermia is strongly dependent upon the survival lifetime of the putative organisms as well as the velocity of the transporter. Velocities between 10 − 100 km s−1 result in the highest probabilities. However, given large enough survival lifetimes, even hypervelocity objects traveling at over 1000 km s−1 have a significant chance of capture, thereby increasing the likelihood of panspermia. Thus, we show that panspermia is not exclusively relegated to solar-system sized scales, and the entire Milky Way could potentially be exchanging biotic components across vast distances.
    Where the telescope ends, the microscope begins. Which of the two has the greater view?

  2. #2
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    It's stil speculation.

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    I think there's more hard evidence that the universe is hostile to life than there is for the natural spreading of life.

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    Quote Originally Posted by Roger E. Moore View Post
    I think there's more hard evidence that the universe is hostile to life than there is for the natural spreading of life.
    What are some examples of that hard evidence?
    Depending on whom you ask, everything is relative.

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    Quote Originally Posted by mkline55 View Post
    What are some examples of that hard evidence?
    Supernovae, mass extinction from geological processes, planetary collisions, superflares and M-dwarf flares, black holes, gamma-ray bursts, and the fact that we have the planet with the only known life in the universe.

    Example reference: Phil Plait's Death from the Skies.

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    closed pending moderator discussion.
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  7. #7
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    Okay, we've discussed.

    Panspermia is a popular but not mainstream idea. As such conjecture is okay here but advocacy belongs in ATM. Please keep that in mind as you discuss the topic.
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  8. #8
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    I've remained skeptical of interstellar panspermia for years, while papers like this are few and far between. The authors speak to this:

    "There is no doubt that rocky material can easily be exchanged between nearby planets, such as Mars and Earth or the planets of the TRAPPIST-1 system (Lingam & Loeb 2018c). Thus, nearly all papers on panspermia focus on interactions within a Solar system (see, however, Adams & Spergel (2005); Li & Adams (2015); Lingam (2016) and references therein). In this paper we conclusively show that panspermia is viable on galactic scales."


    Sometimes I'm confused when popsci blogs cite mainstream science journals but a couple years ago Universe Today covered Galactic Panspermia: Interstellar Dust Could Transport Life from Star to Star where they quote "The proposition that space dust collisions could propel organisms over enormous distances between planets raises some exciting prospects of how life and the atmospheres of planets originated. The streaming of fast space dust is found throughout planetary systems and could be a common factor in proliferating life.”

    Who knows if it happens, or where the line between popular and mainstream is drawn, but I find these studies most interesting!
    Where the telescope ends, the microscope begins. Which of the two has the greater view?

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    Should be interesting to see what the Hayabusa 2 sample return probe returns (as another potential data/test point ... amongst many other hypotheses other than just panspermia as well).

    Looks like the penultimate sampling is planned to take place on the Ryugu asteroid in just a couple of days (Feb 22) and is planned to return to Earth in Dec 2020.

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    BTW, I see Selfsim is on the eve of being a kilopi. Is this an automatic event, or will Selfsim have to do something?
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  11. #11
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    Quote Originally Posted by Tom Mazanec View Post
    BTW, I see Selfsim is on the eve of being a kilopi. Is this an automatic event, or will Selfsim have to do something?
    Its automatic. I recall wishing I had a warning so I could make my Kilopi Post something memorable. I am pretty sure my Kilopi post was something to the effect of "That's cool" or "I agree".

    Back to the topic at hand. I don't see why masses can't be transported by natural means from one galaxy to another over a great deal of time. It would probably look a bit like that video segment in Cosmos showing how "fast" culture could spread across a galaxy, but slower. Exactly how much of that mass would contain life is pretty low. I would be much more comfortable with the idea if only we had some Mars bacteria as a reference point.

    Heck, I'd take long dead Mars bacteria. I believe I still have a newspaper from the 1990/2000s where they announced a rock with seemingly Martian bacteria. The hope is there, but man, I want something more solid than what appeared there.
    Solfe

  12. #12
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    Quote Originally Posted by Selfsim View Post
    Should be interesting to see what the Hayabusa 2 sample return probe returns (as another potential data/test point ... amongst many other hypotheses other than just panspermia as well).

    Looks like the penultimate sampling is planned to take place on the Ryugu asteroid in just a couple of days (Feb 22) and is planned to return to Earth in Dec 2020.
    Yeah, I'm looking forward to this as well. JAXA has some cool missions flying; Tanpopo is specifically testing panspermia hypotheses. And then there's ESA's EXPOSE mission, flying for ten years now, also testing panspermia hypotheses. Slowly but surely...
    Where the telescope ends, the microscope begins. Which of the two has the greater view?

  13. #13
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    Quote Originally Posted by Solfe View Post
    ...
    Heck, I'd take long dead Mars bacteria. I believe I still have a newspaper from the 1990/2000s where they announced a rock with seemingly Martian bacteria. The hope is there, but man, I want something more solid than what appeared there.
    It was '96 and I'm not convinced the story of the Alan Hills meteorite is finished. Science is slow. Only a handful of years ago it was determined ALH840001 was immersed in water on Mars ~ 4G years ago. I suspect it has more to reveal.
    Where the telescope ends, the microscope begins. Which of the two has the greater view?

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