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B Life is less likely on exoplanets

  1. Dec 1, 2017 #1

    wolram

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    https://www.sciencedaily.com/releases/2017/11/171130180031.htm

    However, the question of habitability is highly complex. Researchers led by space physicist Chuanfei Dong of the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) and Princeton University have recently raised doubts about water on -- and thus potential habitability of -- frequently cited exoplanets that orbit red dwarfs, the most common stars in the Milky Way.

    Given that the above is true it seems we are much more likely to be alone in this galaxy, what do you think,
     
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  3. Dec 1, 2017 #2

    Borg

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    I think that it's like saying that because there is no money in my bathroom, that finding money in my house is very unlikely. Not a valid conclusion.
     
  4. Dec 2, 2017 #3
    There's about 100 billion stars in our galaxy alone. We've found about 5,000 possible exoplanets. Even if we assume each one is the only planet around it's star that means we've looked at .000005% of our galaxy. Which is not even remotely the slightest bit of information required to make such a wide generalisation.

    That's more like saying, "There's no money in my bathroom. That must mean there's no money on the entire planet."

    The simple fact is that everything we know about these exoplanets is based on slight variations in light intensity or movement from it's star. Everything after that is just theories and assumptions. So basically we actually know absolutely nothing of significance about these planets.
     
  5. Dec 2, 2017 #4
    JWST should be able to determine further the nature of some exoplanets though.
    For example some idea of whether an atmosphere exists that includes water vapor.
     
  6. Dec 2, 2017 #5

    stefan r

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    I have a fuzzy memory of someone explaining the drake equation to me when I was still in elementary school (1980s) I am fairly confident they said something like "... and suppose one out of a thousand stars have a planet and suppose...". In the mean time the number of stars has increased. There are reasons to believe the number of planets may exceed number of stars. The number of galaxies in the visible universe grew substantially. The number of galaxies was not in Drake's equation but it was in the argument I heard. So looking at the 30 year trend (or 56 if you can remember Drake) the number N has increased by quite a bit. A portion of the red dwarfs having a lower fi does decrease N slightly but that hardly puts a dent in the other gains.
     
  7. Dec 2, 2017 #6

    phinds

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    Although I agree, generally, with your post, I think you underestimate the degree to which we can validly extrapolate information to draw conclusions about exoplanets.
     
  8. Dec 2, 2017 #7

    mfb

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    Or both together. Or microlensing. Or direct imaging. Or orbital stability analyses.
    Add spectroscopic analyses of some planets or their atmospheres. We know several planets with water vapor in the atmosphere. We have measurements of day lengths and even wind speeds and cloud maps of exoplanets.
    Most of these measurements are done with Jupiter-sized planets so far, but what current telescopes can do with them JWST and ELT will do with Earth-sized planets - and much more (e.g. much more direct imaging and spectroscopy of reflected light).
     
  9. Dec 5, 2017 #8
    Only the Drake Equation terms
    R, the average rate of star formations, in our galaxy
    fp, the fraction of formed stars that have planets
    ne, for stars that have planets, the average number of planets that can potentially support life
    fl, the fraction of those planets that actually develop life​
    seem relevant to what I interpret as the key question the OP seems to be asking:
    Does the cited research give strong support for the premise that life in the Milky Way may be so extremely rate that the odds are we on Earth are alone in this galaxy. There remaining Drake Equation terms relate to intelligent life.

    The cited paper suggests that the number of red dwarf stars with liquid watery planets is much less than previously thought. much reducing the estimated value for ne. Even if the paper's conclusions are correct, and ne is say order of magnitude 1% or 0.1% of previous estimates, the product
    R × fp × fl
    would still be pretty large.

    My bias about this topic is about fl. I understand that many scientists think fl is very close to 1 because life formed on earth within a few hundred million years after oceans were formed, and Earth doesn't seem to have any particularly special properties that would effect life starting. As I have discussed in other threads, my bias is that our very large moon may well be what make Earth special. It also seems likely that a candidate planet for having life has a very small chance of having a similar large moon.

    ADDED
    Underlined correction edit in previous paragraph.
    Bold text above for easy reference to it below.
    Sources with quotes:
    https://serc.carleton.edu/NAGTWorkshops/earlyearth/questions/formation_oceans.html
    The very existence of the Isua BIF requires the presence of stable surface water, at least locally for the chemical deposition of the sedimentary components at ca. 3800 Ma.
    We infer that to produce these 'high δ18O' zircons required that the igneous protolith of the zircon must have assimilated or re-melted crustal materials that were altered by low-temperature processes at or near Earth's surface. In other words, surface waters were present by at least 4200 Ma.
    https://en.wikipedia.org/wiki/Timeline_of_the_evolutionary_history_of_life#Hadean_Eon
    4404 MA - First appearance of liquid water on Earth.
    4280 Ma - Earliest appearance of life on Earth
    "Remains of biotic life" were found in 4.1 billion-year-old rocks in Western Australia.[21][22] According to one of the researchers, "If life arose relatively quickly on Earth ... then it could be common in the universe."[21]
    [21[ Borenstein, Seth (October 19, 2015). "Hints of life on what was thought to be desolate early Earth" . Excite. Yonkers, NY: Mindspark Interactive Network. Associated Press. Retrieved 2015-10-20.
    [22] Bell, Elizabeth A.; Boehnike, Patrick; Harrison, T. Mark; et al. (November 24, 2015). "Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon" (PDF). Proc. Natl. Acad. Sci. U.S.A. Washington, D.C.: National Academy of Sciences. 112 (47): 14518–14521.​
    Underlined quoted text above is a source supporting previous bold text.

    Regards,
    Buzz
     
    Last edited: Dec 5, 2017
  10. Dec 5, 2017 #9
    So far there are no exoplanet examples of a binary planet system like Earth/Moon,
    I agree though that a binary planet system within that 'goldylocks zone' could be significant for life because of water tides;
    In our solar system there is Pluto/Charon, but that can be ruled out as a possible place for life because liquid water is impossible.
    It does however demonstrate that planetary binaries are not rare.
     
  11. Dec 5, 2017 #10

    stefan r

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    It is fine to drop the intelligence and just consider life. But I think you still need a modified L. A planet could have evolving bacteria that go extinct. You could also add a form of Fc for the fraction that modifies their atmosphere in an observable way.

    If life pops up rapidly it would appear in the planets around red dwarfs. Then might die later.

    A more stable rotation might facilitate complex life. Tidal estuaries also add a lot of biodiversity. Bacteria seam to survive severe climate disruptions. Place some food in your freezer then let it sit in a hot car for a day. Enough strains of the bacteria survive. Most animals cannot survive switches back and forth from arctic to tropics. Migrating animals might survive. Would be hard to change the climate fast enough to kill Tardigrades. What effect does the moon have on hydrothermal vent ecosystems?
     
  12. Dec 5, 2017 #11

    stefan r

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    Not everyone is so certain: phys.org

     
  13. Dec 5, 2017 #12

    mfb

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    There is also no detection method that would see such a Moon with reasonable probability. Yet.
    We don't know how quickly it started (apart from a range of a few hundred million years), and if it would have started much later we wouldn't have humans around before Earth gets inhospitable. There is no strong argument for any value of fl based on that.
     
  14. Dec 5, 2017 #13
    Pump up the resolution.
    Do you think we could make instruments with that kind of resolution within 100 years?
    Or is that going to depend on new technology which we don't have at present?

    OK, but I think that can only be called speculation, though not unreasonable
     
    Last edited: Dec 5, 2017
  15. Dec 5, 2017 #14
    Hi stefan:

    You make two good points here that suggest the Drake Equation might need some adjustments.

    Regards,
    Buzz
     
  16. Dec 5, 2017 #15

    mfb

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    100 years?

    JWST (2018) might be able to find some Moon-like moons if they exist in reasonable quantity nearby. CHEOPS (2018) could find a few. The ELT (2024) should find some if they transit the planet as seen from us and if we happen to look at the right time. PLATO (2026) will find them.
     
  17. Dec 5, 2017 #16
    Thanks, I had not heard before of this project.
     
  18. Dec 7, 2017 at 3:45 AM #17
    We've found so far quite a number of things that could be a road block for habitability. If the star mass is too low you have the red dwarf problems that are shown in the paper. If the star mass is too large, there may be not enough time for complex life to emerge. Planets with life may quickly go into a snowball state or runaway greenhouse state. Stuff like Gamma Ray Bursts, close encounters with heavy interstellar planets, orbital instabilities or planetary collisions may also destroy life. And yet here we are and the universe is still very young. I also think that "alone" is plausible.
     
  19. Dec 7, 2017 at 9:03 AM #18
    Who is to say that other life needs to be carbon based (even though that makes the most sense)? We search only for life that exists under the same conditions as our own planet. I have no biochemistry knowledge and I could be wrong, but I don't see why it wouldn't be possible for the existence of non carbon based life.
     
  20. Dec 7, 2017 at 11:00 AM #19
    Carbon has unique chemical properties.
    It can combine with other carbon atoms and almost every other element in a practically unlimited number of ways.
    Thus it's reasonable to suggest that life is very highly likely to be carbon based as other similar complex chemistry apparently can't happen.
    Having said that though, there is no reason to suppose that the only possible life forms have to be DNA//RNA based life as on Earth.
     
  21. Dec 7, 2017 at 12:38 PM #20

    anorlunda

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    This thread is becoming repetitive. It has run its course.

    Thread closed.
     
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