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So far, scientists have said they have identified twelve planets that might be habitable.  In fact, there are significant problems with every single planet
identified to date.  For a list of the most habitable exoplanets click here

First, many of these exoplanets (Gliese 581d, Gliese 581g, Gliese 667 Cc, Gliese 163 c, HD 40307 g, 55 Cancri f, GJ 1214 b, HD 85512 b) circle small mass stars.  Many seriously doubt whether life could evolve in these star systems.

M-dwarfs are cooler and much smaller than our sun. They account for about three-quarters of all stars in the Milky Way. Although Earth size planets have been found around such dwarfs, these planets tend to orbit very close to the sun.  Because M dwarfs are small and cool, their temperate zone--also known as the "habitable zone," the region where liquid water might exist is further inward.  New research by the Harvard-Smithsonian Center for Astrophysics (CfA) suggests that there are 17 billion earth-like planets in the Milky Way in an orbit closer than Mercury. In other words, one in six stars has a Earth-like planet in a close orbit.  The problem is, there planets may all be dead worlds.  

Red dwarf planets emit less light so the planet must be closer to it's sun.  Flares on M-dwarfs can be a thousand times stronger than compared to our Sun. Such mega-flares can double the brightness of the star in minutes. Life on the surface of GJ667Cc would have to find a solution to this problem.

In addition, many red dwarfs can lose their light.  They may become covered by sunspots that could reduce the energy output of the star by as much as 40% for periods that may last months.  In other words, random nuclear winters.  Also, red dwarf stars emit very little ultraviolet light, these varying light conditions would be a potential problem for life as we know it.

However, a recent study posed even more problems for low mass stars.

1. Habitable planets that are close to their sun are probably tidally locked so one side of the planet is constantly in daylight while the other side would be frozen in constant darkness. The dark side of these planets will always be too cold to support life and the lighted side could become exposed to too much radiation and the temperature differences would cause extreme weather across the planet.

2. Similarly, tides can cause the planet`s rotation to become perpendicular to its orbit eliminating seasonal variation and again creating dark and light sides with similar problems to 1. In addition, the equator of such a planet could become so hot that it would burn off the atmosphere.

3. Tidal heating causes massive vulcanism. Planets where there are constant lava flows are obviously not habitable.

A recent study estimated there may be as many as 100 billion Earth size planets surrounding dwarf stars in the Milky Way.  The only problem is that they may all be dead worlds.

Second, many other exoplanets revolve around binary or trinary star systems (Kepler-22 b, Kepler-47c).  However, recent research suggests that planets from binary and trinary star systems that produce unstable orbits. Computer simulations suggest that in most cases the binary star system will eventually radically change the orbits of the planets.

Third, Tau Ceti (Tau Ceti e, Tau Ceti f) has an asteroid belt ten times the size of our asteroid belot that would destroy all life in the system.  Also, it's a Tau Ceti is metal-deficient, which deficiency is usually few rocky planets.  In addition, the best guess is that the surface temperature on these planets are oven-like (155 °F, 122 °F).  However, Tau Ceti f may also not have a greenhouse effect so it's average surface temperature would be -31 °F which would leave all the water frozen.

After that quick screening, we're left with no habitable confirmed planets.

Originally posted to USSpinWatcher on Thu Jan 10, 2013 at 05:57 PM PST.

Also republished by SciTech.


Do You Believe Any of These Planets Have Life On Them?

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46%24 votes

| 52 votes | Vote | Results

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Comment Preferences

  •  Unfortunately, we don't have the... (13+ / 0-) to reach any of these planets in a reasonable amount of time (i.e., FTL drive), nor do we have a way of reporting back (subspace radio). If they are inhabited, the life may be much different than anything we know of.

    Float like a manhole cover, sting like a sash weight! Clean Coal Is A Clinker!

    by JeffW on Thu Jan 10, 2013 at 06:08:02 PM PST

    •  I think that we can easily reach... (4+ / 0-)
      Recommended by:
      LordMike, wader, Oh Mary Oh, bevenro

      ...these planets in a relatively short amount of time.

      If the word "we" is understood as meaning "RNA and its ingredients"


      the phrase "relatively short" is understood as meaning "on a galactic timescale."

      You always have to leave stuff behind when you go on a trip.  Why should DNA-based life be any different?  We will certainly have to abandon human bodies and human timescales if we are to extend ourselves between galaxies.

      We need to think of ourselves a little differently: we're the currently manifesting consciousness of DNA...and the problem isn't getting humans to another star, but getting our DNA or an equivalent molecule there and finding it places where it can start new life.

      Freedom isn't "on the march." Freedom dances.

      by WarrenS on Thu Jan 10, 2013 at 07:45:34 PM PST

      [ Parent ]

      •  You're still talking technology that... (3+ / 0-)
        Recommended by:
        WarrenS, wader, Calamity Jean

        ...doesn't yet exist. We can't even send robotic probes out that far and be able to get information back.

        Float like a manhole cover, sting like a sash weight! Clean Coal Is A Clinker!

        by JeffW on Thu Jan 10, 2013 at 07:58:48 PM PST

        [ Parent ]

      •  Why send our DNA? (3+ / 0-)
        Recommended by:
        WarrenS, wader, Calamity Jean

        Send robots out there. Robots don't have our frailties. They can go into environments that we could never survive in. They could build more robots, and those could in turn build more.

        If we follow in their wake, there would be plenty of room for human and robot. The robots could build facilities in advance of our arrival, and leave us the planets habitable by humans. Robots could do the work of terraforming. It would take a while, but what's time to robots.

        Of course, we'd have to advance tremendously in AI, but we have time. The universe could wind up being populated by our robotic children. We'd have to build equipment that can work after centuries in space, but that's a technical difficulty, not a scientific impossibility.

        If we really have to have humans go out there, we could send out craft with robots, frozen embryos and artificial wombs. The craft would land, the robots would build the facilities, and then fire up the artificial wombs. Then the would raise the children to adulthood. It would take a lot of advancement in AI to have a robot that could construct a city and raise children. But we have time.

        The wolfpack eats venison. The lone wolf eats mice.

        by A Citizen on Thu Jan 10, 2013 at 08:22:56 PM PST

        [ Parent ]

      •  this is a good point, but I think people aren't (4+ / 0-)
        Recommended by:
        wader, Calamity Jean, WarrenS, Oh Mary Oh

        quite taking your meaning.

        The way we usually look at it--that people can't do x--is kind of like saying, in 2 billion BC, that cells aren't capable of inventing the internet...

  •  And the search continues... (11+ / 0-)

    This is getting embarrassing as Earth is , so far, the only planet represented in the Miss Universe Pageant!

    "I'd like to thank spiritplumber and LieparDestin for fixing oopsaDaisy's computer who can tip, recc, and hotlist now. I tried but couldn't do it despite her constantly foulmouthing me, so thanks U two." -God

    by oopsaDaisy on Thu Jan 10, 2013 at 06:09:31 PM PST

  •  Not a problem (11+ / 0-)

    We can only see the planets we can see, which we can see only under very special circumstances. We can't see the planets we can't see, which is all the rest.

    The debate here on earth is, what can we confirm, here on earth? The rest of the universe doesn't care if we confirm it or not.

    “Americans are fighters. We're tough, resourceful and creative, and if we have the chance to fight on a level playing field, where everyone pays a fair share and everyone has a real shot, then no one - no one - can stop us. ”-- Elizabeth Warren

    by Positronicus on Thu Jan 10, 2013 at 06:22:02 PM PST

  •  Only Extreme Planets are Easy to See Right Now. (13+ / 0-)

    It's VERY early in the search. I wonder if we could accurately detect our own solar system at 10's of light years away, most or all of the planets, and correctly identify the earth.

    We are called to speak for the weak, for the voiceless, for victims of our nation and for those it calls enemy.... --ML King "Beyond Vietnam"

    by Gooserock on Thu Jan 10, 2013 at 06:30:14 PM PST

    •  That's true! On the Suitability for Vegetation (6+ / 0-)

      Index, Earth only rates 72%. Some exoplanets rate rate higher (Kepler-22 b 96%, Gliese 667C c, 98%).

      •  I'm curious (1+ / 0-)
        Recommended by:

        What would Venus rate on that scale?

        (From billions of miles away, not next door like we are now).

        Rocky planet, about the size of earth, orbiting in the habitable zone (I think) of a yellow main sequence star.

        On paper, looks great. Except the surface temperature is hot enough to melt lead (the Soviets lost several Vanera probes figuring out how to get one to the surface in one piece).

        (-5.50,-6.67): Left Libertarian
        Leadership doesn't mean taking a straw poll and then just throwing up your hands. -Jyrinx

        by Sparhawk on Fri Jan 11, 2013 at 12:47:37 AM PST

        [ Parent ]

        •  it's a zero (0+ / 0-)

          As the chart in the diarist's link shows.

          •  My point is... (0+ / 0-)

            ...we know it's zero because we live next door to it and can look at it in detail.

            The question is: would Venus look habitable looking at it from Alpha Centauri instead of here?

            (-5.50,-6.67): Left Libertarian
            Leadership doesn't mean taking a straw poll and then just throwing up your hands. -Jyrinx

            by Sparhawk on Fri Jan 11, 2013 at 02:04:43 AM PST

            [ Parent ]

            •  Looking further and answering my own question... (1+ / 0-)
              Recommended by:

     seems like Venus doesn't look too good even from far away (far outside the habitable zone, not good earth similarity).

              If you look at a planet like Kepler-22b, Wiki comments:

              Scientists can estimate the possible surface conditions as follows:
              In the absence of an atmosphere, the equilibrium temperature would be approximately -11°C.[citation needed]
              If the atmosphere provides a greenhouse effect similar in magnitude to the one on Earth, the planet would have an average surface temperature of 22 °C (72°F).[8][not in citation given]
              If the atmosphere has a greenhouse effect similar in magnitude to the one on Venus, the planet would have an average surface temperature of 460 °C (860°F).[citation needed]
              I guess it's too hard to speculate about atmosphere from so far away. Scientists just have to sit there and hope the greenhouse value is right.

              (-5.50,-6.67): Left Libertarian
              Leadership doesn't mean taking a straw poll and then just throwing up your hands. -Jyrinx

              by Sparhawk on Fri Jan 11, 2013 at 02:15:38 AM PST

              [ Parent ]

  •  What's the bad news?? n/t (2+ / 0-)
    Recommended by:
    ericlewis0, kyril
  •  Anyone ever consider that humans... (6+ / 0-)

    could be the earliest evolved intelligent life in our solar system?  There will be no advanced space-faring alien race that makes contact with us.  It will be up to the humans to make first contact tens of thousands of years from now.

    Sort of flies in the face of many conventional sci-fi tropes.

  •  Just to provide some perspective (17+ / 0-)

    87.5% of solar system planets aren't habitable, either.

    And the one that is habitable -- wasn't for about the first 25% of its life, and then it was habitable for only certain kinds of life for the next 25% or so until it nearly poisoned its atmosphere with deadly life-destroying oxygen.

    There have been some other setbacks along the way, but life is pretty tenacious once it gets a foothold. It will probably even survive humans.

    ad astra per alia porci

    by harrije on Thu Jan 10, 2013 at 06:36:47 PM PST

  •  The number of prerequisites is (6+ / 0-)


    A planet capable of complex life needs a magnetic field to fend off dangerous cosmic radiation, which means a molten core, which means a combination of tidal friction and heavy elements that undergo radioactive decay. A planet too small would cool regardless, like Mars. Also required is a gas giant like Jupiter to soak up asteroids that would otherwise continually pound the would be Earth.

  •  You're also making the assumption that life on (7+ / 0-)

    other worlds evolved the same way it did here.

    Who's to say that there can't be life based on some weird chemistry that we haven't figured out yet? For example, maybe there is life based on some weird combination of, say, ethanol and silicon compounds.

    We don't want our country back, we want our country FORWARD. --Eclectablog

    by Samer on Thu Jan 10, 2013 at 07:08:39 PM PST

    •  122 degrees F might not be a problem at all. (11+ / 0-)

      There are thermofile organisms on Earth that would find that rather chilly. We might not like it, but life there could be adapted to it.

      The wolfpack eats venison. The lone wolf eats mice.

      by A Citizen on Thu Jan 10, 2013 at 07:24:30 PM PST

      [ Parent ]

      •  Heck, Earth has lifeforms that make us wonder (6+ / 0-)

        "Who ordered that?"

        Some scientists think that there are so many undiscovered archaebacteria species living beneath Earth's surface that they may represent the majority of all life on Earth.

        We don't want our country back, we want our country FORWARD. --Eclectablog

        by Samer on Thu Jan 10, 2013 at 07:36:33 PM PST

        [ Parent ]

        •  Life (4+ / 0-)
          Recommended by:
          JeffW, kyril, exterris, Oh Mary Oh

          Life exists in so many forms here on Earth. Many of these we had thought impossible just a few years ago. It expands greatly where we might expect to find life. If there's liquid water, it might have life.

          The wolfpack eats venison. The lone wolf eats mice.

          by A Citizen on Thu Jan 10, 2013 at 07:55:08 PM PST

          [ Parent ]

          •  Yes, but life exists here already... (0+ / 0-)

            I have no doubt life could adapt to exist in a lot of different situations, but before that life has to form in the first place, and we simply have no idea how likely that is.

            There could be millions of planets more habitable than Earth in the universe, and at the same time none of them might have life.  We have no idea how unlikely it is for life to arise even with all the necessary prerequisites.

            It happened here so we like to think it could happen elsewhere, but it could be that life on Earth is just the result if trillions of trillions of trillions of years of rolling the dice.  And after that many tries the number finally came up, even though the odds of it happening are impossibly small.  

            Or alternatively life could be all over the place, or it could be something between the two extremes.  We simply have no idea.  My only point is that even if a lot of candidates for life exist out there, that doesn't translate into a certainty that life is commonplace, or even exists anywhere else at all.

            •  Look at what scientists believe they know about (0+ / 0-)

              where life could exist within our solar system.  Most of it is not within the habitable range but circling either Saturn or Jupiter.  For example, why wouldn't life exist on Europa?  More water than Earth has and it's warm.  We just can't see it because it's buried under ten miles of ice.  Perhaps exomoons of gas giants that circle closer to their Suns is where most life exists in the universe.

    •  We have no Idea of the chemical compounds (2+ / 0-)
      Recommended by:
      annetteboardman, kyril

      and reactions that could exist on a planet at lets say 1000 F,1500 F or 2500 F,sure we know of an about  individual Elements and Compounds at those temps and some of the complicated reactions mostly from melting ores and lab research but not what they would do when it comes to all the interactions possible on a planetary scale,so there may be life that looks at Earth Temps like we look at planets with Temps of -350 F.

  •  Are we talking earth-like life? (5+ / 0-)

    each planet would contain its own lint and dust. That would be its atmosphere and whatever is within it, including lifeforms.

    We are so used to the Sun being a certain size in the sky but it's not optimal. It's only the distance from there to here. We've developed the way we have because of the conditions, with an emphasis on conditions.

    So perhaps those planets are uninhabitable for humans but that's different from being uninhabitable.

  •  Few things: (1+ / 0-)
    Recommended by:

    1. It doesn't matter if there are other habitable worlds out there because we'll never ever get there. It's not possible. It won't be possible. General and Special Relativity rather preclude that.

    2. This

    Third, Tau Ceti (Tau Ceti e, Tau Ceti f) has an asteroid belt ten times the size of our asteroid belot that would destroy all life in the system.

    is irrelevant. the size of the belt has nothing to do with the presence of life. A large asteroid belt does not automatically mean asteroid impacts, especially since Tau Ceti is somewhat older than our sun, and especially since no large objects have been detected in the outer system that'd perturb the orbits of the speculated asteroids.

    just a little bit bored.

    by terrypinder on Thu Jan 10, 2013 at 07:57:15 PM PST

  •  There is when it comes to life on other worlds (4+ / 0-)

    a theory called panspermia and well there is one for sure life bearing candidate that could have spread life into space an that's Earth itself,the Sun has made give or take 20 trips around the Galaxy each trip takes near 250 million years just think how many possible planets in other Solar Systems could have been exposed to Microscopic Terrestrial Life Forms if they could survive and escape the Gravity of the Sun and get into Interstellar Space.

    •  So far there is no evidence we seeded... (1+ / 0-)
      Recommended by:

      our own solar system, so what are the odds we seeded anything outside of it?  I'll grant that it's possible that the odds of life forming is so rare that it could be more likely to have spread due to being seeded by the Earth, but that is not saying much for the chances of there being extraterrestrial life.  

      Think about it, the organism would have to survive an asteroid impact strong enough to eject it from our planet's atmosphere and launch if into interstellar space. Chances of that are already so close to zero it's not even worth contemplating.  Then it would have to survive the vacuum and radiation of interstellar space.  And after all that it would have to reach a suitable world and survive reentry.

      Think about it honestly: it's nearly, if not completely, impossible.  People don't like to admit it, but there's a strong likelihood that hardly any life exists in the entire universe, let alone our galaxy.

      If it does exist I think it is more likely that the odds of it arising independently are larger than I personally believe.  The odds of it bring seeded from here I think is basically zero.

  •  Obviously the vast majority of Earth-sized worlds (3+ / 0-)
    Recommended by:
    exterris, armd, Oh Mary Oh

    we find are going to be "mostly dead" rocks like Mars, ice balls like Ganymede, volcanic pustules like Io, and caustic hells like Venus, all with varying masses, compositions, and energy input from their stars.  There are just so many different ways to those outcomes that they will naturally dominate the census.

    But the notion of a unique Earth is as ludicrous as a person thinking they're unique - in fact, much more so, since the potential variations in planetary environments is not likely to be as numerous as functioning human brain configurations.  And yet there are thought to be far more terrestrial-mass planets in the galaxy than there are humans on Earth, and that's just one galaxy.

    I also think "habitability" is not the same concept as being "another Earth" - frankly, a number of the bodies in our own solar system we dismiss as hostile are habitable to humans in the context of our technology.  We can go there, survive indefinitely, and probably flourish independently, so "habitability" in my view is a much broader category than is usually understood.  It makes sense to look for things most like Earth, but it doesn't make sense to declare the galaxy a desolate wasteland because the census of the thousand-plus planets we've detected in a small corner of sky using two very limited techniques has not netted us definitive proof of Earth 2 in the handful of years we've been able to search practically.

    It'll be a while before we can say whether or not any given planet is Earthlike with concrete evidence rather than just theoretical examinations of the constrained possibilities.  There would be no way to know that Earth itself was teeming with life from such distances without directly sensing its atmospheric chemistry, and we're also assuming without real basis that these conditions are the best ones for life despite all the crude environmental hacks (like an ozone layer) that life has had to evolve to flourish here.  And why must there be UV light?  Plants evolved to use it because it's the most potent available energy.  Is it chemically impossible to use longer wavelengths in similar, albeit less energetic ways?  Come on.

    Somewhere there's a planet with slightly less gravity orbiting somewhat closer to a somewhat smaller, somewhat cooler orange star that is both more stable and more nurturing than the Sun, and that will be longer-lived, and this planet is to Earth in terms of life what Yosemite is to Nebraska.  And since there's probably one, there's probably many.  But screw those places - the ones that are most relevant to us are the marginal ones we may theoretically some day colonize without having to displace a native biota.

    In Roviet Union, money spends YOU.

    by Troubadour on Thu Jan 10, 2013 at 11:24:33 PM PST

    •  But the thing is... (1+ / 0-)
      Recommended by:

      After all that we have no idea how likely life is to evolve.  In a lot of ways life could be as unlikely as finding a fully assembled working toaster on a desolate planet.  Given enough chances something like that could self assemble, but the odds of it happening are nearly zero.  

      Even there are millions of worlds out there that could sustain life, that doesn't mean any of them have life.  Even with all of the planets in the universe, there is no guarantee there is any other life out there.

      So many lucky coincidences may be required for life to form that the odds could be against it existing in the entire universe.  If we accept infinite time, it could be that millions of universes have formed and dissipated away, before this time when life arose.  We simply have no idea how low the odds are, even in a perfect situation.

      A lot of people seem to have the belief that life is quite prevalent, but I suspect the opposite.  It would not surprise me if evolution to an advanced form is extremely likely once life has formed, but the initial formation of even single celled life and its precursors is infinitesimally rare.

      •  The reasoning goes like this. (1+ / 0-)
        Recommended by:
        Oh Mary Oh

        We know for a fact that Earth is one possible outcome of the mass, size, chemical composition, and solar profile involved, so it seems to border on magical thinking to flirt with the idea that the trillions, quadrillions, quintillions or whatever of similar planetary histories out there all failed.

        Granted, it is one possibility, but it's one among the entire number of other possible outcomes.  You know you exist.  Cogito ergo sum...and such.  And yet how often do you entertain the possibility that there is not one single other person on Earth who shares your basic nature, has never been before, and never will be again?  Or maybe we think we're rare, and that there might be a few like us out there.  But no - if you are a world-class genius who makes society-changing contributions and is the best at everything you do, there are hundreds of thousands of others like you at any given time.  So we'll find plenty of Earths out there eventually.  And sub-Earths fixer-uppers.  And probably a few places that are undeniably better than Earth.  But obviously there will be a lot more dead rocks and hellholes.

        In Roviet Union, money spends YOU.

        by Troubadour on Fri Jan 11, 2013 at 04:07:38 AM PST

        [ Parent ]

  •  At least for the moment, (1+ / 0-)
    Recommended by:
    Oh Mary Oh

    a certain very enlightened bumper sticker I once saw remains true;

    There is no Planet B.

    "Forecast for tomorrow? A few sprinkles of genius with a chance of doom!" -Stewie Griffin

    by quillsinister on Fri Jan 11, 2013 at 02:24:13 AM PST

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