Is there life on Gliese 581g?

September 29, 2010 • 3:37 pm

by Matthew Cobb

A report in The Guardian describes the discovery of an apparently Earth-like planet in orbit around Gliese 581, a red dwarf star about 20 light years away. The key point is that Gliese 581g – as it has been romantically dubbed by the astronomers – is rocky (unlike the vast majority of exoplanets thus far discovered), it has sufficient gravity to potentially maintain an atmosphere and that it is in the “Goldilocks zone” – not so close to its sun that everything would fry, and not so far that everything would freeze.

That having been said, I don’t think we’ll be firing up the warp drive just yet to go and colonise it. Like our Moon, Gliese 581g keeps one face permanently to the sun, the other permanently facing the sidereal gloom. In other words, it would be extremely hot on one side, extremely cold on the other and just right only in a narrow band between the two.

Nevertheless, Steven Vogt, an astronomer at the University of California, Santa Cruz, is quoted as saying “Any emerging life forms would have a wide range of stable climates to choose from and to evolve around, depending on their longitude”. This seems to be jumping the gun somewhat, given they have – literally – only the slightest glimmer to go on. A more important point made by Vogt would seem to be this: “The fact that we were able to detect this planet so quickly and so nearby tells us that planets like this must be really common.”

71 thoughts on “Is there life on Gliese 581g?

  1. “The fact that we were able to detect this planet so quickly and so nearby tells us that planets like this must be really common.”

    … or are really common in our immediate vicinity, as would be expected if there particular conditions more likely to give rise to planets like this. Those conditions, on the other hand, could be really rare.

    1. Definitly…These kind of discoveries fill me with awe. This is absolutely the sign rock/earthlike planets are very common, and as we learn, life is very common. We’re in for exciting times.

    2. …or are really common in our immediate vicinity…

      The fact that it’s in our immediate vicinity now says nothing about a common origin. Our sun orbits the galactic center on a timescale that’s short compared to its age (hundreds of millions of years, if memory serves). So the stars we see nearby are not our siblings; they’re a random collection of strangers with origins all over the galaxy.

  2. theshortearedowl wrote:
    Those conditions, on the other hand, could be really rare.

    Given the trillions of stellar neighborhoods, why would anyone think that any conditions would be really rare? Unless, perhaps, you define “really rare” as only millions or billions of cases.

    1. Well, rarity is a concept of ratios, not absolute numbers. A million out of a trillion is the same as one out of a million. It also depends on what your threshold for “rare” is, which is arbitrary.

      If there were a single habitable planet, on average, in each galaxy, then there would be trillions of habitable worlds in the universe, as there are trillions of galaxies, but from our point of view searching for them here on earth, we’d have almost no chance at all of finding any of them, and we would be justified in concluding that they are rare.

  3. If there is life on the planet, can it be Kristine Kochanski?

    As for:

    “The fact that we were able to detect this planet so quickly and so nearby tells us that planets like this must be really common.”

    That’s nothing but wishful thinking – “beginner’s luck” as they say in the gambling industry. I don’t even agree with the “so quickly” bit since the search for “exoplanets” has been going on for at least 2 decades – perhaps he means that the particular survey he’s working with hadn’t been running all that long. We would need many more observations of planets around nearby stars to get some idea of how common it is for a star to have a planet around it and far more observations to get an idea of where and how common rocky planets are. One thing the model is clear about: a rocky planet can only exist in a region in which a star had previously gone supernova. So back here on earth we’re living in a region which once had a star which exploded and over time our own star and its surrounding planets formed.

    1. “So quickly” in the sense that we’ve only very recently become able to detect small, rocky planets in the goldilocks region rather than gas giants in scorchingly hot (and fast) orbits – which were the only detectable things for most of the time such detections have occurred.

    1. It’s much trickier, I think, because what we really need to know isn’t what kinds of environments life can currently exist in (after billions of generations of evolutionary adaption), but what kinds of environments life can arise in. And given how limited our understanding of abiogenesis is, we’re stilling really groping in the dark on that one.

      We could also consider the possibility of life spreading from world to world, directed or otherwise, but on this count we’re even more in the dark.

  4. …[T]he search for “exoplanets” has been going on for at least 2 decades – perhaps [Vogt] means that the particular survey he’s working with hadn’t been running all that long.

    It’s hard to say from the information given. Perhaps the techniques and supporting technology have also improved in that time frame.

    1. It is only in the last couple of years that they have improved the technology to where they can detect the tiny wobbles exerted by tiny (Earth-sized) planets.

      I am waiting for a habitable Earth-like planet around a K- or G-class star (like our Sun. *That* would be amazing. In addition to tidal locking, the M-class stars (red-dwarfs) can be subject to large changes in heat output, which would make for extreme changes in climate on the tidally locked planet.

  5. I am inclined to lean towards the views of “EnglishAthiest”. I am not of an overly scientific background but the fact that we have observed life on earth in very extreme conditions such as high pressure, high/low temperature, etc leaves me sceptical at this ‘perfect zone’ to develop life. It may not be intelligent or what we long for it to be – mammal-esque – but life can form in the most extraordinary of environments.

    1. The “goldilocks zone” has been challenged for a long time, and not only because of the extremophiles known on earth but because of phenomena observed on some of the moons of the gas giants Jupiter and Saturn. Those planets are too far from the sun to obtain sufficient energy from the sun to create conditions favorable to the development of life, but other things come into play to create suitable environments on some of the moons.

      1. Think of the “goldilocks zone” as one of several potential regions that could be amenable to life. And of these several potentials, it is the only one we know for sure (for now) that yes, definitely, with absolute 100% certainty, life can arise in it. It is also the one we know the most about and can therefore plan life-searching projects with the most confidence that yes, we know enough about what we’re doing that we ought to have a good chance for success.

        So while it is true that there may well be a variety of possibly very different sorts of conditions wherein habitable worlds might be found, the “goldilocks zone” is the one that is most reasonable for us to focus our efforts on first, for practical reasons if for nothing else.

  6. Like our Moon, Gliese 581g keeps one face permanently to the sun, the other permanently facing the sidereal gloom.

    Our Moon is locked to Earth, not to the Sun. There is a far side of the Moon, not a dark side of the Moon.

    1. The comparison to the moon does not suggest Gliese 581g orbits another planet, or that the moon orbits the sun. The comparison is that both of these objects (the moon a G581g) does not have an independent axis of rotation to the body it rotates around, thus one side is always facing the body it orbits. Earth however differs to this because it rotates around an axis, and that axis also rotates around the sun.

  7. Yay! This is very good news! The planet is sufficiently Earth like (as in < 2 g surface gravity) and habitable.

    Based on the Kepler results and the deconvolution of hitherto biased for large planet data, it is indeed confirming earlier predictions that Earth analogs are common, IIRC the predicted date would be this year. That it is in the habitable zone is, as the note, "too early" regarded on known statistics, here the predicted date was within a couple of years. Promising!

    This seems to be jumping the gun somewhat, given they have – literally – only the slightest glimmer to go on.

    Modulo it could be a water planet, it is a good assessment. They do have measurements and models from similar tidal locked atmospheres.

    Also, Gliese 581 is 7-11 Gy old. With twice our age the number of abiogenesis attempts would be exceedingly high. (And our own rapid abiogenesis predicts it is an easy process.)

    @ theshortearedowl:

    Those conditions, on the other hand, could be really rare.

    What conditions would that be? In general, uniformity or more generally the copernican principle predicts that such special conditions themselves are rare.

    @ MadScientist:

    We would need many more observations of planets around nearby stars to get some idea of how common it is for a star to have a planet around it and far more observations to get an idea of where and how common rocky planets are.

    No. The Kepler data set predicts a number of planets ~ 0.5 / star. The mass frequency distribution goes as m^-2 for planets, so most will be terrestrial.

    One thing the model is clear about: a rocky planet can only exist in a region in which a star had previously gone supernova.

    What “model” is that?

    The Sun has a high metallicity, and is for that and other reasons suspected from originating in a cloud seeded with material and prompted to planetary formation by a supernova.

    But the current exoplanet database of ~ 500 planets shows that the Sun lies precisely within a flat maximum of the planet distribution going to _lower_ metallicity.

    There are many unknowns in modeling planetary formation. But now we have enough data to not speculate needlessly.

    1. I meant the cosmological model for the formation of the heavy elements, not any particular computer model. It doesn’t really matter since we can only look for planets around comparatively close stars. I hadn’t had my coffee yet and was thinking “if we could resolve stars in far galaxies, could we look far enough into the past that we find conditions where rocky planets could not exist.”

      Why do you say the Kepler data ‘predicts’ 0.5 planets/star? If you’re looking at the data, shouldn’t that be an inference rather than a prediction? The statement about the Gliese-581g object being common simply because it was detected so soon (however that was defined) is still plain wrong though. If it is what was expected then the discovery is good news because it corroborates the expectations, but otherwise proves nothing.

  8. This whole notion of a “Goldilocks zone” is nonsense. The most likely object in the solar system,k other then the earth, which might have life is Jupiters’ moon Europa which seems to have a liquid ocean covering the entire body under a thick ice sheet. By no stretch of the imagination is Europa in the “Goldilocks zone.” The water is kept liquid by the frictional forces in the moons’ interior generated by Jupiters’ gravitational field.

    1. The “goldilocks zone” is one type of location wherein a habitable world could be found. There is nothing nonsensical about that. It doesn’t mean it is the only kind of location that can harbor habitable worlds.

      Europa, if it turns out to be habitable, would be in a another type of location for habitable worlds. But a strong argument could be made, because the primary energy source (tidal flexing) for Europa-type worlds is much, much less efficient than the primary energy source available for “goldilocks” worlds like earth (light), chances are good that earth-type biospheres will tend to be much more fecund and diverse than Europa-type biospheres.

      1. Hey, the tidal flexing is sufficient to keep the water liquid, which ain’t chopped liver, considering how little energy from the sun that Europa gets.

        Of course, our instrumentation is currently insufficient to detect moons revolving around the extrasolar planets we have so far discovered so, of course, we are relegated to seeking out planets, rather then moons. However, it could well turn out that life is more plentiful on moons then on planets as it would appear that there are a hell of a lot more of the former then the latter.

  9. Unfortunately a planet needs to rotate to conserve its atmosphere. The rotation generates magnetic fields which shield the atmosphere from solar winds. Without the protection from magnetic fields the atmosphere would be stripped from the planet leaving it dry and lifeless. Mars has suffered this fate but who knows, Mars could’ve harboured life at some point, maybe Gliese 581g did to. The really bad news is that earth looks like its following the same fate as Mars. Each year slowing down albeit fractionally but inevitably to a standstill. So we better start looking harder. I do believe there are other habitable exoplanets out there in the universe but I think they are few and far between. Life is rare and precious and should be appreciated. After all we do have front row seats at the universes most marvellous and complex spectacle.

    1. Unfortunately a planet needs to rotate to conserve its atmosphere.

      It does rotate. Once every 37 days, according to the article, in sync with its orbital period.

    2. The rate in which the atmosphere is stripped away depends on a variety of factors beside the potential protection of a magnetic field, such as the thickness of the atmosphere to begin with, and the rate it gets replenished by outgassing from the interior of the planet (ie volcanism). If for example earth completely and permanently lost its magnetic field today, the atmosphere would endure for several billion more years (ie it wouldn’t actually be that big of a problem from the point of view of lifeforms on the surface).

      A small planet like Mars is much more vulnerable because of low gravity having a more tenous hold on the atmospheric gases and faster loss of internal heat reducing volcanism.

      But a planet bigger than earth would have the advantages of higher gravity and more vulcanism. With sufficient mass, in fact, there is almost no atmospheric loss at all.

      We might also have to consider the intensity of the local stellar winds, as that will also greatly affect the rate of atmospheric loss.

    3. Life is rare and precious …

      I’ve never understood what leads anyone to this conclusion. It’s certainly not rare on Earth, we find it in just about every nook and cranny we poke into, no matter how extreme the conditions. Since this is the only evidence there is, it seems to me much more likely that life is common.

  10. My prediction is that solar systems such as ours, with rocky planets on the inner circle and gas giants outside, will be seen as the “norm” within 20 years.

    I suspect the VAST majority of solar systems containing planets will have at least one “Goldilocks” planet.

    Doesn’t prove a thing with regard to life, however. For that, you’ll need a lot more evidence,

    But the right conditions? Common.

    1. Remember that using the same criteria we are using for the “goldilocks zone” for other star systems, there are actually 3 worlds in our solar system in the zone: earth, the moon, and mars. You can even include Venus as a fourth world that used to be in the “goldilocks zone”, in the past when the young sun was less luminous.

      So the nature of the world itself obviously matters as well.

      1. Right. I didn’t mean to imply an Earth in every solar system, only that planets within the zone where life is possible will be commonplace.

        After that, conditions on the planet itself. After that, whatevertheheck started life here in the first place (and I most emphatically do NOT mean “god”).

        I think the issue of life on Mars is still an open question. It’s my impression that the “smart money” these days is that Mars had life in its distant past, and may still have remnants of it today. Google “methane plumes on Mars” for last year’s speculation.

        And while Venus is too hot currently for life-as-we-know-it, that doesn’t say anything about its early development, before the runaway greenhouse effect.

        And then, of course there are the watery moons of Jupiter and Saturn. Tidal heating from the gravitational pull of the planets could be enough to “unlock” life, as it were.

        But no, I’m not expecting bisymmetrical four-limbed chordates with ray guns.

        My impression is that life will be common; intelligent life rare. Intelligent life with curiosity and technology, even more rare.

        As a species, we could well be an N of 1 in a universe chock-a-block full of life.

        Or not. Let’s wait for the data.

  11. That wouldn’t be a bad setting for a biologically-themed science fiction novel, actually.

    You could wind up with a world consisting of three branches from the same sentient species – a temperate branch, a thermophilic branch, and a thermophobic branch.

    Interesting.

    1. Another interesting theme to explore is the idea that they wouldn’t have the concept of day–the amount of light would be constant. Would such creatures need rest? And how would they handle it?

  12. I like the attitude of the planet’s discoverer, who said,

    “Personally, given the ubiquity and propensity of life to flourish wherever it can, I would say, my own personal feeling is that the chances of life on this planet are 100 percent,” said Steven Vogt, a professor of astronomy and astrophysics at the University of California, Santa Cruz, during a press briefing today.”

    I’m with him.

  13. “Unfortunately a planet needs to rotate to conserve its atmosphere. The rotation generates magnetic fields which shield the atmosphere from solar winds. Without the protection from magnetic fields the atmosphere would be stripped from the planet leaving it dry and lifeless.”

    Venus barely rotates (243 days/rotation; much more slowly than Gliese 581g is thought to)…and has an undetectable magnetic field…and yet has a nice thick atmosphere. I conclude that something is wrong with your argument here.

    Wikipedia says the problem with solar wind is the stripping off of the lightest gas, hydrogen. Sunlight splits water, producing H and O, and if the H leaves, you gradually (a) lose your water and (b) get more oxidized; probably neither is good for life.

    On the other had, more gravity = keep more stuff in the atmosphere.

    A bigger problem, presumably, is that one side always faces the sun. This tends to create a situation where water, maybe other parts of the atmosphere freeze out on the cold side, meaning you gradually lose atmosphere/water to solid phase.

    It’s not clear this is fatal though…(a) there’s no proof that there is tidal locking AFAIK; if the planet had a 3:2 rotation or something then we’ve just got long days; (b) if you have enough ocean/atmosphere to circulate heat (e.g. venus) the freezing doesn’t happen anyway; (c) freezing huge amounts of ocean/atmosphere on one side might destabilize a perfect tidal locking anyway; apparently tides in Venus’s atmosphere have somehow or other got it into slow retrograde rotation, of all things.

    1. This story says that the planet is tidally locked. The lead author feels this would give any emerging life forms a variety of stable climates to adapt to. And plenty of time to do it, since as a red dwarf its sun will be around for hundreds of billions of years.

      1. “This story says that the planet is tidally locked.”

        But they have no observations that show that, it is purely a supposition based on how close the planet is to the star.

          1. Tidal locking is indeed common, so it’s a reasonable thing to think — however Mercury is closest to the sun, but has IIRC rotations for every 2 orbits.

            (Maybe this is because of Mercury’s eccentric orbit, and they can rule this out for 581g?)

            I think that the low temperature of the red dwarf Gliese also helps even if the planet is tidally locked…it’s black-body temperature on the sunny side was warm but not mind-blowingly hot…

  14. I am skeptical that this planet could have evolved life as we know it. There are so many subtle and yet eventually essential properties of Earth. For instance, volcanism, magnetic field, tides, oceans, freezing, thawing, and evaporation of water. Without all of these, and possibly the light spectrum from our sun, life could not have evolved here. This is NOT to say that life could have evolved elsewhere and become acclimated to Gliese 581g. The movement of life does not require spaceships (but they do help), refer to the PanSpermia idea. Neither is life limited to the forms in which we know it (water and hydrocarbons).

    In any case, we have only just begun to look for exoplanets. The technology we have for such purposes is quickly improving. When we launch more telescopes which will be stationary and yet far enough from earth to avoid the dust & radiation of the solar system, we should be able to learn much more.

    1. I have to agree, when they say life they really mean us, can we live there. Thats not really the point for me, we assume that life needs air, water or other substances to live when in fact other life forms may require none of them, this argument is equally as safe as saying oh look theres a planet 20k light years away that maybe has life. I am amazed that after so long looking at the moon we still do not know if that has water for sure. There is more imediate questions to answer.

      1. Humans are fairly fragile when compared to other organisms. The hardiness of the Cockroach is well known. Even more robust are the microbes. The mass of Gliese 581g is “3 to 4 times that of Earth” – far too much gravity for humans to live in. We have a higher probability of inhabiting Mars or Venus, and not just because they are close, but because of their masses relative to Earth. But Terran microbes may be able to survive such gravity. I am not sure if such microbes could survive all of the other conditions on Gliese 581g. If extremophile microbes from Earth, with the right characteristics, we introduced onto Gliese 581g, they might survive. I believe it is within human capability, through genetic engineering, to create an organism which could survive there. But to say that there is 100% chance of life on the planet is ludicrous. The planet deserves more study, however, and perhaps the launch of a probe to it (yes I realize the mission would take hundreds of years). But I am not to make any dinner reservations there.

        1. “The mass of Gliese 581g is “3 to 4 times that of Earth” – far too much gravity for humans to live in.”

          IIRC the gravity you experience on the surface doesn’t scale linearly with mass — depends on the diameter of the planet, etc. The moon has 1% of Earth’s mass, but you experience 1/6 of Earth’s gravity on the surface.

          I think the gravity on 581g might be 1.5 Earth’s gravity or less. Quoth some news article:

          If Gliese 581g has a rocky composition similar to the Earth’s, its diameter would be about 1.2 to 1.4 times that of the Earth. It’s gravity is likely to be similar – allowing a human astronaut to walk on the surface upright without difficulty.

          Read more: http://www.dailymail.co.uk/sciencetech/article-1316243/Is-GLIESE-581-g-new-Earth-Planet-20-light-years-away-support-life.html#ixzz11JdumtR1

          “If Gliese 581g has a rocky composition similar to the Earth’s, its diameter would be about 1.2 to 1.4 times that of the Earth. It’s gravity is likely to be similar – allowing a human astronaut to walk on the surface upright without difficulty.”

          FWIW…(this is only interesting for human astronauts, microbial life doesn’t care about gravity except insofar as it influences the atmosphere/ocean

    2. Assuming Glieze 581g is Locked with her Star, most of the ingredients for life could still exist on the planet.

      Volcanism: if the forces are enough to lock it with it’s star, it could be enough to triger plate tectonics which resuslts in volanism.

      Magnetic Field: That could be a problem… a very dangerous one.

      Tides: Gravity from star would be tugging on the planet, causing water to try and move to the exposed pole. As it moves thru hotter and hotter parts, it would evaporate and Convection would then take the clouds back, slowly, to the freezing side; rain would fall before that, restarting the process. If enough water is present (ocean), tides could happen, and erosion could form, not to mention rivers and the likes.

      At least this is how I see it.

  15. Tidal locking raises some interesting questions. I imagine there would be strong, constant global winds formed by convection. Cool, low altitude winds flowing towards the centre of the hot side. The atmosphere would then be heated, rise and form hot high altitude winds flowing to the cool side.

    Would this heat pump effect be enough to prevent all the planets water being locked up in ice on the cold side?

  16. I’m just waiting for the first extra-terrestrial planet with liquid water to be found – that would seem to be a much better bet for a life bearing site.

    1. This one may very well have liquid water. That is what the “habitable zone” is, the distance from the host star where water could be liquid on the surface of a planet.

  17. Here’s my insight, we live in a never ending universe, to believe that earth is the only planet that could sustain life is naive in the very least. to think that we are the only rocky planet is even more absurd. if something is 20k light years away that’s not close, we are human after all it annoys me when they say it’s close, I understand they mean it’s close in astrological terms but really as humans and being as we cannot travel to it, do not have the technology and using the technology we do have would be dead before we got there whats the point. here’s an idea pool all resources on getting to mars first then lets just see what happens from there it’s been 50 years since we went to the moon and they are still trying to judge whether it has water so anything such as this new discovery is just a complete and utter waste of the technology we do have. We might as well utilise the stuff we can rather than guessing on something no one will ever see in our lifetime.

  18. Yeah, this was reported here locally (on the TV “news”) with the headline, “We May Not Be Alone!”

    Well, DUH!

    It was terrible.

    But even worse was the TV “news” statement that a genetic link was shown for ADD because a paper showed a correlation between “ADD and abnormal numbers of chromosomes.”

    How much more poorly can you understand human genetics than to make conclusions about people with normal chromosome counts from those with abnormal chromosome counts. The syndromes induced by abnormal chromosome counts have a whole constellation of problems associated with them.

  19. One thing i find concerning is that Gliese 581g is tidaly locked to its star. and considering that red drawfs have a significantly lesser length of a habitable zone it lies in th 0.3-00.5 AU.
    I’m also certain that any planets in this range will likely suffer from a heavy blast of radiation regardless of how much warmer it is or weather or not G has a protective layer of gases.
    But then there is the magnetic field.

    The only way for the planet to be regulated would be if it was covered in oil.
    Here comes BP with a mining ship!

    1. jigh jokingly speaks of an oil deposit on Gliese 581g. Extraterrestrial mining could be a big deal, and not a joke, as there are predicted to be vast amounts of methane (and probably heavier alkanes) on Titan. But more interesting is what the asteroids have to offer – thousands and thousands of years worth of hi-metal content iron ore, with impurities of many other valuable minerals. I hope and expect that rich sources of Thorium are also present, as that element is the future of nuclear energy for the time to come. We must not be too conservative in our utilization of extraterrestrial resources, for they give us the ability to spread terrestrial life far and wide. Humans are the ultimate seed-bearers, and the measure of our worth is how well we live up to that destiny.

  20. The general public should be more skeptical of these types of ‘discoveries’, and the media is part of the problem why they are not.

    My views on “Why the Public should be skeptical about the newly found ‘Earth-like’ planet Gliese 581 G” may be too long to post here, but can be found at http://bit.ly/aXxzOV (my wordpress blog) or http://bit.ly/aT6yuq (my tumblr blog).

    An excerpt: “Now, I am someone who supports scientific discovery, and I’m not saying that I think the scientific community is wrong about the Gliese 581G planet. What I am saying is that the general public should not automatically accept as fact what the scientific community presents to them, without being made aware of the basis from which the scientific community is making these assumptions. And the Media has a responsibility to not just automatically sensationalize what the scientific community tells them, but to research the processes that were used in making these discoveries and effectively communicate that information to the general public.”

    Thanks -H.E.Miller

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