Gliese 581g -- in the habitable zone (barely)

[Trakar]

Where are you getting your information? From what i've read, its mass is in the range considered 'Earthlike', we know nothing directly of its composition, and if it had an orbit like Earths it would be well away from the H2O triple point region, which really is the major defining characteristic of an 'Earthlike' orbit as far as discussions of planetary habitability go.

I'm hoping its something really weird with a mysterious history to be honest: A mercury sized world loaded with heavy elements, constant volcanism and lots of short lived radio isotopes. Something we can't easily explain, although a tru;y habitable planet would be nice to.

Most of it is derived from the current general understandings of star/stellar-system genesis, formation and evolution. Is venus "Earthlike" (or "venuslike?), and it is pretty close Mass and Composition (+/- 20%) wise. The rocky cores of the ice giants are variably estimated to have been roughly 1-3 Earth masses which formed the cores that "vacuum up" the more refractory outer system "ices." Composition data can be gleaned from the low metallicity of the parent star (Gliese 581), which indicates that this star (and its attendent system) have a much lower concentration of elements heavier than H/(He). The other name for the " H2O triple point region " is the "Goldilock's zone."

[marsbug]

For these purposes I would say Venus is Earthlike, as it orbits within the goldilocks zone and has close to one Earth mass. An alien using the same radial detection method as us could not easily distinguish between the two worlds- and in turn this shows that Venus is an example of the dangers of making conclusions about a world based on just orbit and mass.

There is a great deal that we still don't understand about the formation of planetary systems. It is a long road from the protostar and protoplanetary disk, which initially share the same compostion, to an evolved star system with a stable configuration-a road that can leave any given object in a star system with a very different ratio of elements than its parent sun has. Mercurys iron content, for example, is not predictable from solar iron abundances- thats a result of mercurys specific history of giant impacts.

Given this I think you're making a bit of a big leap by saying 581g is the denuded core of an ice giant. But its a reasonable guess given the very little we know so, ok: why does that make it not interesting? More specifically, (and I really have no idea about this) why does it preclude 581g being habitable?

[whimsyfree]

For these purposes I would say Venus is Earthlike, as it orbits within the goldilocks zone

There's no accepted definition of this goldilocks zone. According to Kasting et al. a really Earth-like planet would experience catastrophic water loss if it were closer than 0.95au to Sol. OTOH it's widely believed that Europa has liquid water, so is Europa in the goldilocks zone?

and has close to one Earth mass. An alien using the same radial detection method as us could not easily distinguish between the two worlds- and in turn this shows that Venus is an example of the dangers of making conclusions about a world based on just orbit and mass.

True, though aliens might be able to do climate modelling too.

Given this I think you're making a bit of a big leap by saying 581g is the denuded core of an ice giant.

For it to be denuded it must have previously been covered. What mechanism would explain the proposed mass loss?

But its a reasonable guess given the very little we know so, ok: why does that make it not interesting? More specifically, (and I really have no idea about this) why does it preclude 581g being habitable?

I don't know what habitable means. Well I know what it means when I'm looking for somewhere to live, but that doesn't seem to be the sense in which you're using it.

[marsbug]

There's no accepted definition of this goldilocks zone. According to Kasting et al. a really Earth-like planet would experience catastrophic water loss if it were closer than 0.95au to Sol. OTOH it's widely believed that Europa has liquid water, so is Europa in the goldilocks zone?

'Goldilocks zone' seems to generally be used to refer to the shell around a star where heat from the star alone is in the right range to allow liquid water, assuming the right conditions of pressure can be met. Europa doesn't lie within that zone, but worlds like Europa Ganymede and Enceladus are good examples of how hard it is to tell from just an objects mass and orbit whether it will have liquid water. Technically Mars lies witin the Goldilocks zone, and liquid water there is very rare if it occurs at all.
So not only is the goldilocks zone not very well defined, it seems to be at best only a rough indicator of possible habitability.

True, though aliens might be able to do climate modelling too.

I don't think they could get Venus current conditions just from mass and orbit, which is all radial velocity techniques will tell them. Although they could I suppose predict them as one possible end state of many.

For it to be denuded it must have previously been covered. What mechanism would explain the proposed mass loss?

Ask Trakar, its his (her?) idea! I think the idea is that the neptune migrated closer to the star and the greater heat and solar wind nearer the star boiled the volatiles away, but you'll have to ask Trakar to confirm thats what he/she means.

I don't know what habitable means. Well I know what it means when I'm looking for somewhere to live, but that doesn't seem to be the sense in which you're using it.

Habitable as in has an energy source (gliese 581 fills that nicely) conditions of temperature and pressure conducive to liquid water (we don't know but it seems possible) and enough H2O to make a significant amount of liquid on the surface (again we can't know at this point). Earlier Trakar said:

the only factor that makes it seem "earthlike" is that it currently resides in an orbit that happens to be close to the triple point range of water, and to me, given the very un-earthlike conditions of its mass, composition, proximity to stellar parent, etc., this one similarity is not enough to much excite or interest me.

Which sounds to me like Trakar is dismissing the possibility of this object being habitable because Trakar has concluded that it is the core of a denuded ice giant. But why could a debuded ice giant core not support liquid water on its surface? Thats the part of his/her argument I don't understand, and I'm asking for clarification.

Whimsyfree, you seem to be tackling me on the finer points of Trakars suggestion, which I can't really answer as well as Trakar. My position is that we don't have enough data to draw any firm conclusions on where this world came from or what its surface conditions are like, so I'm not really comfortable answering questions on the 'denuded ice giant' hypothesis of its origin. If i've msinterpreted could you clarify for me where you're going with your questions?

[eburacum45]

The conditions on Gl 581 g are not well known. Only the mass (3.1 to 4.3 Earth masses) and the orbital parameters are known. It could have any of the following characteristics;

The least dense option would be a waterworld, with a possible diameter of 24000km and a gravity just a bit greater than Earth's (1.1 gees)

The most dense option would be a planet with a very high metallic core fraction, a diameter of 16000 km and a gravity of 1.7 gees. This planet would probably have quite a thick atmosphere.

An in-between option might be a planet of about 18000 km and a gravity of about 1.5 gees. This option might be fairly Earth-like, although I wouldn't particularly like to live there.

We don't know the level of greenhouse effect on this planet, but it could be easily large enough to make it as warm as Earth. That is, assuming that the level of CO₂ in an atmosphere is exactly right. Maybe CO2 levels only come in two flavours, Venus-like and Earth-like with nothing in between.

[Hungry4info]

True, though aliens might be able to do climate modelling too.

Not to disagree with that, but does climate modelling suggest Venus has anything remotely similar to the conditions it is observed to have? I.e. if we discovered a Venus-clone, atmosphere, orbit and all, would we be able to use climate modelling to rule out habitability?

[eburacum45]

This system appears to have no large gas giants. This may be the reason that so many smaller worlds can live together in relatively close, stable orbits.

Another reason might be that this system was never disrupted by a close encounter with another star within the birth cluster. These two factors might have gone together to make a system relatively rich in small-to-middling sized worlds. If so, there might be large numbers of comparable systems out there to be found.

[eburacum45]

Not to disagree with that, but does climate modelling suggest Venus has anything remotely similar to the conditions it is observed to have? I.e. if we discovered a Venus-clone, atmosphere, orbit and all, would we be able to use climate modelling to rule out habitability?

If we can't predict this sort of thing today, I can't see why relatively accurate predictions might not be made in the future, when the state of the art of planetology improves.

However if a Venus-clone turned up in the next survey, there would be some problems with making accurate predictions about it. For a start the mass would only be known within certain error bars, and the density might also be subject to error- that is to say we might be looking at a Venus, or a warmer and heavier Earth, or a slightly lighter planet with no atmosphere at all, or a waterworld.

[Bad Ronald]

Is Gliese 581-g really tidally locked? Is there any proof that it is?

Gliese 581 may be teeming with life,

There's already a suspected ocean planet superearth, which itself may have one or more Earthlike moons.

Even Gliese 581-g may have an Earthlike moon.

So you potentially have 2 superearths & maybe several Earthlike moons.

If there is a 'they' at Gliese 581, have 'they' discovered us? Suppose 'they' have mindboggling telescope technology but are seriously behind in many other ways. Like 'they' have telescopes that can actually see waves on Jaws Beach & sandstorms on Mars, but they have abysmal communications tech, & transitwise, are still using "horse & buggies". Not LITERALLY horse & buggies. 'Their' analogue of them.

[Bynaus]

Is there any proof that it is?

The existence of Gliese 581 g is inferred from physical laws in the first place. The same laws (or other laws derived from the same principles) say that it should be tidally locked, because the tidal dissipation time for a planet at this place and mass is much shorter than the age of the system. So, for all we know, this planet is there and it is tidally locked.

Even Gliese 581-g may have an Earthlike moon.

I doubt that. First, the system is very compact, the hill spheres are very small and the roche-limits relatively large, as the masses of the planets are relatively large (compared with their inner solar system counterparts), leaving almost no dynamical room for moons.
Second, as the planets are tidally locked with their star, any moons will sooner or later crash down on their planet.

[m1omg]

While I value healthy skeptocism, I've noticed (not on this forum, but on others) that many people are basically trying to deny there is any possibility of life on this planet, by nitpicking details and claiming that because the planet is not exactly the same as Earth that no life could have arisen on it?

I remember stumbling upon some guy (it was on Google, but I tried to search for it and I didn't came across of it for the second time, sorry) who was claiming on his blog that Gliese 581 g must have remained lifeless ... because the star supposedly does not radiate enough 3 micrometer IR radiation that is supposedly essential for the origin of life? Really? We do't know basically anything about the origin of life apart from that it may have originated in warm pools of water and organics, and yet some guy claims that the origin of life is fixed to some arbituary type of EM radiation that our Sun supposedly happens to radiate a lot of. It seems to me that it is a type of reasoning similiar to "I watched Smurfs as a child, therefore you cannot grow up without watching Smurfs".

The same with "-12 degrees Celsius is too cold for liquid water", do these guys understand that there are many places where the average temperature is much colder than -12 degrees and life still exists, even macroscopic, multicellular life such as penguins, or, you know, humans like Inuits? Or that our planet was supposed to go through stages when it was around -50 degrees Celsius cold, completely covered by kilometers thick ice (during the Snowball Earth periods), and still, some traces of undersea worms existing in that period were found? Or that "average" is a really misleading thing, because the day side could be much warmer than Earth and depending on the tilt the planet can have seasons? Or the "red dwarfs are old, dying stars" - do these people even bother to at least check something out on Wikipedia? Or the misleading claims in many articles announcing this that the star is a red giant?

Seriously, I think many people want for us to be alone and special. Much of humanity's worldview depends on this belief. While I wouldn't say that the chances of life on this planet are 100 percent, I believe that the planet has a much, much higher chance of life than either Mars or Europa, and it is therefore a very exciting discovery. Besides, it is the first discovered planet (apart from the possible habitable moons orbiting Goldilocks zone orbiting gas giants, not many people know about this, but there are actually many known) that has any real possibility of actual multicellular or even intelligent life existing there.

And to respond to the people mentioning Mars and Venus there - Venus would probably be inferred from a nearby star to have a runaway greenhouse effect, considering scientists inferred this about Gliese 581 c which was touted as "habitable" in the media, all the while everybody who thought about it a bit knew it was probably less habitable than Venus. If aliens have the same sensationalist press as we do, I might imagine alien news mentioning "Sol b" (Venus) as "habitable" , through if their method of discovering planets is anything like our they would've probably discovered Earth before they would discover Venus, due to its lower mass.

And Mars's problem is probably not the amount of warmth it recieves from the Sun, but it's size - I don't believe that Mars would be habitable even if it had the orbit of Earth, it might be habitable for a short time in its "Archean", but the increased insolation would probably leave it with even thinner atmosphere if it had the orbit of Earth. And yes, Mars had temperatures up to +30 degrees Celsius on the equator sometimes. It is not the temperature range that is the worst problem, Earth had similiar temperature range in the past during the Snowball Earth stages, and life survived, the problem is the super-thin atmosphere and the lack of any meaningful geological activity in the present due to small mass.

Anyways, I wouldn't consider the slightly lower than Earth insolation that this planet recieves as a problem, when the Earth was young Sun was just 70 percent as bright as today, yet the Earth was actually warmer than today even after the asteroid bombardement and rampant volcanic activity stopped, due to a greenhouse gas heavy atmosphere. It is true that advanced life changed this atmosphere on Earth later, however this occured cocurrently with the Sun becoming warmer, and I don't believe an ecosystem would suicide itself by decomposing the greenhouse gases that keep it alive and warm. I believe that advanced life is likely there, through it would be probably adapted to retaining more greenhouse gases in the atmosphere than here on Earth. After all, life on Earth is a self-regulating system. There is a reason why there is still free CO2 and methane in the atmosphere of Earth, if plants absorbed all of it the planet would freeze over.

I don't believe this can be a naked core of a Neptune like planet. There are many "super-Earth" planets that were discovered that probably arose this way, but seriously, the temperature and solar winds would have to be extreme to blow the gas of a gas planet away in any reasonable time. This planet is a bit colder than Earth, there are "hot Neptune" planets discovered orbiting closer than Mercury in other systems. The star is older than the Sun, yet 51 Pegasi is supposed to lose only around 5 percent of its mass during the entire time from its birth to the red giant stage of its star. And it is hot like a blast furnace, orbiting a Sunlike star that is far more powerful than this red dwarf, that is even supposed to not be a flare star.

About the reason why there are so many "a few times heavier than Earth planets there" - we already know our Solar system is not the norm. I don't believe that any special mechanism is needed for examplaining this, each star system is unique. I hate science based on "assumptions" and the belief of so many people that we already know everything about the universe. We don't know nothing yet, we are like children who already think they know it and have seen it all. It is laughable. We laugh at 19th century people believing Mars is habitable, yet we believe everything we presume today is correct. Every generation foolishly thinks that it is the one who is the pinnacle of understanding. About the tidal locking - sure, we presumed that about Mercury too. Universe is not a human build, perfectly predictable machine. I am not claiming physics are useless, but we don't know any of the infinite possible other aspects that could have influenced this planet to behave absolutely differently to any of our expectations. A large asteroid impact, alien engineering project, a freak disaster etc. everthing is possible, especially considering the system is much older than ours.

I understand that the skepticism of many people is based on the Fermi paradox. But it presumes that any intelligent species will eventually progress to a space-opera pop scifi stage of interstellar colonization. I believe in more advanced civilization, however I believe them to be as industinguishable to us as our civilization is to ants. We are just basically ants that think a more advanced species is going to build bigger anthills. We don't really think outside of the box because we are limited by the box of our current cognitive level that makes many of us us think we are the universes's ultimate intelligent beings. Or, like a primitive tribe on an island who were never contacted by an advanced civilization until recently despite being just a few hundred kilometers distant from them. Like the Sentinelese http://en.wikipedia.org/wiki/Sentinelese_people .

We are trying to search (and are sending too) for what probably amounts to primitive drumbeats and smoke signals by the standarts of more advanced species (SETI and similiar projects) and wondering why we don't hear anything. To put it bluntly and harshly, we are total fools, in my opinion, who think they've already discovered most of the universes's mysteries while we are just beggining to scratch the surface. But it is not our fault IMHO, anymore than it is a dog's fault that it does not understand the Einstein's theory of relativity. You may argument that we are are sapient ... while dogs or ants are not. But I believe there are levels of mind (if it even can be called that at the higher levels) that are as more advanced than ours than is our awareness compared to the awareness of an ant.

[Vultur]

There may be an issue of time, too. 3 billion years ago or whatever, Mars might have been a much more Earthlike world (liquid water, denser atmosphere).


m1omg, while it's possible that some people want us to be unique, a lot of what I've seen is kind of the opposite -- people 'trying not to get too excited'. (Personally, I hope we find lots of *life*- - but I'd prefer not to meet other technological species - they probably wouldn't be any nicer than we are.)

[m1omg]

About the time, time might made Gliese 581 g habitable more recently - I think red dwarfs have the same pattern of - faint in the beggining, bringter as it ages - like the Sun, so it might have been a frozen iceball for the most of its time and only relatively recently (even like "1 billion years ago" recently, considering the system is 7-11 billion years old) has "waken up" and the oceans became liquid and the life has started. Or perhaps life has been there already, but until recently it was limited because the planet was basically a snowball, just like Earth in certain past epochs.

About the other technological species being non nice - I don't really think they would be similiar enough for us to morally qualify them as "nice" or "non nice". As I mentioned in my post later when I edited it and added a lot more text to it (sorry for a wall of text, but I wanted to express my opinion), I don't believe other alien species would really be anything like from popular sci-fi and space operas. Read Peter Watts's Blindsight or Stephen Baxter's Manifold: Space to see an original take on this issue, pretty hard scifi, althought very terryfing.

Plus, Mars is not like this planet. It was basically destined to lose most of its atmosphere and water early on. This planet is different. It is heavier than Earth. I don't think it has a Venuslike atmosphere through. Venus is actually lighter than Earth, it's atmosphere is not dense because of mass or gravity, it is dense because it was too hot to retain it's oceans for more than its early life (if it even had oceans at all), and so all the CO2 in the rocks and the sea went into the air, then the UV radiation from the Sun destroyed the water in the upper atmosphere that was the remain of the boiled ocean. If you somehow boiled all the CO2 out of rocks and the water, Earth would have the same atmosphere too, it has all the CO2 that Venus has, only most of it is bound in carbonate rocks and the oceans. This planet probably cannot have a Venuslike atmosphere, as it recieves a bit less warmth from it's star than Earth from the Sun, and it's mass prevents it from drying out like Mars, so the worst case scenario in my opinion is that it is a snowball with oceans covered by thick ice, the nest case scenario is that it is a lush gardenworld. It does not have the excess insolation like Venus that would doom it to runwaway greenhouse effect, nor it has the curse of being low mass that would doom it to become a dessicated tundra like Mars.

Edit - Also, any hypothetical aliens would consider Earth to be "barely habitable" as well. I don't believe habitability can be properly judged by the principle of "if it deviates from our home planet, even within acceptable ranges of conditions, its life must be less advanced than ours". I think any alien habitable planet would deviate from each other at least a bit, so what might be "barely habitable" for us might be just as perfect for them and vice versa.

[m1omg]

If anybody wants to see for him/herself what basic properties the planet (or any other planet) might have, this http://www.transhuman.talktalk.net/iw/Geosync.htm calculator can help you (thank you JohnBStone for sending it to me 3 years ago ).

[GalaxyDave]

(1) Is there any data on the approximate age of parent star, 581? - Likewise, approx' age of 581 g?
(2) What types of flora (plants/trees, etc...) might there be on the light side, and possibly the dark side?
A) How massive might "trees" be on the planet, if photosynthesis occurs (as we know it here)?
(3) Purely speculating, if sentient life (poss' humanoid) exists, given the age of the planet and the lightside/darkside situation, what are some possibilities of subsequent civilisation development & evolution?
(4) Given that Gliese 581 g is tidally locked, resulting in permanent lightside/darkside - with global transitional area around it, how and where might animal life and sentient life form, migrate, and develop?
Based on what we know about the parent star/Red Dwarf stars and the planet, please present facts when so able to, and discuss subsequent logical possibilities around the following topics:
(1) Atmosphere
(2) Meteorology/Weather
(3) Possible sentient, even humanoid development
(4) Flora and Fauna

[Trakar]

While I value healthy skeptocism, I've noticed (not on this forum, but on others) that many people are basically trying to deny there is any possibility of life on this planet, by nitpicking details and claiming that because the planet is not exactly the same as Earth that no life could have arisen on it? ...

"Denial" implies that there is positive evidence for life which is being ignored or discounted, please present this evidence.

We know of exactly one planet upon which life as we understand the term has come about. Planets even slightly different from this one example have no visible signs of having produced life. Until we have evidence which compellingly suggests that life can or has arisen under other circumstances it is mere wishful thinking and largely without foundation speculation to talk about life arising under dramatically different conditions.

[Swift]

(1) Is there any data on the approximate age of parent star, 581? - Likewise, approx' age of 581 g?
(2) What types of flora (plants/trees, etc...) might there be on the light side, and possibly the dark side?
A) How massive might "trees" be on the planet, if photosynthesis occurs (as we know it here)?
(3) Purely speculating, if sentient life (poss' humanoid) exists, given the age of the planet and the lightside/darkside situation, what are some possibilities of subsequent civilisation development & evolution?
(4) Given that Gliese 581 g is tidally locked, resulting in permanent lightside/darkside - with global transitional area around it, how and where might animal life and sentient life form, migrate, and develop?
Based on what we know about the parent star/Red Dwarf stars and the planet, please present facts when so able to, and discuss subsequent logical possibilities around the following topics:
(1) Atmosphere
(2) Meteorology/Weather
(3) Possible sentient, even humanoid development
(4) Flora and Fauna

GalaxyDave,

First, welcome to BAUT.

Second, I moved your post to our active thread on this topic. You might wish to look through this thread for answers to at least some of your questions. But I suspect some of them are also currently unanswerable.

[m1omg]

"Denial" implies that there is positive evidence for life which is being ignored or discounted, please present this evidence.

We know of exactly one planet upon which life as we understand the term has come about. Planets even slightly different from this one example have no visible signs of having produced life. Until we have evidence which compellingly suggests that life can or has arisen under other circumstances it is mere wishful thinking and largely without foundation speculation to talk about life arising under dramatically different conditions.

There are no planets just "slightly different" from Earth that we know enough of yet. Mars and Venus are both drastically different from Earth, and it is well known why.

Your position is like a position of somebody who had grown up in a box with no human contact, thus it is "logical" for him to expect no other human beings exist and a human can only live in his little box.

"Evidence, eevidence, blahblahblah..." just because you don't see something does not mean it cannot exist. The planet has probable temperature and size that would predispose it to having life more likely, so the possibility must not be ignored. Just because we Earthbound and know really almost nothing about the universe does not mean we cannot think, propose, speculate.

I don't know you exist. The text you post might have been written by an automaton. Please prove that you exist and that you are a conscious being. You see? This type of "scientific" fundamentalism does not lead to anywhere.

EDIT - Also, there is life living in very "unearthlike" conditions. Sure, it is here on Earth, but it is living in conditions that are non typical for Earth, much harsher than anything probable on Gliese 581 g, and if these conditions were planetwide almost nobody would think of such a planet as remotely suitable for life. Yet they live, in ultrasaline lakes, in the Acatama desert, on nuclear reactors, deep in the crust of Earth, in benzene etc. It is just that Mars and Vemus are far too extremely different from Earth. The conditions don't need to be ideal, those extremophilic microbes live in conditions that would kill a human being thousand times over. So, the planet can be extreme, our planet was like that in the Hadean, Archean and Proterozoic, yet life has arisen here. In fact, if the early Earth was the same as the Earth of today, life would have never arisen, due to free oxygen destroying any precursors etc. And when free oxygen first arose, most of the anaerobic life on Earth went extinct. Just because the Earth of today is best for us does not mean it is best for every form of life, hell, even advanced lifeforms, for example Carboniferous insects would probably suffocate in today's air because ther wouldn't be enough oxygen for them etc.

I've read an argument against this "sure, life can survive in extremes, but it cannot arise there" - but the original conditions on Earth were extreme by today's standards. Hot anoxic seas, atmosphere without free oxygen, with a lot of CO2 and methane, frequent volcanism and asteroid and comet impacts, young, weaker Sun etc.

EDIT 2 - Don't get me wrong, I am not claiming that there definitely is life on Gliese 581 g. I am just saying that it seems probable to me and much more probable than finding it on either Mars or Europa. I wonder why in a different thread in this part of the forum people are speculating over Viking lander's results from Mars, yet people here are trying to disprove the possibility of life on a planet that seems far more likely to have proper conditions for it. Anyways, it should definitely be reasearched further. Anyways, any sign of free oxygen in it's atmosphere would be practically screaming "advanced aerobic life is here!" and if at least water was detected it would up the chances of life enormously (and I'd bet there is water, it is present all over the interstellar medium) and if it has any atmosphere worth mentioning the water is probably present there in liquid state. It is not a clone of Earth, but if science limits its search for life to only Earth clones then we'll never find anything, as each planet is unique.

I don't personally believe there is intelligent life there. But I believe the planet might have a proper biosphere and perhaps a multicellular, advanced one. It is probably not a totally extreme enviroment like Europa or Mars.

[MaDeR]

I believe that the planet has a much, much higher chance of life than either Mars or Europa... The planet has probable temperature and size that would predispose it to having life more likely... people here are trying to disprove the possibility of life on a planet that seems far more likely to have proper conditions for it...But I believe the planet might have a proper biosphere and perhaps a multicellular, advanced one. It is probably not a totally extreme enviroment like Europa or Mars.

You base this all on minimum mass and distance from star. How utterly, utterly sad case of delusion and wishful thinking, not to mention made up factoids like "This planet is a bit colder than Earth" without any basis in reality.

[Trakar]

..."Evidence, eevidence, blahblahblah..." just because you don't see something does not mean it cannot exist...

So this is an issue of faith for you, and not one of scientific reason and evidentiary support,...well and good, but not appropriate for a discussion of what the science and evidences indicate.

...EDIT - Also, there is life living in very "unearthlike" conditions....

Big distinction between conditions life can adapt/evolve to cope with given the time and mild enough alterations in environment to allow such changes, and the conditions neccessary to stimulate abiogenesis in the first place. Conflating and confusing these two seperate conditions is one of the popsci distortions that fuzz the picture rather than focus the considerations.

[Hungry4info]

(1) Is there any data on the approximate age of parent star, 581? - Likewise, approx' age of 581 g?

Estimates vary, but it's fairly old. I've seen numbers as low as 2.3 Gyr, and some around 4+ Gyr.

As for the rest, no data.

You base this all on minimum mass and distance from star.

It's not wishful thinking to say that. He did not say that such things exist, he said they might be there. Within what we know, that's certainly possible. There may well be all sorts of life on that planet.

...not to mention made up factoids like "This planet is a bit colder than Earth" without any basis in reality.

It would have been more accurate to say that the planet receives slightly less energy from its star than Earth does, but I think that was rather understood.

I don't know you exist. The text you post might have been written by an automaton. Please prove that you exist and that you are a conscious being. You see? This type of "scientific" fundamentalism does not lead to anywhere.

This is considerably different. You have much more evidence that Traker exists than you do for life at Gliese 581 g. In the case of the later, it's an issue of it being possible within what we know. We don't know anything about the planet that would preclude the existence of life there. Regarding Traker's existence, we actually have evidence he exists.

[PetersCreek]

You base this all on minimum mass and distance from star. How utterly, utterly sad case of delusion and wishful thinking, not to mention made up factoids like "This planet is a bit colder than Earth" without any basis in reality.

The rude tone and wording of this post was totally unnecessary. Let's have no more of it.

[Trakar]

(1) Is there any data on the approximate age of parent star, 581? - Likewise, approx' age of 581 g?
(2) What types of flora (plants/trees, etc...) might there be on the light side, and possibly the dark side?
A) How massive might "trees" be on the planet, if photosynthesis occurs (as we know it here)?
(3) Purely speculating, if sentient life (poss' humanoid) exists, given the age of the planet and the lightside/darkside situation, what are some possibilities of subsequent civilisation development & evolution?
(4) Given that Gliese 581 g is tidally locked, resulting in permanent lightside/darkside - with global transitional area around it, how and where might animal life and sentient life form, migrate, and develop?
Based on what we know about the parent star/Red Dwarf stars and the planet, please present facts when so able to, and discuss subsequent logical possibilities around the following topics:
(1) Atmosphere
(2) Meteorology/Weather
(3) Possible sentient, even humanoid development
(4) Flora and Fauna

well, most of what you are asking is beyond the current science and evidence is capable of addressing with any real surety.

The approximate age of Gliese 581 (parent star) is estimated to be variously >2Gy, 4.3Gy and ~7/11Gy depending upon how you assess and weight the data held. This particular planet's age is also within that range, a great deal, however depends upon how and where that planet originally formed and its composition, none of which are easily and directly obtainable from the hard data at hand. The questions most contentious, with respect to issues of habitability and the potential for life revolve largely around the composition which is intimately related to where the body was initially formed If it formed in the outer regions of its system and then migrated inward with the resto f the planets in this system (as seems to be the case) then it is going to have much different characteristics than a planet which accreted in the innermost regions of the stellar system.

Nothing in the evidence, thus far, indicates anything about life or the other properties of the planet from which we might be able to evaluate the potential for such life.

Speculating beyond this is just that and no more valid or invalid than such speculations before this planet's discovery.

[Trakar]

...Which sounds to me like Trakar is dismissing the possibility of this object being habitable because Trakar has concluded that it is the core of a denuded ice giant. But why could a debuded ice giant core not support liquid water on its surface? Thats the part of his/her argument I don't understand, and I'm asking for clarification....

Sorry, thread is growing faster than I've been keeping track of posts, the short and quick response is that many M stars go through an an early development phase of intense magnetic activity associated with violent flares and high X and extreme UV fluxes, during their early stages that might well erode the planetary atmospheres of planets which migrate inward to extremely close orbits prior to their outbursts.

[Hungry4info]

Yet consider Gliese 436 b, a transiting hot Neptune. It has still retained its envelope. Gliese 581 b most likely has as well. Furthermore, Gliese 1214 b, closer to the super-Earth mass range, clearly has an envelope, too.

It does not seem the available evidence supports the idea that M dwarfs erode ice giants down to the core.

[m1omg]

MaDeR, I would probably tell you a few four letter words if it was allowed on this forum.
Let's be perfectly rational. No speculation, optimism, or actual thought allowed. Live like a robot.
This is not "faith", this is being human, and being able to imagine things you don't see/don't know of.
I am NOT FREAKING CLAIMING THAT LIFE EXISTS THERE. BUT IT IS MY FREEDOM OF SPEECH AND THOUGHT TO SPECULATE ABOUT IT. OK, SO CAN YOU PLEASE STOP BEING AN [offensive language redacted]?

Trakar, the problem is, the conditions were extreme when abiogenesis occured. 70 percent insolation from the Sun, anoxic greenhouse atmosphere, seas full of organic molecules and acids.
It is even hypothetised that life first emerged in the enviroment around hydrothermal vents. If that is not extreme, than I don't know what is.

About the flares, well, Sunlike stars with hot Jupiters do have superflares all of their lifetime, yet the gas giant survives.
And why should be a naked core of a Neptune type planet be so bad? You've got water and volatiles there, through you might get an all ocean planet.

I meant the "it is colder than Earth", as in, the insolation is lower the Earth.

And neither Venus nor Mars are in the habitable zone. They are in the more wishful thinking habitable zones, but there is no reason they should be. As far as I know current planetary models predict a hot greenhouse for Venus and a frigid desert for Mars. But there are already "super-Mars" (Gliese 581 d) and "super-Venus" (Gliese 581 c) planets in this system. This planet is far closer to having optimum insolation than Venus or Mars. Our habitable zone is 0.95 AU to 1.37 AU by the most recent estimate (1993) on Wikipedia, and neither Mars nor Venus fall into it.

Yes, it can have a Venuslike atmosphere for all what we know. But in my opinion this is more unlikely than anything Earthlike as the planet simply doesn't have enough heat to start the runaway greenhouse effect. Venus got its thick atmosphere by processes that are understood now. Mars has a thin atmosphere, again, for obvious reasons. This planet has no obvious barrier to life, that's my point, not that it is necessarily habitable, we don't know much yet. But it is the most hopeful candidate.

[Trakar]

Yet consider Gliese 436 b, a transiting hot Neptune. It has still retained its envelope.[

Different star, vastly larger planet and different age

Gliese 581 b most likely has as well.

same star and age, but significantly different mass and orbit and no confirmation of atmospheric state. (I wasn't postulating that it was a stripped core planet, merely that proximity may have resulted in the loss of an initially much denser mass of atmosphere).

Furthermore, Gliese 1214 b, closer to the super-Earth mass range, clearly has an envelope, too.

It does not seem the available evidence supports the idea that M dwarfs erode ice giants down to the core.

see above

"The impact of nonthermal loss processes on planet masses from Neptunes to Jupiters" -

The orbital distance at which close-in exoplanets maintain their initial mass is estimated
by modelling the maximum expected nonthermal mass loss rates over several
Gyr. Our results indicate that nonthermal mass loss induced by Coronal Mass Ejections
of a host star can significantly erode weakly magnetized short periodic gas giants.
The observed exoplanets Gliese 876d at 0.0208 AU with a mass of about 0.033
Jupiter masses and 55 Cnc e at 0.045 AU with a mass of about 0.038 Jupiter masses
could be strongly eroded gas giants, while HD69830b, at 0.078 AU, HD160691d at
0.09 AU and HD69830c at 0.18 AU belonged most likely since their origin to the
Neptune-mass domain. The consequences for the planetary population expected to
be discovered with the CoRoTs are: (1) for orbital distances less than about 0.05 AU
weakly magnetized or highly irradiated gas giants may lose a large fraction of their initial
mass and even completely lose their gas envelopes. (2) Observed planetary masses
which resemble theoretically calculated planetary mass spectra at these orbital periods
would indicate a major effect of magnetic field protection. (3) At distances larger than
0.05 AU the impact of loss processes for Hot Jupiters is minor and the observed mass
spectra should be close to the theoretical ones.

[m1omg]

Yes, but this planet is not hot. The insolation there is lower than Earth's. And while flares might have been, by that time the star was still young and so even fainter. I don't think a tiny red dwarf can erode atmosphere off a cold planet.

[Hungry4info]

(I wasn't postulating that it was a stripped core planet, merely that proximity may have resulted in the loss of an initially much denser mass of atmosphere).

Ah, gotcha. A bit like Mars and it's atmospheric history.

[m1omg]

It might be true, but in this case the remaining atmosphere could be still thicker than Earth's.