Gliese 581 g - An Earthlike planet?

[MK Ultra]

http://www.quickpwn.com/2010/10/new-planet-discovered-2010-earth-like-planet-gliese-581g-photo.html

So, a planet has been observed about 20.5 light years away. Not much right? But scientists are calling this the 'most Earthlike planet found yet', and one was heard to claim there is a 100% chance of life there. Now, this is unlikely, but it is certainly an interesting development.

"I'm not a biologist, nor do I want to play one on TV. Personally, given the ubiquity and propensity of life to flourish wherever it can, I would say that, my own personal feeling is that the chances of life on this planet are 100%. I have almost no doubt about it."

I'd like to point out that this isn't a topic for science vs. religion or anything similar, but please discuss these findings.

My personal opinion is that there is life elsewhere, but this may not be the case. I think we might find some life here, though I don't know what scale it would be - i.e. protozoa, amoebae, bacteria etc.

 

[Curtains]

too bad its in another universal time zone. I hope we can find life on another planet and reach it in my lifetime.

 

[cantab]

EDIT: I should have said before - as Kitten Bukkake rightly points out, all this is speculation.

Well..."most Earthlike", it's still a bit off.

It's three to four times the mass of Earth. The gravity increase is actually surprisingly not very much. The bigger issue is what that does to the topography and geology. A larger terrestrial planet is likely to be much more geologically active (but see the below), and also have much reduced elevation.

It's also tidally locked. One side is always facing the star, the other always facing away. Unless the atmosphere is thick enough, this is likely to lead to the night-side being covered in a permanent ice cap if the planet has plenty of water, and the day side being very hot. One might also expect strong winds, I'm not sure on that.

The tidal locking leads to slow rotation, which implies the planet is likely to have a weak or no magnetic field. This won't be good for the atmosphere. On the other hand the star's a red dwarf, which I think might have a lesser stellar wind, and the volcanic outgassing might maintain the atmosphere.

Except that the planet is old. Probably 7-11 billion years, the same as its star. That may mean the geological activity isn't high after all. If it completely stops, then if liquid water stays on the planet for long enough afterwards it will smooth out the surface.

If civilization did arise about our time, the age of the planet gives them another problem - no practical nuclear power, since the amount of U-235 in natural Uranium would be something like 1 or 2 % of what we have on Earth, and enriching Uranium is DIFFICULT for us. They may thus run into energy problems sooner than we will. (Admittedly we today are far from NEEDING nuclear power, so there's room to advance beyond our own present state).

And it's still marginal for the habitable zone. It would need a greenhouse effect rather stronger than Earth's to be above zero celsius at the surface.

All things considered, my expectations of Gliese 581g are not much like Earth. If it has retained its atmosphere it may be completely covered in frigid oceans, with raging storms driven by the day-night heat difference, and quite possibly a lot of sea ice. It could even be a snowball planet. If it loses its atmosphere, it'll probably have a big ice cap on the night side.

 

[Morm]

Another one, eh?

Honestly, life exists or has existed elsewhere. The mathematical probability of it is so overwhelming; more and more evidence is coming to light that life is pretty much auto assembling and with natural selection it's pretty much assured that it exists or has existed.

Cantab, that's some pretty spectacular arm waving you're doing there. I know you're using some uniformitarianism, but that is only reliable for planets we've observed in more than a way that isn't just a star proxy. It's like when my professor told me the exact (to the percent) composition of Pluto but then claimed all we have is extremely fuzzy and pixelated pictures as data; it's just speculation. Let me give you an example:

no practical nuclear power, since the amount of U-235 in natural Uranium would be something like 1 or 2 % of what we have on Earth

So you're making an assumption that nuclear power is pivotal for advanced civilization, then you're giving us some pretty specific numbers on the amount of U-235 on the planet? That's the only reason why I can think you might be speculating on this.

Lets be completely honest: All we know, based on the light flicker and wobble of the star, is that there appears to be a planet within the goldilocks zone. Everything else is speculation. Keep in mind you're making this speculation based solely on light that is old and has traveled a long way. Check out the top post of my blog for some info on this stuff.

 

[cookie]

Except that the planet is old. Probably 7-11 billion years, the same as its star. That may mean the geological activity isn't high after all. If it completely stops, then if liquid water stays on the planet for long enough afterwards it will smooth out the surface.]

being bigger means it maintains a fluid core for longer - Earth is 5 billion years old and still tectonically active.

 

[cantab]

So you're making an assumption that nuclear power is pivotal for advanced civilization, then you're giving us some pretty specific numbers on the amount of U-235 on the planet?

The exact number I admit assumes the same initial concentration as Earth, when the planet formed, which may be badly wrong. The point to take is that an older planet is highly likely to have less fissile uranium.

I think nuclear power would be pivotal for a civilization wanting to do interstellar travel. Denied it, a civilization would have no problems becoming incredibly advanced on its own planet, even throughout its own solar system. But for interstellar journeys, where you can't rely on solar power so you have to take all your fuel with you, well if you've only got chemical fuels that's not going to cut it.
A civilization might be able to make antimatter efficiently in bulk, using it as an ultra-dense energy store. Or maybe power could be "beamed" from the home system. But neither of those seems very safe - the former for obvious reasons, for the latter the beam could get switched off or misaimed. Also since we haven't done the former, and only done the latter on small scales, we don't really know how practical they are.
Lack of nuclear power wouldn't be a showstopper for a civilization, but it would disadvantage it.

Come to think of it, a much bigger disadvantage would be lack of fossil fuels. But this is something I really can't speculate on with any grounding.

Yes, everything I posted is speculation. But I think it's reasonable speculation. Obviously I have to make a whole bunch of assumptions, which I admit neglecting to state. But the alternative is to say nothing at all. And the overarching point is that this "Earthlike" planet is probably as different from Earth as any of our own solar system's other terrestrial planets are.

Regarding your blog post, you say that "Something doesn't add up in my mind- there HAS to be a huge margin of error, so to say things as definitively as I am reading them seems a bit extreme". Yes, and those errors can be understood and quantitative estimates put on them. (Of course there could still be sources of bias we don't understand.) It's the mainstream media that doesn't mention them.

 

[MrIndigo]

Well, the new thing for nuclear fission is apparently Thorium, because there's a fuckton more of it and it avoids the political situations involved with enriched uranium (i.e. The Bomb).

When they do spectral analyses of these exoplanets, I think the things they primarily look for are C, CO2, O, and N (and H, obviously, but that's friggin everywhere); that's their 'evidence of life'.

 

[Athenodoros]

I'd have thought that if one side always faced the earth, then power sources like solar or biocrude would be reliable enough to use quite early on. And I can't imagine that we will end up using Uranium power for space flight. Hydrogen power source, anyone?

And as for the time to get there, at 0.99c you'd take less than three years for a few people to get there, even if we'd not find out about it for a couple of centuries.

Why do they look for C and CO2? I remember one guy thinking that aliens would probably be made of Silicon, or some other group four element, so I would have thought that looking for C wouldn't be very helpful.

 

[Xing]

What is up with this star system? First it was Gliese 581 c, then it's Gliese 581 d, and now Gliese 581 g? A Message From Earth was sent to c and d, but since g lies between those two, which lie on the edges of the habitable zone, g is indeed the most like planet with life on it. I think another A Message From Earth is in order.

 

[cantab]

I'd have thought that if one side always faced the earth, then power sources like solar or biocrude would be reliable enough to use quite early on. And I can't imagine that we will end up using Uranium power for space flight. Hydrogen power source, anyone?

*facepalm* I forgot about nuclear fusion :-S

We're made of carbon, which means carbon is the only element we know can make the long-chain molecules for life. Anything else is less certain.

Osygen would be the big giveaway that something really interesting is going on, since the stuff is highly reactive and thus shouldn't exist at equilibrium. If we detect significant oxygen, then it's being caused either by life or by a process we've never observed in our own solar system. The latter would be just as interesting, there aren't many non-biological ways to make an oxygen-rich atmosphere. (Thermal decomposition of some minerals can do it, but that implies an environment suitable for formation of such minerals has been followed by one making them decompose, which would be evidence for changes in planetary orbits, something that's often been hypothesised for both our own and other stellar systems but not I believe directly evidenced for.)

IIRC silicon exhibits similar chemistry at much lower temperatures - so silicon-based life might have a totally different "habitable zone". If low-T silicon-based life did exist, we'd probably expect it to be slow (reaction rates are slower at lower temperatures) which would give an interesting problem, in that such life could be transmitting to us, but so slowly we can't pick it up. If silicon ET transmits at the rate of one bit per Earth year, then if we picked up the radio signals we'd probably just assume they were natural.

What is up with this star system? First it was Gliese 581 c, then it's Gliese 581 d, and now Gliese 581 g? A Message From Earth was sent to c and d, but since g lies between those two, which lie on the edges of the habitable zone, g is indeed the most like planet with life on it. I think another A Message From Earth is in order.

One feature of the commonly used radial velocity method is we can't tell the plane of the orbits. The method also only gives us minimum masses. (Estimates for maximum mass are based on calculating whether the system could be stable in the long term - this of course assumes the system IS stable, but that's reasonable statistically.)
The closer the orbital plane is to "edge on" to us, the lower the mass of planets we can detect. (If it's completely edge-on we get transit method to spot them too, but that's not the case for the Gliese 581 system)
Also, the star is low mass, meaning it will "wobble" more due to the gravitational influence of the planets.

 

[Morm]

Regarding your blog post, you say that "Something doesn't add up in my mind- there HAS to be a huge margin of error, so to say things as definitively as I am reading them seems a bit extreme". Yes, and those errors can be understood and quantitative estimates put on them. (Of course there could still be sources of bias we don't understand.)

Bingo. Glad you read my post on there. The problem I have is overlooking the errors and then speculating while either ignoring them or by taking one TINY piece of analogous evidence and making an a giant deal out of it, speculating on your speculations.


Just because you have a resource, it doesn't mean it will automatically be used. So having fossil fuels doesn't necessitate modernesque life automatically. Perhaps the species or culture simply hasn't had the epiphany for refining crude oil.

Why do they look for C and CO2? I remember one guy thinking that aliens would probably be made of Silicon, or some other group four element, so I would have thought that looking for C wouldn't be very helpful.

The only life we can effectively search for is life as we know it, simply because we know what to look for. So looking for Carbon IS helpful.

 

[MrIndigo]

Also, Silicon is less likely to have turned into a life form than carbon because it's a larger molecule, thus it doesn't form from supernovae constituents as easily. It's theoretically possible for silicon based lifeforms, but the higher up Group 4 you get the less likely it is that the relevant atoms form and the less likely it is that they bond.