PDA

View Full Version : Episode 34: Discovering Another Earth



Fraser
2007-Apr-30, 08:45 PM
What a week! Astronomers announced the discovery of an Earth-sized planet orbiting the nearby star Gliese 581. We talk about the technique used to discover the planet, the possibilities of finding even smaller planets, and what the future holds for finding another Earth.

<strong><a href="http://media.libsyn.com/media/astronomycast/AstroCast-070430.mp3">Episode 34: Discovering Another Earth (13.6 MB) </a></strong><br />&nbsp;<br />

Read the full blog entry (http://www.astronomycast.com/uncategorized/episode-34-discovering-another-earth/)

ArrowJ
2007-May-01, 01:56 AM
"...you'll know whether there's life in the universe outside of our solar system or not. What more fundamental question could we answer?" - Fraser

I found this statement very interesting, and while I think I could come up with a couple of even more fundamental questions, let me just ask a question instead. If the universe is headed for destruction as we are told time and again on Astronomy Cast (and I agree). What exactly do we benefit from discovering other life? In other words, from a purely atheistic point of view, we will have discovered that we are not the only ultimately purposeless creatures in the universe. Not only have we evolved into thinking beings that will ultimately contribute nothing to existence that will outlive the universe, but there may actually be more thinking beings that will also amount to a grand total of nothing.

Don't get me wrong. I support space exploration and further astronomy via commercial and national avenues. It is just interesting to me as a theist to ask this type of question. After all, if the universe is doomed to destruction then ultimately we are purposeless. I'm not talking about right hear and now, I'm talking about the ultimate outcome of everything that exists.

It's a fairly sad outlook I would say. :eek:

EvilEye
2007-May-01, 07:21 PM
It is in our nature to explore regardless of the outcome. Our problem is that when we DON'T find something, we don't believe it. And when we do, we don't believe it.

jamesabrown
2007-May-01, 07:59 PM
My wife likes it when I give her flowers.

Every time, I think to myself, "What a waste. These are going to be dead in three days."

But my wife still likes it when I give her flowers.

Fraser
2007-May-01, 08:22 PM
That's like asking, since we know we're going to die, why bother living? Because living is fun. Consciousness is better than the void. In my opinion, we've got one life, so we should make the best of it that we can, for ourselves, and the lives of those around us.

And if life may rise up, flourish across the Universe for billions of years and then fade away, that'll just be that. The Universe was the better during that period. And who knows, we might discover a way out of all the grim fates we present on Astronomy Cast.

We know so little about the truth of the Universe, I can't wait to find out more.

ArrowJ
2007-May-01, 09:34 PM
Consciousness is better than the void.

Since my worldview is so often questions as being unsupportable, I would like to ask you to explain to me exactly how you can know that. Have you experienced the void?

Anyway, I guess I already knew what the type of answers I would get, but they simply aren't satisfying enough for my "nature".

"There is but one truly serious philosophical problem, and that is suicide." -- Albert Camus

Enough said. I won't hijack the astronomy forum. Keep up the good work. I enjoy the show...and for the record I can't wait to find out more too.

EricNau
2007-May-01, 11:03 PM
Has this episode been posted yet? ...It isn't showing up in the RSS feed or in iTunes (at least for me).

:confused:

DDPP
2007-May-02, 04:47 AM
It is just interesting to me as a theist to ask this type of question. After all, if the universe is doomed to destruction then ultimately we are purposeless.

It's not reality's job to satisfy our egos. The universe does not owe us any meaning. I think happiness is purpose enough. I don't know why, but Knowing things, the sense of awe I get from looking at an embryo under a microscope or looking up at the stars, the sense of exploration, and other things make me happy. There are plenty of people out there who apparently don't care much about learning, but I do; that is purpose enough for me. I've given life my own purpose. I really don't need anyone else telling me what the purpose of MY life is.

If you don't think living/happiness is purpose enough, what is? What is the purpose of life according to you? Serve god? then what? you die, you go somewhere (heaven/hell), and then what? what was the purpose of getting there? what is the purpose of god? does god have a purpose?

ultimately, you reach a point where there is no higher purpose. Either the sole purpose of something is itself, or there is no ultimate purpose.

What is greater than happiness?

Euler
2007-May-02, 08:33 AM
Has this episode been posted yet? ...It isn't showing up in the RSS feed or in iTunes (at least for me).

:confused:

It's not showing up in iTunes for me either ; guess a download from the website it is then...

parallaxicality
2007-May-02, 01:08 PM
That's like asking, since we know we're going to die, why bother living? Because living is fun. Consciousness is better than the void. In my opinion, we've got one life, so we should make the best of it that we can, for ourselves, and the lives of those around us.

That depends on who you are. Most people on Earth live what we would consider unendurable lives, with no way out. If there is a purpose to our indolent leasure society, then it should be to help those people who have no time for existentialist angst to live tolerable existences. Raises the age-old question about the validity of space exploration of course.

Fraser
2007-May-02, 03:28 PM
I'm not sure why, but Feedburner isn't updating with the latest episode, even though it's actually in the feed.

EvilEye
2007-May-02, 03:47 PM
I like the way Carl Sagan put it. (paraphrased)

"We are a way for the Universe to know itself."

There is your purpose.

DDPP
2007-May-02, 05:14 PM
If there is a purpose to our indolent leasure society, then it should be to help those people who have no time for existentialist angst to live tolerable existences. Raises the age-old question about the validity of space exploration of course.

Of course, even you don't truly believe that. What the heck were you doing sitting in a computer who knows where when you typed that? and now reading this? The very fact that you have a computer means that you value your leisure more than countless other faceless people's lives. You could have used that money to feed someone for I don't know, a week? Yet you chose to use it on something that you don't absolutely have to have to survive, a computer.

I think attaining happiness is pretty much every single human being's purpose. Many of us help others because that makes us happy, or do seemingly altruistic things because we could not be happy by not doing them. Helping others is really never purpose enough.

Actually I'm kind of glad of that. Imagine a world where humans had evolved to be completely altruistic and help others instead of helping themselves be happier... THAT would be a purposeless life, because what would be the point of helping others? even if helping others made them happy, it would not last because to them that's not nearly as important as helping others, and they'd turn right around and help someone else. Nowadays we help them BECAUSE we think happiness is the ultimate purpose, and by helping others we are both increasing our happiness and theirs.

little story- a man is eating some fried rice, and sees a homeless person lying in the streets. He gives him the container of fried rice, trying to save a life. However, the homeless guy turns around and gives it to another homeless guy, which gives it to another one, and another one, and eventually no one gets any rice because it rots.
Alternatively, the first homeless guy takes it to another homeless guy and they split the food, and they each then go to another homeless guy and split the food, etc... until now each one only gets a single rice grain.... and everyone starves to death because they none of them had enough food :P

so... some selfishness is good. (whoa lol... talk about a tangent)

In a world where helping others would be life's purpose, there would BE no purpose. And we would not have any of the technological advances we now have. And I bet more people would die in the long run (even if my extreme case didn't apply above), because technological advances save lives.

parallaxicality
2007-May-02, 05:16 PM
Of course, even you don't truly believe that. What the heck were you doing sitting in a computer who knows where when you typed that? and now reading this? The very fact that you have a computer means that you value your leisure more than countless other faceless people's lives. You could have used that money to feed someone for I don't know, a week? Yet you chose to use it on something that you don't absolutely have to have to survive, a computer.

I'm not an atheist. I'm an agnostic. If I ever decided to go that final mile and actually conclude that my life is the only life I would ever have, and that there would be no final reckoning, and that the only force balancing my immorality was myself, then I would be off to Africa to spend every waking moment of the rest of my life digging wells. Which is one reason why I have yet to draw that conclusion.

Rororoyourboat
2007-May-03, 05:06 AM
I was just wondering if this discovery has gotten any response from religious organizations or other groups (non-evolutionary). Wouldn't the fact that there is life on other planets crush non-evolution believers and threaten our religious uniqueness in our universe? :wall:

~T.Ro

ArrowJ
2007-May-03, 05:14 AM
I was just wondering if this discovery has gotten any response from religious organizations or other groups (non-evolutionary). Wouldn't the fact that there is life on other planets crush non-evolution believers and threaten our religious uniqueness in our universe? :wall:

~T.Ro

If God created life on one planet what would prevent Him from doing it on another?

Rororoyourboat
2007-May-03, 05:24 AM
If God created life on one planet what would prevent Him from doing it on another?

I'm a Christian and a full evolutionary believer. Also, I am completely open to the fact that God could create life on other planets, maybe even humans...
better or worse? v1.0, 2.0? woah...

but I just feel that if I was a very strong, religious, and even ignorant Christian or whatever religion, I would feel almost jealous or, for lack of better word, abandoned if there were other humans on other planets created by God... even though, if any life does exist, the organisms would look unimaginably different.

I don't want to offend anyone or raise disputes because of this very sensitive topic, just blogging some thoughts.

parallaxicality
2007-May-03, 07:16 AM
The only thing that could possibly "crush" anti-evolutionary thought is if we made contact with an extraterrestrial civilisation that was both older and more technologically advanced than our own. The most basic tenet of the creationist argument is that humans are exceptional. If it were shown that we weren't, then the whole basis for creationism would be annulled.

DDPP
2007-May-03, 07:50 AM
Nah. Many would just say that the devil made them.

parallaxicality
2007-May-03, 01:15 PM
That would be a hard argument to maintain if they turned out to be more peaceful and benevolent than we are.

ArrowJ
2007-May-03, 04:11 PM
The most basic tenet of the creationist argument is that humans are exceptional. If it were shown that we weren't, then the whole basis for creationism would be annulled.

I would argue that God has the right to make another group of beings that are also special. While we believe that everything in the Bible is truth, we do not believe that everything that is truth is in the Bible.

DDPP
2007-May-03, 05:43 PM
That would be a hard argument to maintain if they turned out to be more peaceful and benevolent than we are.

No, the devil is not below stooping to being nice in order to get people to hell. You didn't know that? lol

Don't underestimate most creationists' mental gymnastic abilities. all their arguments are ALREADY impossible to maintain. If they can say god created the light from the stars already on it's way, it's not a big leap to say the devil created the aliens... and any supporting details.

or, of course, they could just say "I would argue that God has the right to make another group of beings that are also special."

lol.

Creationism is here to stay, no matter what you throw at it.

ArrowJ
2007-May-03, 06:11 PM
If they can say god created the light from the stars already on it's way, it's not a big leap to say the devil created the aliens... and any supporting details.

I'm a Christian and I don't believe that God created the light from the stars already on it's way. Furthermore, we could only postulate as to the special nature (or lack thereof) of alien life. The Bible does not speak to this issue and our information would be limited. We do not have the freedom to make the Bible say what is comfortable for us. That is not to say that this doesn't happen, but when it does it is the result of a lack of proper hermeneutics, and a desire to make the Bible more convenient to ones presuppositions.



or, of course, they could just say "I would argue that God has the right to make another group of beings that are also special."

I'm not overly impressed with your wit here. If I believe there is an overwhelming amount of evidence for the existence of God, then it would be arrogant on my part to limit his special creation to only our planet. I'm not arguing how God might have done this (evolution/special creation/etc), I'm only saying that if God exists then it is possible that He has created other life and not told us about it.

DDPP
2007-May-03, 06:25 PM
I'm a Christian and I don't believe that God created the light from the stars already on it's way.

Oh I know. You mentioned that in the other thread. I meant that most creationists' beliefs won't change (not including kids or fence creationists). You already don't believe that, so you're excluded. However, you still wouldn't believe in evolution. That was my point. You're a (old earth) creationist, and you would still be a creationist regardless of other life on the universe. Young earth creationists would still be young earth creationists.


I'm not overly impressed with your wit here. If I believe there is an overwhelming amount of evidence for the existence of God, then it would be arrogant on my part to limit his special creation to only our planet.

That's irrelevant. I was answering to what parallaxicality said: "The only thing that could possibly "crush" anti-evolutionary thought is if we made contact with an extraterrestrial civilisation that was both older and more technologically advanced than our own."

You exemplified how you would still not accept evolution even if there were older, more intelligent life forms in the universe.


I'm not arguing how God might have done this (evolution/special creation/etc), I'm only saying that if God exists then it is possible that He has created other life and not told us about it.

Yeah, but you still wouldn't accept evolution. Would you?

Fraser
2007-May-03, 10:06 PM
Please don't derail this thread into a religious discussion.

clint
2007-May-03, 10:58 PM
Please don't derail this thread into a religious discussion.

Ok, here are some practical questions about this amazing discovery
- I'm trying to imagine the conditions on that planet:

1) I guess since the mass of that planet is approx. 5 times the earth's,
anybody would weigh 5 times as much as on earth, right?
(that would be 500 kg for me :sick: )

And thus any (imaginary) native land-based live would have to be adapted to this.
What about a completely water-covered world, though?
Water-based life would be much less affected by higher gravity, correct?
(like e.g. whales on earth)

2) What about the very exotic conditions in that star system?
(from an earth perspective, of course - maybe it's actually OUR solar system which is strange)

Correct me if I'm wrong, but that Super-earth is rotating way closer around its star than Mercury to the Sun, is that right?
And then there is a Neptune-like planet even closer???
WOW!!!!!! :eek:

This constellation should cause some REALLY weird effects on the planet's surface! Any ideas?
- Probably huge tides (if it has oceans) and/or lots of vulcanic activity? (especially everytime its star and 'Neptune' line up)
- Plus extreme weather patterns, caused by the insanely short orbit around its star (maybe on a very eliptical path, too)?
- Lots of radiation because of the extreme proximity to its star?
- Would it be capable of holding any moons, with the gravitational disturbances of a Neptune-like planet that close?

EvilEye
2007-May-06, 01:43 AM
I won't tell you what I believe. However I will tell you that for anyone to deny the facts of evolution is being foolish.

Faith is a good thing. It helps us go day to day without the hopelessness that would otherwise accompany us on the purposeless ride we call life.

Hope is even better.

Those two things aside, what is important is that we work together to make the best of what we have now... not the easiest... the BEST.

Sadly, that doesn't seem to be the case.

Evolution and Creationism are not butting heads. One is a Fact based theory, and the other is a belief. You can't compare them.

An opinion cannot be proven true or false, but facts can.

marcushedenstrom
2007-May-06, 06:09 PM
1) I guess since the mass of that planet is approx. 5 times the earth's,
anybody would weigh 5 times as much as on earth, right?
(that would be 500 kg for me :sick: )

Remember that the planet's radius is estimated to be 150 percent of the Earth's radius. So while there's more mass, you'll be farther away from it. 5 times the mass and 1.5 times the distance; that would make about 2.2 times the Earth's gravitational force at the surface.

EvilEye
2007-May-07, 03:49 AM
Remember that the planet's radius is estimated to be 150 percent of the Earth's radius. So while there's more mass, you'll be farther away from it. 5 times the mass and 1.5 times the distance; that would make about 2.2 times the Earth's gravitational force at the surface.

Yes. So instead of weighing 180 lbs, I would weigh 396 lbs. Not impossible, but evolution there would make for some very short, extremely strong creatures. If they visisted us here on Earth, we would say "what's up pipsqueak?" and they would reply by throwing a baseball half a mile.

clint
2007-May-07, 09:18 PM
...5 times the mass and 1.5 times the distance; that would make about 2.2 times the Earth's gravitational force at the surface.


... evolution there would make for some very short, extremely strong creatures. If they visisted us here on Earth, we would say "what's up pipsqueak?" and they would reply by throwing a baseball half a mile.

Haha, sounds like Shrek would be just fine there :lol:

What about (hypothetical) waterlife?
Am I right that - everything else being equal - double gravity would make much less difference for, let's say, fish, whales - or even human divers?

DDPP
2007-May-07, 10:05 PM
Am I right that - everything else being equal - double gravity would make much less difference for, let's say, fish, whales - or even human divers?

It all depends on density of your body vs. the surrounding water. If it's high/low you would be more affected by gravity than if it is low/high, or both were the same.

For example, if you lived in water and had an air-filled bladder (like most bony fish), the gravity wouldn't matter. The bladder would allow you to control how dense you are relative to the surroundings (by compressing it or relaxing it), and therefore how much you "weigh". If you were a human and the water was REALLY salty (like in the black sea) you would actually float to the surface. If it was fresh water, you could sink to the bottom, but gravity wouldn't affect you too much because most of your body is made out of water.

... so in general, you're right. Gravity wouldn't have such a big impact underwater on life as we know it.

EvilEye
2007-May-08, 06:45 AM
It all depends on density of your body vs. the surrounding water. If it's high/low you would be more affected by gravity than if it is low/high, or both were the same.

For example, if you lived in water and had an air-filled bladder (like most bony fish), the gravity wouldn't matter. The bladder would allow you to control how dense you are relative to the surroundings (by compressing it or relaxing it), and therefore how much you "weigh". If you were a human and the water was REALLY salty (like in the black sea) you would actually float to the surface. If it was fresh water, you could sink to the bottom, but gravity wouldn't affect you too much because most of your body is made out of water.

... so in general, you're right. Gravity wouldn't have such a big impact underwater on life as we know it.

Isn't what you're talking about more related to density than gravity?

Gravity would have a major effect on the pressure (psi) of water at 2.2X relative to the pressure on Earth.

Swimming at 50 feet there for a human would be like diving to 110 feet here.

DDPP
2007-May-08, 04:22 PM
Isn't what you're talking about more related to density than gravity?

Well yeah. But if your body is less dense than the water surrounding it, you will float up and therefore you wouldn't need strong bones or whatever to deal with gravity pushing you down.


Gravity would have a major effect on the pressure (psi) of water at 2.2X relative to the pressure on Earth.

Swimming at 50 feet there for a human would be like diving to 110 feet here.

Hmm. Hadn't thought of that. Of course, the exact numbers would also depend on how much atmosphere that planet has...

but anyway, human-like organisms could live in shallow seas (assuming there are any) or just generally near the surface, and the pressure changes wouldn't affect them too much. Or there could be organisms similar to deep-sea fish, or those which migrate (here on earth) from the deep ocean to the surface each night (or like sperm whales, which dive down deep in order to find Squid and other things to eat)... They'd have to be careful about pressure, but I don't think the changes would be too drastic...no? I still think organisms would be less affected by gravity than if they lived on land.

And they could certainly have soft bodies and be huge.

clint
2007-May-18, 10:17 AM
...
2) What about the very exotic conditions in that star system?
(from an earth perspective, of course - maybe it's actually OUR solar system which is strange)

Correct me if I'm wrong, but that Super-earth is rotating way closer around its star than Mercury to the Sun, is that right?
And then there is a Neptune-like planet even closer???
WOW!!!!!! :eek:

This constellation should cause some REALLY weird effects on the planet's surface! Any ideas?
- Probably huge tides (if it has oceans) and/or lots of vulcanic activity? (especially everytime its star and 'Neptune' line up)
- Plus extreme weather patterns, caused by the insanely short orbit around its star (maybe on a very eliptical path, too)?
- Lots of radiation because of the extreme proximity to its star?
- Would it be capable of holding any moons, with the gravitational disturbances of a Neptune-like planet that close?

Sorry for quoting myself, but I feel we haven't really given this all the debate it deserves - so I'll make another try.

For me, the most fascinating thing about Gliese 581c (apart form potentially holding liquid water, of course)
is the mind-blowingly exotic conditions in that system.
(e.g. SEVERAL planets INSIDE Mercury's orbit )

And the fact that maybe THOSE are the 'normal' planetary systems, since brown dwarfs are so much more frequent than our type of star (Sun).

1) This really defies all our earlier conceptions about planetary systems, doesn't it? Does this maybe represent the typical solar system?

2) I'm trying to imagine how weird those conditions might actually 'feel' like on Gliese 581c (see my quote above). Any thoughts?

Nimwe
2007-May-28, 05:29 PM
I'm a new listener to the Astronomy Cast, and new reader here, but I thought this would be an appropriate place to mention a link concerning Gliese 581c.

The following link goes to an article in the online journal The Geochemical News, published by the Geochemical Society (http://www.geochemsoc.org/). The article provides a speculative but geologically plausible description of possible conditions on this newly-discovered planet (including some speculation about possible life there). It's sort of a literary analog to an 'artist's conception' of the planet.

http://gnews.wustl.edu/gn131/gliese581c.htm

Anyway, thanks for the great podcast. :)

timb
2007-May-28, 08:00 PM
I'm a new listener to the Astronomy Cast, and new reader here, but I thought this would be an appropriate place to mention a link concerning Gliese 581c.

The following link goes to an article in the online journal The Geochemical News, published by the Geochemical Society (http://www.geochemsoc.org/). The article provides a speculative but geologically plausible description of possible conditions on this newly-discovered planet (including some speculation about possible life there). It's sort of a literary analog to an 'artist's conception' of the planet.

http://gnews.wustl.edu/gn131/gliese581c.htm

Anyway, thanks for the great podcast. :)

Assumes that the planet will, despite "somewhat lower metal contents but substantially higher volatile contents than the inner worlds of our own star system", have only limited water, not enough to cover the entire surface. Also doesn't seem to understand that H2O is a greenshouse gas. A thick CO2 atmosphere would make both sides of the planet extremely hot (cf Venus, the 120 day night makes no difference to the temperature).

Nimwe
2007-May-29, 01:48 AM
Water is a greenhouse gas, it's true, and on a per molecule basis has a similar magnitude of infrared absorbance - and therefore radiative forcing potential - as CO2. However, the effect of water vapor on global atmospheric heat trapping is strongly dependant on its average atmospheric concentration. That, in turn, tends to be strongly heterogeneous regionally, varying on Earth from about 0 to 4% depending on latitude, average surface temperature, wind patterns, and availability of evaporating liquid water at the surface.

On a planet as described in the narrative, absolute global H2O vapor concentration would be likely limited by freeze-out on the night side and low availability of surface liquid on the day side. So the relative humidity, and therefore the absolute concentration of water vapor, would be globally low, with a relative maximum near the terminator (over a liquid ocean) and a minimum at both poles. So, the average global effect of H2O on absolute radiative forcing would likely be minimal.

As far as a higher volatile content producing a global ocean, that is one potential model, and it may be more accurate. However, the model described in the narrative seems to suggest that due to tidal locking effects, at any given moment much of the available H2O reservoir is held as a solid on the night side. This could be a realistic model, given that the rate of viscous relaxation of ice would be the rate-limiting step in delivery of liquid H2O to the terminator environment. That step would likely be slower than the rate of H2O vapor delivery to the night side, resulting in a low average global concentration of H2O vapor and a limit to the amount of liquid water there could be on the day side. It would probably take some rheological calculations of the rate of viscous relaxation of ice in the heavier gravity, along with the significant distance (Gliese 581c is probably a larger planet than Earth) the glaciers would have to travel to reach the terminator, and some estimate of the total reservoir of surface H2O, to make a definitive conclusion.

One thing the author didn't mention but which would probably be a factor on Gliese 581c; crustal strain produced by tidal effects. On a sphere experiencing anisotropic stress, you'd expect strain fractures along the equator perpendicular to the axis of stress (in this case the tidal pull direction, oriented to the day/night 'poles'). Along the terminator there would be latitudinal rifting of the crust, forming immense grabens into which a liquid ocean would tend to accumulate. The deepest lake on Earth is Lake Baikal (Russia), formed over a graben resulting from continental rifting. It's likely a similar process would occur on Gliese 581c, but there resulting in an equatorial ring of graben-bound seas.

With so many variables, it seems the best we can do without direct evidence is come up with a suite of possible models constrained by known factors. That still leaves room for some fun speculation, for now. :)

timb
2007-May-29, 10:49 AM
Water is a greenhouse gas, it's true, and on a per molecule basis has a similar magnitude of infrared absorbance - and therefore radiative forcing potential - as CO2. However, the effect of water vapor on global atmospheric heat trapping is strongly dependant on its average atmospheric concentration. That, in turn, tends to be strongly heterogeneous regionally, varying on Earth from about 0 to 4% depending on latitude, average surface temperature, wind patterns, and availability of evaporating liquid water at the surface.

On a planet as described in the narrative, absolute global H2O vapor concentration would be likely limited by freeze-out on the night side and low availability of surface liquid on the day side. So the relative humidity, and therefore the absolute concentration of water vapor, would be globally low, with a relative maximum near the terminator (over a liquid ocean) and a minimum at both poles. So, the average global effect of H2O on absolute radiative forcing would likely be minimal.


I think you'd need some pretty special topography to make that work. What's stopping a massive water flow from the cold to the hot side? Unless you assume all the highland is on the day side and all the ocean basins are on the cold side. If there is an ocean basin that spans the terminator then you're going to have massive evaporation/boiling there. You only have to evaporate a small percentage of an ocean to add massively to the atmospheric greenhouse, and evaporates that condensed out as snow and rain are likely to fall where they are most available for flow back to the hot side, close to the terminator, not at the pole of cold.

Exactly what happened along the way to replace the primordial hydrogen, helium, and methane atmosphere with carbon dioxide isn't explained.

Nimwe
2007-May-29, 02:31 PM
But remember that the intensity of solar insolation would be weakest near the terminator, and you'd have the nearby glaciers acting as a thermal sink. The result should be a dry, cool environment. You wouldn't expect to see high surface temperatures anywhere except near the dayside pole. As far as topography goes, I think the article's model assumes that there isn't much vertical exaggeration because of the higher gravity. In any event, ice would just follow whatever regional topographic gradients already exist, and there would undoubtedly be nightside regions of tectonic uplift where massive continental glaciers simply flow around the rocky massifs. The key variable would be total available surface H2O: too little and all of it builds up permanently on the night side, flattens itself out, but none ever relaxes completely to the terminator. In such a model, oceans would be precluded.

It's a good point about global temperatures in a thick atmosphere, with Venus as an example. We don't know the actual atmospheric composition of Gliese 581c, so its atmosphere remains a free parameter in any model of that world's global geochemistry. However, it's important to note that Venus has a very heavy atmosphere, about 93 bars at the datum, and is mostly CO2. Also its cloud cover (the formation of which is still something of an unresolved issue) assists in heat retention, and most importantly Venus receives a great deal more insolation than would a planet orbiting Gliese 581, even at the proximity of planet c.

If Gliese 581c had an atmosphere very similar to Venus, it might also have a runaway greenhouse environment. If its atmosphere is substantially thinner, or contains a large partial pressure of infrared-inactive components (e.g. N2), a runaway greenhouse would be unlikely, as would a global distribution of intense heat. Gliese 581 is a very dim star; only about 1% as bright as the Sun. At 1 AU distance, the blackbody temperature of an Earth duplicate would be low enough to freeze out most of our atmosphere. Even as close as Gliese 581c is to its primary, its dayside pole would still receive only a fraction of the energy that the planet Mercury receives from the Sun.

About primordial H2, etc.: the gravity of Gliese 581c might make retention of even the lightest gases (H2, He) possible, and if the planet formed farther from its primary and wandered closer at a later date, this would be even more plausible. However, in our system the inner planets were stripped of their primordial atmospheres by intense solar winds during the T-Tauri phase of solar formation. A red dwarf would have a weaker T-Tauri phase, but would still exhibit a more energetic phase of solar activity as it formed. Gliese 581 is a variable star, which probably contributed even more violence to its birth. It's probable that inner worlds in the Gliese 581 system would have undergone some atmospheric stripping, making a modern H2 and He atmosphere around a terrestrial planet unlikely.

I look forward to future spectroscopic observations of Gliese 581c's atmosphere. Such data would settle many of these questions, and teach us a lot about planetary formation processes around red dwarf stars.

clint
2007-May-29, 07:43 PM
The following link goes to an article in the online journal The Geochemical News, published by the Geochemical Society (http://www.geochemsoc.org/). The article provides a speculative but geologically plausible description of possible conditions on this newly-discovered planet (including some speculation about possible life there). It's sort of a literary analog to an 'artist's conception' of the planet.

http://gnews.wustl.edu/gn131/gliese581c.htm

Anyway, thanks for the great podcast. :)
WHOAAA, now that is a COOL link!

Might be a bit speculative, but hey,
we're talking about the first earth-like planet we've found
- if that doesn't make our imagination run a little wild, what else will ever?!! :)

Thank you for sharing it Nimwe!!!

PS: can't wait to read through the rest of the posts tonight
- finally we're getting into the debate :) :) :)
(this thread was going a bit astray at first)

m1omg
2007-Jun-03, 05:52 PM
"...you'll know whether there's life in the universe outside of our solar system or not. What more fundamental question could we answer?" - Fraser

I found this statement very interesting, and while I think I could come up with a couple of even more fundamental questions, let me just ask a question instead. If the universe is headed for destruction as we are told time and again on Astronomy Cast (and I agree). What exactly do we benefit from discovering other life? In other words, from a purely atheistic point of view, we will have discovered that we are not the only ultimately purposeless creatures in the universe. Not only have we evolved into thinking beings that will ultimately contribute nothing to existence that will outlive the universe, but there may actually be more thinking beings that will also amount to a grand total of nothing.

Don't get me wrong. I support space exploration and further astronomy via commercial and national avenues. It is just interesting to me as a theist to ask this type of question. After all, if the universe is doomed to destruction then ultimately we are purposeless. I'm not talking about right hear and now, I'm talking about the ultimate outcome of everything that exists.

It's a fairly sad outlook I would say. :eek:

Oh, emos, stop crying:lol::), these babbles about the end of the universe are just babbles , enyoy living :):):), the live is short, so why not enyoy it :), and please dont trust that babbles about the end of universe these are blablas

m1omg
2007-Jun-03, 05:55 PM
Since my worldview is so often questions as being unsupportable, I would like to ask you to explain to me exactly how you can know that. Have you experienced the void?

Anyway, I guess I already knew what the type of answers I would get, but they simply aren't satisfying enough for my "nature".

"There is but one truly serious philosophical problem, and that is suicide." -- Albert Camus

Enough said. I won't hijack the astronomy forum. Keep up the good work. I enjoy the show...and for the record I can't wait to find out more too.

OMG YOU WANT "EVIDENCE" FOR EVERYTHING!:eek: Some things are true without evidence.