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Leiningen
2004-Mar-25, 10:53 PM
Hello.

English isn't my native language and I never even properly learned English, so don't be too harsh, if some formulations or spellings don't make sense. :)
I have read about the idea that intelligent life could be extremely rare, because of the fact, that the Earth-Moon-system only came into existence due to an extremely unusual collision more than four billion years ago, and that such an extremely unusual large moon would be necessary for the planet Earth to be stable enough to allow this long biologic evolution which led to intelligent life.
But now it seems that the structure of our entire solar system as a whole is not nearly typical at all. It seems that there are lots and lots of solar systems with very large planets, giant Jupiters or even brown dwarfes relatively near to the sun of a solar system, some of them in the habitable zone. And all the moons/trabants of these objects would be in the habitable zone as well and would have the size of terrestrial planets.
Could these objects be the typical place regarding the evolvement of intelligent life, rather than lone planets with an untypical moon, like the Earth-Moon-system?

JohnOwens
2004-Mar-25, 11:14 PM
And all the moons/trabants of these objects would be in the habitable zone as well and would have the size of terrestrial planets.
Just a little translation help, what you call "trabant" we call "satellite". :)

ingrast
2004-Mar-25, 11:19 PM
To be a newbie, you are rather well informed.

This is a tantalizing question, since evidence both for and against the existence of extraterrestrial life has been accumulating in large quantities.

Something like substracting two very large numbers, you change one of them ever so slightly (as a percentage) and the outcome may jump from negative to positive or the reverse in a blink.

I have posted a recent 2 part article (http://www.suite101.com/article.cfm/12057/107180)where I survey the current state of affairs with regards to the search for extraterrestrial intelligence. You may find both information and interesting links to follow on the subject.
Hope this can help

Cougar
2004-Mar-26, 12:14 AM
There appears to be a pretty big gap between "life" and "intelligent life". In our case, it took between 3 and 4 billion years to go from "life" to radio communications, etc. At any rate, according to Stuart Kauffman of the Santa Fe Institute (http://www.santafe.edu/sfi/People/kauffman/athomePreface.html), simple life should be pretty abundant since it's only a matter of of having a diverse enough collection of molecules. Once a threshold is crossed, autocatalysis or self-organization is nearly inevitable. So simple life is pretty much at home in the universe. (http://www.santafe.edu/sfi/People/kauffman/athomePreface.html)

It's unclear whether it's inevitable to eventually evolve into intelligent life of the sort that could send communications to other star systems. There's self-organizaiton and natural selection, but much also depends on chance and contingency. What if the asteroid that wiped out the dinosaurs had missed?

Mr. Milton Banana
2004-Mar-26, 12:17 AM
Heya! :D

Carl Sagan covered this in his book, COSMOS, about hypothetical life on a Jovian planet. There is even an illustration (done by Ron Miller, I think-GREAT painting =D> ), which contains creatures known as "hunters" and "floaters". Jupiter's atmosphere, according to Sagan, is probably similar to that of early Earth. There is also lightning on Jupiter as well.

However, one of the arguments against life on such a planet is the violent weather. As I see it, Jupiter is half-planet, half star. If you were able to fly through its atmosphere, my guess is that it would resemble our sky in many aspects-except that there would be an ocean of clouds below, with monstrous thunderheads ripping out of this cloud deck-like in the Ron Miller painting. However, the clouds cover what is probably a scalding ocean of liquid hydrogen-which, if there is a surface, must reach thousands of degrees. This is what comprises most of Jupiter's bulk. The intense heat is what causes Jupiter's volatile weather.

The problem is that winds can reach near 400 mph at times, and any organic molecules could be carried to deeper depths and possibly be destroyed by the heat. Keep in mind this: when the Galileo spacecraft dropped its probe into Jupiter's atmosphere, its final reading at 175 miles down was 22 earth atmospheres (bars) at 300 degrees Fahrenheit. Supposedly, it also got windier with depth.

As far as I know, no creature can survive 300-degree temperatures. But it's a huge universe, and I could be woefully wrong.

8)

Nereid
2004-Mar-26, 12:28 AM
Hi Leiningen!

Peter Ward and Donald Brownlee cover the points in your question in their book "Rare Earth" at some length. IIRC, the Moon plays an important role in creating and maintaining conditions favourable to the development of what they call 'complex life'. By this they mean multi-cellular organisms, or the sorts of critters that were to be found in Cambrian (and late pre-Cambrian) seas. They left alone the question of 'intelligent life', and that's none too surprising given how uncertain their work on 'multi-cellular life' is!

Oh, the Moon? It stablises the Earth's rotational axis, so taming the extremes of climate the planet would experience if the axis wandered chaotically between 0 and 90 degrees - which it would without the Moon!

BTW, they also make a case for large amounts of land - but not too much - are all but essential; a 'water world' likely won't give rise to us'ns. :([/code]

Brady Yoon
2004-Mar-26, 02:40 AM
Most definitely. If life can form on a rocky planet such as ours, why not on a gas giant? Life that is common to life on Earth is probably the exception, not the rule. But of course, we really don't know anything yet.

Grand Vizier
2004-Mar-26, 03:04 AM
If life can form on a rocky planet such as ours, why not on a gas giant?

I'd like to think so, too. But there is a problem. The general idea is that bodies of water, even if they are relatively small, allow such rapid mixing that many many combinations of complex molecules can be 'tried out' against each other. It's a sort of computation.

So with huge continuously connected oceans and seas like Earth's, enormous 'computational' capabilities are possible. But with Jupiters (and Venuses too, I'd add), you might, at a given atmospheric layer, have the right temperatures and pressures for, say, RNA to form - but the substrate, in this case water, in those atmospheres is necessarily going to be in the form of discontinuous droplets high in the atmosphere. That wouldn't allow the high-speed interactions that chemical evolution requires, in my opinion.

Having said that - supposing that this simply slows evolution down. Life arose very early on Earth, we now know that. If 'atmospheric life' is simply held back some, then who is to say there are not Jovian bacteria or archaeans (or equivalents)? I'd find it hard to buy into the idea of multicellular life, though...

Ilya
2004-Mar-26, 04:11 AM
Heya! :D

Carl Sagan covered this in his book, COSMOS, about hypothetical life on a Jovian planet. There is even an illustration (done by Ron Miller, I think-GREAT painting =D> ), which contains creatures known as "hunters" and "floaters". Jupiter's atmosphere, according to Sagan, is probably similar to that of early Earth. There is also lightning on Jupiter as well.

However, one of the arguments against life on such a planet is the violent weather.

I think you misunderstood Leiningen's post. He was not talking about life on a gas giant, but about life on a moon of a gas giant located within its star's habitable zone. Now we know that such things exist, which Sagan did not.

Swift
2004-Mar-26, 01:54 PM
Leiningen, welcome to the board.

I think Earth-sized moons of gas-giant planets might be excellent places for either life or intelligent life. There is speculation that Titan may have life. But we have very limited data.

We have discussed on the board before how necessary the moon was for the development of life on Earth. Here for example
http://www.badastronomy.com/phpBB/viewtopic.php?t=12206.
I don't think we have reached a consensus. I'm not sure how rare events such as the big collision that created the moon are in the universe. Such collisions might be common in early solar system. Again, no data.

As far as the fact that many of the objects found in orbit of other stars are brown dwarfs, giant jupiters, and hot jupiters, I think we need to be a little careful in assuming that means they are the most common (I just heard a talk about this at the Cleveland Museum of Natural History). Given our present techniques and instruments for finding extra-solar planets, these are not only the easiest ones to find, but we do not presently have the ability to even see a jupiter-sized planet (with a jupiter orbit) around most other stars. You only can see what you have the ability to see. As the techniques have improved, we have found a bigger and bigger variety in size and orbits.

tracer
2004-Mar-26, 04:09 PM
I think Earth-sized moons of gas-giant planets might be excellent places for either life or intelligent life.
And I think Earth-sized moons of gas-giant planets might be extremely hard to find. As far as "terrestrial" objects go, the Earth is huuuuuuuge! It's the biggest solid object known to humankind, not counting Jupiter's core and white dwarfs. Ganymede, the biggest gas-giant moon we know of, has only 40% of the Earth's diameter -- it's smaller than Mars, fer cryin' out loud.

eburacum45
2004-Mar-26, 04:56 PM
The strength of the magnetic field might be the most important consideration with earthlike moons of gas giants; Jupiter's magnetic field is so strong, it traps radioactive particles in a torus around it- a torus which coincides with the orbits of most of the Galilean moons, and renders them a high radiation environment.

Conversely, Saturn's magnetic field is weak, and Titan orbits partly within it, and partly outside it; when Titan is unprotected by Saturn's field, it is exosed to effects from major solar flares and wind events- a bad event, like the ones observed recently, could cause sputtering and atmosphere loss.

The interaction between the magnetic field of an iron cored earth-like moon and that of a gas giant would be complex and- interesting-.
But it might just protect any biosphere which forms-

and perhaps lifeforms could then transfer to the gas giant atmosphere, an environment which could support life, but probably not abiogenesis.

Ut
2004-Mar-26, 05:00 PM
And I think it depends on the radius of the moon's orbit, and how long it takes for tidal lock to occur. If the moon locks before life begins, then any tides would be caused by the star, and be much weaker. There'd be less mixing of the tidel pools, and, if the particular theory which I'm drawing from here is right (I'm not saying it is), life would take much longer to form. Hence, it would be more rare on these bodies.

Then, of course, there's the radiation factor. Depending on the gas giant, it could have radiation belts the strength of Jupiter's or higher. One would have to hope this moon doesn't pass through the radiation zone.

Let's not forget the increased chance of impact a body orbing such a planet would have. Big planets attract more passing debris than small ones. More over, we had the Moon to help lessen he kick here. It acted as a shield.

If the conditions were right, there's no reason why it wouldn't be possible. We still don't know those conditions, though...

jfribrg
2004-Mar-26, 05:24 PM
Hello.

English isn't my native language and I never even properly learned English, so don't be too harsh, if some formulations or spellings don't make sense.

How I wish I could understand a second language as well as Leiningen understand's English!!

SiriMurthy
2004-Mar-26, 06:02 PM
Welcome to the board, Leiningen.

The questions I would ask:

1. Was Moon necessary for the life to begin on Earth?
2. What role does Moon play on the evolution of "intelligent life" on Earth?
3. Could we have evolved even without Moon?

I have read some arguments that Moon stabilized Earth's rotation and the orbit around the Sun. Is that really the case or is it just a speculation? I mean, Mars has stabilized rotation and revolution even though it has only two tiny moons. Would the things have been different if Mars had a moon the size of our Moon?

iFire
2004-Mar-26, 06:49 PM
Hello.

English isn't my native language and I never even properly learned English, so don't be too harsh, if some formulations or spellings don't make sense.

How I wish I could understand a second language as well as Leiningen understand's English!!

He speaks English better than most of the people I know... and I'm American... that might be the problem though :-?

Anyway, I was kinda wondering, is it possible that if a Jovian planet to have a moon, with a moon to itself, similar to our Earth-moon system? Sorry if this sounds n00bish, but I am a 15 year old freshman whos just getting into astronomy.

daver
2004-Mar-26, 07:06 PM
Anyway, I was kinda wondering, is it possible that if a Jovian planet to have a moon, with a moon to itself, similar to our Earth-moon system? Sorry if this sounds n00bish, but I am a 15 year old freshman whos just getting into astronomy.

There was a thread a while back on whether moons could have moons; you might try looking for it. As I recall, the upshot was "probably not", or only for a short period of time--it's too easy for the moon to get perturbed out.

SiriMurthy
2004-Mar-26, 07:21 PM
...is it possible that if a Jovian planet to have a moon, with a moon to itself, similar to our Earth-moon system?

Interesting question. I doubt it though, unless a body revolves around one of the planets that is a part of a binary system?? If we can put an artificial satellite in an orbit around our Moon, can we really rule out a small natural body to orbit a moon? My belief is that eventually such a satellite of a moon will get knocked out of it's orbit. I will leave it to experts on this board to answer this question.

:roll: #-o

Leiningen
2004-Mar-30, 12:02 AM
Hello!

Finally I'm back! You guys wrote a lot of very interesting replies! Thank you for the informations, the compliments and the welcome-messages! :D
Do we already have some idea, how many Earth-sized moons could be circling a giant Jupiter? I'm not talking about a planet which is equal in size and mass to Jupiter. No, I'm rather talking about a planet with 12 or 15 times the mass of Jupiter. And what about the possible satellites of a brown dwarf? I guess we won't find Earth-sized moons circling a planet which is identical to our Jupiter, but how many big (really *big*) moons/satellites could be circling all these giant Jupiters and brown dwarfes? Is there some kind of established mathematical pattern which can be used to give a profound presumption regarding the number of possible big moons/satellites circling a giant Jupiter or brown dwarf, correlating with the mass of the assumed giant Jupiter or brown dwarf?
I hope this formulation made sense at all! :(

eburacum45
2004-Mar-30, 05:30 AM
I am not aware of the results of any simulations of the formation of moons around gas gaints; one restriction is that planets very near the star will not be able to have moons in stable orbits,

but in the comfort zone of a yellow dwarf moon orbits can be stable so there should be no problem with a habitable moon around a gas giant in the zone. Examples of gas giants in the habitable zone include 47 Ursa Majoris and Gamma Cephei.


Some informative links
http://www.extrasolar.net/planet.asp?PlanetID=16
http://www.extrasolar.net/planet.asp?PlanetID=235
http://www.ibiblio.org/astrobiology/index.php?page=planet09
http://www.nocturne.org/pipermail/worldbuilding/1999-January/002746.html


and a view of my imaginary world Anomie
more details here
http://www.orionsarm.com/worlds/Silence.html

http://www.eburacum45.5u.com/images/anomie_and_silence2.jpg

Taibak
2004-Mar-30, 03:45 PM
I suppose the other problem would be making sure that the moon is within the gas giant's 'habitable zone.' Like Eburacum45 said, you want the protection of the planet's magnetic field, but don't want to be in its Van Allen Belts. Like Ut said, tides are also an issue. I disagree that you need tide pools to create life, so being close enough to the planet to be tidally locked isn't necessarily a problem. The catch is that you don't want to be so close that tides are continually ripping the moon's crust apart, like with Io.

Kaptain K
2004-Mar-30, 05:17 PM
The extreme flexing of Io is not so much caused by the tides tides from Jupiter, as by the tidal interaction from the other three major moons.

ChesleyFan
2004-Mar-30, 06:19 PM
Having said that - supposing that this simply slows evolution down. Life arose very early on Earth, we now know that. If 'atmospheric life' is simply held back some, then who is to say there are not Jovian bacteria or archaeans (or equivalents)? I'd find it hard to buy into the idea of multicellular life, though...

On the other hand, there are some models of planetary formation showing that the gas giants formed much earlier than the rocky planets, giving Jovian life a jump-start on it's terrestrial counterparts.

Granted, were only talking some milions of years, though, so Jupitarians (or whatever you choose to call them) are probably still behind us...

kelly
2004-Mar-31, 07:06 AM
Anyone ever wonder why there are such huge Jupiter like planets so close to their star in the first place? Seems kinda unlike our system.. <Solar wind usually blows out light things such as hydrogen> So I think anything goes over there.. moons with moons? Sure! why not?? 8)

eburacum45
2004-Mar-31, 07:39 AM
Check out this thread for more information on that topic;
http://www.badastronomy.com/phpBB/viewtopic.php?t=12301

Brady Yoon
2004-Mar-31, 08:17 AM
The extreme flexing of Io is not so much caused by the tides tides from Jupiter, as by the tidal interaction from the other three major moons
Is this because the gravity of Jupiter has already tidally locked Io with Jupiter so the tidal forces are always the same in direction, but the other moons pull it in different directions? Can someon explain?

kelly
2004-Mar-31, 07:08 PM
Thank u for the link. I this is what I am planning to do in Graduate school. So I'm doing lots of research before hand, so I can form a good set of questions to think about to ask my supervisor. Its a super cool area of astronomy..

eburacum45
2004-Apr-01, 08:24 AM
Here is a very good summary of this subject;
http://skyandtelescope.com/resources/seti/article_255_1.asp

yorkshire_guy
2004-Apr-04, 06:45 PM
As far as the fact that many of the objects found in orbit of other stars are brown dwarfs, giant jupiters, and hot jupiters, I think we need to be a little careful in assuming that means they are the most common (I just heard a talk about this at the Cleveland Museum of Natural History). Given our present techniques and instruments for finding extra-solar planets, these are not only the easiest ones to find, but we do not presently have the ability to even see a jupiter-sized planet (with a jupiter orbit) around most other stars. You only can see what you have the ability to see. As the techniques have improved, we have found a bigger and bigger variety in size and orbits.

Hello Board .... I'm a newbie here too! I agree strongly with what Swift is saying above about not assuming the "Hot Jupiter" type planetary systems are the most common. The radial velocity method of detecting exo-planets is severely biased in favour of large objects orbiting close to the star. I may be wrong about this but I think it is also biased towards detecting planets in highly eccentric orbits. Thus the detection of solar-system type arrangements is not favourable. This doesn't mean we haven't detected planetary systems like our own - its just harder. For instance, we have found a Jupiter-mass planet orbiting the Sun-type star Gleise 777A in a circular orbit at 3.6AU with a period of 7 years. This is very like our system and would definitely allow an Earth-like planet orbiting within the habitable zone. My hunch is that systems like our own are probably the most common around solitary stars. As far as life goes, I suspect there are lots of wierd niches in the universe where some kind of short-term microbial life is able to exist - perhaps including moons of Hot Jupiters. However, a planet like the Earth (with or without the Moon - although the Moon certainly helped!) probably offers the best chance of the sort of long-term stable environment which would allow more advanced life to develop. When you look at the Earth, almost everything seems to be right. The Sun is the right type of star - small enough to be long-lived (unlike Blue-White stars), but massive enough to push its habitable zone out to a safe distance from its solar actively (unlike Red Dwarf stars). The Earth is large enough to hold onto its atmosphere - unlike Mars. However, if it was much more massive it may well be too geologically active for stable life, as well as having too thick an atmosphere. The Earth has a liquid iron core which generates a magnetosphere to protect us from solar radiation and cosmic rays - unlike Mars. The Earth is rotating quick enough to avoid big variations in temperature between night and day sides (probably a legacy of the collision which formed the Moon). The existence of Jupiter at 5AU protects us from the worst of the comets hurtling in from the Oort cloud. We're pretty lucky come to think of it!