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Scientists confirm there is an ocean of water in Jupiter's moon Ganymede.

Dinwar said:
Makes getting there a tad difficult, but ice is more forgiving than, say, basalt.
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Actually, I'm not so sure. Ice becomes plastic under high pressure. Of course, the gravity is lower....

Hans
 
Puppycow said:
:boggled:

Have we actually drilled down that far and taken samples?

What does this "life" consist of?
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http://en.wikipedia.org/wiki/Lithophile

I just realized I messed up--it's the crust, not the mantle (blame stress; I'm waiting on a phone call amounting to "honey, meet me at the hospital and bring cigars"). I thought "lithosphere" and wrote "mantle". But the logic is that there's more room under the surface than on it, so even relatively sparse life in the crust would dominate biomass.

MRC_Hans said:
Actually, I'm not so sure. Ice becomes plastic under high pressure.
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So can basalt, but your point is very good. The main reason we don't have super-deep holes is because the pressure keeps deforming our drill bits. Add increased plasticity and things can get ugly. My favorite drill rigs (DPT-equiped track-mounted GeoProbes) won't cut it!
 
nvidiot said:
Those aren't plants. And we're talking about basic life not multicellular complicated life that arose relatively recently on Earth.

Any sufficiently large energy gradient, like a temperature difference between higher and lower levels, can be used to extract useful energy for life.
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If 'basic' life can emerge in those oceans, then multicellular life could emerge also. There is no known barrier between unicellular and multicellular life. Multicellular life on earth evolved from unicellular life on earth.

The conditional probability may be small. Single celled life on earth appeared in the fossil record maybe 4 BYA. There is some controversy whether these are real fossils or not. However, let us say that there were prokaryotes (i.e., bacteria) that emerged about 4 BYA. The earth itself seems to have cooled down sufficient to permit liquid water about 4.3 BYA. So that the emergence of bacteria may have took only 0.3 BY.

Multicellular life seems to have appeared less than 1 BYA. There may have been some colonial bacteria about 1 BYA, but colonial isn't quite multicellular. The first animals in the fossil record appear about 0.8 BYA. There is no evidence of multicellular plants until about 0.4 BYA. Therefore, it probably took 3.2 BY for truly multicellular life, animals, to evolve.

So it appears that evolution took far longer to develop the first animals then It took to develop the first bacteria. the emergence of bacteria took about 10% the total age of the earth, and the emergence of animals took about 80% the total age of the earth.

This doesn't mean it is impossible for multicellular life to emerge on one of the outer planet moons. Animals and plants per se are improbable on other planets, even if there is unicellular life. However, there could be multicellular analogues to animals and plants out there.

The plant analogues would have to rely on chemosynthesis, of course. No sun. However, there is no reason to think this is impossible. The animals that live in the deep water vents show how multicellular life can live off chemotrophs. So maybe there are 'animaloids' in the oceans on the gas giant moons. If there is life at all, then it could be anything.

Maybe the Star Spawn of Cthulu?
 
Darwin123 said:
If 'basic' life can emerge in those oceans, then multicellular life could emerge also. There is no known barrier between unicellular and multicellular life. Multicellular life on earth evolved from unicellular life on earth.
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I've highlighted the problematic word. There has to be SOME explanation for the multi-billion year gap between "life arose" and multicelluar life. A barrier between uni- and multicellularity is the most likely explanation.

The more significant issue, far as I'm concerned, is the issue of looking for "plants" or "animals" on other planets. Those are things that arose on THIS planet; there's no reason to expect them on other planets.
 
Dinwar said:
I've highlighted the problematic word. There has to be SOME explanation for the multi-billion year gap between "life arose" and multicelluar life. A barrier between uni- and multicellularity is the most likely explanation.
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Or it could be that the oceans had changed enough to allow it. The cyano-bacteria was busy polluting the planet with oxygen and it may have been the tipping point that let multicellular life be successful. I suspect the first MC life predated on the single cell critters.
 
Given an ocean and a weak source of energy which might generate some pockets with an adequate temperature, I agree life can emerge some time before the Big Crunch.

As it was suggested, multicellular life needed eons to evolve from the single coordination available in colonies, multi-nuclei cells, and primitive symbiotic steps to the awe of the specialization in a 480-cell I-cannot-remember-its-name. A high step for evolution, with almost none of its "keeping what works" and galaxies of its "getting rid of what doesn't".

Oversimplifying it, don't forget the lapse between life in Earth developing lignin-making beings and lignin-eating beings.
 
Darwin123 said:
This doesn't mean it is impossible for multicellular life to emerge on one of the outer planet moons. Animals and plants per se are improbable on other planets, even if there is unicellular life. However, there could be multicellular analogues to animals and plants out there.

The plant analogues would have to rely on chemosynthesis, of course. No sun. However, there is no reason to think this is impossible. The animals that live in the deep water vents show how multicellular life can live off chemotrophs.
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I agree with everything in your post. If there really is plant/animal life in the solar system outside of earth, these moons would be my bet.


Darwin said:
So maybe there are 'animaloids' in the oceans on the gas giant moons. If there is life at all, then it could be anything.

Maybe the Star Spawn of Cthulu?
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Not far off, in my opinion.
 
aleCcowaN said:
As it was suggested, multicellular life needed eons to evolve from the single coordination available in colonies, multi-nuclei cells, and primitive symbiotic steps to the awe of the specialization in a 480-cell I-cannot-remember-its-name.
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Did it take that long?

It's a serious question. To say "It took X years to evolve Y", the assumption is that that time period covers start to finish. However, I know of no line of evidence suggesting that unicellular organisms on Earth were evolving towards multicellularity. An equally valid explanation for the data is that for 3 billion years or so they evolved in different directions.

It's very likely that some event precipitated the leap from unicellular to multicellular organisms. The introduction of some new nutrient, the randm formulation of some novel protein, an increase or decrease in volcanic activity--events of that nature have been proposed for other biological leaps. For examle, the Cambrian Explosion is thought by some to be due to increased availability of nutrients used to make skeletons. The field of study is biogeochemistry, for those interested. If some event precipitated the rise of multicellularity, it's a serious error to use the time during which life on Earth was unicellular as an estimate for the odds of finding multicellular life. What we should be looking at is (again, assuming some event triggered the shift) the odds of that event, or similar, happening.
 
Dinwar said:
Why?
Again, the majority of Earth's biomass is thought to be in the mantle, far from any photosynthetic influence. If life on Ganymede arose near volcanic vents (a hypothesized mechanism for life on Earth arising, and a plausible one for life anywhere to arise) a thick crust of ice would be essentially irrelevant to them, if not beneficial (the radiation environment around gas giants isn't exactly healthy for known or hypothesized life forms).

Makes getting there a tad difficult, but ice is more forgiving than, say, basalt.
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Asked and answered, your honor.
 
Dinwar said:
Did it take that long?
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It depends on what you're focusing. In the case of a bot trying to break a password by a brute-force attack, I consider the lapse to span from the first second the bot started its attack to the very second the password is broken. I don't consider the span to be the last try that breaks the password. And no, I don't consider evolution to have being looking for multicellularism and finally finding it. In the context of speculating about life in Ganymede (without falling for the fantasies of our fellow forum member Kathie Bondar), those eons are most likely necessary there to have a chance of developing complex life. The environment there doesn't promise a volume of activity and events together with a context showing enough stability yet enough change, for us to expect an evolutional speed faster than Earth's.

About the rest of your post, it seems to lump external influences -like volcanoes or nutrients- with not well defined internal changes -a new protein- as a structural change. Of course, developing the biochemical paths that allow cell differentiation requires a lot of useful proteins to be "created" by random mutations. But it's enough to say that the structural changes from single-cell to multi-cell organisms were internal and them to be tried against a changing environment wasn't any surprise.

Like any innovation, multi-cellular organisms required a set of changes to be achieved together in their "inner workings". While getting there, partial changes had to be kept without compromising the survival of the individual organisms. So, like the brute-force robotic attack, eons passed while, yes, what can be regarded as trying in many directions, and at some point the "password was broken".

Multicellularism is arguably the most important innovation in the history of life on Earth. Even meiosis, with its final achievement, sexual reproduction, is less impressive from a cold biological standpoint.

What I am willing to concede is that the enormous set of changes necessary to generate the structural leap into multi-cellularism is probably easier to achieve in a context of pretty stable environmental conditions, rather than the "all the bets are off" context of any sudden change like a volcano or a new nutrient. And in that matter Ganymede might have some advantage.
 
aleCcowaN said:
(much snipped)

Multicellularism is arguably the most important innovation in the history of life on Earth. Even meiosis, with its final achievement, sexual reproduction, is less impressive from a cold biological standpoint.
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Is there some distinguishing feature you have in mind which distinguishes from commensalism, colony forming, or other ecologies with variation in cell types?

Is it because the needed variation is contained in a single genome with variable expression, instead of cell-specific genomes?
 
marplots said:
Is there some distinguishing feature you have in mind which distinguishes from commensalism, colony forming, or other ecologies with variation in cell types?

Is it because the needed variation is contained in a single genome with variable expression, instead of cell-specific genomes?
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We may think also in lichens' symbiotic relationships as an example of what might have happened in archaic stages of life. However the photobiont doesn't contain genetic information to make chitin and the mycobiont doesn't contain genetic information to make chlorophyll. But still lichens can reproduce and thrive.

Imagine the intermediate stages for that to develop by natural selection into a single haploid cell that can grow into a muti-cellular orchestra to produce, if it survives the process, another single haploid cell that will develop in the exact same way.
 
aleCcowaN said:
About the rest of your post, it seems to lump external influences -like volcanoes or nutrients- with not well defined internal changes -a new protein- as a structural change.
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My point is, sudden changes have occurred in the past--I specifically mentioned the Cambrian Explosion and the biogeochemical papers because they illustrate that. You're right, it would require a series of adaptations, but I have strong doubts that it took 3+ billion years. And as no one has presented any evidence that it DID take that long, it seems premature to use it as a means of estimating odds.

By the way, for differentiation among cells, I suggest looking into bryozoans. There are colonies of those critters that have adapted to the point where each organism has its own function, analogous to cellular differentiation in multicellular organisms.
 
Dinwar said:
By the way, for differentiation among cells, I suggest looking into bryozoans.
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But, zoöns are multi-cellular, and they had to be that way first. As for cooperation and specialization -including reproduction-, a bee hive is a good example, but it's all built departing form a genome that already knew how to do the trick for an individual.
 
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