have they found anything?

There is evidence that Mars once had vast amounts of water. There may still be water deep underground. Titan has water under its ice mantle. I don't think there's a shortage of water in the solar system. Comets are mainly ice. Until Earth like planets are discovered in the galaxy, it may be a very scarce resource. Certainly, if carbon as well as water is discovered, it bodes well for finding life in the cosmos.
 
amb said:
There is evidence that Mars once had vast amounts of water. There may still be water deep underground. Titan has water under its ice mantle. I don't think there's a shortage of water in the solar system.
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What do you mean by "shortage"? That's more an economic term that relies on some idea of need or demand.

I'm just pointing out that liquid water exists in relatively few places in the solar system. Also, we have studied the solar system at least to some extent (way more than we have any extra solar planet!), and have turned up no evidence of ubiquitous microbial life.

Comets are mainly ice.
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Not liquid water, though. And we have also studied comets and even taken samples. So far no microbial life has been found. I'm certainly not claiming it's impossible for microbial life to be transported on comets or meteorites, but the claim that microbial life is ubiquitous in our solar system is known to be false.
 
Well then, my argument grows another leg doesn't it? If microbial life is scarce, imagine animal life's scarcity.

Seriously though, we won't know if Mars doesn't posses microbial life until we actually search for it deep underground. So far, only the surface has been tested, and from what I read, that results weren't 100% accurate. There are some who believe that the Viking probes, especially Gil Levin who designed the experiments. according to him Viking had likely detected life on Mars. But he and A Joe Miller, a cell biologist at the Uni of Southern California who was also part of the Viking team are 90% certain in that conclusion. All others thought the results were negative.
 
amb said:
Well then, my argument grows another leg doesn't it? If microbial life is scarce, imagine animal life's scarcity.
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No. Your argument is that microbial life is common--even ubiquitous in the solar system. The fact that it's not so undermines your position.

Also, you're playing with undefined words--like scarce, rare and common. I think everyone in this conversation agrees that stuff in the galaxy and universe is so spread out in space and time that we're not likely ever to encounter another civilization.

However, you're alone in asserting that those other civilizations don't exist. Or that they number fewer than a dozen in the universe--a number you suggested some time ago in this thread.

By the way, if they number maybe a dozen per galaxy, you realize that means they number in the billions in the universe? Again, there's scarce, and then there's scarce.
 
amb said:
Seriously though, we won't know if Mars doesn't posses microbial life until we actually search for it deep underground. So far, only the surface has been tested, and from what I read, that results weren't 100% accurate. There are some who believe that the Viking probes, especially Gil Levin who designed the experiments. according to him Viking had likely detected life on Mars. But he and A Joe Miller, a cell biologist at the Uni of Southern California who was also part of the Viking team are 90% certain in that conclusion. All others thought the results were negative.
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I agree with you here. The methane plumes are pretty strong evidence too. And soon we'll find out (from the ratio of deuterium in the water vapor in said methane) whether they were of abiotic origin or not.

So you realize it's been nearly 35 years since Viking landed on Mars to conduct the first test for life there, and we still don't know for sure. And Mars is right next door, in astronomical terms.

ETA: The problem with the Viking tests was that even though one of them came out positive, scientists realized that there were abiotic reactions that could have caused that result. So the result was inconclusive. And we realized that in the absence of obvious and recognizable life forms or off balance planetary homeostasis, it's a lot more difficult to discern for sure whether or not there is life.

Yet you're ready to make pronouncements on the likelihood of life on extrasolar planets throughout the galaxy and beyond!
 
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JoeTheJuggler said:
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I'm just pointing out that liquid water exists in relatively few places in the solar system. Also, we have studied the solar system at least to some extent (way more than we have any extra solar planet!), and have turned up no evidence of ubiquitous microbial life.

Not liquid water, though. And we have also studied comets and even taken samples. So far no microbial life has been found. I'm certainly not claiming it's impossible for microbial life to be transported on comets or meteorites, but the claim that microbial life is ubiquitous in our solar system is known to be false.
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Liquid water may not be an essential requirement for life:
http://www3.interscience.wiley.com/journal/118504021/abstract
http://www.sciencedaily.com/releases/2009/10/091001101333.htm

Ubiquitous is almost always used in some form of hyperbole, so exactly what Amb meant isn't completely clear with regard to his claim about the ubiquitous life. The possibility that microbial life in the solar system might be fairly common outside of the Earth hasn't been ruled out.

When life can be found in deep mines, ocean vents, glaciers and ponds with various forms of extreme chemistry and temperature I think the possibility of microbial life in the solar system beyond the Earth is looking pretty good.
 
Fair enough. But the best description of our current knowledge on ET microbial life in the solar system is, "We don't know."

Since we don't know the answer to this question in our own solar system, it is premature to draw conclusions about life or complex life in the galaxy or universe at large based on the absence of evidence.

I think we're going to learn that the line between not-life and life will become less and less clear. As I showed in the stuff about abiogenesis, you can argue that competition (and natural selection) begins even with the simplest self-replicating molecules.

Even with Mars, I suspect we won't have a banner-headline making announcment that we're certain life exists or existed (or not) on Mars. Instead, we'll have a gradual accumulation of stronger and stronger evidence one way or the other. At some point, we'll have a pretty certain answer.

I hope I'm wrong and we discover something sensational, like a relatively complex biosphere located underground or some such.
 
What about the multiverse hypothesis? All other, or most universes are sterile except for this one.
The possibilities are endless and infinite. If life as described by such physicists as Paul Davies is such an unlikely event as to be less than zero, the multiverse makes sense.
There may be an infinite number of universes, no one knows the answer, YET. At best we can speculate.
 
LarianLeQuella said:
Even if that was relevant to this discussion, where do you get the assertion that " All other, or most universes are sterile except for this one." I take it you have not read Victor Stenger's work? I copied some of it here for reference: http://larianlequella.com/2008/10/is-universe-fine-tuned-for-us.shtml
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Thank you for that link. Very interesting reading. Stenger is one of my favourite physicists.

Here is something else you may find interesting.

http://radio.seti.org/episodes/Formula_One_The_Drake_Equation
 
amb said:
Stenger is one of my favourite physicists.
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My atheist group just hosted him for a lecture here in town (on The New Atheism). He said something that was intriguing, and sort of on topic to this discussion. He said that despite all the sci-fi and space opera, we really are pretty much stuck with the Earth for as long as we survive.

It's a point where I think Stephen Hawking is wrong.
 
Of course that makes sense. By just leaving the Earth's atmosphere man needs a life support system to survive. No other planet in the universe can have the exact same conditions as the Earth. Even a close almost clone of Earth would kill a man coming into contact with its atmosphere. Were are attached to the Earth by an invisible umbilical chord so to speak.
 
amb said:
Of course that makes sense. By just leaving the Earth's atmosphere man needs a life support system to survive. No other planet in the universe can have the exact same conditions as the Earth. Even a close almost clone of Earth would kill a man coming into contact with its atmosphere. Were are attached to the Earth by an invisible umbilical chord so to speak.
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Not to mention the incredible expense in time and energy to transport any significant number of colonists on what would probably be a decades-long (if not generations long) flight where we would need to carry absolutely everything needed to sustain life the entire time. (That's even if you consider that we might find a very Earth-like planet within 100 light years or so.)

Look at what a huge economic expense the Apollo Moon landing was, and that was only to get two guys to the surface for a relatively short time.

Looks like we really do need to take care of the planet as if it were the only one that could ever support us.
 
amb said:
Of course that makes sense. By just leaving the Earth's atmosphere man needs a life support system to survive. No other planet in the universe can have the exact same conditions as the Earth. Even a close almost clone of Earth would kill a man coming into contact with its atmosphere. Were are attached to the Earth by an invisible umbilical chord so to speak.
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Once again, amb, I agree with you in the main but you have to watch out for that absolutism. "No other planet", when there have to be billions of them? Man here has experimented with extended breathing of a large range of gas mixtures and pressures here on earth; it seems that as long as there is sufficient oxygen (yes, that's likely a rarity in itself) and no poisons, a range of possible atmospheres are usable:

Oxygen-Nitrogen
Oxygen-inert (helium, argon, xenon, neon)
pure oxygen
oxygen partial pressure from .16 to 1.5 bars (in mixtures with truly inert gasses, the total immersed pressure can rise much higher).

And that's before we consider possible biological and/or mechanical symbiotes/prostheses. As Joe says, we just don't know enough yet.
 
amb said:
As Joe says, even one hundred light years to a suitable planet would take us centuries to get there, even if we can reach the astronomical speed of 10% the speed of light.

That's before biological questions even arise.
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But what's wrong with spending centuries on a voyage? I imagine our descendants will be very different from us, different enough that our ideas of what the following mean may differ greatly from there's:

- a long time
- far away
- expensive
- etc. :P

I also find it very likely that over the next few hundred years we will find ways to make our way in space, on astronomical bodies much different from the earth: ie. comets and asteroids, etc. Which means we may move in much shorter steps first out into the oort cloud, and then from there to the far off "oort clouds" of other stars.
Even if earth like planets are not common, comets are likely to be.

Will we be able to live on them without outside supplies? Personally, I think so. There are all engineering problems, the resources are there, and humans are very good at solving engineering problems. As shadron said, this may be accompanied by major changes in our biology (so major, perhaps, that thousands of years from now we won't know our descendants at all).

Of course this is very speculative, but its just what I happen to find likely, as we have all been saying, no one really knows.
 
Roboramma said:
But what's wrong with spending centuries on a voyage? I imagine our descendants will be very different from us, different enough that our ideas of what the following mean may differ greatly from there's:

- a long time
- far away
- expensive
- etc. :P
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Yes. I'm certainly not claiming that it's impossible for us ever to colonize other planets, but I disagree with Hawkings, for example, when he says that it's our destiny. That lightspeed limit doesn't seem likely to go away or be circumvented.

Travelling to another planet is very unlike our ancestors of 500 or so years ago crossing the Atlantic. They did not have to carry along every bit of oxygen, food and fuel they would need.

At any rate, my point is, that colonizing other worlds will never be a solution to the problems we have here (population, global warming, pollution, depletion of resources). There is no way getting a significant number of us off the planet can ever be less costly than solving the problems here. (And many of these problems wouldn't be solved but only postponed even if we could move a substantial portion of the population elsewhere.)

I think that's the way Stenger made that pronouncement. We really are stuck with the Earth as our home.
 
Oh, I think that's all true: the problems of interstellar travel, while I think they are soluble, are orders of magnitude greater than, for instance, global warming.
 
Roboramma said:
Oh, I think that's all true: the problems of interstellar travel, while I think they are soluble, are orders of magnitude greater than, for instance, global warming.
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My suspicion is that they are not solvable or if they are solvable civilizations are destroyed before there is much interstellar travel.

1. Fermi's paradox kind of makes sense to me here. If interstellar is possible where are the little green men? OK, it's not a proof but there's been a lot of time for the little green men to build their space ships and visit us, so far they've left no evidence that they were here but maybe they've been here and the evidence was destroyed I suppose

2. Even if limited interstellar space was possible I'm not sure that a civilization is going to put the resources into blasting a very few people into the great unknown for perhaps multiple generations.

3. Long term exposure to space radiation looks like it might be a difficult problem to solve. I could envision some giant space ship surrounded by a massive water and lead barrier. That might help with the pesky problem of any tiny particles hitting the ship with massive kinetic energy and blowing huge holes in it. But the need for thick heavy radiation shielding will substantially increase the resources required for this venture and that already looks like a major stumbling block.

4. My guess is that at least some of amb's pessimism is well placed and the goldilocks type planets are uncommon and there just may not be one near enough to us to get to in even a few generations.

Still as I wrote this I was kind of amazed by all the things I don't know about the future and the unpredictable ways things might go. Maybe people end up with greatly lengthened lives and traveling through space for a few hundred years seems like an ok thing to do, Maybe mass launchers turn out to be pretty easy to do and getting big chunks of stuff into space isn't that big a deal. Maybe the giant space based planet hunting telescopes get built and people learn enough about a target planet some place that finding a planet with conditions adequate for human life becomes possible.

Or maybe we just kill ourselves before any of this stuff becomes possible in some massive nuclear exchange.

I'm old enough that I don't expect to have gained much insight as to the viability of any of the technology needed for interstellar space before I breath my last breath. Maybe some of the youngin's in this forum might get a glimmer of insight in their lifetimes, but I'm pretty sure none of them will live to see somebody blast off for another star in their lifetimes either.
 
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