for Planets with Life.

From Astrobiology.com:

Increasing the lifespan of our biosphere--from roughly 1 billion to 2.3 billion years--has intriguing implications for the search for life elsewhere in the universe. The length of the existence of advanced life is a variable in the Drake equation, astronomer Frank Drake's famous formula for estimating the number of intelligent extraterrestrial civilizations in the galaxy. Doubling the duration of Earth's biosphere effectively doubles the odds that intelligent life will be found elsewhere in the galaxy.

"It didn't take very long to produce life on the planet, but it takes a very long time to develop advanced life," says Yung. On Earth, this process took four billion years. "Adding an additional billion years gives us more time to develop, and more time to encounter advanced civilizations, whose own existence might be prolonged by this mechanism. It gives us a chance to meet.

So, where does your calculation of Drake's equation leave you now?

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"Where the telescope ends, the microscope begins. Which of the two has the greater view?" - Hugo

"Men occasionally stumble over the truth, but most pick themselves up and hurry off as if nothing had happened." - Churchill

Interesting.

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"Science is physics and astronomy." -Me
"There is absolutely no law in physics that prevents time travel." -Dr. Michio Kaku

We cannot ascertain the values of some of the variables involved with any degree of precision, therefore we are "left" at the same "place" we were before.

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"The facts gentlemen, and nothing but the facts, for careful eyes are narrowly watching." Isaac Asimov

Yet another variable which means nothing.

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"Where the telescope ends, the microscope begins. Which of the two has the greater view?" - Hugo

"Men occasionally stumble over the truth, but most pick themselves up and hurry off as if nothing had happened." - Churchill

To paraphrase: Exponential growth is not possible in the galaxy for a star faring race because their home planet has finite resources and energy. Huh? Am I missing something about that apparently flawed analogy?

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Always challenge the assumptions

No, it doesn't tell us anything new. For that matter, the "exponential growth" issue is an old one, often discussed in one form or another.

Quoting from the article:

That's nonsense. It's unclear exactly what Fermi said (there are many claims), but I absolutely do not recall any implication that interstellar growth would be exponential.

Well, duh. ANY finite limits will eventually stop exponential expansion. Exponential expansion throughout the universe would be stopped by, among other things, the speed of light.

There might be interstellar civilizations. There might not be. This doesn't tell us whether there would be or not. It isn't useful.

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Disclaimer: Avatar is not an official NASA image and does not imply any specific interplanetary or interstellar capability.

The Leif Ericson Cruiser

I think that Physorg.com have missed the point of this paper.
here it is;
http://arxiv.org/ftp/arxiv/papers/0906/0906.0568.pdf

They point out that exponential growth must fail at some point, limited as it is by resources and by the speed of light. They then make the leap of logic that any intelligent civilisation is unlikely to choose exponential expansion as a strategy because it is unsustainable; they call this the 'Sustainability Solution'. They say that the 'Sustainability Solution' suggests that some previous ET civilisations might have tried expanding exponentially, then collapsed and vanished. We might find relics of their former civilisation out there if we explore far enough.

They do acknowledge that a civilisation might expand exponentially for a while, then switch to sustainability when the galaxy is fully colonised; but they simply dismiss this option by saying that we don't see them, so none have managed this trick. They don't really explain how an interstellar civilisation can comprehensively collapse in a short time, especially as parts of the civilisation would be so far from each other that they would be almost completely causally independent of each other.

Another solution to Fermi's Paradox to add to the list, I think. Not necessarily the right one by any means.

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Thanks, eburacum, for digging up that paper and your thoughts.
I disagree with their Sustainability Solution too as it would have to apply to every ETi in the universe (omniverse?).

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"Where the telescope ends, the microscope begins. Which of the two has the greater view?" - Hugo

"Men occasionally stumble over the truth, but most pick themselves up and hurry off as if nothing had happened." - Churchill

It's all really guesswork. They do not even know how life originated on earth yet.

I got stung by a bee for the first time and I was impressed by how much feeling of fire that venom causes. It impresses me what complex molecules exist in life forms. So getting life going and getting complex creatures ain't no small thing.

Only the SETI experiments, and the solar system probes will ever show if life is in the universe. And even if it is, we'll be lucky to find it.

Guesswork indeed; we don't even know if Life originated on Earth, let alone how.
While the SETI is faced with exceedingly low odds I suspect probes and more science on and around bodies in our own solar system will reveal microbial life; luck on one hand, on purpose the other.

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"Where the telescope ends, the microscope begins. Which of the two has the greater view?" - Hugo

"Men occasionally stumble over the truth, but most pick themselves up and hurry off as if nothing had happened." - Churchill

Your panspermia nonsense is getting very old. If you have evidence...credible evidence that life on Earth originated some place other than Earth then present that evidence...otherwise your wild speculations are just that, and have no place on a science board.

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"The facts gentlemen, and nothing but the facts, for careful eyes are narrowly watching." Isaac Asimov

To be fair, the idea of local panspermia within a planetary system is an option which remains open. Life in our Solar System may have originated on Mars, or Europa, or Ceres, or any one of a number of objects, and passed to Earth inside ejected meteors. We might even be able to determine if this is the case by examining these worlds in detail - they might have biospheres, or fossils, which are related to the life on our world. However the possibility of local panspermia does not imply interstellar panspermia, nor does it imply that life is widespread in the universe.

Even if every suitable object in the Solar System has at some time become infected by interplanetary microbes, we may still be the only planetary system in the Universe that has developed life.

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I'm a reasonable person. I have no difficulities being "fair" once sufficient evidence is presented.

Speculation...given the evidence available right now, the "default" or mundane "answer" is that life on Earth originated on Earth.

I welcome any evidence to "counter" that, however I see no reason to "allow" for panspermia when there is absolutely no evidence for it.

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"The facts gentlemen, and nothing but the facts, for careful eyes are narrowly watching." Isaac Asimov

The idea of local panspermia is probably mostly useful as an explanation for data that is not yet available. If, for instance, we find traces of life on Mars (or Europa or Ceres, or elsewhere) that turns out to share a common ancestor with life on Earth, that makes the possibility of local panspermia much more likely.
Additionally, such a discovery would make an origin somewhere other than Earth (but within the Solar System) a more likely option, since (of all the bodies in the Solar System where life might have originated) the Earth has the highest escape velocity, so is least likely to be the origin of life-bearing rocks.

But, as I've said, this is all speculation, intended to interpret data which is not available yet. Why is it important? Well, it may be the case that our probes do in fact find evidence of life in our Solar System (outside of the Earth) in the relatively near future. The possibility of local panspermia can be used to demonstrate that such a discovery need not have any implications for life outside our Solar System; we may have several planets infected with life around our Sun, but despite this possibility, there may be no other life anywhere else in the observable Universe.

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New Orion's Arm Site . The Starlark . Against a Diamond Sky (OA Novella Collection) . OA Flickr set

Not to derail the debate, but is there another title you might use for local panspermia? If it were across the galaxy, it might be pangalactospermia (maybe?); is there any sort of prefix meaning widely solar systemic or related to inner planetary bodies?

The concept is sometimes called 'lithopanspermia' or 'ballistic panspermia'
http://www.daviddarling.info/encyclo...lithopans.html
http://www.daviddarling.info/encyclo.../ballpans.html

The good thing about the concept is that calculations can, and have, been made to determine how likely such transfers are. Between a low-gravity object (such as Mars) and a high-gravity object (such as the Earth) the odds are quite good, over billions of years; the other way round, not quite so good.

The odds of translocation between stars are very low indeed, except when stars are relatively close together in their birth clusters. However the odds of life emerging in a young cluster are probably quite low, but not zero: see.
http://www.spaceref.com/news/viewsr.html?pid=16536

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From the "Martian meteorite", we have an actual example for that "transfer"...but so far it is the transfer of material, not microbial life.

So even though the "mechansm" is in place, without actual detection of life, the question remains speculative.

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"The facts gentlemen, and nothing but the facts, for careful eyes are narrowly watching." Isaac Asimov

Quite true. I would not be at all surprised if this mechanism has never happened, at least not in this solar system.

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Rubbish.
Questions surrounding the origin of life, whether on Earth or no, have every place on a science board.
I didn't claim evidence for exogenesis, I said we don't know if Life originated on Earth. Do you? Or is that too, an assumption, speculation? Yes, it may seem the simplest assumption but it's assumption none the less. Bottom line: we don't know.
Suggesting panspermia hypotheses as "wild speculations" goes beyond mere skepticism.

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"Where the telescope ends, the microscope begins. Which of the two has the greater view?" - Hugo

"Men occasionally stumble over the truth, but most pick themselves up and hurry off as if nothing had happened." - Churchill

Wouldn't this be an extreme violation of Copernican principle?

To me, the simplest and most logical assumption is "nothing special here; similar ingredients in similar environments gives similar results."

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"Where the telescope ends, the microscope begins. Which of the two has the greater view?" - Hugo

"Men occasionally stumble over the truth, but most pick themselves up and hurry off as if nothing had happened." - Churchill

Questions are fine, but when speculation concerning origin of life goes to ridiculous extremes, it might as well be posted on GLP.

You say you're not making a claim, but then you say that you don't know where life on Earth originated....which is in itself a claim.

The "default" answer to the question is that Earth life originated on Earth. Anything else is speculation...simple as that.

Now if you have evidence that life here originated elsewhere, then present it. But then you say you don't have evidence...meaning you are speculating.

Without evidence to the contrary, we do know, you just don't want to accept the "mundane" explanation as it is counter to your "pet" ideas.

Hogwash....(gotta thank Jay for that one..I really like it. )

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"The facts gentlemen, and nothing but the facts, for careful eyes are narrowly watching." Isaac Asimov

This is why I'd been simply ignoring you ...

I don't find ridiculous extremes in panspermia hypotheses, do you?

By this, you're claiming we do know Life originated on Earth.
I disagree, where's your evidence?

I say we don't; no claim, just intellectual honesty.
True skepticism.

Rubbish.
Life's ingredients are more abundant off planet than on. The mechanisms and physical processes everywhere. Life appeared, already highly complex with cell walls and DNA as soon as Earth cooled; Begs questions which lead us off planet.

Curiously, every example of Life we know comes from other Life, yet we assume Life came from nonLife, on Earth.


We don't know.

I accept your mundane assumption but not your conclusion.
We do not know.

If you're claiming we know Life originated on Earth, please present your evidence.

Hogwash.

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"Where the telescope ends, the microscope begins. Which of the two has the greater view?" - Hugo

"Men occasionally stumble over the truth, but most pick themselves up and hurry off as if nothing had happened." - Churchill

This would seem to be a seperate idea from panspermia. In panspermia, life is transporting between the stars, we provide many evidences and explanations as why this is highly unlikely. Beyong this is the idea of lifes ingredient in space. this is much more mundane and we will all agree; most complex atoms form in stars, they are available for simple chemistry in pre-solar nebulae, and can be incorporated in proto-planets - they are the available for the further evolution into life in the hot wet pressure cooker of a young planet. But what you say above does not follow.

Given an understanding of the devastatingly ubiquitous role of contingency, and the dependence on initial conditions (eg; the planet), that is apparent in the history of life that we do know, that similar outcomes of life will result from similar ingredients is highly unlikely. The only way that would be possible is for a continuous record of the information bearing part of life (the DNA for example) to be transmitted which would indeed require panspermia, but for which there is no positive evidence, some negative evidence, and plenty of arguments against.

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plenty of woo, at the hotel hoagaland...

Panspermia is literally "everywhere seeds."
Are not the ingredients, complex organic material, the "seeds" if you will, of life as we know it observed everywhere?
I've read this referred to as pseudopanspermia as it doesn't involve the transport but I don't think it's a separate idea.

Consensus seems to be that microbial life, at least, will be ubiquitous, even among rare earthers.
Ballistic- or lithopanspermia too, seem generally agreed upon as more plausible than previously believed.
Some meteorites are older than our solar system, proving they came from interstellar space while recent estimates suggested their transit as little as 3 million years.
Can bacterial spores or microbes lay dormant or even survive such rigors as interstellar travel?
We don't think so, but we don't know.

Again, even rare earthers like Ward and Brownlee suggest microbial life will be found to be ubiquitous, even while their "rare earth" is largely built on contigency arguments.

Whatever the case, for me, the simplest assumption is nothing special here.

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"Where the telescope ends, the microscope begins. Which of the two has the greater view?" - Hugo

"Men occasionally stumble over the truth, but most pick themselves up and hurry off as if nothing had happened." - Churchill

Nice "attempt" at shifting the burden of proof...you ask this "as if" it somehow requires extraordinary evidence to demonstrate validity. It does not. The fact that life can be found everywhere on Earth is the default answer to the question of origin of life.

The evidence for life originating on Earth is all around you, yet you have chosen to deny it in favor of an unproven idea with no evidence to support it. Since you don't base your opinion on evidence, just what do you base your opinion on??

If the answer to that question would cause you to break board rules, I'll understand if you don't answer.

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"The facts gentlemen, and nothing but the facts, for careful eyes are narrowly watching." Isaac Asimov

RAF you fail to acknowledge that Life originating on Earth is also an assumption; we do not know this.

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"Where the telescope ends, the microscope begins. Which of the two has the greater view?" - Hugo

"Men occasionally stumble over the truth, but most pick themselves up and hurry off as if nothing had happened." - Churchill

Which is the more reasonable assumption?...that life originated here, where we actually have evidence of life, or elsewhere, where we have no evidence of life at all.

One or the other, A.DIM....which is it?

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"The facts gentlemen, and nothing but the facts, for careful eyes are narrowly watching." Isaac Asimov

I answered in #19: "Yes, it may seem the simplest assumption but it's assumption none the less. Bottom line: we don't know."


Answer me this: How is it any more reasonable that while there is no evidence for Life from nonLife, and every example of Life on Earth comes from other Life, it's less extraordinary to assume it did?

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"Where the telescope ends, the microscope begins. Which of the two has the greater view?" - Hugo

"Men occasionally stumble over the truth, but most pick themselves up and hurry off as if nothing had happened." - Churchill

Where did I say "simplest"? I asked what was the most reasonable assumption. Can you answer that question?

Who says there is no evidence of life from non-life...again, you purposefully ignore the "example" of life on Earth in favor of unproven speculation.

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"The facts gentlemen, and nothing but the facts, for careful eyes are narrowly watching." Isaac Asimov

No, I don't see it as any more reasonable.
I understand why it's the default assumption, the simplest, but I don't find it any more reasonable.
We simply don't know.

Haven't we determined how much can be gleaned from a single example?
Exactly nothing.

Only willful ignorance would suggest otherwise.

Now, if you show evidence for Life from nonLife, I might reconsider it having happened on Earth. Otherwise, you hang on to your assumption and I'll hang on to mine, until more evidence is given.

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"Where the telescope ends, the microscope begins. Which of the two has the greater view?" - Hugo

"Men occasionally stumble over the truth, but most pick themselves up and hurry off as if nothing had happened." - Churchill