Panspermia, anyone?

[McCoy]

Re: Panspermia, anyone?

 

remains a telling example of the phenomenon of [/size]urban myth

Must be one hell of an urban myth, NASA seems to be standing by it.

 

Forthcoming anniversary

Space historians will recall that the journey to the stars has more than one life form on its passenger list: the names of a dozen Apollo astronauts who walked on the moon and one inadvertent stowaway, a common bacteria, Streptococcus mitis, the only known survivor of unprotected space travel. As Marshall astronomers and biologists met recently to discuss biological limits to life on Earth, the question of how an Earth bacteria could survive in a vacuum without nutrients, water and radiation protection was less speculative than might first be imagined. A little more than a month before the forthcoming millennium celebration, NASA will mark without fanfare the thirty year anniversary of documenting a microbe's first successful journey from Earth.

 

Apollo 12 remembered

 

In 1991, as Apollo 12 Commander Pete Conrad reviewed the transcripts of his conversations relayed from the moon back to Earth, the significance of the only known microbial survivor of harsh interplanetary travel struck him as profound:

 

"I always thought the most significant thing that we ever found on the whole...Moon was that little bacteria who came back and lived and nobody ever said [anything] about it."

 

Left, Above: Astronaut Pete Conrad (photographed by crew mate Alan Bean) inspects Surveyor 3's camera assembly. Surveyor 3 landed on the moon on April 20, 1967, at 2.94° S, 23.34° W in Oceanus Procellarum.On Nov. 12, 1969, Conrad and Bean piloted the Apollo 12 Lunar Module (background) to a landing 156 m (512 ft) away.

 

Although the space-faring microbe was described in a 1970 Newsweek article, along with features in Sky and Telescope and Aviation Week and Space Technology, the significance of a living organism surviving for nearly three years in the harsh lunar environment may only now be placed in perspective, after three decades of the biological revolution in understanding life and its favored conditions. As the lunar voyagers answered a similar question more than a century ago, in Jules Verne's classic, From the Earth to the Moon: "To those who maintain that the planets are not inhabited one may reply: You might be perfectly in the right, if you could only show that the earth is the best possible world."

 

The remarkable lunar survivor from Apollo 12 thus gives scientific pause.

http://science.nasa.gov/newhome/headlines/ast01sep98_1.htm

 

JPL is hedging their bets, but note that they consider the contamination after return hypothesis to be a minority opinion.

 

The Surveyor 3 spacecraft was launched in April 1967 and was exposed on the lunar surface for 31 months before the Apollo 12 mission. The Apollo 12 Lunar Module landed approximately 160 meters from the Surveyor 3 spacecraft. The crew retrieved several pieces of the Surveyor, including the TV camera and associated electrical cables, the sample scoop, and two pieces of aluminum tubing. These items were returned to Earth and analyzed to determine how they were affected by exposure to the lunar environment.

 

A number of microscopic craters were observed on the returned pieces. Some were probably the result of micrometeorite bombardment of the Moon. Many of these craters were on the side of the Surveyor facing the Lunar Module. It is likely that these are the result of a sand-blasting effect from dust that was blown away from the Apollo landing site by rocket exhaust. Some darkening of painted surfaces due to the effects of solar radiation was also observed. Several nuts, bolts, and screws were disassembled after being returned to Earth, and none were found to have become cold-welded by their exposure to space.

 

A particularly important aspect of the Surveyor 3 analysis was the search for living material on the spacecraft. Surveyor was not sterilized prior to launch, and scientists wanted to know if terrestrial microorganisms had survived for two and a half years in space. One research group found a small amount of the bacteria Streptococcus mitis in a piece of foam from inside the TV camera. They believed that these bacteria had survived in this location since before launch. They only found evidence for living material in one of 33 samples from various parts of Surveyor that they cultured. Another research group found no evidence of life inside a section of electrical cable. Some people associated with the curation of the Surveyor 3 materials have suggested that the one positive detection of life may be the result of accidental contamination of the material after it was returned to Earth.

http://www.lpi.usra.edu/lunar/missions/apollo/apollo_12/experiments/surveyor/

 

(Note that these are .gov and .edu sites, perhapse less given to wild specualtion than some .com ones.)

[L. Marcus]

Re: Panspermia, anyone?

 

Could I see the math on how you arrived at that conclusion?

 

Life appeared on Earth almost as soon as conditions were right for it to do so. Had to be a fairly simple process, yet despite our knowledge of conditions on Earth at that time we have been unable to replicate the experiment. Given my current state of ignorance about the origin of life it seems at least as likely to have been brought here from Elsewhere as to have originiated here so quickly.

 

Of course, if Mars, Europa and Titan do turn out to be lifeless, that will pretty much put the nail in the coffin of Panspermia.

Note that "quickly" in this case means tens or hundreds of million years, and the laboratory of nature as includinf the entire planet. How long did the scientists keep on with their experiments? I guess no longer than a decade, tops. So expand the time table by a factor of a million, and the size of the test tube by much, much more, and Hey Presto!

[Nyrath]

Re: Panspermia, anyone?

 

Gaming-wise there is an appeal to panspermia. It justifies having a galaxy full of life and even having the life being more or less interedible.

And more than that, if you are Captain Kirk.

 

Gaming wise it also explains why most of the aliens are humanoid, instead of looking like a cross between a jellyfish and a tarantula.

[Markdoc]

Re: Panspermia, anyone?

 

Note that "quickly" in this case means tens or hundreds of million years' date=' and the laboratory of nature as includinf the entire planet. How long did the scientists keep on with their experiments? I guess no longer than a decade, tops. So expand the time table by a factor of a million, and the size of the test tube by much, much more, and Hey Presto![/quote']

 

Pretty much. There's still debate about how old life is: first because well-preserved early cambrian strata are very rare and secondly, because single-celled organisms don't tend to fossilise that well.

 

The oldest identifiable single-celled organisms are a touch under 600 million years old. If those really are among the earliest, it means the Earth was devoid of life for 90% of its existence.

 

There is, however an "if" at the beginning of that sentence and plenty ofpeople have argued for a much earlier genesis - after perhaps as little as a billion years (meaning that life has been here for 80% of the Earth's life span).

 

Me, I ain't qualified to judge, though I generally accept the "late arrival" date as being more conservative.

 

Either way, the presence of life here, but not on other planets of our solar system (and its date of origin) doesn't automatically rule out panspermia (though I think it's a daft concept, myself) simply because it could be a rare event. Carefully checking all other bodies in our solar system increases our sample size from one to a couple of dozen: still nothing, given the size of the universe.

 

cheers, Mark

[Kristopher]

Re: Panspermia, anyone?

 

Could I see the math on how you arrived at that conclusion?

 

Life had to originate somewhere, and the odds of that happening anywhere that it could are about the same, so that's a wash between life on Earth originating here, and originating somewhere else.

 

Where the rediculous, Rube-Goldberg, longshot odds for panspermia come in, is in getting life here from somewhere else. Some life-inhabitted body somewhere has to be blown apart, with life-bearing bits sent flying, and the life has to survive that. It then has to suvive in space, facing vacuum and cold and cosmic rays and myriad other threats -- for millions of years to have any hope of getting anywhere, and the life-friendly era of most planets would pass in the time it might take that "ark" ( ) to cross the distance. Then that rock has to not pass off into the intergalactic void, not hit a star, not hit the vast majority of planets that won't support one whit of life (look at our system, look at the planets we've found elsewhere so far), and keep in mind that space is mostly space, empty void. Then if that rock does happen, on the slimmest of hopeful odds, reach another planet that could support life, after millions and millions of years, if that life has survived all that time, then the life also has to survive entry into the new atmosphere and impact with the surface.

 

And all that has to happen on top of whatever has to happen for life to start wherever it starts. Thus, far longer odds for life to come from anywhere else than to have originated on any planet/moon where it is found.

 

Life appeared on Earth almost as soon as conditions were right for it to do so. Had to be a fairly simple process' date=' yet despite our knowledge of conditions on Earth at that time we have been unable to replicate the experiment. Given my current state of ignorance about the origin of life it seems at least as likely to have been brought here from Elsewhere as to have originiated here so quickly.[/quote']

 

The oldest hint of life, the oldest thing that might be a fossil of a microbe, is 3.8 billion years old. But "originated so quickly" seems an odd statement when one is talking about millions of years. If conditions became right for life on Earth 3.81 billions years ago, that's 10 million years for life to come about before that maybe-fossil was formed.

 

Of course' date=' if Mars, Europa and Titan do turn out to be lifeless, that will pretty much put the nail in the coffin of Panspermia.[/quote']

 

Actually, if Mars, Europe, Encedalus, etc, turn out to have or to have had life, that doesn't change the longshot odds on panspermia one bit. Only if that life turns out to be very similar to life on Earth does it even raise the odds just a minescule bit. (If Titan has life, it won't have life similar to that on Earth, it's too cold and the chemistry is too dissimilar.) But the odds are still better that life originated in each of those places on its own, right there where it is.

 

Panspermia is a dodge, an avoidance of the basic question of how by concentrating on where.

[Cancer]

Re: Panspermia, anyone?

 

Pretty much. There's still debate about how old life is: first because well-preserved early cambrian strata are very rare and secondly, because single-celled organisms don't tend to fossilise that well.

 

The oldest identifiable single-celled organisms are a touch under 600 million years old. If those really are among the earliest, it means the Earth was devoid of life for 90% of its existence.

 

I've got citations in front of me that contradict that. There seem to be pretty secure microfossils in rocks dated to 3.5 Gya and possible but not conclusive geochemical signs as old as 3.8 Gya. The stromatolite fossils found at Warrawoona Gap with age 3.5 Gyr seem secure. The 600 million-year number is the one I remember for the oldest multicelled fossils.

 

I'm looking at a graduate-level textbook, "Planets and Life: the Emerging Science of Astrobiology", W.T. Sullivan and J.A. Baross, eds, Cambridge U Press 2007.

[Markdoc]

Re: Panspermia, anyone?

 

I've got citations in front of me that contradict that. There seem to be pretty secure microfossils in rocks dated to 3.5 Gya and possible but not conclusive geochemical signs as old as 3.8 Gya. The stromatolite fossils found at Warrawoona Gap with age 3.5 Gyr seem secure. The 600 million-year number is the one I remember for the oldest multicelled fossils.

 

I'm looking at a graduate-level textbook, "Planets and Life: the Emerging Science of Astrobiology", W.T. Sullivan and J.A. Baross, eds, Cambridge U Press 2007.

 

I admit freely to not being an expert here - so maybe the controversy has been resolved, or has become a fringe debate (that's why I mentioned both options).

 

Last I read though, the research papers were still being flung back and forth between groups who were saying "Yes! Early microfossils!" and those who were saying "No! Abiogenic ultramafics!"

http://www.ias.ac.in/currsci/jul102002/15.pdf

 

As of last month, the debate still seems to be going on.

http://www.liebertonline.com/doi/abs/10.1089/ast.2006.0098

 

cheers, Mark

[Vestnik]

Re: Panspermia, anyone?

 

 

Last I read though, the research papers were still being flung back and forth between groups who were saying "Yes! Early microfossils!" and those who were saying "No! Abiogenic ultramafics!"

 

I miss academia.

[L. Marcus]

Re: Panspermia, anyone?

 

I'm heading back in.

[Clonus]

Re: Panspermia, anyone?

 

And more than that, if you are Captain Kirk.

 

Gaming wise it also explains why most of the aliens are humanoid, instead of looking like a cross between a jellyfish and a tarantula.

 

Not especially since we're talking terraforming efforts that would have to occur hundreds of millions of years ago to cover Earth, although later traffic might account for it. But then my galaxy of humanoids is set 50,000 years in the future. We are the precursors.

[McCoy]

Re: Panspermia, anyone?

 

Note that "quickly" in this case means tens or hundreds of million years' date=' [/quote']

Tens, but not hundreds of millions

 

How long did the scientists keep on with their experiments? I guess no longer than a decade' date=' tops. [/quote']

Some Miller-Urey experiments have been running since 1953.

[McCoy]

Re: Panspermia, anyone?

 

Life had to originate somewhere' date=' [/quote']

Agree

 

and the odds of that happening anywhere that it could are about the same' date=' so that's a wash between life on Earth originating here, and originating somewhere else. [/quote']

Disagree, the universe is about 99.a google of 9's per cent "somewhere else," so I would hardly call that even odds.

 

Where the rediculous' date=' Rube-Goldberg, longshot odds for panspermia come in, is in getting life here from somewhere else. Some life-inhabitted body somewhere has to be blown apart, [/quote']

Objection, presumes facts not in evidence, that life can only occure on planets or simular "bodies."

 

What if life originated in a warm nebula that later froze into comets? Just a hypothesis, but one that cannot be experimentally disproven. Yet.

[McCoy]

Re: Panspermia, anyone?

 

(If Titan has life' date=' it won't have life similar to that on Earth, it's too cold and the chemistry is too dissimilar.) [/quote']

I wish I knew as much as you do about the geology of Titan if you can state that as fact.

 

What I know is there is a lot of methane in the atmosphere of Titan, and every mechanism I know of for producing methane from rock involves liquid water. While the surface is cold enough for ammonia to condense into a liquid, evidence is there are subsurface "hot spots."

[Kristopher]

Re: Panspermia, anyone?

 

Disagree' date=' the universe is about 99.a google of 9's per cent "somewhere else," so I would hardly call that even odds.[/quote']

 

Life had to originate somewhere. The odds are just as good that it originated here as they are that it originated anywhere else it could have originated. Now, read my long post on the subject again. What makes the odds so much worse for life here to have originated anywhere else is the one in a trillion chance of that life ever getting from there to here intact and at exactly the right point in time.

 

Objection' date=' presumes facts not in evidence, that life can only occure on planets or simular "bodies." [/quote']

 

Where else is one going to find liquid water, complex organic molecules, protection from cosmic rays and hard radation, reliable sources of energy (from light, geothermal activity, chemical sources, whatever), and everything else needed for life to exist, let along for it originate?

 

What if life originated in a warm nebula that later froze into comets? Just a hypothesis' date=' but one that cannot be experimentally disproven. Yet.[/quote']

 

So the matter in this nebula, this cloud of gas, is in the correct pressure and temperature band for liquid water to exist, and dense enough for chemicals to come together, and chemically active enough for complex organic molecules to form, and somehow protected from hard radiation and cosmic rays?

 

I'm fairly certain that no such thing actually exists outside of the gravity wells of large bodies.

 

So no, there's no presumption of anything on my part.

 

The only presumption here is the long series of multiple "but what if?" statements that is needed by panspermia.

[Kristopher]

Re: Panspermia, anyone?

 

I wish I knew as much as you do about the geology of Titan if you can state that as fact.

 

What I know is there is a lot of methane in the atmosphere of Titan, and every mechanism I know of for producing methane from rock involves liquid water. While the surface is cold enough for ammonia to condense into a liquid, evidence is there are subsurface "hot spots."

 

The methane has to come from rock? There's a lot of methane in the universe that obviously did not come from rocks and liquid water.

 

And you're not willing to posit a different mechanism for the origin of methane on Titan, but you are willing to posit a way from earth-like life to thrive there, and to have come from some faroff place?

 

Um...OK.

 

Anyway, something might have changed, but I've never heard of Titan as a serious candidate for "life as we know it", unlike Europa or Encedalus.

[McCoy]

Re: Panspermia, anyone?

 

The methane has to come from rock? There's a lot of methane in the universe that obviously did not come from rocks and liquid water.

There is a smoke ring of methane around Saturn, simular to the sulphur ring Io makes around Jupiter. Saturn is pulling methane off Titan at a rate to deplete the atmospher in a few million years. So either there are a lot of comet impacts bringing new methane to Titan, or it is renewing the methane in its atmosphere by some mechanism.

 

And you're not willing to posit a different mechanism for the origin of methane on Titan' date=' but you are willing to posit a way from earth-like life to thrive there, and to have come from some faroff place? [/quote']

When you see hoofprints, think horses, not zebras. Yes there could be different methods of making methane I'm unaware of. There could be different ways of making life that you're unaware of. (I don't know a single way to make life. I know more than one to make methane.) But the mechanism for Titan renewing its atmosphere that doesn't involve unknown geological processes is that tidal stress causes subsurace hotspots where liquid water can exist.

 

Anyway' date=' something might have changed, but I've never heard of Titan as a serious candidate for "life as we know it", unlike Europa or Encedalus.[/quote']

 

Fortes, A.D. (2000). "Exobiological implications of a possible ammonia-water ocean inside Titan". Icarus 146 (2): 444–452.

 

You stipulate liquid water on Encedalus, what makes you so certain it cannot exist on Titan, same average distance from the Sun?

[Clonus]

Re: Panspermia, anyone?

 

Agree

 

 

Disagree, the universe is about 99.a google of 9's per cent "somewhere else," so I would hardly call that even odds.

 

 

The size of the universe in toto doesn't matter, since there wouldn't be time for life to get here from anywhere except the very closest stars. And of course you'd need an actual method for the life to travel not merely though the atmosphere, but into the heart of that asteroid from where-ever it did originate.

[Kristopher]

Re: Panspermia, anyone?

 

There is a smoke ring of methane around Saturn, simular to the sulphur ring Io makes around Jupiter. Saturn is pulling methane off Titan at a rate to deplete the atmospher in a few million years. So either there are a lot of comet impacts bringing new methane to Titan, or it is renewing the methane in its atmosphere by some mechanism.

 

 

When you see hoofprints, think horses, not zebras. Yes there could be different methods of making methane I'm unaware of. There could be different ways of making life that you're unaware of. (I don't know a single way to make life. I know more than one to make methane.) But the mechanism for Titan renewing its atmosphere that doesn't involve unknown geological processes is that tidal stress causes subsurace hotspots where liquid water can exist.

 

Fortes, A.D. (2000). "Exobiological implications of a possible ammonia-water ocean inside Titan". Icarus 146 (2): 444–452.

 

You stipulate liquid water on Encedalus, what makes you so certain it cannot exist on Titan, same average distance from the Sun?

 

I'm not certain why this ended up focusing on Titan. The possibility of liquid water on Titan doesn't change the core issues of the panspermia debate one way or the other. I only mentioned it because until this conversation, the last word I had on Titan was that it was simply too cold and too dry to support earthlike life, and I'm prone to mention such things.

 

Encedalus has water geysers and an ice surface, indicating that their might be water under the surface.

[McCoy]

Re: Panspermia, anyone?

 

The size of the universe in toto doesn't matter' date=' since there wouldn't be time for life to get here from anywhere except the very closest stars. [/quote']

May I point out that the sun has probably orbited the galaxy center some twenty times, give or take, since its formation, probably passing through an average of one spiral arm each orbit. In other words, a lot of stars have been the closest stars over our geological history.

 

And of course you'd need an actual method for the life to travel not merely though the atmosphere' date=' but into the heart of that asteroid from where-ever it did originate.[/quote']

I still favor the "baked Alaska" hypothesis, simple replicators delivered to the surface frozen in the nuclei of comets.

 

It is possible that life begain independently on Earth, and that the creation of life is so simple a trick that when we figure it out we will feel stupid for not Getting It centuries earlier.

 

Or it is possible that life cannot originate under Earth-like conditions and had to get here from Somewhere Else.

 

Too many unknows, too many missing variables to say which is more likely. Neither can be ruled out with currently available data.

 

Or there is a third hypothesis, that life is so unlikely that Earth is the only place in the galaxy, possibly the universe, were it exist. I find that one less likely than the other two, but still cannot be totally dismissed.

 

I don't know which one is correct, and my point is none of you do either. Insufficent data.

[Clonus]

Re: Panspermia, anyone?

 

May I point out that the sun has probably orbited the galaxy center some twenty times, give or take, since its formation, probably passing through an average of one spiral arm each orbit. In other words, a lot of stars have been the closest stars over our geological history.

 

 

I still favor the "baked Alaska" hypothesis, simple replicators delivered to the surface frozen in the nuclei of comets.

 

 

The trick is getting them into the nuclei in the first place.

[Kristopher]

Re: Panspermia, anyone?

 

May I point out that the sun has probably orbited the galaxy center some twenty times, give or take, since its formation, probably passing through an average of one spiral arm each orbit. In other words, a lot of stars have been the closest stars over our geological history.

 

 

I still favor the "baked Alaska" hypothesis, simple replicators delivered to the surface frozen in the nuclei of comets.

 

It is possible that life begain independently on Earth, and that the creation of life is so simple a trick that when we figure it out we will feel stupid for not Getting It centuries earlier.

 

Or it is possible that life cannot originate under Earth-like conditions and had to get here from Somewhere Else.

 

Too many unknows, too many missing variables to say which is more likely. Neither can be ruled out with currently available data.

 

Or there is a third hypothesis, that life is so unlikely that Earth is the only place in the galaxy, possibly the universe, were it exist. I find that one less likely than the other two, but still cannot be totally dismissed.

 

I don't know which one is correct, and my point is none of you do either. Insufficent data.

 

We have enough data to show which is likely, and which is not at all likely -- which is a dodge and a pipedream.

[McCoy]

Re: Panspermia, anyone?

 

We have enough data to show which is likely' date=' and which is not at all likely -- which is a dodge and a pipedream.[/quote']

Except that's also the Creationist arguement, that abiogenesis without Divine Intervention is just too improbable.

[L. Marcus]

Re: Panspermia, anyone?

 

Yes, but those people are teh crayzee!

 

[Kristopher]

Re: Panspermia, anyone?

 

Except that's also the Creationist arguement' date=' that abiogenesis without Divine Intervention is just too improbable.[/quote']

 

Well, actually, no, I'm not making the same argument, at all.

 

Go back and read all my posts on the matter, again, and then go think about it for a while.

 

However probable it is for life to originate on its own, panspermia requires a list of improbably steps before breakfast just to be feasible. And then wherever the life floating around the universe originally came from, at that place, it's just as likely or unlikely to have originated there as it was on Earth. I've posted the Rube Goldberg process that's required for panspermia to work more than once.

 

Just take a look at two of the more unlikely steps: first, that it starts out headed for any star system at all from where it starts out, and second, that while passing through a star system, it happens to hit a place that supports life.

 

In the first part, go out in the country and look up at the night sky -- what percentage of the sky you see is star, and how much is black? Keep in mind that stars look bigger than they really are, in terms of angular size from Earth. Ignoring gravity, if you could fire off a rock from here, and did so in a random direction, what are the odds it reaches a star instead of intergalactic space?

 

In the second part, if the sun were the size of a softball (97mm), the earth would be .8mm across, and would be 10.423 meters away. Alpha Centauri would be 2815 km away. A single rock, on that scale, is nanoscopic. What are the odds of that rock hitting Earth as it passes through?

 

Space is far bigger and far more empty than most people easily grasp. And that's just the two "big and empty" factors. Never mind the "how does it get launched" and "how does it survive the long journey" and "how does it survive reentry" factors.

 

I'm not saying that panspermia isn't true because it's improbable. I'm saying that it's as probable as life (however probable that is), and then adjusted for all the myriad improbabilities of getting that life here, which makes it very, very improbable, to the point of being really just a way of avoiding the question of how by concentrating on questions of where that we're in no position to answer -- when really, the odds are heavily stacked in favor of life on Earth originating on Earth.

[Kristopher]

Re: Panspermia, anyone?

 

Space is big, and we're not:

 

http://www.exploratorium.edu/ronh/solar_system/