A new Journal of Cosmology article says that sealed deep in the water-clay-full sort of (CI1 carbonaceous) meteorites that likely come from comets, one consistently finds forms that look visually and chemically like ancient bacteria fossils. Typical reactions:
in all reality there is like a 99.99% that this claim is wrong, but Hoover is not stupid, despite what other condescending critics say, most have a very limited knowledge of his past.
if u cared to read the article, this guy has identified three undiscovered bacteria. To argue that he misidentified a mineral build up for a life form is wouldn't add up with his reputation so far.
2ndly how can u get anyone credible to back his claim when the life he discovered does not contain nitrogen, like really. Im assuming the way he introduced it to the public was a last resort.
Im sure Hoover is biased as hell, but he knows what hes doing. Everyone who has been a skeptic in the post has made the logical decision. but dismissing it as already wrong with such little information is ignorance.
I am pretty sure that the whole thing is BS but it is still disappointing to see that a large portion of the criticism deals with the author's and journal's credentials instead of the actual data.
1) As far as I can tell, the measurements of amino acid ratios were not performed in this study, but are taken from previous studies from different laboratories. The references and methods are a bit confused, so I can't be certain of this. Assuming that is the case, these ratios are not associated specifically with the filaments, and have been known for years. I'd add that the odd shapes constitute the bulk of their "results". Clearly Hoover thought it was important.
2) As with filament formation, there are known abiotic mechanisms for the synthesis and enantioenrichment of amino acids. The fact that the most prevalent amino acids in the meteorite are things like glycine, AIB and isovaline, all common products of the Miller-Urey synthesis, tends to bolster the case that these are abiotic. Hoover barely mentions let alone offers any evidence to exclude this possibility. I'd also note that there's a lot of argument over the precise ee measurements in murchison that Hoover ignores. The 96%ee for glu is at the extreme end of the range argued by different investigators.
The point here isn't that these meteorites definitely don't contain life (or its remains); we don't know. But there are many ways for abiotic mechanisms to produce evidence that an incautious investigator will take to indicate life, thus any paper claiming to have found life but failing to exclude these mechanisms is most likely incorrect.
I think there's a simple explanation: Robin's a contrarian - he's not trying to maximise the probability of being right, he's trying to maximise the probability of supporting something unlikely-seeming that turns out to be right.
The big evidence is not the odd shapes, but amino acid ratios, which are characteristic of fossilized organic matter. For example:
The meteorite Ivuna Cl1 contained 372 parts per billion of l glutamic acid, but only 8 parts per billion of d glutamic acid, indicating that that glutamic acid came from living things. That there was glutamic acid but no leucine, as is typical in earthly organic fossils, indicates that those living things died millions or billions of years ago, hence unlikely to be the product of earthly contamination of the meteorite. Finding traces of biological amino acids with what look like fossilized earthly microorganisms is a pretty good indication that these are indeed real fossils
The argument for pamspermia I find plausible is a variant of the Fermi paradox. We know that there are living things on Earth that appear to be capable of living in incredibly hostile-to-us environments, surviving years of hard vacuum and radiation and cold, etc., so we can see that it's possible for life to move between planets. It's plausible that it might even sometimes move between stars--at comet speeds, I think you could get from here to the nearest star in under a million years. Now, we don't know how long it took to get life started on Earth after conditions were right, but if we imagine it takes a billion years to get the stars to align perfectly to get life to arise and survive once you've got hospitable conditions for it, life arising once might very well spread out to other stars from occasional glancing blows from meteors, life-bearing planets being smashed to bits and scattered by big collisions, etc., before it can arise locally.
I think the critical parameters there are, first, what's the expected time for life to arise independently, and second, what's the expected time for a life-bearing package to get from life-bearing-planet A to life-ready planet B. As best I can tell, we don't know enough to have more than a rough guess at either number, but I'm no expert.
I suspect the main reason why extraordinary evidence is needed for extraterrestrial life is less that it would be a huge scientific coup (though that's clearly an issue), but that it would shake up so many peoples' worldview in such big ways.
The "original" (but unrelated to this one) alien-microbes-in-a-meteorite-paper was published in Science in 1996 (http://www.sciencemag.org/c..., and the senior author was Dick Zare of Stanford, who was at the time perhaps the most high-status analytical chemist in the world. So if other scientists are waiting to bite on a high-status scientist publishing this kind of work, they already had their chance -- 15 years ago. I think the skepticism over the newer work in Journal of Cosmology comes in part from the fact that, well, the title of the paper on the journal website contains a link to a book on Amazon. That's kind of sketchy.
this post explains the main problem with the paper's conclusions: Minerals can often form odd shapes, particularly filaments, and this has fooled fossil bacteria hunters in the past.There's going to be a high false positive rate for these papers, given publication bias and the fact that there are many more things that could look like alien life to the incautious eye but are not, than actual traces of alien life. Under those conditions it makes sense to be highly skeptical of any new paper, and to require thorough controls before believing its conclusions.
Can someone point me to actual evidence of panspermia? It always seemed like a cop-out to me. "We can't figure out how life originated so quickly on Earth, so perhaps it came from somewhere else!"
And are you suggesting that this life evolves in comets? And still looks like early Earth life, and looks the same from different comets? Is there only one way for primitive life to turn out? Is there even enough energy available in a comet ecosystem to produce life?
Plus I thought comets had a similar age to the Earth. If life could evolve there since the formation of the solar system, why not on Earth?
If that's the case, it's not the classic panspermia of the Earth being seeded from elsewhere. Instead, you are claiming that life originates everywhere, even under conditions as diverse as comets vs. undersea vents -- and it all comes out looking similar, with similar chemical signatures!
No offense Robin, but I think PZ Myers, a biologist, is more qualified than an economist to evaluate these claims. Also, from my prior experience reading his blog he seems to be reasonable and accurate.
The point is that that last common ancestor may have come from space.
ps. this has obvious grammatical errors, my b.
but props to you Hanson, your articles are a fun read.
http://www.nasa.gov/centers...
go to link
in all reality there is like a 99.99% that this claim is wrong, but Hoover is not stupid, despite what other condescending critics say, most have a very limited knowledge of his past.
if u cared to read the article, this guy has identified three undiscovered bacteria. To argue that he misidentified a mineral build up for a life form is wouldn't add up with his reputation so far.
2ndly how can u get anyone credible to back his claim when the life he discovered does not contain nitrogen, like really. Im assuming the way he introduced it to the public was a last resort.
Im sure Hoover is biased as hell, but he knows what hes doing. Everyone who has been a skeptic in the post has made the logical decision. but dismissing it as already wrong with such little information is ignorance.
I am pretty sure that the whole thing is BS but it is still disappointing to see that a large portion of the criticism deals with the author's and journal's credentials instead of the actual data.
Really? I'd think with the Great Filter implications of panspermia, he'd very much want it not to be true.
This doesn't provide encouragement to those hoping this discovery would be substantiated.
1) As far as I can tell, the measurements of amino acid ratios were not performed in this study, but are taken from previous studies from different laboratories. The references and methods are a bit confused, so I can't be certain of this. Assuming that is the case, these ratios are not associated specifically with the filaments, and have been known for years. I'd add that the odd shapes constitute the bulk of their "results". Clearly Hoover thought it was important.
2) As with filament formation, there are known abiotic mechanisms for the synthesis and enantioenrichment of amino acids. The fact that the most prevalent amino acids in the meteorite are things like glycine, AIB and isovaline, all common products of the Miller-Urey synthesis, tends to bolster the case that these are abiotic. Hoover barely mentions let alone offers any evidence to exclude this possibility. I'd also note that there's a lot of argument over the precise ee measurements in murchison that Hoover ignores. The 96%ee for glu is at the extreme end of the range argued by different investigators.
The point here isn't that these meteorites definitely don't contain life (or its remains); we don't know. But there are many ways for abiotic mechanisms to produce evidence that an incautious investigator will take to indicate life, thus any paper claiming to have found life but failing to exclude these mechanisms is most likely incorrect.
I think there's a simple explanation: Robin's a contrarian - he's not trying to maximise the probability of being right, he's trying to maximise the probability of supporting something unlikely-seeming that turns out to be right.
The big evidence is not the odd shapes, but amino acid ratios, which are characteristic of fossilized organic matter. For example:
The meteorite Ivuna Cl1 contained 372 parts per billion of l glutamic acid, but only 8 parts per billion of d glutamic acid, indicating that that glutamic acid came from living things. That there was glutamic acid but no leucine, as is typical in earthly organic fossils, indicates that those living things died millions or billions of years ago, hence unlikely to be the product of earthly contamination of the meteorite. Finding traces of biological amino acids with what look like fossilized earthly microorganisms is a pretty good indication that these are indeed real fossils
Fourthed. This area seems to be one of Robin's blindspots.
Michael G:
The argument for pamspermia I find plausible is a variant of the Fermi paradox. We know that there are living things on Earth that appear to be capable of living in incredibly hostile-to-us environments, surviving years of hard vacuum and radiation and cold, etc., so we can see that it's possible for life to move between planets. It's plausible that it might even sometimes move between stars--at comet speeds, I think you could get from here to the nearest star in under a million years. Now, we don't know how long it took to get life started on Earth after conditions were right, but if we imagine it takes a billion years to get the stars to align perfectly to get life to arise and survive once you've got hospitable conditions for it, life arising once might very well spread out to other stars from occasional glancing blows from meteors, life-bearing planets being smashed to bits and scattered by big collisions, etc., before it can arise locally.
I think the critical parameters there are, first, what's the expected time for life to arise independently, and second, what's the expected time for a life-bearing package to get from life-bearing-planet A to life-ready planet B. As best I can tell, we don't know enough to have more than a rough guess at either number, but I'm no expert.
I suspect the main reason why extraordinary evidence is needed for extraterrestrial life is less that it would be a huge scientific coup (though that's clearly an issue), but that it would shake up so many peoples' worldview in such big ways.
The "original" (but unrelated to this one) alien-microbes-in-a-meteorite-paper was published in Science in 1996 (http://www.sciencemag.org/c..., and the senior author was Dick Zare of Stanford, who was at the time perhaps the most high-status analytical chemist in the world. So if other scientists are waiting to bite on a high-status scientist publishing this kind of work, they already had their chance -- 15 years ago. I think the skepticism over the newer work in Journal of Cosmology comes in part from the fact that, well, the title of the paper on the journal website contains a link to a book on Amazon. That's kind of sketchy.
this post explains the main problem with the paper's conclusions: Minerals can often form odd shapes, particularly filaments, and this has fooled fossil bacteria hunters in the past.There's going to be a high false positive rate for these papers, given publication bias and the fact that there are many more things that could look like alien life to the incautious eye but are not, than actual traces of alien life. Under those conditions it makes sense to be highly skeptical of any new paper, and to require thorough controls before believing its conclusions.
Thirded.
Can someone point me to actual evidence of panspermia? It always seemed like a cop-out to me. "We can't figure out how life originated so quickly on Earth, so perhaps it came from somewhere else!"
And are you suggesting that this life evolves in comets? And still looks like early Earth life, and looks the same from different comets? Is there only one way for primitive life to turn out? Is there even enough energy available in a comet ecosystem to produce life?
Plus I thought comets had a similar age to the Earth. If life could evolve there since the formation of the solar system, why not on Earth?
If that's the case, it's not the classic panspermia of the Earth being seeded from elsewhere. Instead, you are claiming that life originates everywhere, even under conditions as diverse as comets vs. undersea vents -- and it all comes out looking similar, with similar chemical signatures!
No offense Robin, but I think PZ Myers, a biologist, is more qualified than an economist to evaluate these claims. Also, from my prior experience reading his blog he seems to be reasonable and accurate.