Nasa news conference (re: Arsenic-based life form?)

I have to say I share what a couple other people have already expressed - this was a very disappointing announcement. It was also pretty much what I expected, not the specifics, but just that it would be something very mundane. I'm sure the people who work in this field are very excited (with good reason), and I believe the NASA people are correct when they say it improves the chances that life out in the void doesn't have to be like Earth-based life, but as PZ Meyers said, its just an extremophile that can be coaxed into using arsenic in place of phosphorus. Big whoop.This is just a case of NASA over-hyping during a period of budgetary pressure.--Percy

I'm not pooh-poohing the discovery, I'm pooh-poohing the buildup and hype. This isn't a discovery that warrants this kind of showcasing. This recently discovered extremophile is a just another example of the evolution of terrestrial lifeforms in action. While one can't predict the specifics of what will be discovered in the future, this is exactly the kind of thing that one would expect. I'm sure there are many more similarly amazing things waiting to be discovered in extreme environments such as arsenic lakes and black smokers and dead seas and buried deep within the ground and so forth.I think the next time NASA ballyhoos some announcement related to the search for extraterrestrial life that it should really be much more directly related.--Percy

Before the discovery of nylon metabolizing bacteria, if you had asked the world's molecular biologists if bacteria could evolve to take advantage of nylon I hope they would have come down clearly on the side of it being possible. Before the discovery of life around black smokers, if you had asked the world's molecular biologists if life could exist at such high temperatures I hope they would have believed it was possible. We now have plenty of examples of organisms evolving the ability to live in extreme environments, metabolize new chemicals, and evolve immunity or tolerance to poisons and such. If molecular biologists truly would have collectively objected "not on this Earth" to the possibility of microbes evolving the ability to incorporate arsenic or any poison then I would find that unexpected.I assume, or at least hope, that those searching for signs of extraterrestrial life assume that the type of life found on Earth is not the only type of life possible. It would seem to make little sense to conclude, for example, that "The signatures we're observing for life-related elements and molecules on planet X is not what we see here on Earth, therefore this planet cannot harbor life."The definitions of life I've liked most talk about metabolism and reproduction and so forth, not about requiring carbon and oxygen and phosphorus and such. I hope exobiologists feel the same way.--PercyEdited by Percy, : Grammar.

Uh, yes we are talking about tolerating and incorporating arsenic. I guess to someone who assumed that evolutionary change was limited to nucleotides, genes and chromosomes it must seem an incredible thing, but the assumption doesn't seem warranted and it isn't one I've ever shared myself. Jurassic Park had it right: "Life will find a way."--Percy

I don't think Crashfrog and myself are saying that it isn't cool stuff. It *is* very cool!But it isn't a case of, "Omigod, who would ever have imagined that life could ever use any chemicals but those we already know it uses! I'm stunned. Amazed! Flummoxed! Flabbergasted!" And as an aside, I think the more we learn about what was actually discovered we'll find that they discovered less than was implied. I'll be pleasantly surprised to be proven wrong, but I think NASA exaggerated the significance, but they had committed themselves for who knows what reason and so were driven to make the discovery seem as amazing and unexpected as possible. Like the nightly news, they have to make every event seem as significant or dire or whatever as possible to maintain the public's attention.Anyone remember the original Star Trek from the 1960's? There was one episode about the Horta, a lifeform based upon silicon instead of carbon, a common speculation in science fiction. Today's youngest exobiologists are the grandchildren of people who grew up with Star Trek. Now nearly a half century later I would have expected we're all familiar with the concept that the fundamental building blocks of life don't have to be just like our own, and that just like Burger King life in each environment can have things its own way.--Percy

Someone earlier mentioned that PZ Myers had blogged about this, and I just now got around to reading it: The whole thing is well worth reading, only takes a couple minutes, but here's a fuller excerpt of the key part, and he pretty much confirms what us skeptics have been saying: --Percy

Today's New York Times posted an article about the discovery: This quote focuses on what is probably the core of our difference of opinion: The "fixed constants of life"? Did microbiologists as a group really believe that carbon, oxygen, phosphorus, and so forth, were "fixed constants of life"? If they did then I guess this discovery ranks way up there in significance. But I think it's much more like what Taq described in Message 61, that the significance is not that it changes our thinking, but rather that it verifies a broadly held expectation.For me this is a case of, "Yep, just the kind of thing we would expect. Isn't adaptation amazing!" Evolutionary adaptation is always exploring and pushing up against the boundaries of what is possible. If something is possible then evolution will find it. Just look at the way genetic algorithms find solutions undreamt of by human designers. Where is the amazement of evolution finding solutions in nature that we didn't know were possible?I just feel that all the attention and speculation leading up to the news conference was not justified by the substance that NASA eventually presented.--Percy

Can I assume that we know that nitrogen can't substitute for phosphorus and silicon can't substitute for carbon in the same way we knew that arsenic can't substitute for phosphorus?At the NASA news conference one of the scientists explained why it was thought that arsenic could not replace phosphorus in the DNA backbone. Using a steel chain he explained how strong phosphorus bonds are, then he replaced one of the steel links with one crafted from crinkled up aluminum foil to illustrate how weak arsenic bonds are. A DNA backbone with some phosphorus replaced by arsenic would not be able to stay together for long and would soon split into fragments.This argues against arsenic replacing phosphorus in the DNA backbone, but if it turns out it did (something they don't yet know) then what does that say about how sure we are about the impossibility of nitrogen and silicon as substitutes?And of course the same arguments apply for cell chemistry outside DNA.--Percy