Mono Lake in California, with the bacteria (inset) that lives there. Credit: Science

NASA Finds a “Weird” Kind of Life on Earth

Article Updated: 24 Dec , 2015

by

No, NASA has not found life on another planet, but has found life here on Earth that is almost “alien” to our narrow, phosphate-based view of life. Scientists have discovered — or “trained,” actually — a type of bacteria that can live and grow almost entirely on a poison, arsenic, and incorporates it into its DNA. This “weird” form of life, which can use something other than phosphorus — what we think of as a basic building block of life — is quite different from what we think of as life on Earth. It doesn’t directly provide proof of a “shadow biosphere,” a second form of life that lives side-by-side with other life on our planet, but does suggest that the requirements for life’s beginnings and foundations may be more flexible than we thought. This means life elsewhere in the solar system and beyond could arise in a multitude of conditions.

“Our findings are a reminder that life-as-we-know-it could be much more flexible than we generally assume or can imagine,” said Felise Wolfe-Simon, lead author of a new paper in Science. “If something here on Earth can do something so unexpected, what else can life do that we haven’t seen yet?”

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The salt-loving bacteria, strain GFAJ-1 of the Halomonadaceae family of Gammaproteobacteria,came from the toxic and briny Mono Lake, near Yosemite Park in California. The lake has no outlet, so over millennia has become one of the highest natural concentrations of arsenic on Earth.

Although the bacteria did not subsist entirely on arsenic in the lake, the researchers took the bacteria in the lab grew it in Petri dishes in which phosphate salt was gradually replaced by arsenic, until the bacteria could grow without needing phosphate, an essential building block for various macromolecules present in all cells, including nucleic acids, lipids and proteins.

Using radio-tracers, the team closely followed the path of arsenic in the bacteria; from the chemical’s uptake to its incorporation into various cellular components. Arsenic had completely replaced phosphate in the molecules of the bacteria, right down its DNA.

“Life as we know it requires particular chemical elements and excludes others,” said Ariel Anbar, a biogeochemist and astrobiologist from Arizona State University. “But are those the only options? How different could life be? One of the guiding principles in the search for life on other planets, and of our astrobiology program, is that we should ‘follow the elements. Felisa’s study teaches us that we ought to think harder about which elements to follow.”

Felisa Wolfe-Simon, right, a NASA astrobiology research fellow in residence at the USGS, and Ronald Oremland, an expert in arsenic microbiology at the USGS, examine sediment in August 2009 from Mono Lake in eastern California. Credit: Henry Bortman

Wolfe-Simon added, “We took what we do know about the ‘constants’ in biology, specifically that life requires the six elements CHNOPS (carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur) in three components, namely DNA, proteins and fats, and used that as a basis to ask experimentally testable hypotheses even here on Earth.”

The idea that arsenic might be a substitute for phosphorus in life on Earth, was proposed by Wolfe-Simon and developed into a collaboration with Anbar and theoretical physicist and cosmologist Paul Davies. Their hypothesis was published in January 2009, in a paper titled “Did nature also choose arsenic?” in the International Journal of Astrobiology.

“We not only hypothesized that biochemical systems analogous to those known today could utilize arsenate in the equivalent biological role as phosphate,” said Wolfe-Simon “but also that such organisms could have evolved on the ancient Earth and might persist in unusual environments today.”

This new research is the first time that shows a microorganism is able to use a toxic chemical to sustain growth and life.

Sources: Science, paper



43 Responses

  1. K-PAX says:

    “Our findings are a reminder that life-as-we-know-it could be much more flexible than we generally assume or can imagine,” Felise Wolfe-Simon

  2. healeyb says:

    This is such amazing news! Can we please start funding NASA more, please?

  3. Watching this now on NASA TV; very exciting research! If only entertainment spending could be forwarded to this kind of research focus, imagine where our species could be!

  4. GekkoNZ says:

    “If only entertainment spending could be forwarded to this kind of research focus, imagine where our species could be!”

    We would be knowledgeable but bored 🙂

  5. @GEKKONZ Really? Ya true, (not to generalize…) but to generalize, most people are pretty dumb… they actually do have the mental capacity to learn, but hey… that requires work!

  6. Nafin says:

    Mono lake is gorgeous, it is the second saltiest body of water on the planet and has been shrinking due to the LA aqueduct (which siphons water from its feeder streams) for decades which threatens the chemical process that occurs when the fresh water feeding the lake meets with the brine of the lake resulting in the interesting salt formations you see in the picture that do not exist anywhere else, it also results in a steady climb of the salt content of the water body and will eventually kill the brine shrimp and possibly the strange bacteria that live in it. This is one extreme environment we’d better research before it evaporates,

    A warning, don’t go swimming in this lake in summer with dry skin, been there, regretted that.

  7. Jon Hanford says:

    It really is fun to see the enthusiasm these researchers display in describing their findings at this press conference, which has just ended (their phosphorous guy sounded positively breathless). And they actually fielded some really tough, insightful questions (not too many “where’s ET?” queries). And certainly, a reference to Star Trek’s “Devil in the Dark” episode (w-the Horta) made my day. 🙂

  8. Hon. Salacious B. Crumb says:

    Surely it ain’t alien if it has DNA in it. (I pray not, otherwise we will be having those panspermia nutters on our backs forevermore!

    As for poor Nafin, I’d be worried about going to sleep at night after swimming in Mono Lake!.Who knows, you might wake up one morning at be transmogrified into on of these critters.

    Q. Was Mono Lake actually named after the dreaded mononucleosis, I wonder? The inset in the image sure looks like a large phagocytic white blood cell with a simple oval nucleus and clear, grayish cytoplasm.

    I still think Sarah Palin is likely the best prime candidate for alien life! (I mean, she says she can see Russia from her backyard in Alaska — and no human I know could do the same. Besides, who else could come back from the brink of extinction in last presidential election in the US to become a force again in the next one!

  9. Hey Crumb – easy with the nut gun…

    While there’s obviously no evidence for Panspermia, there was also no evidence for extrasolar planets before we had the capability to detect them. Sometimes, lack of evidence is not evidence of a lack.

    The idea is not discountable. It is not likely that high level functioning organisms can cross interstellar or interplanetary space, and while it is clear that simple molecules can, their transfer is not needed since they can form spontaneously on any planet.

    BUT – can a self-replicating precursor, or fragments of an organism, which are unlikely to form spontaneously on a planet be more likely to form once (either in space or on a different planet) and then self seed? Maybe. I don’t see an argument to why this is a nutjob theory.

    We’ll find some answers within our lifetimes within the solar system, and maybe some indirect answers about what goes on in other systems.

    Inquiring minds want to know!

  10. Torbjorn Larsson OM says:

    It will be interesting to poke behind the article paywall. (Nuts, I should have realized Science or Nature had this _before_ going home.)

    Cells usually sequester elements they find poisonous, either they use them (say, iron) or not (say, mercury). They say they found arsenic associated with DNA by markers, but if that is that all they have on DNA specifically it is thin gruel; arsenic and DNA could perhaps simply associate. (Say, wrapping DNA around protein sequestered arsenic clumps.)

    This new research is the first time that shows a microorganism is able to use a toxic chemical to sustain growth and life.

    Perhaps it was meant to be “_the_ toxic chemical”, because bacterias using perchlorates as food is using a chemical which is highly toxic to organisms with a nervous system.

  11. Meate says:

    @Nafin

    I’m not sure where Mono Lake lies in the list of saltiest lakes, but it’s not second. Lake Asal (~35% [salt content]), the Dead Sea (~34%), the Great Salt Lake (~25%) and a few lakes in the Antarctica (~40%) have much higher salt concentrations than Mono Lake (~10%).

  12. capper says:

    Hmmmm…. I always kinda figured Crumb would have liked having nuts on his back.

  13. Bariman43 says:

    I find it more awkward that he used the word “nutters” right after the word panspermia >.<

    Anyway, this monumental breakthrough is mentioned almost everywhere I go! If life really is this flexible with the elements that make it up, then life just might be more common that we originally thought!

  14. tdaonp says:

    The definition of life has changed. Instead of the six building blocks all life seemed to be build with, it now turns out life can improvise a little. As many a science fiction writer predicted.

    http://thesecondopiniontribune.blogspot.com/2010/12/and-again-science-fiction-writers-led.html

  15. Tony Ryals says:

    Pretty amazing however still doesn’t hurt the concept of organic-inorganic coevolution.It almost strengthens it….

    Organic-Inorganic Coevolution …

    by Tony Ryals

    Before life made a cell it must have occurred,
    Carbon and minerals wrote their first word,
    It was the basis of the biospheric revolution,
    Organic-inorganic co-evolution,
    From the simplest life-form viral,
    To the most complex evolutionary spiral,
    Dances within a watery solution,
    Using the elements of organic-inorganic co-evolution
    Even the genetic strand has the phosphorous mineral in its carbon configuration
    Phosphorous holds not only the key to energy transformation,
    And life’s respiration
    But is also essential to store life’s genetic information,
    And eventually human intellectualization,
    And what would be chlorophyll,
    Without magnesium its carbon bonds to fill ?,
    Without the magnesium impetus,
    There’d be no photosynthesis,
    And what would be the enzyme nitrogenase,
    Without molybdenum to fill its carbonaceous space,
    Nitrogenase alone would lack the inspiration,
    To perform prokaryotic nitrogen fixation,
    Without molybdenum fertilization,
    And long before hemoglobin came along,
    Other iron-containing heme groups sang their song,
    Before these iron-carbon molecules evolved for respiration,
    They protected oxygen-sensitive molecules from oxidation,
    After photosynthesis led to oxygen’s liberation,
    There’d be no vitamin B-12 or cobalamine,
    If cobalt hadn’t co-evolved with carbon
    To make this vitamin,
    And what to the biosphere would it have meant,
    If selenium hadn’t evolved with carbon
    to form an anti-oxidant,
    Molybdenum calcium iron and sulfur,
    Chromium magnesium potassium copper,
    Liebig’s law of the minimum,
    And law of the maximum,
    You can’t have too much and you can’t have too little,
    You must be somewhere in the middle,
    Copper in feed lots makes pigs grow fast,
    But then their copper-loaded excrement poisons the grass,
    Can’t survive the future without respecting the biosphere’s past,
    The traces of life are in your head,
    Bacteria will use them when you’re dead.

    http://malta.indymedia.org/node/8810

  16. astronary says:

    Bravo! : )

  17. Hon. Salacious B. Crumb says:

    I said;

    “Surely it ain’t alien if it has DNA in it. (I pray not, otherwise we will be having those panspermia nutters on our backs forevermore!”)

    I made such an assessment, mostly because some panspermia proponents have made comments here at UT in the past that WERE really made by so-called nutters! (NOTE: Actually, not all panspermia proponents are nutters)

    I’d think that if an organism has DNA, it is probably from earth and not necessarily from elsewhere! If it were alien it is far more likely to have a completely different structural and chemical organisation; and even a different energy source (I.e. radioactivity.) (An example is in the Michael Crichton sci-fi film “The Andromeda Strain” (1969).)

    Whilst finding an organism that uses arsenic instead of phosphates to keep itself alive and functioning seem astounding, but it does not mean that these microscopic critters are really (or necessarily) ‘alien” but have instead have adopted (or even, dare I say, evolved) to their very harsh environment. Frankly, I do find it more amazing that there is life well below the surface of the earth or organism around superheated volcanic vents in the ocean, than this story. I’m sure the first microorganisms on earth, now extinction, would have been just as amazing as the ones found it this current story. I can even imagine whole strains of creatures with bizarre biology
    As for the criticisms about the ‘nutters’, my general take on panspermia is that it too is generally control by proponents with agendas and undisclosed motives. I.e. Based on maintaining some Christian (and some other) religious beliefs against the advanced in human biology — specifically DNA and the origin of life. Their common arguments centre on the fact that if creation of life is from elsewhere, it gives the “a get out of jail free card” for creation by some supernatural entity’s intervention aka “a Creator.”
    Whilst having such beliefs might be OK, it is not science nor is it the motivation of science to validate such agendas. IMO it is true that people should rigorously question everything about science and the conclusions it draws, it should not be openly used so randomly as to justify in what one thinks is right, or true, or moral, or evn hopeful. Science is based on the hard evidence presented, and artificially using it to promote ones belief, just shows it really isn’t science.
    As for our dear madCapper blogger here constantly needing to deriding my every word (in what is obviously reaction to my critical thinking processes), clearly shows a somewhat limited depth of understanding. Say something of your own man!!! Just a hint of some opinion or knowledge would be real appreciated. Ta!

  18. GBendt says:

    If you think you know all the essential demands life needs to flourish, it may teach you the lesson that it can replace a missing essential demand if it needs to do so. It is somehow prepared to cope with the unforeseeable. Are we?

  19. Hon. Salacious B. Crumb says:

    @ Gbendt,

    I agree, and philosophically, this is quite true!
    However, it does not necessarily mean it is alien but life instead is far more diverse. … and that IS a very important distinction.

    Ask yourself, how many different species have ever lived on our planet since the first signs of life?

  20. capper says:

    Dear mr.Crumb

    You brought it upon yourself by constantly picking fights with people who disagree with you. Don’t be surprised when someone finally calls you on it.

    If you go back over all of my responses to your “every word”, you will see that I only respond when you are trolling. That includes this article. When you are actually sticking to the topic and behaving, I ignore you. If you don’t want me writing counter-troll to your troll, then simply stop carrying on with it and you’ll never hear from me again. Trolling is not “critical thinking”.

  21. Hon. Salacious B. Crumb says:

    @ madCapper

    “You brought it upon yourself by constantly picking fights with people who disagree with you”

    So what has this to do with you then? Am I picking fights with you? Are you now self-appointing and promoting yourself now as the “arbitrator of trolling”? Have you become the new ‘moral compass’ of all these UT stories?

    Clearly you are totally incapable or unable to make a comment on this story. This makes you as relevant as your own piffling significant is as much as one of these tiny little microbes!

    Say what you want, because all it does is just makes you look more foolish. So be it.

  22. Hon. Salacious B. Crumb says:

    Hmmmm…. I always kinda figured madCapper would have liked having nuts on his back.

  23. Run says:

    Well I’m completely new to reading this website (about a week now) and having read quite a few comments here it is the Crumb guy who seems to be making himself look foolish, and the Capper guy seems to be talking sense. So feel free to argue amongst yourselves but don’t bring us lurkers into it, otherwise you might find you don’t like what assessments we’re making.

  24. Lawrence B. Crowell says:

    The next step would be to synthesize nucleotides with arsenic replacing phosphorus, and then to recruit these into cells, or maybe these cells. So it the DNA codes for some compound easily identifiable these could be detected. So if the 60s ribosomes of these prokaryotes are able to parse arsensate (instead of phosphate) mRNA, or if the transcriptase is able to act on arsenate DNA then you would have a biochemical signature of the functional role of arsenated RNA or DNA.

    LC

  25. Hon. Salacious B. Crumb says:

    Lawrence.

    Good point. I wonder what this might imply for the assembling of RNA to make the DNA. Could be a difficult problem is replication of these bacteria?

  26. Hon. Salacious B. Crumb says:

    Thanks for the nice cryptic messages here Run.

    Nothing beat a blog comment that tries and take sides as if it were some democratic process. As for “bring lurkers in”,

    You words are remarkably similar and close to Capper point of view here. Don’t tell me you have resorted to duplicate avatars on one site just to back up your own statements here? (I hope not) “Bring in lurkers”? Well, I thought some were already here!! (wink, wink!)

    Please, Run, like I said to Capper here. Don’t sit in the background bemoaning stances taken by others. Why don’t you and Capper tell us what YOU THINK of these new aliens among us? I’m interested, as I am sure most of the readers of this article are!

    Are you cynical of this story, and have questioned it implications?
    Do you think this important or panspermia driven (possibly with alliterative motives?
    Did NASA’s press release on all the television news programs with Felisa Wolfe-Simon really creep you out? (here demonic look was much of a concern./)
    Why did she desperately avoid looking directly at the camera?
    Is she being deceptive?
    Or does Felisa Wolfe-Simon groundbreaking oceanographic research on using arsenic for photosynthesis really just seems a little too convenient?

    This is what critical think is important.

    Let’s. Why don’t you visit another interesting site (with the video), and tells us what you think? NASA Will Release Announcement On Alien Life In Press Release [Video]

    [I also still worry about the name of the researches behind this, Ariel Anbar! Wasn’t that the name of the mermaid in animation film “The Little Mermaid?]

    I think you will find that trolls usually don’t observe such things, now do they?

  27. Hon. Salacious B. Crumb says:

    Run. Are you cynical of this story, and have questioned it implications?
    Do you think this important or panspermia driven (possibly with alliterative motives?
    Did NASA’s press release on all the television news programs with Felisa Wolfe-Simon really creep you out? (here demonic look was much of a concern./)
    Why did she desperately avoid looking directly at the camera?
    Is she being deceptive?
    Or does Felisa Wolfe-Simon groundbreaking oceanographic research on using arsenic for photosynthesis really just seems a little too convenient?

    This is why critical think is so important.

    Let’s see. Why don’t you visit another interesting site (with the video), and tells us what you think? Confirmed : Life Still Beyond Earth Unknown

    [I also still worry about the name of the researches behind this, Ariel Anbar! Wasn’t that the name of the mermaid in animation film “The Little Mermaid?]

    I think you will find that trolls usually don’t observe such things, now do they?

  28. Hon. Salacious B. Crumb says:

    Thanks for the nice cryptic messages here Run.

    Your words are remarkably similar and close to Capper point of view here. Don’t tell me you have resorted to duplicate avatars on one site just to back up your own statements here? (I hope not) “Bring in lurkers”? Well, I thought some were already here!! (wink, wink!)

    Please, Run, like I said to Capper here. Don’t sit in the background bemoaning stances taken by others. Why don’t you and Capper tell us what YOU THINK of these new aliens among us? I’m interested, as I am sure most of the readers of this article are!

    Run. Are you cynical of this story, and have questioned it implications?
    Do you think this important or panspermia driven (possibly with alliterative motives?
    Did NASA’s press release on all the television news programs with Felisa Wolfe-Simon really creep you out? (here demonic look was much of a concern./)
    Why did she desperately avoid looking directly at the camera?
    Is she being deceptive?
    Or does Felisa Wolfe-Simon groundbreaking oceanographic research on using arsenic for photosynthesis really just seems a little too convenient?

    This is why critical think is so important.

    Let’s see. Why don’t you visit another interesting site (with the video), and tells us what you think?

    [I also still worry about the name of the researches behind this, Ariel Anbar! Wasn’t that the name of the mermaid in animation film “The Little Mermaid?]

    I think you will find that trolls usually don’t observe such things, now do they?

  29. neoguru says:

    Yawl ain’t seen nuthin’ yet! I’m predicting that alien biological material will be substantially different then Earthly biochemicals. I’d be astonished if we find alien DNA or even something that closely resembles it. It’s gonna be waay different.

  30. Lawrence B. Crowell says:

    One thing I find interesting about this are the completely off the wall comments being made, and elsewhere as well.

    Crumb: I was listening to the Science AAAS podcast yesterday on this. The skeptic on this was indicating how it would take a huge amount of research to determine if the As is incorporated into the molecular biology of the cell. I imagined a lab dedicated to lots of quantitative chemistry and so forth. Then it dawned on me that an initial determination does not require a molecule by molecule analysis. Assume a DNA is made with a nucleotide sequence with the phosphodiester linkage replaced by a arsenodiester linkage. I am not sure how to do that, but I imagine it can be accomplished by various chemical means. It might just mean using the standard regent process with the PO_4 replaced with AsO_4. Then one links together a sequence that codes for some compound not found in these prokaryotes. If the arsentated DNA works then clearly the transcriptase is able to read the arsenated DNA. One can then repeat a similar process with the RNA, and if this is expressed then the ribosome can read the arsenated RNA and parse its information into a polypeptide. This could be done with various controls, such as with these cells free of arsenic and then in an environment that is arsenic rich and phosphorous starved.

    I can’t say for sure, but As in the linkage of DNA could have drastic changes in the structure. DNA is rather remarkable molecule that has a 36deg twist on each nucleotide sequence. I could well imagine that some of these physical properties are changed in at least subtle ways, which would make complex As based life impossible.

    LC

  31. Tramman says:

    One thing that has intrigued me for years is that all forms of life on this planet work the same way: they are all RNA & DNA based and nothing has ever been discovered that works fundamentally differently. This substitution of arsenic for phosphorus is only a slight variation, showing, as has been said already, that life as we know it is a bit more flexible than previously thought. This is a planet that has had a wide range of different conditions over the last few billion years, including some most unsuitable for present forms of life, culminating in one that’s absolutely perfect for life (or was before humans evolved!). Yet all forms of life here are the basically the same. This leads to one of only two conclusions: either our form of life is ubiquitous and every time it evolved, which imay have been regularly, it looks the same or it is incredibly rare, appearing only once even on this of all planets the most propitious for life. The fact that it seems to be possible to trace an unbroken tree of life from the most primitive to the most advanced species might point to the second conclusion. In which case, SETI is a waste of time!

  32. jhnsn d-s says:

    And God called the dry [land] Earth; and the gathering together of the waters[mayim] he called Seas[yam]…And God said, Let the waters[mayim] bring forth abundantly the moving creature that hath life, and fowl [that] may fly above the earth in the open firmament of heaven. Ge 1:10, 20

    QUOTE: “The lake has no outlet,…”

    http://www.universetoday.com/81106/nasa-finds-a-weird-kind-of-life-on-earth/#more-81106

  33. Aqua says:

    Did you know that there is a hot mineral spring in the middle of Mono Lake? It used to be a destination for many hot water soak lovers. It is now fenced in and closed off to the GP in an effort to stabilize the habitat and restore the damage done by invasive activities in the past. Put yer canoe away. HeyUP!

  34. Torbjorn Larsson OM says:

    @ Meate:

    Thank you, that was very interesting!

    I note that Lake Assal goes from 35 % surface salinity to 40 % at depth, btw.

    @ tdaonp:

    The definition of life has changed.

    Not the general definition, no. The evolution process is what life operates under, and it can be defined as “Evolution is a process that results in heritable changes in a population spread over many generations.” (Cw “Gravitation is a process that results in accelerations in a mass by another mass.”)

    If you wish, a framing process definition can be parsed down to exclude software (genetic algorithms) and hardware (von Neumann machines) and retain software (biological evolution). You can further add on metabolism to arrive at the common “NASA definition”, but that is an operative definition designed to quickly recognize life.

    The most general case is to look for systems that operate under the evolution process.

    @ HSBC:

    dare I say, evolved

    Certainly, they are phylogenetically distant relatives to E. coli, AFAIU. That cells evolves to adapt to arsenic is witnessed by bacteria using it as redox sink instead of oxygen, and even in metabolism; it is the later stages that are poisonous (short-circuiting out making ATP, I believe), not the earliest ones.

    @ LC:

    to synthesize nucleotides with arsenic replacing phosphorus

    As Wolfe-Simon et al notes, arsenic mononucleotides forms spontaneously, while our phospate mononucleotides needs an enzymatic system. Among them NAD, a cellular energy “currency” (but not ADP/ATP).

    From this it has been hypothesized that arsenic could have been a protobiotic forerunner to phosphate, which later could have been adopted since it is ~ 1000 more ubiquitous. Of course, the downside to this reactivity is that arsenic mononucleotides hydrolyze in hours instead of days.

  35. Duncan Ivry says:

    It’s fascinating how flexible a *certain* form of life is. But, I think, it’s a little bit premature saying life as such is much more flexible than we thought. Compare this one additional piece of flexibility to the many, many, more or less complex, more or less strange, living beings we already know about! Above that it’s remarkable for me, that several experts of biology in my country characterize, what those researchers around Felise Wolfe-Simon did, as mainly hype.

    And to the commenter Run, saying: “Well I’m completely new to reading this website (about a week now) and having read quite a few comments here …”
    Sorry, but … your power of judgment is really impressing, if you know what I mean 😉

  36. Aqua says:

    @Lawrence B. Crowell .. as usual, thanks! Now… think Mars.

  37. Aqua says:

    There are unexpectedly high concentrations of silica, potassium, sulfur and chlorine in the Martian soil… but it is low in magnesium. Any thoughts on that?

  38. Torbjorn Larsson OM says:

    @ Trammaan:

    … culminating in one that’s absolutely perfect for life … This leads to one of only two conclusions: either our form of life is ubiquitous and every time it evolved, which imay have been regularly, it looks the same or it is incredibly rare, appearing only once even on this of all planets the most propitious for life.

    I don’t see how you can confine it to only two pathways, even using your faulty assumption of “perfect”; evolution is a local hill climber, “good enough” means a viable population spawns a viable population. It would take an infinite population infinite time (or an infinitely large genome) to resolve even a _local_ fitness peak with infinite resolution – provided it can be reached by genetically initiated functions at all!

    In reality we know that there was a DNA LUCA. (There’s a Nature paper on the probability for LUCA vs the probability for, say, two ancestors: something like 10^2000 or so IIRC.) We also believe for good reasons that there was a RNA world with an LCA which descendant’s resulted in the LUCA. So there would have been a lot of paring down.

    Already Darwin was clear over the reason there “can be only one”; already established life tend to gobble up competitors but also new, naturally less competitive, protobiotic attempts. And of course over time the changed geology means there is little chance of later attempts; for example oxygenated atmosphere is not conducive for that.

    I recently made a comment on the simplest Poisson model of protobiotic attempts being testable with Earth as observation; testable because we can observe life so early (at most ~ 1 Gy after Earth coalescence), and consistent with easy abiogenesis. (Though the statistics of only one data point stinks, of course. Still, it can’t be rejected!)

    SETI may be a waste of time, depends on civilization density and lifetime, but looking for signs of other biospheres on exoplanets is definitely not! Prediction of easy abiogenesis and recent prediction of many Earth analogs makes it an endeavor with an expected large return.

  39. Aqua says:

    Calcium Carbonate is also present in abundance?

  40. Aqua says:

    Mix with a little Aqua and serve over crushed ice….

  41. Torbjorn Larsson OM says:

    Duh! “retain software” – retain wetware. Cute fail!

    @ Duncan Ivry:

    Not hype, but I browsed the paper now – it is handwaving on the DNA substitution. My guess earlier may be good.

    First, they use a DNA cleaning method that isn’t characterized for pureness AFAIU. It works for PCR, so it removes small RNA et cetera remains. But proteins et cetera? I dunno.

    Second, they find that _all_ arsenic is situated in a chemical environment reminding of DNA by nanoSIMS. Phosphor in DNA is ~ 4 % of total. What is the likelihood of all proteins, lipids et cetera resembling DNA chemically in near-neighborhood interactions, atom placement et cetera? I find that very fishy.

    Having thrown out the tow question marks as very quick and totally unfair layman armchair analysis, there is actually no sound support yet for arsenate as DNA backbone, from where I stand. The question is of course if that is anywhere close to facts, or at least were your countrymen experts stands.

  42. Lawrence B. Crowell says:

    @ Torbjorn Larsson OM: The ACS article, which I presume is referenced by Wolfe-Simon, suggests that arsenated nucleotides should then be commerically available by some of these bio-companies out there. The sort of experiments I outline above are not that difficult to perform, though it requires some investment on the part of somebody such as myself who does not have currently access to the gene-kits and the like. In fact to do any of this requires PCR, and if the TAQ replicase can work with arsenated nucleotides that would be interesting in its own right.

    LC

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