The NASA Astrobiology News Conference

Tomorrow (2nd December) at 2pm EST NASA will hold a press conference “to discuss an astrobiology finding that will impact the search for evidence of extraterrestrial life” This sounds fairly exciting and of course it’s an invitation to science bloggers to speculate about  what they might have discovered. At a previous press conference in 1996 NASA announced that it had found bacteria-like structures in a meteorite that had come to Earth from Mars. Could tomorrow’s announcement be something similar?

The only clue we get is a list of scientists who will attend the press conference and who are probably the authors of a paper to be published in Science on the discovery, whatever it is. Here is a brief summary of their profiles

  • Mary Voytek: A microbiologist interested in aquatic microbial ecology and biogeochemistry. She has studies life in extreme conditions on Earth suxh as deep-sea hydrothermal vents and terrestrial deep-subsurface sites and is an Interim Senior Scientist for Astrobiology in the Science Mission Directorate at NASA HQ.
  • Felisa Wolfe-Simon:a NASA Astrobiology Research Fellow through the NAI and Exobiology at NASA. She has studied (hypothetical) life forms with unusual chemistry including arsenic-based life.
  • Pamela Conrad: Works at NASA’s Virtual Planetary Laboratory and studies signatures for life and planetary habitability assessment.
  • Steven Benner: A biochemist who runs a laboratory that aims to create artificial life. The lab also studies bio-signatures from planets other than Earth and is working with NASA to deign the next generation of probes to Mars
  • James Elser: A researcher in the field of biological stoichiometry, the study of balance of energy and multiple chemical elements in living systems. Currently, he is an active member of the ASU’s NASA-funded Astrobiology project “Follow the Elements”

So what do we think this is about? The intriguing possibility is that the team has indeed found some biological signature indicating the possibility of extraterrestrial life. It could be something as simple as oxygen or an amino acid. This could be an observation from a probe looking at a planet or moon in the solar system such as Mars, Titan, Europa or Rhea. Alternatively it could be from another metiorite found on Earth, or a comet. A discovery related to exoplanet searches is also possible but does not seem to be such a good fit.

Of course it is also possible that the discovery is something less extraterrestrial, such as an unusual life-form found on Earth. It is not likely to be the discovery of a radio signal from extraterrestrials because the expert profiles are wrong, but who knows?

Update (2-Dec-2010): The announcement turns out to be that the scientists have taken a microbe from the arsenic rich waters of lake Como and put it in a soup which is rich in arsenic and low in phosphorus.

Arsenic is highly poisonous to us because it is chemically similar to phosphorus and replaces phosphorus in the molecules in our body, but it is not close enough for this to work. However, what was found was that there is one bacteria from the lake that takes in the arsenic and continues to live and subdivide. In particular the phosphorus in the DNA of the bacteria gets replaced with arsenic.

This is interesting because it means that DNA based extraterrestrial life might evolve in environments that don’t have phosphorus.

Some websites are still reporting that they have discovered a completely new type of lifeform that uses arsenic instead of phosphorus. This is not quite the situation. Instead it is a conventional microbe with a remarkable ability to use arsenic instead of phosphorus when necessary.

Update (3-Dec-2010): There was an interesting moment in the press conference when Benner tried to explain why he is so sceptical about this discovery. He said that phosphor gets incorporated into life’s molecules through a complex sequence of 14 enzyme catalysed reactions. Although arsenic is chemically similar to Phosphorus, it is not so similar that it could substitute into such a reaction sequence, therefore it is hard to see how it could get into DNA.

Wolfe-Simon came back with a simple response. While phosphor based chemicals are hard to produce, their arsenic based counterparts form spontaneously in a testtube when you mix the chemicals together!

Of course this does not completely answer the objection, it is still hard to see how an alternative chemical pathway can exist inside these bacteria, but if Wolfe-Simon has done her work well, that is exactly what is happening.

If we speculate a little beyond what was said the implication for the formation of life both on Earth and extraterrestrial is startling. It is one of the great puzzles of science that basic life arose spontaneously from the primordial soup on Earth. If the chemical reactions that life uses are so complex how could they have arisen naturally?

Suppose the Lake Como bacteria is not just a remarkable micro-organism that has adapted to an arsenic based environment. Could it be a throw-back to an earlier form of life that evolved from scratch in a chemical soup where the molecules for life could form spontaneously using arsenic instead of phosphor?

Arsenic based molecules are less stable than their phosphorus equivalents, so if an arsenic based micro-organism could adapt to using phosphorus it would be able to make the leap to water dominated environments where evolution can progress. So the Como Lake bacteria may not be phosphorus based life that adapted to arsenic at all. It could be arsenic based life that adapted to use phosphorus, but unlike other more evolved cells, it retains the mechanisms needed to live off arsenic.

 

 


21 Responses to The NASA Astrobiology News Conference

  1. Lawrence B. Crowell says:

    This might have something to do with the close look by the Cassini spacecraft at Encaledus and the geysers there. It is either that or maybe Sarah Palin has been found to be a space alien due to her out of the world remarks. She recently accused a non-American of being “unAmerican.”

  2. Bill K says:

    Rumors elsewhere on the net indicate that this news conference is about the discovery of arsenophilic bacteria in Mono Lake, CA. On the other hand, the mere fact that I can Google “arsenophilic bacteria” indicates that they are not entirely new!

    The geysers on Enceladus are thought to arise from ancient underground Mentos deposits.

    • Philip Gibbs says:

      That would be a good fit to the description of the press conference and to the research areas of the experts. But bacteria that eat arsenic and use it for photosynthesis were already known to be in Mono Lake since at least two years ago.

      There must be a new twist.

    • Lawrence B. Crowell says:

      I like the Mentos idea. There is a lot of power in them and you can go a long way :-)

      I built a liquid propelled rocket where I used mentos & coke to pressurize the fuel & oxydant tanks and force the propellants into the thrust bottle.

      The only problem with the Mentos theory with Enceladus is you need lots of coke — in liquid form.

      There is some scuttlebutt about arsenic.

  3. Philip Gibbs says:

    With the announcement approaching some of the speculations are sounding very interesting. Given that they are going to announce something about bacterial lifeforms in the arsenic rich environment of Como Lake, what can we expect?

    Some people are saying that this is not just a lifeform that has adapted to using arsenic. It is a lifeform very unlike anything we are familiar with. Are they going to suggest that it represents a completely separate zoological tree with no evolutionary connection to other life on Earth, or is it just a very different branch of the same tree? Perhaps it is a precursor that shows how life began before the environment was able to support more conventional lifeforms.

    It will be interesting to see what they think and what implications they propose for astrobiology. Is there a similar environment elsewhere in the solarsystem, or is there just a general conclusion about the diversity of life?

  4. Bill K says:

    “… microorganisms in Mono Lake which use arsenic in their DNA instead of phosphorus.”

    • Philip Gibbs says:

      Could an organism using arsenic in its DNA evolve into one using phosphorus, or vice versa?

      It will be useful to know if the organism uses only arsenic, or some arsenic and some phosphorus, if that is possible.

      • Lawrence B. Crowell says:

        Chances are that these prokaryotes in the past employed phosphorus, but then were exposed to an increasingly rich arsenic environment. The molecular machinery and its genetic coding were selected for. Arsenic tends to act like phosphorus (the outer electron shell is similar etc), but also gums up the works. However, it is remarkable that evolution can adapt life forms in the way to substitute phosphorus for arsenic.

        I am not at all clear why this is being hailed as some extra terrestrial biology result. If this is arsenic life, then this is completely in line with terrestrial biological evolution.

      • Philip Gibbs says:

        The main reason it is being hailed as an extra terrestrial biology result is that it was funded out of NASA’s astrobiology program.

        Of course it does tell us a little about how life might exist in different chemical environments.

  5. Philip Gibbs says:

    Reading some reports on the Science article, I understand that they did not simply find an organism using arsenic instead of phosphorus in its DNA They took a bacteria from the lake and let it reproduce in an environment with lots of arsenic and little phosphorus. As the bacteria reproduced it used some arsenic instead of phosphorus in its DNA.

    There is no suggestion of a separate evolutionary branch as some people have speculated, but it does imply that extraterrestrial life could evolve without phosphorus by using arsenic instead.

  6. Lawrence B. Crowell says:

    I just heard the podcast. This sounds a bit like what I suspected. However, it has not been substantiated that arsenic is encorporated in polypeptides and nucleotides. However, without phosphorus and with lots of arsenic it is not an unreasonable hypothesis to say arsenic is fully encorporated. The article is in science express on the Science website.

  7. Ulla says:

    The microorganism substitutes arsenic for phosphorus in its cell components. This means also DNA, ATP, cellmembranes? Building parts of itself out of arsenic, say the researcher. P is a centralatom in a chiral structure.
    Wolfe-Simon learned that about one-tenth of the arsenic absorbed by the bacteria ended up in their nucleic acids, with very little of P.

    Arsenic disrupts metabolic pathways because chemically it behaves similarly to phosphate. Problems: hydrolyzing in contact with water, stabilization because of the reactivity, maybe symmetry. Lipids is a buffert.

    But ATP is a molecule for protonpumping. The energytransfer is altered too?

    http://www.astrobio.net/exclusive/3698/thriving-on-arsenic

    On http://www.nasa.gov/topics/universe/features/astrobiology_toxic_chemical.html
    there is a picture and the bacterias look more ‘clumsy’. Also a video

    • Philip Gibbs says:

      One of the experts on the panel was a sceptic who did not believe the arsenic was going into the DNA.

      • Ulla says:

        This is an interesting topic, but so little is told. Humans can tolerate some amounts of arsenic if they are slowly accommodated to it, but it is storaged in bones. These bacterias have vacuoles instead? Are they transporting arsenic to the outside? (Probably) And arsenic was incorporated, but they never told how longlived these cultures were. No LD-value? Only a number about 10 % was mentioned.

        They also did not tell about the existence of both together, what happened then. Was P preferred? It ought to be as it is more stable. In Discoverymagazine was said they used arsenic INSTEAD of water, and that would be really something new. These bacterias lived in a POND, and supposedly there was water. Water is an absolute requirement for life? The question if P was an absolute requirement was also not answered. Recycling of P could happen in a small scale.

        Theoretically this is interesting, because it highlights the need for stability of DNA, and the ev. life creation on Earth without oxygen and with much more reducing and poisonous conditions. How did they handle the stability then? Or was the creation of DNA such a stabilisating pathway?

        What meant the more frequent appearance of oxygen?

        This also tells something about the need for methylation – acetylation of DNA?

  8. Philip Gibbs says:

    So by now there are a few good blog posts around describing what the discovery was about e.g. http://blogs.discovermagazine.com/notrocketscience/2010/12/02/mono-lake-bacteria-build-their-dna-using-arsenic-and-no-this-isnt-about-aliens/

  9. Bill K says:

    Also, XKCD is on top of the story. http://xkcd.com/829/

  10. Lawrence B. Crowell says:

    The announcement appears premature, or the stated conclusions are not warranted by the data.

  11. Philip Gibbs says:

    It looks like they will have to do more work to convince the sceptics!

  12. Lawrence B. Crowell says:

    An initial determination does not require a molecule by molecule analysis. 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. 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.
    The authors more or less assumed that since the environment was phosphate depleted that arsenic was a surrogate. That is a plausible hypothesis, but not demonstrated here. This is what seems to be the big thing that got them in trouble, they jumped the gun, and AAAS Science was hasty in admitting a paper which was deemed as having high impact.

  13. Ulla says:

    This As could be a scaled-up version of P :) I know what you think of this, but sincerely. There is a point.

    Those bacterias have simply found a way to handle the decoherence, as Life has found out to handle the decoherence (create coherence and synchrony). In that light the finding is extremely interesting.

    Mass isn’t fundamental, says Marco Frasca. http://marcofrasca.wordpress.com/2010/11/28/some-reflections/

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