Tuesday, May 27, 2008

Search for life on Mars







Neil Saunders says:

(1) Is there life on Mars now?
(2) Was there ever life on Mars?
(3) Will Phoenix find and positive evidence?


  1. Wouldn't you just love to run some shotgun sequencing on that red dirt?

  2. Among the reasons I am interested in metagenomics ....

  3. The question is, does Martian life contain DNA as we know it, or is its genetic material different?

    I'm guessing that we'll find life on Mars, and it will be related to life on Earth through cross-contamination between the two planets.

  4. I agree. The main reason I think we will find evidence for life on Mars is the high probability of cross contamination between the planets. Of course, it would be much cooler to find independently evolved life ...

  5. I think they'll find evidence of formerly liquid water -- evidence that only a geologist will really be able to understand, but that they will dumb down for us -- but no direct evidence of current or past life.

    I think that if there ever had been widespread life on Mars that it's still there, but deep under the ground, like those freaky rock-eating SLiMEs ("subsurface lithoautotrophic microbial ecosystems"). It's hard to imagine (a) microbes not digging in that deep if they had the chance, and (b) systems like that going extinct once they're established.

  6. Gilbert Levin, designer of the labelled release experiment on the Viking landers, maintains that we already found Martian microbial life. Judge for yourself, he's collected a lot of data together at his website.

  7. Not sure I buy the Viking lander labelled release experiments as good evidence for life. Too many other possible explanations from what I remember. But I will (dutifully) check out his website.

    And I agree with CP -- if there ever had been life on Mars that was in some microbial form, I am fairly certain it would be really frigging hard to wipe it out.

  8. The official NASA line on the LR experiment was an inorganic reaction: reactive oxygen species in the regolith, if I remember right. They also cite the absence of liquid water and the failure of the GC instrument to detect organic compounds.

    Levin counters that at certain times of day, liquid water can exist. He also claims that the GC instrument lacked sensitivity; there are supposedly Arctic soils on earth in which the same instrument would not detect carbon, but microbes are known to be present.

    It's interesting stuff - well worth revisiting, I think.

  9. I agree that cross contamination makes it pretty likely that there has been life on Mars. (There's an interesting idea -- Norm Sleep's, I think -- that in the early solar system the ability to stow away on meteorites was actively selected for, because after a planetesimal hits your world and turns the atmosphere to live steam, a meteorite that's been flung off and takes a couple of thousand years to come back, which is typical in such things, is the safest place to be.)

    Whether it persisted or not seems open. I suppose I agree that wiping it out would be hard (though wouldn't potassium decay within the cell screw your genome over million year time scales?) but the very very end of the tail could be extremely thin. Chances of sampling it in a few scoops would seem remote. Nor does Phoenix have any life detection capacity per se.

  10. Oliver --

    I like this concept of early selection for ability to stow away on meteorites but have not read Sleep's stuff (it is was his) on this (or anyone else's his). If such stuff was occurring, it would be important to know what the ratio of time spent "in asteroido" was versus "in planeto"

    Neil ---

    I guess I will brose some of the stuff on Levin's site ...

    Oliver --

    If microbial life were to show up on anteroids that were hitting Mars every so often, it would seem to me reasonably probably that some of this life could find something to do for a bit on Mars. I guess the key questions relate to what types of microbes show up on Mars and this would depend on where the asteroid came from in the first place and how long and where it was floating around in space.

    But it seems to me that if you take some random sample of the current earth and make it reasonabl big (big enough to become an as)teroid) that somewhere in that rock there would be some microbes that could survive for a while if the rock was in space just as if it was sitting on earth.

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  12. The results of the Viking experiments on Mars were not shelved and labeled "case closed." At least not by Dr. Gilbert V. Levin, designer of the Labeled Release (LR) life detection experiments. He has his conclusions at his website: http://mars.spherix.com/mars.html. A quote from the first page:

    "Of all the many hypotheses offered over the years to explain the LR Mars results, the only possibility fitting all the relevant data is that microbial life exists in the top layer of the Martian surface."

    This page has a long list of downloadable reference documents.