From Ethan Siegel at Forbes:
The first test was performed first, and came back negative. The second test was next, and also came back negative. By time the third test was performed, with both landers in situ, the prospects were pretty grim, but the data was taken anyway. To the surprise of almost everyone, both Viking 1 and 2 detected metabolized, radioactive carbon-14 as part of the carbon dioxide emitted. They even took their samples from different locations: one from soil in direct sunlight, the other from soil found under a rock. In both samples, the carbon dioxide emission was immediate and sustained after the first injection. To great excitement and fanfare, the team led by Gilbert Levin thought they had their first signature of life on Mars.
The team held their breath as the control experiment was performed, and this is where things get fishy. Subsequent injections of radioactive nutrients failed to produce any response; what we were seeing was consistent with either organic or purely chemical, inorganic processes. Perhaps there wasn’t life on Mars, after all. Despite the initial declaration — that if any of the three tests came back positive, we’d announce life on Mars — these results seemed to be inconclusive. In the forty years since, we’ve never replicated the experiment, and we still don’t know for certain. More.
Our favorite physicist, Rob Sheldon, thinks they did find life but—as Siegel goes on to say—only a manned mission can really tell us.

What made you lardasses think that robots could do all the work for us?
See also: Rob Sheldon reflects on the hunt for water on Mars
What we know and don’t know about the origin of life
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as to this quote from the article:
Before any Sheldon Coopers sign up and pack their bags to go live on Mars, perhaps a few warnings are in order:
And once you get to Mars it is no picnic either. Besides the fact that Mars has no magnetic field or Ozone to protect you from cosmic rays, the soil of Mars is ‘toxic’
Of related note, salt is ‘very effective at dismembering membranes and preventing RNA units (monomers) from forming polymers any longer than two links (dimers)’
Also of note: it is interesting to note man’s failure to build, right here on ‘friendly’ Earth, a miniature, self-enclosed, ecology in which humans could live for any extended period of time.
Maintaining a suitable ecology for an extended period of time appears to be a far more complex affair than Martian wannabes had first presumed:
Please note, that if even one type of bacteria group did not exist in this complex cycle of biogeochemical interdependence between different bacteria, that was illustrated on the third page of the preceding site, then all of the different bacteria would soon die out. This essential biogeochemical interdependence, of the most primitive different types of bacteria that we have evidence of on ancient earth, makes the origin of life ‘problem’ for neo-Darwinists that much worse. For now not only do neo-Darwinists have to explain how the ‘miracle of life’ happened once with the origin of photosynthetic bacteria, but they must now also explain how all these different types bacteria, that photosynthetic bacteria are dependent on, in this irreducibly complex biogeochemical web, miraculously arose just in time to supply the necessary nutrients, in their biogeochemical link in the chain, for the photosynthetic bacteria, as well as each other, to continue to survive.
as well:
Verse. Quote and Inspirational:
Ethan Siegel, like many involved in the NASA press releases, misrepresents the results of the Labelled Release Experiment, whose PI was Gil Levin. Gil was muzzled by NASA for 30 years, but upon his retirement, published all the papers that NASA wouldn’t let him release.
http://www.gillevin.com/Mars/R.....femars.htm
It is unfortunate that Ethan didn’t go to Gil’s website and read the papers, but instead spouted the “official” line from the censored (and misleading) NASA reports.
(a) the gas chromatograph that “didn’t see life” was shown upon Earth testing to have a clogged Palladium filter. Its backup couldn’t see life on Earth either, which the LRE could detect. Gil suggests that his experiment was at least 1000x more sensitive than the one that had Carl Sagan as an investigator–and possibly 100,000x more sensitive.
(b) Seigel conveniently forgets to mention that LRE had a control. Each time they saw something growing, they did a 2nd test where they baked the soil at 300C and then added the nutrients. Each time the control saw nothing.
(c) The result of adding nutrients several times was not as Siegel reported. Gil says that the results are consistent with bacteria on Earth that behave identically. The initial pulse of new nutrients suppresses growth, a bit like overeating at Thanksgiving, but later leads to further growth. This is not consistent with chemical or non-biological models.
(d) NASA standard line was that super-metallo-peroxides could mimic this behavior, and thus LRE was not 100% proof of life. Further, argued NASA, Mars was bone dry and couldn’t support life.
(e) Both of these statements were in-your-face falsehoods. Gil did many experiments with super-metallo-peroxides and showed that they couldn’t mimic his results. Furthermore, should these peroxides exist, there would be hydrogen peroxide in the atmosphere, which there wasn’t. It was a desperate theory without support.
Finally, although it took 10 years to get published because NASA suppressed the images, (as in removing them from the archive), they took pictures of snow on Mars with the same Viking lander that collected Gil’s data. That’s proof positive that Mars is not a desert and that life can find water. They knew this even while they were shutting down Gil’s publication of the discovery of life.
So start a campaign to get Gil’s work recognized, and nominate him for the Nobel Prize. He’s 89 and won’t be with us much longer. And his detractors need to be shamed into silence.
Dr Sheldon,
What do you think NASA’s motive for covering up these discoveries is?