6 of 7 people found the following review helpful:
5.0 out of 5 stars
Barry DiGregorio presents evidence for life on Mars., October 7, 1999
By A Customer
This review is from: Mars: The Living Planet (Hardcover)
In this book DiGregorio admirably discusses evidence for the conclusion that the Viking missions did in fact discover life on Mars. This is the view of Drs. Gilbert Levin and Patricia Ann Straat, who developed one of the instruments, the Labeled Release experiment, that flew on Viking. The book presents very exciting up to date information on exotic organisms, extremophiles, that might be found on other planets. NASA itself is investigating such possibilities with its Astrobiology program. Finally, the book argues that since some experiments on Viking gave very definite life signs, missions such as Mars Sample Return should not be undertaken until the issue is resolved conclusively.
For the last twenty years, Dr. Levin has consistently argued that no non-biological explanation faithfully reproduces the results seen in his experiment. Dr. Levin has shown great insight in regards to the life on Mars issue. As discussed in DiGregorio's book, he suggested to the imaging team that there were other colors on Mars than just dull browns and reds. This was verified by members of the Viking imaging team who confirmed there were blue and green patches on rocks that changed seasonally. Levin argued that the dry conditions and (apparent) low organic content in the Mars soil did not preclude the existence of life. Since the Viking missions, it has been confirmed that certain organisms can live within igneous rock surving on non-organic chemicals for nutrients and on water that trickles through cracks in the rock. Levin argued in a paper on liquid water on Mars that a widely cited paper concluding that liquid water could not exist on the Martian surface was based on a faulty assumption that water vapor was evenly distributed through the Martian atmospheric column. The Pathfinder mission confirmed that water vapor was restricted to the bottom 1 to 3km above the Martian surface.
Another factor that Digregorio discusses in his book is the evidence that there may be active volcanism on Mars. This is important to the life issue since this indicates heat and or hydrothemal systems on the Martian surface. And the National Science Foundation's report on the Mars Sample Return mission admits that such would increase the chance for life on Mars. Recently from Mars Global Surveyor images it has been concluded that Mars lava flows could be as young as 200 thousand years, which would make it virtually certain that volcanism continues today.
In reading over the history of the controversy over the conflicting results from the Vking missions, it occurs to me there is a basic flaw in subsequent investigations to resolve the issue. They all assume there was something wrong with Levin's Labeled Release experiment and the GCMS, which indicated no organics on Mars, was right. DiGregorio discusses the fact that it was first believed there was a problem in the LRx when it gave positive responses. But the engineering team confirmed it was operating properly. In contrast, there was one important factor with the GCMS that was definitely wrong, and two others that possibly were "wrong". As DiGregorio mentions, the Viking GCMS NEVER GOT AN INDICATION THAT SAMPLES WERE ACTUALLY DELIVERED TO THE CHAMBER. This indicates that either there was a flaw in the mechanism detecting sample delivery or the GCMS never got a large enough sample to register. If the second is true then that has clear implications for its failure to detect organics on Mars. Two other failings of the Viking GCMS is that it could be "poisoned" by soil with high sulfur content, known to be true of Mars, and the fact that it could not detect the organic equivalent of fewer than a million cells per gram.
Given these facts you would think that at least some research would have gone into showing how the GCMS could have given a wrong result. Yet all the research (other than Levin's) went to showing why the LRx was wrong. Why? Scientists are a conservative bunch. Rather than making the truly revolutionary claim that life had been discovered on Mars, they simply preferred to make the safe assumption that the instruments indicating life present were flawed. However, the history of science shows that great discoveries are made when scientists with insight go beyond the safe assumptions, and view the evidence dispassionately and go wherever it leads. What should have given scientists pause is the fact that the conclusion that the GCMS was right and the LRx wrong was based not on scientific factors but solely on the assumption that that is the way things should be.
So how can we determine whether it was the LRx or the GCMS that was flawed? A recent paper by Yen, Murray, and Rossman may give a clue: Water content of the Martian soil: Laboratory simulations of reflectance spectra Authors: YEN, A. S.; MURRAY, B. C.; ROSSMAN, G. R. Journal: Journal of Geophysical Research, v. 103, No. E5, p. 11,125 (1998).
This paper shows there is a discepancy between the water content of the Martian soil as determined by the GCMS and determined by all other Earth-based and orbiter observations, perhaps by a factor of 1 to 2 orders of magnitude. The upcoming Mars Polar Lander due to land on Mars in December will test the water content of the Martian soil. If it confirms the high water content of all the observations other than the GCMS, then that would indicate a gross error in the GCMS water analysis and by extension in the organic analysis as well.
Bob Clark
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2 of 2 people found the following review helpful:
5.0 out of 5 stars
what is evidence?, July 1, 2003
This review is from: Mars: The Living Planet (Hardcover)
Reading this book took me back over the years to the 1976 viking lander life detection experiments. I have a doctorate in cell biology and have worked extensively with cells in culture. Thus, the label release experiments seemed pretty indicative of metabolism in the martian soil sample, hence life. The fact that the uptake of labeled nutrients was prevented if the soil was pre-heated (steralization) was also consistent with life which could be destroyed by heat. These results seemed to be pretty strong indicators of some sort of microbiol presence in the soil. At this point everyone seemed excited. Then came the gas chromatography which failed to detect organic material. The conclusion was immediately reached that the martian soiled contain no life but had an "interesting chemistry". Howver, what we had was conflicting results which usually calls for further experimentation rather than dismissing one set of data out of hand.
Thus I was delighted to see Digregorio et al's book on the library shelves. The authors argue convincingly that the label release experiments were properly done and also points out potential problems with the chromatography experiments which should have been examined more closely. He also discusses other intrigueing observations, such as the presence of green hues on the martian rocks suggesting photosynthetic organisms. Perhaps one of his most telling arguments concerns the use of the word "evidence." Evidence is a set of one one or more observations which support a given hypothesis. Certainly the label release experiments would fall into the category of evidence for life. Furthermore, no one seems to have shown that the experiments leading to these results were flawed. Thus the statement made again and again that the viking lander experiments failed to show evidence of life is wrong. While the authors can't prove conclusively that there is life on Mars, they certainly make a strong case for examining the question further. I would recommend this book strongly to anyone interested in exobiology.
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1 of 1 people found the following review helpful:
5.0 out of 5 stars
SKY & TELESCOPE MAGAZINE REVIEWS "MARS THE LIVING PLANET", February 26, 1999
By A Customer
This review is from: Mars: The Living Planet (Hardcover)
Review from Sky & Telescope magazine page 69 - April 1998:"Space writer Barry DiGregorio's tome centers on the notion that the Viking landers discovered evidence for biological activity on Mars, but this evidence was misinterpreted or intentionally suppessed.DiGregorio's book tells the story of Gilbert Levin, Pricipal Investigator of the Labeled Release (LR) experiments aboard the two Viking probes that landed on Mars a generation ago. On both landings, the LR raised eyebrows when it "fed" carbon 14-laced nutrients to samles of Martian soil: unaltered soil quickly gave off carbon dioxide containing the radioactive tracer, whle a "sterilized (heated) sample did not.The nine LR results have been widely attributed to still-unidentified oxidants, but Levin and LR coinvestigator Patricia Ann Straat still maintain that microorganisms of some kind had metabolized the labeled food. While sounding at times like a conspiracy tract, DiGregorio's thoroughly documented narrative challenges Levin's critics to pen a popular level rebuttal".--Review by Joshua Roth
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