![]() Ergo, the Red Planet was officially dead. One reason for his interpretation is that the type of organics detected - chlorinated hydrocarbons - were not at the time expected to exist on Mars.īased on all this conflicting evidence, Soffen concluded, in his famous words, “No bodies, no life.” Without organic molecules, there just couldn’t be life on Mars. The instrument did detect trace amounts of organic compounds, but they were interpreted by the experiment’s principal investigator, Klaus Biemann, to be contamination from Earth. Project scientist Jerry Soffen waited for the results from the GC-MS. What to do with these mixed results? The mission scientists were under pressure - the public wanted to know. The “gas exchange experiment,” designed to measure the exchange of gases resulting from biological activity, provided confusing results, and showed no evidence of biology. The first result coming in from the “pyrolytic release experiment,” designed to measure organic synthesis reactions associated with life, was also positive, but later ones were negative. The “labeled release experiment” led by Gil Levin, designed to detect metabolic activity, yielded positive results, although later data from the same experiment cast some doubt on that. The mission scientists agreed prior to the landings that if even one of these experiments was positive, it would mean life on Mars was detected. NASA’s twin Mars landers carried three such experiments and another instrument called a gas chromatograph-mass spectrometer (GC-MS) to look for organic molecules. Viking Life Detection experimentsĪ similar case is the controversy surrounding the Viking Life Detection experiments of the 1970s. However, given the apparent misinterpretation of the “fossil” images, you don’t find many scientists who will give ALH84001 a second look. ![]() In other words, fossils, or even dormant life, could conceivably have made the journey from one planet to another intact. One point even the critics agree on is that the interior of the meteorite was never heated above 40° C during its journey from Mars to Antarctica. Some of the McKay team’s lines of argument have weakened while others have grown stronger, but I still find it plausible, as McKay says, that the most parsimonious explanation for their findings is biology. The close spatial association of reducing and oxidizing regions within the rock - which is typical of microbial interactions - and the presence of magnetite chains of high purity, which are indicative of a certain type of bacteria called magnetotactic bacteria, are intriguing. Yet, there are good scientific arguments that the meteorite does, in fact, contain evidence of past life. And as a result of the controversy over the misinterpreted “fossils,” most scientists lost interest in ALH84001. They’re more commonly interpreted as products of mineralization, not biology. Nowadays no one, or at least no one I know, really thinks these worm-like structures are microbes. Images contained in McKay’s paper were widely circulated by the press, purporting to show the Martian fossils. Some readers may remember the famous 1996 paper in the journal Science by David McKay from NASA’s Johnson Space Center, which motivated president Bill Clinton to announce in a memorable press conference the possible discovery of fossilized life on Mars. We’ll need additional evidence - for example, geochemical analyses - to verify what our eyes are telling us. But that will almost never be enough to prove the existence of extraterrestrial life. It’s a common pitfall to jump to conclusions when a new object looks like something familiar. ![]() I receive quite a few emails every year from people claiming to have found a lizard, fossil bone, or some other large-scale evidence of biology on another planet. Looks can deceive because our brain is always trying to extrapolate a familiar structure or pattern from anything we observe. Credit: NASA / JPL / Public Domain via Wikipedia ![]()
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