![]() 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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