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To MARS with MER - Life?
In 1996, two decades after Viking landed on Mars, came an announcement that really did resound around the world. It all began with meteorite found on the cold, frozen ice of the Antarctic. What made this meteorite special was that it was one of a special class of rocky objects from space whose chemical composition made researchers confident they came from Mars--blasted off by some ancient cosmic collision, and then falling to Earth.
It was known as "ALH84001", discovered in the Allan Hills as the first find of the 1984 Antarctic research season.
When scientists at NASA’s Johnson Space Center, where the moon rocks brought back by Apollo had been analyzed, looked at ALH84001 in detail they found something so astonishing that they kept it to themselves until they’d carefully checked their results. Along with many chemical and magnetic signatures closely associated with microbial activity down here on Earth, they saw what looked like microfossils. They knew sometimes inanimate processes made objects which look lifelike, but they argued that taken altogether the evidence meant we were seeing the very first evidence of any kind of life from beyond Earth.
Of course, many other researchers were skeptical: NASA even invited one of them to its press conference, where he said he knew no terrestrial life as small as the possible Martian fossils. Soon after, in the kind of debate which typifies science and makes it so exciting, other researchers found "nanofossils" much closer in size to what was seen in ALH 84001. More recently, one of the JSC researchers, Kathy Thomas-Keptra, studied some of the tiny magnetic crystals found in the meteorite under a very high-powered kind of microscope: she saw that these crystals had a shape resembling the tiny magnetic compasses which earthly microbes use to orient themselves. Kathy and her team said they knew of no purely chemical process which made such crystals. But the fascinating debate continues...