Signs of Life on Mars' Meteorite?

A new analysis of a 13,000-year-old Mars meteorite, retrieved from Antarctica, has rekindled the debate about whether the ancient rock holds signs of past microbial Martian life. The study is highlights much of the previous initial research, published in 1996, suggesting that very nanometer sized iron sulfide and iron oxide grains in the meteorite had biological origins. Additionally, tiny, worm shaped objects in the rock, known as ALH84001, could be the fossilized remains of Martian microbes. ALH84001 is theorized to be one of the oldest pieces of the solar system, proposed to have crystallized from molten rock 4.5 billion years ago. In September 2005, Vicky Hamilton of the University of Hawaii presented an analysis of the origin of ALH 84001 using data from the Mars Global Surveyor and Mars Odyssey spacecraft orbiting Mars. According to the analysis, the Valles Marineris canyon appears to be the source of the meteorite. Unfortunately, the analysis was not conclusive, in part because it was limited to parts of Mars not obscured by dust. The research was widely panned, and the NASA team making claims for life on Mars eventually stopped fighting. However, now in 2009, a team of experts at the NASA Johnson Space Center, have looked at the rock again using a new analysis technique, called ion beam milling. Ion beam milling thins samples until they are transparent to electrons by firing ions. They concluded that there is enough evidence to rule out at least one geological process as the one that formed the nanocrystal iron grains. That leaves something that was once living, leaving biology as a possible cause. The scientists also point out the similarity between magnetites found in the Martian meteorite and a type of Earth bacteria on land known as magnetotactic bacteria. "They look virtually identical," said Dennis Bazylinski, a geo-microbiologist at the University of Nevada, About 25 percent of the magnetites in ALH84001 have an elongated structure typical of magnetic bacteria on Earth. This is not enough however to satisfy Michael Fuller, who researches magnetism at the University of Hawaii's Institute of Geophysics and Planetology." The grain-sized distribution is pretty small, once iron particles get smaller than about 20 nanometers, the magnetism breaks down. Most of them (the grains discussed in the new research) appear too small. It doesn't look to me that they are very similar to magnetotactic bacteria," he said. Fuller also says he is not convinced the magnetites in the Mars rock couldn't have been produced by shock when the meteorite blasted through Earth's atmosphere. A similar shock process produces small iron particles in the lunar soil, he added. "It seems to me that they haven't really solved the whole thing. I remain a skeptic. "But Bazylinski argues the research puts a nail in the coffin of one geological theory, that the magnetites were formed by the melting of tiny carbonate disks found in the meteorite. "It'd be great if this was bacteria. I'd be the first one to carry the flag. But this one meteorite is not going to answer the question of whether there was life on ancient Mars or not," said Bazylinski. The question of if there ever was life on Mars continues…

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