![]() ![]() Scientists don't know for sure how life got started on Earth, but they think it required some kind of burst of energy to start it off. Zachary Adam, now a graduate student at Montana State University in Bozeman, suggested the possibility in a 2007 paper in the journal Astrobiology, which he wrote as a graduate student at the University of Washington. Cullenįurthermore, the nuclear reactors themselves could have provided an even greater boon to life by giving it the spark it needed to originate in the first place, some scientists think. This cartoon shows a possible mechanism by which oxygenic photosynthesis could lead to formation of natural fission reactors. I think that most people view ionizing radiation as a bad thing, but thats not always necessarily so." Thats the quantity that natural selection is going to act upon, and it might help to promote change in organisms with time. "The ionizing radiation would actually provide some genetic variation," Cullen said. However, life hanging out on the outskirts of a nuclear reactor might have received a smaller dose of radiation not enough to kill it, but enough to introduce mutations in its genetic code that could have boosted the diversity in the local population. If organisms were living too close to the site of a reactor, they could have been wiped out completely. The ionizing radiation released by a nuclear reaction can damage DNA, the precious instruction code built into every cell of life. In 1972, French miners in Gabon, Africa discovered evidence that a natural nuclear reactor had formed about 2 billion years ago from a concentration of the fissionable element uranium 235. However, because there is such a poor geologic record left from so long ago, scientists have very little way of confirming this idea. "It certainly seems more than likely that these sorts of reactors would have been much more common in the Earth's early history because the amount you need is actually quite small," Cullen told Astrobiology Magazine. They found that during the Archean epoch, between around 2.5 billion and 4 billion years ago, natural nuclear reactors could have been relatively frequent. Coogan, a colleague at the University of Victoria, researched how likely these reactions were when Earth was much younger, based on how much uranium in a given area is necessary for the material to go critical and start a self-sustaining fission reaction. "As far as we know, we only have evidence of natural reactors forming and operating at the one site in Gabon, but that demonstrates that it's possible, and our calculations suggest it was much more probable earlier in Earth's history," said Jay Cullen of the University of Victoria in Canada.Ĭullen and Laurence A. Scientists think a concentration of uranium 235 there went critical around 2 billion years ago and underwent fission, just as it does inside man-made nuclear reactors. In fact, that's the scenario most supported by studies. It was as if the material had already gone through a nuclear reaction and been used up. French miners discovered that the uranium samples they extracted were depleted in the rare isotope uranium 235, the only naturally occurring material on Earth capable of sustaining fission reactions. The only known examples of natural nuclear reactors on Earth were discovered in the Oklo region of Gabon, Africa, in 1972. This energy could prove beneficial and highly detrimental to developing life, depending on the circumstances. The reaction releases a powerful punch of energy. Natural nuclear reactors occur when deposits of the radioactive element uranium build up in one spot, and eventually ignite a self-sustaining nuclear chain reaction where uranium divides, in a process called fission, producing other elements. If they did exist, the large amounts of radiation and energy released by such reactors would have had complicated effects on any life developing on this or other worlds, experts say. There's also reason to think other planets might have had their own naturally occurring nuclear reactors, though evidence to confirm this is hazy. Evidence for a cluster of natural nuclear reactors has been found on Earth, and some scientists say our planet may have had many more in its ancient past.
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