A team of international researchers claims to have found what could be the first proof of life beyond our planet: clumps of extraterrestrial bacteria in the Earth?s upper atmosphere. Although they are similar to bacteria on Earth, the scientists say the living cells found in samples of air from the edge of the planet?s atmosphere are too far away to have come from Earth.
?There is now unambiguous evidence for the presence of clumps of living cells in air samples from as high up as 25 miles, well above the local tropopause, above which no air from lower down would normally be transported,? says Professor Chandra Wickramasinghe, an astronomer at Cardiff University in Wales. ?A prima facie case for a space incidence of bacteria onto the Earth may have been established.?
Wickramasinghe and scientists from India collected the space bugs from samples of stratospheric air using the Indian Space Research Organization?s cryogenic sampler payload flown on balloons from a launch pad in southern India. Using a fluorescent dye, the scientists detected living cells in the sample and estimated by the way their distribution varied with height that they are falling to earth from space. They estimate that as much as a third of a ton of biological material is raining down over the entire planet daily.
Professor David Lloyd, a microbiologist at Cardiff University who examined the space bugs, says they look like common terrestrial bacteria but there is no explanation of how they could have risen so high. ?There would have to be some unusual event which would take particles from the Earth to a height of 40 kilometers,? he says.
The bacteria could have hitched a ride on a rocket or satellite into space or they really could be from another planet. ?We have no evidence for one or the other as yet,? says Lloyd. ?The most likely possibility is that the bacteria have arrived from another planet. I?d like to think that, at any rate. It?s the first pointer that it is possible to get evidence that there is life on other planets.? He?s tried, so far unsuccessfully, to grow the bacteria in a culture but says he hasn?t found the right conditions yet.
Wickramasinghe is convinced the space bugs provide strong support for the panspermia theory, which suggests that life may have come from outer space in the form of germs or spores. ?We have argued for more than two decades that terrestrial life was brought down to Earth by comets and that cometary material containing micro-organisms must still reach us in large quantities,? he says.
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