Lamentably , bacteria are not the only manufacturers of methane . It can also be produced by geological processes . Methane might mean life on Mars , but it might not . What makes the discovery of phosphine in Venus ’ air so compelling is that the researchers have racked their brains trying to come up with ways to explain its presence short of invoking biology . They ’ ve considered the likelihood of weird chemical processes in the atmosphere that could produce it , or the possibility that it was spewed out of volcanoes below . Even the reactions caused by meteors that streak through the clouds or the chemical effects of lightning were considered . But the scientists couldn ’ t find a plausible non-biological explanation . Nonetheless , they remain cautious . History is littered with claims of extraterrestrial biology that later proved suspect or just plain wrong , from the canals on Mars to the squiggly , microscopic features seen in a martian meteorite . Everyone who ’ s claimed to have established the existence of life elsewhere has been seriously challenged . The strong consensus of science is that our world is the only place in the universe where life is known to exist . To prove otherwise is a tantalizing goal , but the proof needs to be indisputable . So , caution reigns . Sara Seager , an MIT professor of physics and planetary science and a member of the research team , put it this way . “ There could be two explanations . One that there is some unknown chemical process that could somehow produce the phosphine . The second is that … there ’ s life .” But Venusian life ? Yes , Venus has long been called Earth ’ s twin , primarily because the two planets are the same size . But it ’ s not the favored twin : spacecraft have revealed a baked landscape , with
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