If aliens aren't going to visit us in a flying saucer, we've got to find a way to determine whether they're out there, minding their own business on some faraway exoplanet. Unfortunately, one of the best proposed methods of doing it is likely to result in a whole bunch of false positives, according to a researcher at MIT.
There's a lot of ways that astronomers and SETI researchers are looking for inhabited planets—we're looking into intercepting radio transmissions, sending some out ourselves, looking for biological components on Mars, and even looking for alien pollution—but analyzing exoplanets' atmospheres for "biosphere gases" (the ones given off by life) is one of the more promising and realistic techniques.
At least, that's what we thought. But a new paper published in Proceedings of the National Academies of Sciences by Sara Seager, a planetary researcher at MIT, suggests that maybe atmosphere analysis isn't all it's cracked up to be.
That's because exoplanets are incredibly diverse, and the gases we're likely to run into (and that could be suspected to be coming from living things) could have perfectly normal geological origins.
"False positives will, in many cases, be a problem, and in the end, we will have to develop a framework for assigning a probability to a given planet to have signs of life," she wrote.
In other words, it's entirely possible that we find a planet in which the atmosphere is made up of oxygen or methane or some other gas we're looking for, and it turns out to have no life whatsoever. And, when we're talking aliens, false positives are a pretty huge deal, as is any sort of uncertainty.
Rather than making contact with aliens or having some sort of definitive knowledge that they exist, instead we'll probably enter a time period where humans are pretty sure there's life out there somewhere, and where we're pretty sure where it might be living, but one in which we don't really know for sure. Which, while exciting, is kind of a bummer.
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