Boffins have warned that humanity may have missed out on finding aliens because we are looking for the wrong signs.
A researcher at the University of St Andrews said we could draw closer to “a profound moment for humanity”, if only we followed his rules on how to find life out in deepest space.
He warned that the presence of a single chemical such as oxygen, ozone or methane in the atmosphere of exoplanets was not enough to suggest they were capable of sustaining life.
Dr Mark Claire, a Research Fellow in the University’s School of Geography and Geosciences, said all these gases needed to be present at the same time, rather than alone.
“We set out to discover if the detection of oxygen, ozone, and methane in the atmosphere of an exoplanet around another star, in another solar system, would be a strong indication of life existing on such a planet," he said.
“We simulated thousands of lifeless planetary atmospheres, and found that in some cases, detectable quantities of methane and ozone were produced by chemical reactions in the atmosphere.
“Our work strengthens the belief that the existence of detectable levels of oxygen, ozone and methane together would be a convincing sign of life on another planet. However, the existence of only one of these gases is not, and would result in a ‘false positive’ signal."
The way to find life properly involves looking for all three, he concluded, using extra-sensitive telescopes.
Dr Shawn Domagal-Goldman, of NASA’s Goddard Space Flight Centre, added: “It's like college students and pizza. If you see pizza in a room, and there's also college students in the room, chances are the pizza was freshly delivered, because students will eat the pizza quickly.
“The same goes for methane and oxygen. If both are seen together in an atmosphere, the methane was freshly delivered because the oxygen will be part of a network of reactions that will consume the methane. Therefore, you know the methane is being replenished. The best way to replenish methane in the presence of oxygen is with life.”
A paper on the research was published in the The Astrophysical Journal. ®