BARELY a month goes by these days without the detection of a tantalising “sign of life” in an alien atmosphere. With the James Webb Space Telescope’s unmatched ability to probe the chemistry of distant worlds – and so many promising exoplanets to set our sights on – today’s astronomers are increasingly confident that their generation will be the one to discover life beyond Earth.
That is a thrilling possibility, no doubt. But with it comes great responsibility. Given the magnitude of the question of whether life exists elsewhere in the universe, and the public interest that goes with it, we must be realistic about the chances of a definitive discovery based on the remote detection of molecular signatures associated with life on Earth.
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For all the hyperventilating headlines, the reality is that it may be impossible to get conclusive evidence of life on other worlds this way because we may never know enough about their atmospheric chemistry to rule out non-biological explanations, as we explore in our feature “How excited should we be by signs of life spotted on alien worlds?”.
Rightly, astrobiologists aren’t giving up on the idea. But, for now, it seems like the evidence they provide will continue to be tentative at best. This means that astronomers – and those of us reporting on their work – can’t become the boy who cried wolf when it comes to finding extraterrestrial life. The danger is that overblown claims, and the inevitable letdowns, encourage cynicism.
With that in mind, we should welcome recent proposals for a framework to assess and communicate the credibility of detections of life elsewhere. When considering such a framework, it is clear that we are still very much in the first throes of an enormously challenging endeavour. But we mustn’t let that devalue the progress we are making in scrutinising the reliability of our current biosignatures and seeking more robust ones. These are among the vital first steps on the road that could ultimately lead to unambiguous evidence that we are not alone, a discovery that we can all be confident about.
