How excited should we be by signs of life spotted on alien worlds?

“DON’T beryllium excited,” says Sara Seager. She is talking astir putative signs of beingness from observations of the atmospheres of different worlds, and her words are a sobering counterbalance to hyperbolic headlines.

Of course, a genuine sighting of the signature of beingness beyond Earth would beryllium thing but humdrum. On the contrary, it would beryllium momentous. Given that we person investigated conscionable a tiny fraction of the galore billions of planets assumed to beryllium successful our ain galaxy, it would connote that beingness is abundant successful the universe.

That explains the dependable drumbeat of stories astir molecular “biosignatures” spotted connected different worlds, acknowledgment chiefly to the James Webb Space Telescope (JWST). Last September alone, it detected carbon dioxide connected Jupiter’s icy satellite Europa that appears to travel from its perchance life-friendly concealed water and, possibly, dimethyl sulphide connected exoplanet K2-18b, a chemic produced connected Earth lone by surviving things. “Tantalising motion of imaginable beingness connected faraway world,” was the BBC’s take.

But Seager, an astrobiologist astatine the Massachusetts Institute of Technology, urges caution for bully reason: erstwhile it comes to grounds for extraterrestrial life, the distant detection of molecules tends to beryllium inconclusive. Even if the detection proves reliable – and that is often a large if – determination whitethorn good beryllium a plausible non-biological mentation for a chemical’s presence.

To marque consciousness of specified findings, then, and to calibrate our excitement astir the chances they herald aliens, it pays to get to grips with the promises and pitfalls of the biosignatures we hunt for. Can they ever supply definitive impervious of life?

When astrobiologists speech astir seeking atmospheric biosignatures,…