The search for life on extrasolar worlds by way of spectroscopic biosignature detection is among the most compelling scientific endeavors of the next decades. An article just published on PNAS by Amedeo Balbi (of Tor Vergata Physics Department) and Claudio Grimaldi (of Ecole Polytechnique Fédérale de Lausanne) explores the implications of either discovering or ruling out the presence of detectable biosignatures on planets within a few tens of light years from Earth, a distance within reach of future searches. Using a Bayesian methodology, the study shows that not detecting biosignatures in such sample volume would bring no added information about the galactic population of life-hosting exoplanets. Conversely, if life arose independently on other planets, even a single detection would imply exobiospheres to be more abundant than pulsars. Putative interstellar transfer of life through the panspermia mechanism may, however, significantly lower this estimate.
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