Astronomers are still arguing about whether we have recently seen the “strongest evidence” for alien life yet, or simply nothing at all. Now, the researchers behind the original bold claim have reanalysed the data and say they have yet more evidence for molecules with no origin outside of biology – but critics say this new work undermines the original efforts.

Since Nikku Madhusudhan at the University of Cambridge and his colleagues announced their remarkable finding that K2-18b, a super-Earth 124 light years away, showed “strong evidence” for an atmosphere containing the molecules…