There are known abiotic pathways. They've been ruled out.
There are unknown biotic pathways known to exist (from the press conference, biotic phosphane production on earth apparently still has some large question marks attached?).
There might be unknown abiotic pathways ('unknown unknowns'). In principle, there could be some clever way to rule them out based on the constraints of the Venusian environment.
There are unknown biotic pathways known to exist (from the press conference, biotic phosphane production on earth apparently still has some large question marks attached?).
There might be unknown abiotic pathways ('unknown unknowns'). In principle, there could be some clever way to rule them out based on the constraints of the Venusian environment.