The experimental conditions of circumneutral pH and 288 K, as
well as the ZnS semiconductor photocatalyst particles
(sphalerite),
are believed to have been prevalent in the waters of early Earth.4
Although thermal reaction pathways on mineral surfaces, such as
on FeS or FeS2, have long been hypothesized as important in
prebiotic chemistry as possible natural scaffolds for primitive
catalysis of slow reactions,9 absent thus far have been demonstrations
of rapid and high efficiency conversions within putative
prebiotic metabolic systems. The importance, therefore, of the
described photochemical results is that new reaction pathways are
opened by the interactions of excited-state species and radicals,
that the sun’s photons are harvested so that highly endoergic redox
reactions can be driven, and that because of high overpotentials
these reaction rates can be very rapid with high yields at moderate
temperatures. These findings therefore both establish and constrain
the plausibility of the occurrence of heretofore difficult chemical
conversions in prebiotic metabolic systems.