Organometallic Compounds as Carriers of Extraterrestrial Cyanide in Primitive Meteorites

Extraterrestrial delivery of cyanide may have been crucial for the origin of life on Earth since cyanide is involved in the abiotic synthesis of numerous organic compounds found in extant life; however, little is known about the abundance and species of cyanide present in meteorites. Here, we report cyanide abundance in a set of CM chondrites ranging from 50 ± 1 to 2472 ± 38 nmol·g⁻¹, which relates to the degree of aqueous alteration of the meteorite and indicates that parent body processing influenced cyanide abundance. Analysis of the Lewis Cliff 85311 meteorite shows that its releasable cyanide is primarily in the form of [Fe^II(CN)₅(CO)]³⁻ and [Fe^II(CN)₄(CO)₂]²⁻. Meteoritic delivery of iron cyanocarbonyl complexes to early Earth likely provided an important point source of free cyanide. Iron cyanocarbonyl complexes may have served as precursors to the unusual Fe^II(CN)(CO) moieties that form the catalytic centers of hydrogenases, which are thought to be among the earliest enzymes.