The Eos article, Comets and Life (March 28, 1989), reports on the work of Paul Thomas, Christophere Chyba, Carl Sagan and Leigh Brookshaw on cometary impact production of cyanides and other organics that may have been precursors of life. The article was based on material presented at the 20th Lunar and Planetary Science Conference [Thomas et al, 1989].
As pointed out in the article, comets may contain 20% organic matter in the form of a complex interbonded mass. This kerogen-like material contains CN bonds as well as CC and CO bonds. Evidence for cyanide protection from light-element “CHON” solids was observed in the recent Halley's comet encounter in the form of CN plumes [Eberhardt et al., 1986; Schlosser et al., 1986]. An additional, and possibly more important source of cyanide, is HCN, which was observed [Schloerb et al., 1986] to be emitted from Halley's comet as part of the normal neutral gas emission with an abundance equal to 10−3 that of H2O. H2O is the dominant volatile species in comets and appears to constitute 80% or more of the total molecular release [Mendis, 1986].