Carbon monoxide in cometary ice

Carbon monoxide has been positively identified by means of ultraviolet fluorescence in the Fourth Positive System in two comets, West (1976 VI) and Bradfield (1979 X). In both cases, the spatial distribution of the emission is consistent with the CO being a 'parent' molecule, present in the cometary ice, rather than a dissociation product of a polyatomic species such as CO2 or HCOH. However, the abundance of CO relative to that of H2O is more than an order of magnitude smaller for comet Bradfield than for comet West. Further data on CO are expected with the use of more sensitive ultraviolet instruments such as the ASTRO spectrographs which will observe P/Halley in March 1986.