  CO is an important component in many N2/CH4 atmospheres including Titan,
Triton, and Pluto, and has also been detected in the atmosphere of a number of
exoplanets. Numerous experimental simulations have been carried out in the
laboratory to understand the chemistry in N2/CH4 atmospheres, but very few
simulations have included CO in the initial gas mixtures. The effect of CO on
the chemistry occurring in these atmospheres is still poorly understood. We
have investigated the effect of CO on both gas and solid phase chemistry in a
series of planetary atmosphere simulation experiments using gas mixtures of CO,
CH4, and N2 with a range of CO mixing ratios from 0.05% to 5% at low
temperature (~100 K). We find that CO affects the gas phase chemistry, the
density, and the composition of the solids. Specifically, with the increase of
CO in the initial gases, there is less H2 but more H2O, HCN, C2H5N/HCNO and CO2
produced in the gas phase, while the density, oxygen content, and degree of
unsaturation of the solids increase. The results indicate that CO has an
important impact on the chemistry occurring in our experiments and accordingly
in planetary atmospheres.
