  Organic haze plays a key role in many planetary processes ranging from
influencing the radiation budget of an atmosphere to serving as a source of
prebiotic molecules on the surface. Numerous experiments have investigated the
aerosols produced by exposing mixtures of N$_{2}$/CH$_{4}$ to a variety of
energy sources. However, many N$_{2}$/CH$_{4}$ atmospheres in both our solar
system and extrasolar planetary systems also contain CO. We have conducted a
series of atmosphere simulation experiments to investigate the effect of CO on
formation and particle size of planetary haze analogues for a range of CO
mixing ratios using two different energy sources, spark discharge and UV. We
find that CO strongly affects both number density and particle size of the
aerosols produced in our experiments and indicates that CO may play an
important, previously unexplored, role in aerosol chemistry in planetary
atmospheres.
