New results from the Herschel Observatory have reconfirmed previous findings of Neptune’s dual sources of carbon monoxide. Eric Hand of Nature News provided an overview of these results, which also discusses our own results on Neptune’s CO abundance from the AKARI mid-infrared observations (referenced below).
Fletcher, L. N. , Drossart, P. , Burgdorf, M. , Orton, G. S. & Encrenaz, T. Astron. Astrophys. 514, A17 (2010).