CH 4 probably detected, CO being sought. H 2 O ice appears to dominate the surface, but other ices and refractory solids may exist. No CH 4 or CO yet detected, but currently being sought. Sublimation wind flowing from S. pole northward detected. Cometary activity possible in the future.
P s a few microbars at most.
O 2 detected in ice, induced by charged particle bombardment. Hubble Space Telescope UV spectra show a feature tentatively attributed to solid O 3 generated in the ice. Rich hydrocarbon inventory in stratosphere.