re: CO2 Cause and effect...Mars a dying wolrd?
Nick says: "Where does Ozone on mars come from? From photolytic CO2 and H2O that contribute molecular oxygen to the atmosphere, which recombines to O2 and O3. Arguably, surface activity of minerals exposed to UV can catalyse additional O3 production on the surfaces of dust grains."
CO2 is dissociated by UV to CO and O2, yet the CO2 levels on Mars don't very much from nearly 30 years of observations. Atmospheric sputtering of O2 is detectable. Also, it is possible that the O3 in the Martian atmospehre is a left over from an age when Mars had more oxygen. If Mars is an example of a dying world, this is what you would expect to find.
BD