Why doesn't Titan have a carbon dioxide atmosphere?

Question

Earth's primitive atmosphere had large amounts of carbon dioxide, as did the ancient Martian atmosphere. Venus's current atmosphere is no exception either. So why does Titan have next to none of this compound? Is it due to its location with respect to the Sun?

Answer 1

The chemistry of Titan's atmosphere is complex, with reactions occurring between carbon dioxide, oxygen, carbon monoxide, hydroxl, and other compounds. This means that carbon dioxide production and destruction takes place through a variety of reactions (Samuelson et al. 1983), some spurred by ultraviolet light from the Sun (and hence photodissociation). In other words, comparing Titan to Earth and Mars ignores a variety of rich chemical processes; right away, the comparison shouldn't hold.

All that said, the primary source of carbon dioxide loss on Titan is condensation, with photolysis playing a secondary role (Horst et al. 2008). With a surface temperature of 94 Kelvin, Titan is much colder than either Earth or Mars - well below the freezing point of carbon dioxide. Even if you were to add a large influx of carbon dioxide to Titan, much of it would very quickly (from an astronomical point of view) condense into solid form and fall to the surface. Indeed, much of Titan's surface contains significant amounts of dry ice.