Considering how extremely strong some greenhouse gases are, emitting large amounts of them could be used for terraforming worlds in the outer solar system. It helps that different greenhouse gases blocks different parts of the infrared heat radiation spectrum, so different greenhouse gases together have a greater greenhouse effect than the sum of them. Unlike in the case of Mars, the ozone layer depletion caused by some very strong greenhouse gases like CFC would not be much of a problem due to the much lower levels of ultraviolet radiation that far out in the Solar System. It also helps that even an atmosphere without ozone is a better UV shield than flat-out vacuum.