Planet Atmospheres

In the Jovian planets the primary gas is hydrogen. 'Though in Venus and Mars it is carbon dioxide.
I would go to Mercury because they have some oxygen so it would be easier to breath. Also, it is a smaller planet and would be easier to take care of it if I were to be there for a while. You could control how much pollution is happening when you have a smaller planet. Even though it is very close to the sun, we could make things to help protect us. Maybe someday, be able to walk around without protective gear.