Answer:
there is no "one" gas unique to earth, earth is the most unique planet in our solar system it has so many different gases that don't exist on other planets
Explanation:
Earth's atmosphere is roughly 78 percent nitrogen and 21 percent oxygen, with trace amounts of water, argon, carbon dioxide and other gases. Nowhere else in the solar system is there an atmosphere loaded with free oxygen, which is vital to one of the other unique features of Earth: life.
