Which planet has an atmosphere dominated by nitrogen and oxygen with trace gases?

• A. Mars
• B. Venus
• C. Earth
• D. Jupiter

Answer: (C)

Atmospheric composition varies among planets, and the air we breathe is primarily nitrogen and oxygen, with smaller amounts of other gases. Earth has an atmosphere that is about 78% nitrogen and 21% oxygen, with trace amounts of argon, carbon dioxide, neon, helium, methane, and water vapor. This specific mix is not found on the other planets listed: Mars has a thin atmosphere dominated by carbon dioxide; Venus has a very thick carbon dioxide atmosphere with extremely high surface pressure; Jupiter’s atmosphere is mainly hydrogen and helium. The nitrogen–oxygen composition of Earth is what sets its air apart and supports the life-friendly environment we experience.