Which planet has a thin atmosphere dominated by carbon dioxide?

Which planet has a thin atmosphere dominated by carbon dioxide?

• A. Mars
• B. Mercury
• C. Jupiter
• D. Saturn

Answer: (A)

The main idea is how the atmosphere’s composition defines what you would call it. Mars fits the description because its atmosphere is mostly carbon dioxide, making it CO2-dominated, yet very thin—surface pressure is only about 6 to 7 millibars, far less dense than Earth's. Mercury has only a tiny, almost negligible atmosphere that isn’t CO2-dominated. Jupiter and Saturn have thick, deep atmospheres dominated by hydrogen and helium, with carbon dioxide present only in small amounts. So Mars is the planet with a thin atmosphere where carbon dioxide is the main component.

The main idea is how the atmosphere’s composition defines what you would call it. Mars fits the description because its atmosphere is mostly carbon dioxide, making it CO2-dominated, yet very thin—surface pressure is only about 6 to 7 millibars, far less dense than Earth's. Mercury has only a tiny, almost negligible atmosphere that isn’t CO2-dominated. Jupiter and Saturn have thick, deep atmospheres dominated by hydrogen and helium, with carbon dioxide present only in small amounts. So Mars is the planet with a thin atmosphere where carbon dioxide is the main component.