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The Curiosity rover has tasted Mars’ air: It is made mostly of carbon dioxide with hints of other gases.
The measurements by the most advanced spacecraft to land on the red planet closely match what the twin Viking landers detected in the late 1970s and what scientists have gleaned from Martian meteorites, rock fragments that fell to Earth.
Mars’ atmosphere is overwhelmingly dominated by carbon dioxide, unlike Earth’s air, which is a mix of nitrogen and oxygen.
There was a small surprise: while Viking found nitrogen to be the second most abundant gas in the Martian air, Curiosity’s measurements revealed a nearly equal abundance of nitrogen and argon, a stable noble gas.