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Rover analyzes atmosphere on Mars

The Curiosity rover has determined the Martian air is made mostly of carbon dioxide with hints of other gases.

NASA/AP

The Curiosity rover has determined the Martian air is made mostly of carbon dioxide with hints of other gases.

LOS ANGELES — 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 that fell to Earth.

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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.

Mission scientists are puzzled but suspect it might have to do with the different tools used to sample the atmosphere.

‘‘It’s more or less an interesting observation’’ but does not change the notion that Mars lost most of its original atmosphere to space, transforming the planet into a cold desert, said Paul Mahaffy of NASA’s Goddard Space Flight Center, who is in charge of Curiosity’s air sampling experiments.

The nuclear-powered, six-wheeled rover set down in an ancient crater near the Martian equator almost a year ago. The atmospheric measurements were detailed in two studies appearing in Friday’s issue of the journal Science.

While ‘‘there’s nothing profoundly different’’ between what Curiosity found and previous results, the new work is more detailed, said Michael Mumma of Goddard, who is not part of the mission.

Neither study dwelled on the issue of methane gas, which was detected on Mars by telescopes several years ago.

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