ON EARTH, most of the methane in the atmosphere has been belched by living organisms, so finding the gas on Mars would be happy news for seekers after extraterrestrial life. Sadly, news announced on December 12th, at the annual meeting of the American Geophysical Union (AGU), in Washington, DC, was anything but happy. Preliminary results from ExoMars Trace Gas Orbiter, a European craft that has been circling Mars for the past two years, give a thumbs-down to the idea that there is methane in its atmosphere.
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