Year in Review: Methane shortage on Mars

Trace of gas not enough to be sign of life

A LITTLE GAS  The concentration of methane in the Martian atmosphere measured by the rover Curiosity is one ten-thousandth that on Earth. High levels of methane on Mars would have been a compelling indication of life there.

JPL-Caltech/NASA and MSSS

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After months of searching, the NASA rover Curiosity detected no appreciable methane in Mars’ atmosphere, disappointing scientists who had hoped to find a strong sign of life on the Red Planet.