NASA rover dims hopes for Martian methane

If the Curiosity finding holds up, it would raise questions about one of the most intriguing discoveries made about Mars in recent years: that periodic and large-scale plumes of organic methane are released from beneath the planet's surface.
"We consider this to be a quite definitive conclusion, and we're very confident with it," Chris Webster, manager of the Planetary Science Instrument Office at NASA's Jet Propulsion Laboratory in Pasadena, California, said of the new rover readings reported in the journal Science.
"It puts an upper limit on the background methane on Mars that is very constraining of any scenarios for its production on the planet."
The special interest in the gas comes from the fact that some 90 percent of the methane on Earth is the product of living microbes. Signs of methane plumes in the Martian atmosphere seen by Earth-based telescopes had earlier raised hopes of detecting similar microbial life hidden under the Martian surface.
Full story