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Curiosity rover's inability to find methane on Mars contradicts previous theories of life on the planet.

The findings, published in the journal Science, follows Curiosity's journey on the red planet as it searched for methane, a gas that is considered a possible biomarker of life, and has so far found none of it.

"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."

Curiosity has been on Mars for over a year now, travelling back and forth along the planet in search for methane.

"Based on previous measurements, we were expecting to go there and find 10 parts per billion (ppbv) or more, and we were excited about finding it. So when you go to search for something and you don't find it, there's a sense of disappointment," said Dr Chris Webster, the principal investigator on Curiosity's Tuneable Laser Spectrometer (TLS).

From the data collected, it has not been possible to discern any methane to within the present limits of the TLS's sensitivity.

This means that if the gas is there, it can constitute no more than 1.3ppbv of the atmosphere - equivalent to just over 10,000 tones of the gas, according to the BBC news.

Speculation over potential life on Earth became rife after telescopes on Earth and a spacecraft orbiting Mars reported a huge cloud of methane rising over Mars in 2003.

The new research suggests that the methane levels Curiosity detected on the ground are so low that the likelihood of a biological source is vanishingly small.

"Methane is a very well understood gas that is quite stable," Webster said. "We know how long it lasts and how it is destroyed over decades."

While it is conceivable that something exists in the Martian atmosphere that destroys methane at a much faster pace than on Earth, "we have no evidence, no observations of what it might be," he said.