The controversial matter of methane gas on Mars -- is it really there and if so is it being created by some kind of life ?-- has gotten a little more complicated thanks to some recent sampling by NASA's Curiosity rover on the Red Planet.

While the methane levels Curiosity detected in some previous rounds of scientific experiments were lower than expected, a mysterious "spike" in the levels -- which lasted 2 full months -- was also recently recorded, scientists at NASA's Jet Propulsion Laboratory in Pasadena, Calif., are reporting.

The significance of the methane detection by the rover lies in the simple fact that methane gas cannot exist for long and is eventually broken down by sunlight and by chemical reactions in the Martian atmosphere.

At most, methane would last a couple of hundred years, the scientists say, a blink of an eye in terms of planetary history.

So it's new, not ancient, which raises the question: where is it coming from, or more to the point, what it making it?

It may have a geological origin, researchers are quick to point out, and yet it could also be waste products belched out by living microbes, raising the possibility that Mars is not a dead planet.

"We can't rule it out," says JPL researcher Chris Webster. "It's equally likely to be geophysical or biogenic. ... The fact that we've seen it, in a sense, argues that the stock in a possible biogenic source went up."

The new findings, coming after previous science from the rover that suggested there wasn't as much methane as some previous Mars missions had reported, will likely encourage astrobiologists, says Webster, lead author of a study reporting the results in the journal Science.

"They completely blow open the whole debate on Mars methane," he says. "I think it's going to create a lot of enthusiasm within the planetary community."

Adding to the excitement surrounding the methane measurements, Curiosity team scientists are also reporting they've confirmed a finding of carbon-based organic molecules in a rock sample analyzed by the rover's onboard science instruments.

While not a direct sign of life, either past or present, they add strength to the argument put forward by some scientists that Mars once had the ingredients necessary for life, and may have them still.

"In part, Curiosity was built to explore for organics," says mission project scientist John P. Grotzinger, "and we found them."

Methane plus organics is creating considerable excitement in the scientific community, he acknowledges.

"This is really a great moment for the mission," he said at a meeting of the American Geophysical Union in San Francisco.