Is Curiosity responsible for Mars methane readings?

Chuck Bednar for – @BednarChuck

One of the reasons the Curiosity rover was sent to Mars was to determine once and for all if the Red Planet was emitting methane, but could it have actually further muddled matters instead by giving off the chemical compound itself?

That’s the issue investigated by Johnny Bontemps of Astrobiology Magazine in a story published earlier this week by Discovery News. The gist of it is this: nearly five decades ago, Mariner 7 first purportedly detected methane near the south pole. While that turned out to be a false signal, orbiting spacecraft and Earth-based telescopes again detected methane in 2003 and 2004.

Since most of the methane found on Earth comes from living organisms, the possibility that the gas also exists on Mars has understandably been of great interest to researchers. When Curiosity made its way to the Red Planet, it tested the planet’s atmosphere six times from October 2012 to June 2013, but was unable to detect even the slightest trace of methane.

Then, according to Bontemps, a few months later, the rover suddenly detected a burst of the gas in four measurements conducted over an eight-week span. The Curiosity team carefully analyzed things for an entire year to make sure that this was not an anomaly before officially announcing in December 2014 that the rover had officially confirmed the presence of methane on Mars.

Or had it?

Not everyone is convinced that Curiosity proven that the chemical compound exists on Mars. Kevin Zahnle, a scientist at NASA’s Ames Researcher Center in Moffett Field, California, who was not involved in the research, said he believed that the methane is not native to the planet, but is actually coming from the rover itself.

As Bontemps explained, Curiosity has a chamber that contains methane at a concentration some 1,000 times higher than that it supposedly detected in Mars’ atmosphere. That methane traveled to the Red Planet from Earth along with the rover, and once Curiosity landed in Gale Crater, its laser spectrometer reportedly detected an unusually high amount of methane in the area.

The Curiosity team soon determined that some air of Earth origin had leaked into the instrument when it was waiting to be launched, and most of the methane was expelled from the vehicle, with just a small amount left for calibration purposes. Scientists insist there is no evidence of any leakage from this methane store, and that it was not the source of the readings.

Chris Webster, a senior research scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, and lead author of the recent Mars methane study, told Bontemps that the amount of methane on the rover is too small to produce the amount detected in the atmosphere, but Zahnle argues that terrestrial air could have found its way to other parts of the rover.

Webster and Paul Mahaffy, principal investigator on Curiosity’s Sample Analysis at Mars (SAM) suite of instruments, said that it is “unlikely” that the rover itself is the source of the methane, but Chris McKay, a researcher at NASA Ames and co-author on the January paper, said that Zahnle’s concerns are valid, and that the possibility that the methane is originating from the rover itself “should still be considered until completely ruled out.”


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