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Curiosity Finds No Methane on Mars - But Not For Lack of Trying

Curiosity snapped this self portrait of itself at a site dubbed “Rocknest.” The mini Cooper-sized rover has checked out more than rocks however, it has also sniffed the Martian air for possible signs of life. Photo Credit: NASA/JPL-Caltech/Malin Space Science Systems

The Mars Science Laboratory (MSL) rover Curiosity has been hard at it since touching down on the dusty surface of the Red Planet Aug. 6. One of the recent things that the six-wheeled, nearly one-ton rover has been trying to find out is what happened to the Martian atmosphere.

Mars’ atmosphere is approximately 100 times thinner than the Earth’s and is comprised primarily of carbon dioxide. It is thought that in the distant past Mars once had a much thicker atmosphere.

There are a number of potential sources for methane gas that do not have biological sources. Some of them are detailed in this NASA infographic. Image Credit: NASA/JPL-Caltech, SAM/GSFC

Curiosity carries with it a series of instruments that allows it sample the atmosphere and analyze it.

Findings from the Sample Analysis at Mars (SAM) instruments indicate that a portion of the atmosphere was lost due to a natural process where heavier isotopes were retained whereas others were not.

SAM showed a 5 percent increase in these heavier isotopes over what initial estimates predicted. It appears that lighter isotopes are being lost to space.

NASA is planning on following through with research into the evolution of the Martian atmosphere when it sends the Mars Atmosphere and Volatile Evolution, or MAVEN orbiter to Mars in 2014.

One of the main gases that Curiosity has been sniffing for is methane. SAM searched for this gas as it can be a sign of life (methane is produced by both biological and non-biological sources). The SAM instrument detected little-to-no methane.

“Methane is clearly not an abundant gas at the Gale Crater site, if it is there at all. At this point in the mission we’re just excited to be searching for it,” said SAM TLS lead Chris Webster of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif. “While we determine upper limits on low values, atmospheric variability in the Martian atmosphere could yet hold surprises for us.”

New results from the Sample Analysis at Mars, or SAM, instrument on NASA’s Curiosity rover show that the lighter forms of certain volatiles, also called isotopes, have preferentially escaped from the atmosphere, leaving behind a larger proportion of heavy isotopes. Image Credit: NASA/JPL-Caltech

Scientists have had little luck finding methane on Mars either from Earth-based observations or via satellites orbiting the Red Planet.

The rover’s SAM instrument has the Tunable Laser Spectrometer (TLS) which allows the search for methane to take place on Mars. It was this instrument that told scientists that, at best, the Mars atmosphere (at least the atmosphere surrounding Gale Crater where Curiosity landed) only contains one part methane per billion of Martian atmosphere. Throw in the uncertainty factor? That amount could well be zero parts per billion.

“With these first atmospheric measurements we already can see the power of having a complex chemical laboratory like SAM on the surface of Mars,” said SAM Principal Investigator Paul Mahaffy of NASA’s Goddard Space Flight Center in Greenbelt, Md. “Both atmospheric and solid sample analyses are crucial for understanding Mars’ habitability.”

This picture shows a lab demonstration of the measurement chamber inside the Tunable Laser Spectrometer, an instrument that is part of the Sample Analysis at Mars investigation on NASA’s Curiosity rover. This demonstration uses visible lasers – rather than the infrared ones on the actual spectrometer – to show how the lasers bounce between the mirrors in the measurement chamber. Photo Credit: NASA/JPL-Caltech

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