Curiosity Samples The Martian Atmosphere
November 2, 2012

Curiosity Finds That Martian Atmosphere Is Much Thinner Than Earth

Lee Rannals for - Your Universe Online

NASA said on Friday that its Curiosity rover has helped determine Mars' atmosphere is 100 times thinner than Earth's.

Curiosity has been performing scientific experiments while positioned at "Rocknest," a site near Gale Crater. While parked, the rover has ingested and analyzed samples of the atmosphere.

Findings from the Sample Analysis at Mars (SAM) instruments onboard Curiosity suggest that a loss of a fraction of the atmosphere has taken place on the Red Planet, resulting from a physical process favoring retention of heavier isotopes of certain elements.

The initial results show an increase of five percent in heavier isotopes of carbon in the atmospheric carbon dioxide compared to estimates of the isotopic ratios present when Mars formed. These ratios of heavier isotopes to lighter ones suggest the top of the atmosphere may have been lost to interplanetary space.

Losses at the top of the atmosphere would deplete lighter isotopes. NASA said isotopes of argon also show enrichment of the heavy isotopes, matching previous estimates of atmosphere composition derived from studies of Martian meteorites on Earth.

Scientists believe that in Mars' distant past, its environment may have been quite different, with persistent water and a thicker atmosphere.

NASA's Mars Atmosphere and Volatile Evolution (MAVEN) mission will be investigating possible losses from the upper atmosphere when it arrives at the Red Planet in 2014.

SAM also made the most sensitive measurements ever to search for methane gas on Mars. NASA said preliminary results reveal little to no methane. This gas is of interest to scientists because it is a precursor chemical for life.

Methane has been difficult to detect from Earth or the current generation of Mars orbiters because the gas exists on Mars in just traces.

The Tunable Laser Spectrometer (TLS) in SAM helps provide the first search conducted within the Martian atmosphere for this molecule.

"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 in Pasadena, California. "While we determine upper limits on low values, atmospheric variability in the Martian atmosphere could yet hold surprises for us."

During Curiosity's two-year prime mission, it will use an instrument called a gas chromatograph that separates and identifies gases. It will also analyze samples of soil and rock, as well as more atmosphere samples.

"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, Maryland. "Both atmospheric and solid sample analyses are crucial for understanding Mars' habitability."

Image 2 (below): 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. Image Credit: NASA/JPL-Caltech