First glimpse of Mars' vanishing atmosphere

Three views of an escaping atmosphere, obtained by MAVEN’s Imaging Ultraviolet Spectrograph. By observing all of the products of water and carbon dioxide breakdown, MAVEN's remote sensing team can characterize the processes that drive atmospheric loss on Mars.

The upper atmosphere of Mars is barely clinging to the planet, first data from NASA's Maven mission show.

Maven, short for Mars Atmosphere and Volatile Evolution, is already exceeding expectations NASA says, even before all its instruments are calibrated to send back data in a co-ordinated way.

But scientists have already received unprecedented ultraviolet images of the tenuous oxygen, hydrogen, and carbon molecules (which once were water and carbon dioxide near the surface) surrounding the planet. It is Maven's mission to find out our Mars lost its atmosphere, turning it from a warm, wet planet into the cold, dry one it is today.

Once scientists know how the molecules are stripped away, they should be able to reconstruct a picture of what Mars was like when it was younger.

"All the instruments are showing data quality that is better than anticipated at this early stage of the mission," said Bruce Jakosky, Maven Principal Investigator at the University of Colorado, Boulder.

"It's turning out to be an easy and straightforward spacecraft to fly, at least so far. It really looks as if we're headed for an exciting science mission."

NASA researchers believe solar energetic particles (SEPs) – streams of high-speed particles blasted from the sun – are one possible mechanism for driving the planet's atmospheric loss.

Maven observed a solar storm of SEPs that arrived at Mars on 29 September.

"After traveling through interplanetary space, these energetic particles of mostly protons deposit their energy in the upper atmosphere of Mars," said SEP instrument lead Davin Larson of the Space Sciences Laboratory at the University of California, Berkeley.

"A SEP event like this typically occurs every couple weeks. Once all the instruments are turned on, we expect to also be able to track the response of the upper atmosphere to them."

Maven has also observed the edges of the Martian atmosphere using the Imaging Ultraviolet Spectrograph (IUVS), which is sensitive to the sunlight reflected by the upper atmosphere atoms.

"With these observations, MAVEN's IUVS has obtained the most complete picture of the extended Martian upper atmosphere ever made," said Remote Sensing Team member Mike Chaffin of the University of Colorado, Boulder.

"By measuring the extended upper atmosphere of the planet, MAVEN directly probes how these atoms escape to space. The observations support our current understanding that the upper atmosphere of Mars, when compared to Venus and Earth, is only tenuously bound by the Red Planet's weak gravity."

IUVS also created a map of the atmospheric ozone on Mars by detecting the absorption of ultraviolet sunlight by the molecule – usually only observable for Earth.

There will be about two more weeks of instrument calibration and testing before Maven starts its primary science mission.

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