Though it might not seem like it today, Mars once had an atmosphere thick enough to sustain liquid water on the surface. It isn’t entirely clear what happened over the last four billion years that changed those conditions, but NASA’s Mars Atmosphere and Volatile EvolutioN (MAVEN) orbiter will attempt to find out by studying what is left of the red planet’s upper atmosphere. MAVEN reached Mars on September 21 and though it is still making adjustments to its orbit and turning instruments on, it has already sent back the first data describing the variable composition of the upper atmosphere.
A contributing factor to the loss of the martian atmosphere is believed to be high-speed solar energetic particles (SEP). During times of solar activity, such as during flares or coronal mass ejections, SEPs can shoot out from the sun and potentially help strip away the atmosphere of Mars. MAVEN has an instrument to detect and study SEPs and wasted no time. Days after MAVEN entered orbit, a solar flare kicked out SEPs that reached Mars on September 29.
"After traveling through interplanetary space, these energetic particles of mostly protons deposit their energy in the upper atmosphere of Mars," Davin Larson said in a press release. Larson is the SEP instrument lead. "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."
The upper atmosphere is the final barrier that prevents this material from escaping into space. It is very thin, and held together by the red planet’s gravity, which is only 38% as strong as Earth’s.
Image Credit: University of Colorado/NASA
Using the Imaging Ultraviolet Spectrograph (IUVS), the team was able to construct an ozone map (pictured above) of the carbon, oxygen, and hydrogen within the upper atmosphere; the three products of the breakdown of carbon dioxide and water. Tracking these molecules can help scientists understand how the atmosphere is being stripped away, and thus how the conditions of the surface of Mars have changed so drastically over time. The map revealed to scientists that the atmosphere of Mars is highly variable.
"With these maps we have the kind of complete and simultaneous coverage of Mars that is usually only possible for Earth," added MAVEN researcher Justin Deighan. "On Earth, ozone destruction by refrigerator CFCs is the cause of the polar ozone hole. On Mars, ozone is just as easily destroyed by the byproducts of water vapor breakdown by ultraviolet sunlight. Tracking the ozone lets us track the photochemical processes taking place in the Martian atmosphere. We'll be exploring this in more complete detail during MAVEN's primary science mission.”
This commissioning phase, where MAVEN is making adjustments and testing out instruments, will continue for another two weeks. In the first week of November, MAVEN will begin the primary science mission which is expected to last for one Earth year.
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