Wednesday, 15 October 2014

NASA's 1st MAVEN Findings Solve Mystery of Mars' Lost Atmosphere --"Only Tenuously Bound by the Planet’s Weak Gravity"


NASA’s MAVEN spacecraft has provided scientists their first look at a storm of energetic solar particles at Mars and produced unprecedented ultraviolet images of the tenuous oxygen, hydrogen and carbon coronas surrounding the Red Planet, said University of Colorado Boulder Professor Bruce Jakosky, the mission’s principal investigator. The hydrogen and oxygen coronas of Mars are the tenuous outer fringe of the planet’s upper atmosphere, where the edge of the atmosphere meets space. In this region, atoms that were once a part of carbon dioxide or water molecules near the surface can escape to space, according to MAVEN scientists.

Water and carbon dioxide control the climate, so following them allows scientists to understand the history of Mars over the last four billion years and to track the change from a warm and wet climate to the cold, dry climate present today. MAVEN observed the edges of the Martian atmosphere using the CU-Boulder-built Imaging Ultraviolet Spectrograph (IUVS), which is sensitive to the sunlight reflected by the atoms.

In addition, the new observations allowed scientists to make a comprehensive map of highly variable ozone in the Martian atmosphere underlying the coronas, he said. The spacecraft entered Mars’ orbit Sept. 21 and is in the process of lowering its orbit and testing its instruments. The $671 million Mars Atmosphere and Volatile EvolutioN mission, or MAVEN, was launched toward Mars on Nov. 18, 2013, to help solve the mystery of how the Red Planet lost most of its atmosphere.

“Everything is performing well so far,” said Jakosky of CU-Boulder’s Laboratory for Atmospheric and Space Physics. “All of the instruments have now been turned on, and although they are not yet fully checked out, they are functioning nominally.

“All the instruments are showing data quality that is better than anticipated at this early stage of the mission,” said Jakosky, also a professor in CU-Boulder’s geological sciences department. “The spacecraft is performing beautifully. 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.”

Solar Energetic Particles (SEPs) are streams of high-speed particles blasted from the sun during explosive solar activity like flares or Coronal Mass Ejections (CMEs). Around Earth, SEP storms can damage the sensitive electronics on satellites. At Mars, they are thought to be one possible mechanism for driving atmospheric loss.

A solar flare on Sept. 26 produced a CME that was observed by NASA satellites on both sides of the sun. Computer models of the CME propagation successfully predicted the disturbance and the accompanying SEPs would reach Mars on Sept. 29.

“After traveling through interplanetary space, these energetic particles, 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 of weeks. Once all the instruments are turned on, we expect to also be able to track the response of the upper atmosphere to them.”

“With these observations, MAVEN’s IUVS has obtained the most complete picture of the extended Martian upper atmosphere ever made,” said IUVS team member and CU-Boulder doctoral student Mike Chaffin of the Department of Astrophysical and Planetary Sciences. “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 planet’s weak gravity.”

The National Geographic image below shows Mars Noachian period, about 4 billion years ago when the Vastitas Bolearis filled with water, the large lake at the bottom right is the Meridiani. The Opportunity Rover found evidence of such an inner sea.


The image at the top of the page from the 2005 Viking Orbiter is a famous one, which for the first time clearly showed an atmosphere.

IUVS also helped scientists create a map of the atmospheric ozone on Mars by detecting the absorption of ultraviolet sunlight by the molecule. “With these maps we have the kind of complete and simultaneous coverage of Mars that is usually only possible for Earth,” said CU-Boulder Research Associate Justin Deighan, an IUVS team member from LASP. “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 broken down by ultraviolet sunlight.

“Tracking the ozone lets us track the photochemical processes taking place in the Martian atmosphere,” said Deighan. “We’ll be exploring this in more complete detail during MAVEN’s primary science mission.”

There will be about two weeks of additional instrument calibration and testing before MAVEN starts its primary science mission. This includes an end-to-end test of relaying data between NASA’s Curiosity rover on the surface of Mars and Earth using the MAVEN mission’s Electra telecommunications relay. The mission is aiming to start science in early to mid-November.

CU-Boulder provided two science instruments and leads science operations, as well as education and public outreach, for the MAVEN mission, which has contributed roughly $300 million to Colorado’s economy. UC Berkeley’s Space Sciences Laboratory also provided four science instruments for the mission.

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