NASA's
Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft has provided
scientists their first look at a storm of energetic solar particles at
Mars, produced unprecedented ultraviolet images of the tenuous oxygen,
hydrogen, and carbon coronas surrounding the Red Planet, and yielded a
comprehensive map of highly-variable ozone in the atmosphere underlying
the coronas.
The spacecraft, which entered Mars' orbit Sept. 21, now is lowering
its orbit and testing its instruments. MAVEN was launched to Mars in
November 2013, to help solve the mystery of how the Red Planet lost most
of its atmosphere.
"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.
"All instruments have now been turned on -- although not yet fully
checked out -- and are functioning nominally. 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 predicted the disturbance and the accompanying SEPs would
reach Mars on Sept. 29. MAVEN's Solar Energetic Particle instrument was
able to observe the onset of the event that day.
"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."
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. These molecules
control the climate, so following them allows us 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 we see today.
MAVEN observed the edges of the Martian atmosphere using the Imaging
Ultraviolet Spectrograph (IUVS), which is sensitive to the sunlight
reflected by these atoms.
"With these observations, MAVEN's IUVS has obtained the most complete
picture of the extended Martian upper atmosphere ever made," said MAVEN
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.
"With these maps we have the kind of complete and simultaneous
coverage of Mars that is usually only possible for Earth," said MAVEN
Remote Sensing Team member Justin Deighan of the University of Colorado,
Boulder. "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."
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 to transmit data between NASA's Curiosity
rover on the surface of Mars and Earth using the MAVEN mission's Electra
telecommunications relay. The mission aims to start full science
gathering in early to mid-November.
MAVEN's principal investigator is based at the University of
Colorado's Laboratory for Atmospheric and Space Physics. The university
provided two science instruments and leads science operations, as well
as education and public outreach, for the mission. The University of
California at Berkeley's Space Sciences Laboratory also provided four
science instruments for the mission. NASA's Goddard Space Flight Center
in Greenbelt, Maryland manages the MAVEN project and provided two
science instruments for the mission. Lockheed Martin built the
spacecraft and is responsible for mission operations. NASA's Jet
Propulsion Laboratory in Pasadena, California provides navigation and
Deep Space Network support, as well as the Electra telecommunications
relay hardware and operations.