[meteorite-list] NASA's MAVEN Mission Identifies Links in Chain Leading to Atmospheric Loss

[Ron Baalke]

http://www.nasa.gov/press/goddard/2014/december/nasa-s-maven-mission-identifies-links-in-chain-leading-to-atmospheric-loss/

December 15, 2014
RELEASE 14-042

NASA's MAVEN Mission Identifies Links in Chain Leading to Atmospheric Loss

Early discoveries by NASA's newest Mars orbiter are starting to reveal 
key features about the loss of the planet's atmosphere to space over time.
The findings are among the first returns from NASA's Mars Atmosphere and 
Volatile Evolution (MAVEN) mission, which entered its science phase on 
Nov. 16. The observations reveal a new process by which the solar wind 
can penetrate deep into a planetary atmosphere. They include the first 
comprehensive measurements of the composition of Mars' upper atmosphere 
and electrically charged ionosphere. The results also offer an unprecedented 
view of ions as they gain the energy that will lead to their to escape 
from the atmosphere.

"We are beginning to see the links in a chain that begins with solar-driven 
processes acting on gas in the upper atmosphere and leads to atmospheric 
loss," said Bruce Jakosky, MAVEN principal investigator with the Laboratory 
for Atmospheric and Space Physics at the University of Colorado, Boulder. 
"Over the course of the full mission, we'll be able to fill in this picture 
and really understand the processes by which the atmosphere changed over 
time."

On each orbit around Mars, MAVEN dips into the ionosphere - the layer 
of ions and electrons extending from about 75 to 300 miles above the surface. 
This layer serves as a kind of shield around the planet, deflecting the 
solar wind, an intense stream of hot, high-energy particles from the sun.

Scientists have long thought that measurements of the solar wind could 
be made only before these particles hit the invisible boundary of the 
ionosphere. MAVEN's Solar Wind Ion Analyzer, however, has discovered a 
stream of solar-wind particles that are not deflected but penetrate deep 
into Mars' upper atmosphere and ionosphere.

Interactions in the upper atmosphere appear to transform this stream of 
ions into a neutral form that can penetrate to surprisingly low altitudes. 
Deep in the ionosphere, the stream emerges, almost Houdini-like, in ion 
form again. The reappearance of these ions, which retain characteristics 
of the pristine solar wind, provides a new way to track the properties 
of the solar wind and may make it easier to link drivers of atmospheric 
loss directly to activity in the upper atmosphere and ionosphere.

MAVEN's Neutral Gas and Ion Mass Spectrometer is exploring the nature 
of the reservoir from which gases are escaping by conducting the first 
comprehensive analysis of the composition of the upper atmosphere and 
 ionosphere. These studies will help researchers make connections between 
the lower atmosphere, which controls climate, and the upper atmosphere, 
where the loss is occurring.

The instrument has measured the abundances of many gases in ion and neutral 
forms, revealing well-defined structure in the upper atmosphere and ionosphere, 
in contrast to the lower atmosphere, where gases are well-mixed. The variations 
in these abundances over time will provide new insights into the physics 
and chemistry of this region and have already provided evidence of significant 
upper-atmospheric "weather" that has not been measured in detail before.

New insight into how gases leave the atmosphere is being provided by the 
spacecraft's Suprathermal and Thermal Ion Composition (STATIC) instrument. 
Within hours after being turned on at Mars, STATIC detected the "polar 
plume" of ions escaping from Mars. This measurement is important in determining 
the rate of atmospheric loss.

As the satellite dips down into the atmosphere, STATIC identifies the 
cold ionosphere at closest approach and subsequently measures the heating 
of this charged gas to escape velocities as MAVEN rises in altitude. The 
energized ions ultimately break free of the planet's gravity as they move 
along a plume that extends behind Mars.

The MAVEN spacecraft and its instruments have the full technical capability 
proposed in 2007 and are on track to carry out the primary science mission. 
The MAVEN team delivered the spacecraft to Mars on schedule, launching 
on the very day in 2013 projected by the team 5 years earlier. MAVEN was 
also delivered well under the confirmed budget established by NASA in 
2010.

The team's success can be attributed to a focused science mission that 
matched the available funding and diligent management of resources. There 
were also minimal changes in requirements on the hardware or science capabilities 
that could have driven costs. It also reflects good coordination between 
the principal investigator; the project management at NASA's Goddard Space 
Flight Center; the Mars Program Office at NASA's Jet Propulsion Laboratory 
in Pasadena, California; and the Mars Exploration Program at NASA Headquarters.

The entire project team contributed to MAVEN's success to date, including 
the management team, the spacecraft and science-instrument institutions, 
and the launch-services provider.

"The MAVEN spacecraft and its instruments are fully operational and well 
on their way to carrying out the primary science mission," said Jim Green, 
director of NASA's Planetary Science Division at NASA Headquarters in 
Washington. "The management team's outstanding work enabled the project 
to be delivered on schedule and under budget."

MAVEN's principal investigator is based at the University of Colorado's 
Laboratory for Atmospheric and Space Physics in Boulder, and NASA's Goddard 
Space Flight Center in Greenbelt, Maryland, manages the mission.

For more information about NASA's MAVEN mission, visit: http://www.nasa.gov/maven

Nancy Neal-Jones
NASA's Goddard Space Flight Center, Greenbelt, Maryland
301-286-0039
nancy.n.jones at nasa.gov

Elizabeth Zubritsky
NASA's Goddard Space Flight Center, Greenbelt, Maryland
301-614-5438
elizabeth.a.zubritsky at nasa.gov