Tracing the Big Picture of Mars' Atmosphere

Feature Aug. 26, 2010

Tracing the Big Picture of Mars' Atmosphere

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2010-280&cid=release_2010-280

One of the instruments on a 2016 mission to orbit Mars will provide daily maps of global, pole-to-
pole, vertical distributions of the temperature, dust, water vapor and ice clouds in the Martian
atmosphere.

The joint European-American mission, ExoMars Trace Gas Orbiter, will seek faint gaseous clues
about possible life on Mars. This instrument, called the ExoMars Climate Sounder, will supply
crucial context with its daily profiling of the atmosphere's changing structure.

The European Space Agency and NASA have selected five instruments for ExoMars Trace Gas
Orbiter. The European Space Agency will provide one instrument and the spacecraft. NASA will
provide four instruments, including ExoMars Climate Sounder, which is coming from NASA's Jet
Propulsion Laboratory, Pasadena, Calif.

Two of the other selected instruments are spectrometers -- one each from Europe and the United
States -- designed to detect very low concentrations of methane and other important trace gases in
the Martian atmosphere.

"To put the trace-gas measurements into context, you need to know the background structure and
circulation of the atmosphere," said JPL's Tim Schofield, principal investigator for the ExoMars
Climate Sounder. "We will provide the information needed to understand the distribution of trace
gases identified by the spectrometers. We'll do this by characterizing the role of atmospheric
circulation and aerosols, such as dust and ice, in trace-gas transport and in chemical reactions in the atmosphere affecting trace gases."

The ExoMars Climate Sounder is an infrared radiometer designed to operate continuously, day and
night, from the spacecraft's orbit about 400 kilometers (about 250 miles) above the Martian surface.
It can pivot to point downward or toward the horizon, measuring temperature, water vapor, dust
and ices for each 5-kilometer (3-mile) increment in height throughout the atmosphere from ground
level to 90 kilometers (56 miles) altitude.

Schofield and his international team have two other main goals for the investigation, besides aiding
in interpretation of trace-gas detections.

One is to extend the climate mapping record currently coming from a similar instrument, the Mars
Climate Sounder, on NASA's Mars Reconnaissance Orbiter, which has been working at Mars since
2006. The orbital geometry of the Mars Reconnaissance Orbiter mission enables this sounder to
record atmospheric profiles only at about 3 p.m. and 3 a.m. during the Martian day, except near the
poles. The ExoMars Trace Gas Orbiter will fly an orbital pattern that allows the spacecraft to collect
data at all times of day, at all latitudes.

"We'll fill in information about variability at different times of day, and we'll add to the number of
Mars years for understanding year-to-year variability," said Schofield. "The most obvious year-to-
year change is that some years have global dust storms and others don't. We'd like to learn whether
there's anything predictive for anticipating the big dust storms, and what makes them so variable
from year to year."

A third research goal is to assist future landings on Mars by supplying information about the
variable density of the atmosphere. At a chosen landing site, atmospheric density can change from
one day to the next, affecting a spacecraft's descent.

"We want to provide background climatology for what to expect at a given site, in a given season,
for a particular time of day, and also nearly real-time information for the atmospheric structure in
the days leading up to the landing of a spacecraft launched after 2016," said Schofield.

The 2016 ExoMars Trace Gas Orbiter is the first in a series of planned Mars mission collaborations
of the European Space Agency and NASA. A variable presence of small amounts of methane in the
Martian atmosphere has been indicated from orbital and Earth-based observations. A key goal of
the mission is to gain a better understanding of methane and other trace gases that could be
evidence about possible biological activity. Methane can be produced both biologically and
without life.

Besides the two spectrometers and the climate sounder, the orbiter's selected instruments include
two NASA-provided imagers: a high-resolution, stereo, color imager, and a wide-angle, color,
weather camera. The orbiter will also serve as a communications relay for missions on the surface
of Mars and will carry a European-built descent-and-landing demonstration module designed to
operate for a few days on the Mars surface. JPL, a division of the California Institute of
Technology, manages NASA's roles in the mission.

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