A possible mission to Mars in 2007 would scrutinize the martian
atmosphere for any chemical traces of life, or even environments
supportive of life, anywhere on the planet.

An international team led by Dr. Mark Allen, an atmospheric chemist at
NASA’s Jet Propulsion Laboratory, Pasadena, Calif., developed the
mission proposal named Mars Volcanic Emission and Life Scout, or
Marvel. Today, NASA announced that Marvel is one of four finalists
in competition for the first Mars Scout Mission for the 2007 launch
opportunity. Final selection by the NASA associate administrator for
space science, Dr. Edward Weiler, will be made by late next summer.

“One of the most exciting questions people ask is whether life exists
elsewhere,” Allen said. “A lot of us on this team think that if life
ever existed on Mars, there is a good chance life still exists if
there is any place warm and wet.”

Scientists in recent years have been developing strategies for how
life on planets around other stars might be detected from what’s in a
planet’s atmosphere. Allen’s team turned that thinking toward Mars.

For example, many types of microbes, including those living in cows’
guts, produce methane. “Marvel will have such great sensitivity that
if you had just three cows anywhere on Mars, we would be able to
detect the amount of methane added to the atmosphere,” he said.

The mission would equip a Mars orbiter with two types of instruments
that have proven useful in studying Earth’s atmosphere from Earth
orbit. One, an infrared solar occultation spectrometer, would look
sideways through Mars’ atmosphere toward the setting or rising Sun for
an extremely sensitive reading of what chemicals are in the thin air
that the sunlight passes through before hitting the instrument. The
other, a submillimeter spectrometer, would look through any dust in
the atmosphere to seek localized atmospheric concentrations of the
chemicals of interest.

“By the end of this decade, Marvel could either detect and localize
any existing life and active volcanism on Mars or put extremely
stringent limits on their existence,” Allen said.

The submillimeter spectrometer would also be used to seek localized
concentrations of water vapor in the atmosphere, a strategy to
identify places where subsurface water sources are actively venting.

As one novel feature of the mission, the submillimeter spectrometer
could be re-tuned from Earth to enable detection of interesting
substances that the occultation spectrometer discovers in trace
amounts. The instrument would then map the occurrences of the
substance globally.

JPL would manage the Marvel mission and would build both
spectrometers. A third instrument, a camera for showing the context
of cloud conditions during the atmospheric measurements, would be
supplied by the Canadian Space Agency. Lockheed Martin Astronautics,
Denver, Colo., would build and operate the spacecraft. Designs for the
mission, the spacecraft and operations draw heavily from the
successful 2001 Mars Odyssey mission, now in orbit at Mars. A
20-member international science team has worked with Allen to plan how
to achieve the research goals.

If selected as NASA’s first Mars Scout mission, Marvel would launch in
the third quarter of 2007, arrive at Mars about a year later, use
aerobraking to achieve the best shape for its polar orbit pattern,
then begin its primary science mission in October 2008 to examine Mars
for a full 22-month martian year.

The other three Mars Scout mission concepts selected and their
principal investigators are: Sample Collection for Investigation of
Mars, led by Professor Laurie Leshin of Arizona State University,
Tempe; the Aerial Regional-scale Environmental Survey, led by Dr. Joel
Levine, NASA Langley Research Center, Hampton, Va.; and Phoenix, led
by Dr. Peter Smith of the University of Arizona, Tucson.

JPL, a division of the California Institute of Technology, Pasadena,
manages the Mars Scout Program for the NASA Office of Space Science,
Washington, D.C.