A neutron spectrometer designed and
built at the U.S. Department of Energy’s Los Alamos National Laboratory
is aboard NASA’s Mars Odyssey set to launch Saturday from Cape Canaveral
Air Force Station in Florida.

A similar Los Alamos instrument aboard NASA’s Lunar Prospector provided
compelling evidence for water-ice at the moon’s poles.

Los Alamos’ neutron spectrometer will map the water table in the upper
meter of the Martian soil, helping scientists to understand the climatic
history of the red planet and also provide information on the location
and quantity of water available for future exploration and possible
colonization. The neutron spectrometer will also map the basaltic lava
cover, measure the seasonal variation of dry ice snowfall at the poles
and provide the necessary neutron data needed to convert the gamma ray
data into elemental compositional abundances.

“We are excited and nervous about the launch. You never know what will
happen — you just hope it gets off the ground and makes it into orbit
around Mars and sends us back data,” said Bob Reedy a nuclear scientist
at Los Alamos attending the launch who has been a part of the National
Aeronautics and Space Administration Mars Gamma-Ray team for fifteen
years and experienced the disappointment of the past two failed Mars

Neutrons are generated when galactic cosmic rays slam into the nuclei
of atoms on the planet’s surface, ejecting neutrons skyward with enough
energy to reach an orbiting spacecraft. Elements create their own unique
distribution of neutron energy — fast, thermal or epithermal — and
these neutron flux signatures allow scientists to determine the
elemental composition of the soil based upon the data received from
the instruments.

The neutron spectrometer will map Mars’ basaltic lava by measuring
fast neutrons indicative of a major component of the lava — iron.
By looking for a drop in epithermal neutron flux the scientists will
locate hydrogen, most commonly in the form of water molecules, on or
below the Martian surface. Hydrogen in the soil efficiently absorbs
the energy from neutrons, preventing them from escaping the surface
and being detected by the spectrometer.

Studying Mars will help answer questions about Earth’s formation and
the origin and evolution of the solar system. But Bill Feldman, Los
Alamos’ principal investigator on the design and construction of the
neutron spectrometer says, “A paramount question of interest is, why
doesn’t life exist on Mars? Our understanding of what elements are
necessary to foster and sustain life here on Earth exist on Mars,
but yet life does not appear to have existed there. If life does not
exist, nor never did exist on Mars, what makes Earth so unique that
it can support life?”

Three weeks after launch as the spacecraft cruises toward Mars the
neutron spectrometer will be turned on. Mars Odyssey will reach Mars
in October after its 286 million-mile journey and gradually tighten
its orbit to get into its mapping orbit sometime in January. At that
point all instruments aboard Mars Odyssey will begin sending data
about the red planet back to Earth.

The other instruments aboard the 1,600-pound spacecraft include a
thermal-emission imaging system, a gamma-ray spectrometer and a
radiation monitor. The Mars Odyssey mission is designed to map the
mineral and chemical make-up of the Martian surface and the location
of water and shallow buried ice, and for the first time study the
radiation environment of the planet to gauge the risk for future

The neutron spectrometer was designed and constructed by a team of
scientists and engineers from Los Alamos’ Space and Atmospheric
Sciences and Space Instrumentation and System Engineering groups
headed by Feldman, Ken Fuller, Steven Storms, Danny Everett, Glenn
Thornton and Jerry Longmire.

Los Alamos has been flying neutron spectrometers since 1963 in support
of the U.S. nuclear treaty verification program. The present design
used for Mars Odyssey was developed in mid 1980 in support of the
U.S. strategic defense initiative.