Los Alamos Releases New Maps of Mars Water
July 24, 2003
LOS ALAMOS, N.M., July 24, 2003 - "Breathtaking" new maps of likely
sites of water on Mars showcase their association with geologic
features such as Vallis Marineris, the largest canyon in the solar
The maps detail the distribution of water-equivalent hydrogen as
revealed by Los Alamos National Laboratory-developed instruments
aboard NASA's Mars Odyssey spacecraft. In an upcoming talk at the
Sixth International Conference on Mars at the California Institute of
Technology, in Pasadena, Los Alamos space scientist Bill Feldman and
coworkers will offer current estimates of the total amount of water
stored near the Martian surface. His presentation will be at 1:20
p.m., Friday, July 25.
|Distribution of Water on Mars
Overlay of water equivalent hydrogen abundances and a shade relief map derived from MOLA topography. Mass percents of water were determined from epithermal neutron counting rates using the Neutron Spectrometer aboard Mars Odyssey between February 2002 and April 2003.
For more than a year, Los Alamos' neutron spectrometer has been
carefully mapping the hydrogen content of the planet's surface by
measuring changes in neutrons given off by soil, an indicator of
hydrogen likely in the form of water-ice. The new color maps are
available at http://www.lanl.gov/worldview/news/photos/mars.shtml
"The new pictures are just breathtaking, the water-equivalent
hydrogen follows the geographic features beautifully," said Feldman.
"There's a lane of hydrogen-rich material following the western
slopes of the biggest volcanoes in the solar system, a maximum
reading sits right on Elysium mons, and another maximum is in the
deepest canyon in the solar system."
The new maps combine images from the Mars Orbiter Laser Altimeter
(MOLA) on the Mars Global Surveyor with Mars Odyssey spectrometer
data through more than half a Martian year of 687 Earth days. From
about 55 degrees latitude to the poles, Mars boasts extensive
deposits of soils that are rich in water-ice, bearing an average of
50 percent water by mass. In other words, Feldman said, a typical
pound of soil scooped up in those polar regions would yield an
average of half a pound of water if it were heated in an oven.
The tell-tale traces of hydrogen, and therefore the presence of
hydrated minerals, also are found in lower concentrations closer to
Mars' equator, ranging from two to 10 percent water by mass.
Surprisingly, two large areas, one within Arabia Terra, the
1,900-mile-wide Martian desert, and another on the opposite side of
the planet, show indications of relatively large concentrations of
Scientists are attracted to two possible theories of how all that
water got into the Martian soils and rocks.
The vast water icecaps at the poles may be the source. The thickness
of the icecaps themselves may be enough to bottle up geothermal heat
from below, increasing the temperature at the bottom and melting the
bottom layer of the icecaps, which then could feed a global water
On the other hand, there is evidence that about a million years or so
ago, Mars' axis was tilted about 35 degrees, which might have caused
the polar icecaps to evaporate and briefly create enough water in the
atmosphere to make ice stable planet-wide. The resultant thick layer
of frost may then have combined chemically with hydrogen-hungry soils
"We're not ready yet to precisely describe the abundance and
stratigraphy of these deposits, but the neutron spectrometer shows
water ice close to the surface in many locations, and buried
elsewhere beneath several inches of dry soils," Feldman said. "Some
theories predict these deposits may extend a half mile or more
beneath the surface; if so, their total water content may be
sufficient to account for the missing water budget of Mars."
In fact, a team of Los Alamos scientists has begun a research project
to interpret the Mars Odyssey data and their ramifications for the
history of Mars' climate. The project is funded through the
Laboratory Directed Research and Development program - which funds
innovative science with a portion of the Laboratory's operating
budget - and seeks to develop a global Martian hydrology model, using
vast amounts of remote sensing data, topography maps and experimental
results on water loading of minerals.
Members of the Planetary Science team at Los Alamos working with
Feldman on the Odyssey project include Bruce Barraclough, David Bish,
Dorothea Delapp, Richard Elphic, Herbert Funsten, Olivier Gasnault,
David Lawrence, G. McKinney, Kurt Moore, Robert Tokar, Thomas
Prettyman, David Vaniman and Roger Wiens as well as Sylvestre Maurice
of the Observatoire Midi-Pyrénées (France), S.W. Squyres of Cornell
University, and Jeff Plaut of the Jet Propulsion Laboratory.
Los Alamos' neutron spectrometer, a more sensitive version of the
instrument that found water ice on the moon five years ago, is one
component of the gamma-ray spectrometer suite of instruments aboard
Odyssey. W.T. Boynton of the University of Arizona leads the
gamma-ray spectrometer team.
The neutron spectrometer looks for neutrons generated when cosmic
rays slam into the nuclei of atoms on the planet's surface, ejecting
neutrons skyward with enough energy to reach the Odyssey spacecraft
250 miles above the surface.
Elements create their own unique distribution of neutron energy -
fast, thermal or epithermal - and these neutron flux signatures are
shaped by the elements that make up the soil and how they are
distributed. Thermal neutrons are low-energy neutrons in thermal
contact with the soil; epithermal neutrons are intermediate,
scattering down in energy after bouncing off soil material; and fast
neutrons are the highest-energy neutrons produced in the interaction
between high-energy galactic cosmic rays and the soil.
By looking for a decrease in epithermal neutron flux, researchers can
locate hydrogen. Hydrogen in the soil efficiently absorbs the energy
from neutrons, reducing their flux in the surface and also the flux
that escapes the surface to space where it is detected by the
spectrometer. Since hydrogen is likely in the form of water-ice at
high latitudes, the spectrometer can measure directly, a yard or so
deep into the Martian surface, the amount of ice and how it changes
with the seasons.
The Los Alamos expertise in neutron spectroscopy stems from longtime
nuclear nonproliferation work at the Laboratory, funded by the U.S.
Department of Energy's National Nuclear Security Administration. The
ability to measure and detect signatures of nuclear materials is a
vital component of the Laboratory's mission to reduce the threats
from weapons of mass destruction.
Mars Odyssey was launched from Cape Canaveral Air Force Station in
April 2001 and arrived in Martian orbit in late October 2001. During
the rest of the spacecraft's 917-day science mission, Los Alamos'
neutron spectrometer will continue to improve the hydrogen map and
solve more Martian moisture mysteries.
Jet Propulsion Laboratory, a division of the California Institute of
Technology in Pasadena, manages the Mars Odyssey mission for NASA's
Office of Space Science in Washington, D.C. Investigators at Arizona
State University in Tempe, the University of Arizona in Tucson and
NASA's Johnson Space Center, Houston, operate the science
instruments. Additional science partners are located at the Russian
Aviation and Space Agency and at Los Alamos National Laboratories,
New Mexico. Lockheed Martin Astronautics, Denver, the prime
contractor for the project, developed and built the orbiter. Mission
operations are conducted jointly from Lockheed Martin and from JPL.
Los Alamos National Laboratory is operated by the University of
California for the National Nuclear Security Administration (NNSA) of
the U.S. Department of Energy and works in partnership with NNSA's
Sandia and Lawrence Livermore national laboratories to support NNSA
in its mission.
Los Alamos develops and applies science and technology to ensure the
safety and reliability of the U.S. nuclear deterrent; reduce the
threat of weapons of mass destruction, proliferation and terrorism;
and solve national problems in defense, energy, environment and
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