Researchers with the Department of Energy's Los Alamos National
Laboratory have determined that Mars has enough water to sustain
human exploratory missions.


Graphic shows a cross-section of the depth of the ice changing with
latitude. Credit: NASA/JPL/University of Arizona/Los Alamos National
Laboratories


A neutron spectrometer, designed and built at Los Alamos and flown
aboard NASA's Mars Odyssey, has been mapping the Red planet for the
past three months for hydrogen, an indicator of water-ice.

The results appear in the May 31 issue of Science magazine.

"The surface soils of Mars are rich in hydrogen," said Los Alamos'
principal investigator Bill Feldman. "Soil extending 60 degrees from
the Martian poles contain from 35 percent to 100 percent of water-ice
buried beneath a shallow overburden of hydrogen-poor soil. Although
scientists have known that water ice is stable close to the surface
in these regions, our new measurements are the first to give the
amount of near-surface water on Mars.

"The amount of water present on Mars is sufficiently large that it
can support future human exploration activities," Feldman
continued. "We have anticipated these results for 17 years and are
excited that all of our wishes and hard work have been fulfilled."

The neutron spectrometer maps show that the large region that extends
from the poles to within about 50 degrees of the equator contains
Mars' most abundant reservoirs of hydrogen, or water ice. The large
expanses at low to middle latitudes of Mars also contain significant
amounts of hydrogen, which are most likely deposits of chemically
and/or physically bound water and/or hydroxyl radicals - one hydrogen
atom bound to one oxygen atom.

The neutron spectrometer data are supported by simultaneous
measurements made using Mars Odyssey's gamma-ray spectrometer,
operated by the University of Arizona.


Thermal (top) and epithermal (bottom) polar maps show neutrons above
the south (left) and north (right) polar caps. Enhancements of the
thermal fluxes at both caps show that the central portion of the
north cap is covered by dry-ice frost because it is late winter. The
residual polar cap at the south cap also is covered by a thick layer
of dry ice even though it is late summer. The maps of epithermal
neutrons show a high abundance of subsurface water ice near the
surface south of about negative 60 degrees latitude and within a ring
that almost completely surrounds the central portion of the north
polar cap that is covered by a thick layer of dry-ice frost. A
meridional lane extending southward from the mouth of Chasma Borealis
is probably covered by a thin layer of dry ice frost at this time of
year (late northern winter). Credit: NASA/JPL/University of
Arizona/Los Alamos National Laboratories


Los Alamos' neutron spectrometer began mapping the Martian surface
while it was summer in the south and winter in the north. It revealed
the extent to which the northern and southern polar caps are covered
in a thick layer of carbon dioxide, or dry ice. During winter, the
carbon dioxide layers extend from the poles to within about 60
degrees of the equator because the dry ice frost settles out of the
atmosphere when temperatures fall about 186 degrees below zero
Fahrenheit. During the warmer summer the carbon dioxide layer
evaporates completely in the north but remains as a thick cover of
the residual polar cap in the south.

The first successful attempt to measure the global distribution of
neutrons about a planetary body was made using a similar neutron
spectrometer aboard Lunar Prospector. Comparisons between the lunar
and Martian neutron spectrometer data reveal that Mars' soil is
richer in hydrogen than is the moon's soil by more than several
factors of 10 to several factors of 1,000.

Los Alamos neutron spectrometer will continue to measure neutrons
that leak outward from the upper meter of the Martian soil for
several more years. Mars Odyssey's orbit is such that the entire
planet's surface is sampled in four-degree longitudinal increments
weekly.

Scientists will use these data not only to determine the amount of
water on Mars, but to map the basaltic lava cover, measure the
seasonal variation of dry-ice frost that covers both poles during
their winter months and help interpret data from the gamma-ray
spectrometer to determine the quantity and composition of the most
abundant elements on the planet.

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