LOS ALAMOS, N.M., March 12, 2001 — This week scientists from The
Department of Energy’s Los Alamos National Laboratory present their
latest findings from NASA’s Lunar Prospector mission at the Lunar and
Planetary Science Conference in Houston, Texas.

“Lunar Prospector has revolutionized our view of the Moon — we just
didn’t realize how much it revolutionized it. And there is a whole
community of people out there in the planetary science world that is
excited about and interested in the Lunar Prospector data,” said Rick
Elphic, a Los Alamos scientist.

The Los Alamos studies include data on Moonquake activity, further
confirmation of the presence of water-ice on the moon, and mapping of iron
and titanium using gamma-rays emitted when cosmic rays slam into the lunar

Los Alamos scientists built three of the five instruments that were aboard
the Lunar Prospector spacecraft that orbited the Moon for nearly 19 months
gathering data, and then was intentionally crashed in the Moon’s south
pole in a final attempt to extract additional information about water on
the Moon.

The data gathered by the Lunar Prospector and analyzed by Los Alamos
scientists also provided the first global elemental lunar study to date.

“You can’t take samples of just a few locations on the Moon, like the
Apollo missions did, and say you know the composition of the whole Moon.
It would be like taking a rock from Paris and Los Angeles and a snap
shot of Tokyo and saying you know everything about Earth’s composition.
It’s like a detective story — you have to put all of the pieces of
information together to see the whole picture,” David Lawrence, a Los
Alamos researcher, said.

Los Alamos scientists present a few pieces from this puzzle this week at
the conference. The scientific goals for the Lunar Prospector were to
answer long-standing questions about the Moon, its resources — including
water — its structure, and its origins.

Los Alamos scientists at the conference include Lawrence and Tom Prettyman,
who present the first Lunar Prospector Gamma-Ray Spectrometer measurements
of lunar iron abundance. Elphic and Prettyman, who present titanium data
that suggest previous measurements were twice as high as the actual
abundance. Olivier Gasnault, who presents neutron data that correlates
the atomic mass of the soil to neutron flux. William Feldman, who provides
further evidence that the enhanced hydrogen abundance at the lunar poles
is in the form of water ice. Stefanie Lawson, who presents the first
Alpha-Particle Spectrometer measurements on tectonic activity and Elphic
also presents computer simulation data that confirm actual measurement

Lawrence’s gamma-ray spectrometry data give the first overall iron
composition measurements of the entire lunar surface. Iron abundance
is a crucial piece in understanding lunar composition because iron is
a major constituent of all lunar rocks, and iron abundance reveals
information about how the Moon formed and changed over time.

Both iron and titanium are fundamental elements in the lava — or maria
flood basalt — plains on the Moon’s surface that are seen from Earth
as the “dark spots” of the Moon.

The Department of Defense’s earlier Clementine mission measured iron and
titanium by using ultraviolet, visible, and near-infrared spectroscopy
and concluded there is more iron and titanium in the dark spots and less
in the light-colored spots. “Their overall measurements of the entire
Moon’s elemental composition is based on empirical relationships. They
empirically identified that a certain reflectance correlates with a
given abundance. But this correlation was based upon the limited soil
samples gathered on the Apollo missions,” Lawrence said.

Lawrence’s results show that the Clementine abundance measurements for
returned sample locations agree quite well with the Lunar Prospector’s
gamma-ray spectrometer measurements; however the abundance derived by
Clementine in locations not sampled by Apollo will need to be revised
based on the Lunar Prospector gamma-ray spectrometer data.

Elphic’s Neutron Spectrometer data on the concentration of titanium in
the maria flood basalt regions contradicts the concentrations inferred
by the correlation drawn between the Clementine and Apollo missions.
Elphic’s findings indicate there is half as much titanium in the basalt
regions as the previous data suggested.

“These results have potential ramifications for two areas. First, for
understanding the source regions and history of lunar basaltic volcanism
and secondly for the future colonization of the Moon. If we intend to
use indigenous resources when we colonize it’s important to know what
we have available and where we can find it,” Elphic said.

“No one has ever looked at the Moon — or any other planetary body —
with ‘neutron eyes.’ It is a whole different way of seeing things and
it is very exciting,” said Elphic. Lunar Prospector carried neutron
detectors that measured neutrons in three energy ranges emitted by the
lunar surface.

In another study, Gasnault determined the relationship between the fast
neutron fluxes emitted from the lunar surface and the average weight —
atomic mass — of the soil. “The calculations show that the number of
neutrons produced is proportional to the atomic mass of the soil,”
Gasnault said.

The first neutrons that escape after the lunar soil is hit by cosmic rays
are indicative of the composition of the soil. Different elements, when
hit by cosmic rays, will produce a different number of neutrons, which
will eventually reach different energies called fast, thermal or
epithermal. Neutrons termed fast neutrons are indicative of iron and
titanium. This information helps determine the elemental composition of
the soil.

“The remarkable difference in composition between the two faces of the
Moon is surprising for a small planet. This is one of the great mysteries
of the Moon,” said Gasnault.

Gasnault also worked out a combined analysis of fast neutron data and
thorium abundance on the lunar surface. Thorium is a subsurface material
brought to the surface by meteor impacts and volcanic activity. Using
this analysis Gasnault believes they have found another impact basin near
the large Imbrium basin.

Feldman’s Neutron Spectrometer data coupled with calculations of
sublimation processes of hydrogen compounds confirmed previous indications
that the hydrogen in the permanently shaded regions of the lunar poles is
in the form of water ice.

Sublimation is the process by which solids are transformed directly to the
vapor state without passing through the liquid phase.

“Sublimation is the only mechanism that can account for observed
differences between the hydrogen content of sunlit and permanently shaded
craters near lunar poles,” Feldman said.

The partially shaded — or partially sunny — regions of the poles reach
minus 234 degrees Fahrenheit but the permanently shaded regions remain at
minus 315 F. Going above or below minus 279 F determines whether the
water-ice will sublimate or be trapped forever. So in the partially
sunny regions of the poles the water-ice will sublimate, whereas in the
permanently shaded regions it will be trapped indefinitely. Hydrogen by
itself is not stable at these temperatures and will only remain if it
forms bonds — becomes water-ice for example — so the hydrogen detected
in the permanently shaded regions of the poles must be in the form of

It is estimated that each pole may contain up to one billion tons of
frozen water ice spread throughout the soil.

Feldman said, “These data suggest an exciting scenario for lunar
colonization. The polar regions that border the permanently shaded
craters are also in the sunlight 80-85 percent of the time and would
make optimal space station sites. The stations would have access to the
water-ice and the sunlight would provide solar power. And by being near
the poles you see Earth most of the time, which means you can communicate.”

Lawson presents measurements of near-surface uranium gained from the
Alpha-Particle Spectrometer data. The Alpha-Particle Spectrometer measured
radon and polonium gasses that escaped from below the surface through
conduits created by tectonic, or Moonquake, activity. Polonium is a decay
product of radon, which in turn is a decay product of uranium. When
detected, they both indicate the presence of uranium.

Elphic presents a poster on computer simulations used to model neutron
emissions from the surface, their flight into space and their detection
by Lunar Prospector spectrometers. “The good news about these
simulations,” Elphic said, “is that they agree with measurements from
the Lunar Prospector. If they didn’t it would have raised doubts about
our data.”

The three instruments built by Los Alamos scientists were the Neutron
Spectrometer designed to measure the surface abundance of lunar materials
with special emphasis placed on the search for polar water-ice deposits
as implied by hydrogen abundances; the Gamma-Ray Spectrometer designed
to provide maps of the major and trace elements in the lunar surface; and
the Alpha-Particle Spectrometer designed to measure the history of gas
release events on the Moon.

Los Alamos’ Lunar Prospector team of the Space and Atmospheric Sciences
Group submitted 15 abstracts to the conference and is represented by nine
scientists presenting both posters and talks and attending meetings.

Prospector is a NASA Discovery Mission that places emphasis on science
and “faster, better, cheaper” mission design and development.