Scientists from the U.S. Department of Energy's Los Alamos National Laboratory are lead authors on four of the papers in Science, with significant contributions from the Observatoire Midi-Pyrenees in Toulouse, France. Los Alamos built three of Lunar Prospector's five onboard instruments. The additional analysis also shows the water is likely confined to localized areas near the poles, rather than spread out evenly across the polar regions, as was assumed in making the earlier estimates. Water amounts, inferred from measurements of hydrogen in the lunar soil, are of great interest because of their potential impact on plans for colonization. Los Alamos scientists built Lunar Prospector's neutron spectrometer, gamma ray spectrometer and alpha particle spectrometer.
Spectrometers measure the numbers and energies of particles or photons encountered.
When a cosmic ray hits a nucleus it can eject neutron particles or high-energy gamma ray photons in response. Some of the neutrons and gamma rays travel upward where instruments aboard Lunar Prospector intercept them. The moon once was hot and molten and as it cooled minerals crystallized and sank to form the core, if they were heavy, or floated upward to form the crust, if they were light. The last material to solidify contained thorium, potassium, gadolinium and samarium, which do not readily incorporate into minerals. Thorium and potassium create standout gamma-ray signals, and their emissions neatly trace out Mare Imbrium's outer rim.