This indication that water on the Moon comes from different sources - accounting for the varying organic compounds contained within - is reported in Space.com.
Measurements from India's Chandrayaan-1 moon probe (which found frozen water in 40 craters) and from NASA's recent Lunar Crater Observation and Sensing Satellite (LCROSS) mission (which slammed into the moon last October to test soil content from the resulting impact plume and found additional water) suggest that three different varieties of lunar water have been identified.
Paul Spudis of Houston's Lunar and Planetary Institute told Space.com that in addition to nearly pure ice, there is also a "fluffy mix of ice crystals and dirt" found by LCROSS. Instruments on Chandrayaan-1 also detected a thin layer of water that "comes and goes" across the surface.
The initial impact of LCROSS released water and hydroxyl, with small bits of pure ice mixed in, from the surface layer. Beneath that, water from a deeper layer was released, likely from a much earlier time period.
That water, Spudis said, contains more water ice, in addition to a variety of molecular compounds - sulfur dioxide (SO2), methanol (CH3OH), and diacetylene (H2C4).
This layer, at least one-half-meter below the surface, "is probably older than the ice we're finding on the surface," he said.
While some surface water likely comes from bodies that have impacted the moon over the eons - comets, for example, which are primarily ice - Spudis told Space.com that some water might be formed on the moon.
"Protons in the solar wind can make small amounts of water continuously on the lunar surface by interacting with metal oxides in the rocks," he said.