… Archived data from Cassini, which passed by the moon in 1999 on its way to Saturn, provided confirmation of this water/hydroxyl signal. The water would have to be absorbed or trapped in the glass and minerals at the lunar surface, Roger Clark of the U.S. Geological Survey wrote in a study detailing Cassini’s findings.
The Cassini readings show a global distribution of the water signal, though it also appears stronger near the poles (and low in the lunar maria).
Finally, the Deep Impact spacecraft, as part of its extended EPOXI mission, made infrared detections of water and hydroxyl as well. Those observations were made at the request of the M3 team, as part of a calibration exercise during several close approaches of the Earth-moon system en route to its planned flyby of Comet 103P/Hartley 2 in November 2010.
Deep Impact detected the signal at all latitudes above 10 degrees N, though once again, the poles showed the strongest signals. With its multiple passes, Deep Impact was able to observe the same regions at different times of the lunar day. At noon, when the sun’s rays were strongest, the water feature was lowest. The feature was strongest during the lunar morning.
“The Deep Impact observations of the moon not only unequivocally confirm the presence of [water/hydroxyl] on the lunar surface, but also reveal that the entire lunar surface is hydrated during at least some portion of the lunar day,” the authors wrote in their study.
The findings of all three spacecraft “provide unambiguous evidence for the presence of hydroxyl or water,” Paul Lacey of the University of Hawaii said in an essay accompanying the three studies. Lacey was not involved in any of the missions.
The new data “prompt a critical reexamination of the notion that the moon is dry. It is not,” Lacey wrote.
Combined, the findings show that the moon’s hydration process is a dynamic one, driven by the daily changes in solar radiation hitting any given spot on the surface.
The sun might also have something to do with how the water got there.
Where the water comes from
There are potentially two types of water on the moon: icy material brought from outside sources, such as water-bearing comets striking the surface, or water that has its source on the moon. This endogenic water may arise from the interaction of the solar wind with moon rocks and soils. – msn