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Sunday, April 4, 2010

Update: Water on the Moon

Back in December, I wrote about finding water on the moon. At the time, it was thought that the water was dispersed throughout the lunar regolith, or silty surface. New measurements show that this was partly wrong.

According to Paul Spudis of the Lunar and Planetary Institute in Houston, Texas:

So far we've found three types of moon water. We have Mini-SAR's thick lenses of nearly pure crater ice, LCROSS's fluffy mix of ice crystals and dirt, and M-cube's thin layer that comes and goes all across the surface of the moon.

Spudis was referring to two instruments (the Miniature Synthetic Aperture Radar and the Moon Mineralogy Mapper) found on India's Chandrayaan-1 moon probe, as well as to the LCROSS spacecraft that was smashed into the moon on Oct. 9, 2009. Evidence of water was immediately apparent upon impact. Since then, the data has been further analyzed. Anthony Colaprete, LCROSS principal investigator, now says that the spacecraft kicked up two different layers of water-containing soil. The top layer contained ice crystals and water bound up with soil minerals, a type of water found all over the lunar surface. Below that first layer was an older layer containing even more water, plus such compounds as sulfur dioxide (SO2), methanol (CH3OH), and at least one organic molecule, diacetylene (H2C4).

Meanwhile, Mini-SAR has found two meter deep deposits of nearly pure water ice in 40 different craters. Spudis postulates that these very different forms of water, thinly mixed through the lunar regolith, or forming large ice patches, originate from different sources. The trace amounts of water in the soil could have been made from protons interacting with metal oxides in the dirt. This possibility seems likely, since this type of water appears to be recently replenished. Ice patches in the craters, on the other hand, probably have an extralunar source.

Wherever the water came from, there seems to be plenty of it on the moon.

Hat tip: