Saturday science subject: The Moon, comets, and water

Last Saturday, we wrote about how NASA's Lunar Crater Observation and Sensing Satellite (LCROSS) has discovered a substantial amount of water on the Moon. There was talk about comets, not solar wind, being the source of the water pretty early on, and New Scientist now says "evidence is mounting" in favor of the comet hypothesis.

Lunar scientists gathered and went over the LCROSS data at the Lunar Exploration Analysis Group meeting in Houston, Texas, earlier this week. The case for comets indeed looks pretty strong:

The first line of evidence comes from compounds that vaporise readily, called volatiles. LCROSS found spectral signs of volatiles containing carbon and hydrogen – likely methane and ethanol – as well as others such as ammonia and carbon dioxide. "It appears that we impacted into a very volatile-rich area," LCROSS principal scientist Tony Colaprete told the conference.

These compounds should have been mostly lost to space billions of years ago, when the moon coalesced from the debris of an impact between the Earth and a Mars-sized object. Water formed through an interaction with the solar wind would therefore be relatively pure – and free of volatiles.

Comets, meanwhile, are "known to contain volatiles such as methane." The amount of water found also constitutes further evidence—New Scientist says solar wind would only form water at a 1% concentration in lunar soil, but the water found by LCROSS was reportedly more plentiful.

This is all good news for manned lunar missions. Colaprete estimates hydorgen concentrations "in the range of several per cent," and hydrogen could be used as fuel to get astronauts back home. Other elements like ethanol and methane could also serve a similar purpose. That prospect has some folks pretty excited. New Scientist quotes Noah Petro of NASA's Goddard Space Flight Center as saying, "LCROSS has given us our ticket back to the moon."

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