The North Pole (lower, right) of the Moon.
Credit: NASA
WASHINGTON, D.C.: Ice sheets, two to three metres thick, have been found in lunar craters near the North Pole, leading scientists to estimate there's billions of tonnes of ice on the Moon.
Water was first discovered on the Moon in September 2009, bound up in minerals. Before that it was suspected that the Moon was bone dry.
And in March 2010, researchers discovered ice on the North Pole, though researchers were not sure how much: NASA estimates were 600 million tonnes.
Water, water, everywhere
Using synthetic aperture radar (SAR), a type of imaging that allows scientists to see in the dark, Paul Spudis, a geologist at the Lunar and Planetary Institute in Houston, Texas, and his team of researchers, observed pockets of thick ice near the North Pole of the Moon.
"What we have found in the last few months is truly astounding," said Spudis. "After years of debate about whether the Moon has water or not, we find it in three different settings and styles."
Water on the Moon can be found in large sheets, in small pieces mixed into loose material covering rock, or as water absorbed into minerals.
Ice 2 - 3 metres thick
Large amounts of water molecules are reaching the permanently dark, cold areas in polar craters and are being trapped there, said Spudis.
SAR technology allows researchers to use radio waves, which reflect off the lunar surface, to see areas of the Moon that are in permanent shadow, previously uncharted territory.
Recent studies suggest that the ice must be two to three meters thick in some areas but that it is not evenly distributed, meaning that it may have been displaced by a comet or an asteroid.
Water comes from space, not Moon interior
"Though some lunar volcanic rocks do contain a tiny amount of water, the water being measured on the surface almost certainly comes from space and not the lunar interior," said Linda Elkins-Tanton, a geologist at Massachusetts Institute of Technology in Boston.
NASA's Lunar CRater Observation and Sensing Satellite (LCROSS) discovered water in the Cabeus Crater near the Moon's South Pole back in October, 2009, by using spectrometry, or light emissions to determine the composition of materials.
This latest discovery only strengthens what scientists have suspected - that water exists in large quantities on the Moon at both poles.
Billions of tons of ice
"The total amount of ice is still being studied, but it will most certainly run into the billions of tonnes," said Spudis.
Studying these areas and the secrets they hold will likely give scientists valuable insight not only into the history of the Moon, but that of the solar system as well. "A whole new field of science has begun: Lunar hydrology," said Spudis.
Adds Elkins-Tanton: "That three teams simultaneously measured this phenomenon lets us know the measurements are real, the science good, and the next step of understanding is ready to be taken."
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