Moon has more water than previously thought, according to a new study by NASA-funded researchers.
The latest findings have raised new questions about theories of moon's origin.
For the first time, researchers have measured water from the moon in the form of tiny globules of molten rock, which have turned to glass-like material trapped within crystals. Data from these newly-discovered lunar melt inclusions indicate the water content of lunar magma is 100 times higher than earlier studies suggested.
The inclusions were found in lunar sample, the famous high-titanium orange glass soil of volcanic origin collected during the Apollo 17 mission in 1972. The scientific team measured the water content of the inclusions, which were formed during explosive eruptions on the moon about 3.7 billion years ago.
Meanwhile, the results, which were published in the May 26 issue of Science Express, also raised questions about aspects of the giant impact theory of how the moon was created. That theory predicted very low water content of lunar rock due to catastrophic degassing during the collision of Earth with a Mars-sized body very early in its history.
The study also provides additional scientific justification for returning similar samples from other planetary bodies in the solar system.
Water plays a critical role in determining the tectonic behavior of planetary surfaces, the melting point of planetary interiors and the location and eruptive style of planetary volcanoes, said Erik Hauri, a geochemist with the Carnegie Institution of Washington and lead author of the study. I can conceive of no sample type that would be more important to return to Earth than these volcanic glass samples ejected by explosive volcanism, which have been mapped not only on the moon but throughout the inner solar system.
In contrast to most volcanic deposits, the lunar melt inclusions are encased in crystals that prevent the escape of water and other volatiles during eruption.
These samples provide the best window we have on the amount of water in the interior of the moon where the orange glass came from, said science team member James Van Orman of Case Western Reserve University in Cleveland.
In a 2008 study led by Alberto Saal of Brown University, the same team reported the first evidence of water in lunar volcanic glasses. They used magma degassing models to estimate how much water was originally in the magmas before eruption.
The bottom line is that in 2008, we said the primitive water content in the lunar magmas should be similar to lavas coming from the Earth's depleted upper mantle, Saal said. Now, we have proven that is indeed the case.
The study also puts a new twist on the origin of water-ice detected in craters at the lunar poles by several recent NASA missions. The ice has been attributed to comet and meteor impacts, but the researchers believe it is possible that some of the ice came from water released by the eruption of lunar magmas eons ago.