[meteorite-list] Research Suggests Water Content Of Moon Interior Underestimated

[Ron Baalke]

June 14, 2010

Dwayne Brown 
Headquarters, Washington                                    
202-358-1726 
dwayne.c.brown at nasa.gov 

Tina McDowell 
Carnegie Institution of Washington 
202-939-1120 
tmcdowell at ciw.edu 

RELEASE: 10-144

RESEARCH SUGGESTS WATER CONTENT OF MOON INTERIOR UNDERESTIMATED

WASHINGTON -- NASA-funded scientists estimate from recent research 
that the volume of water molecules locked inside minerals in the 
moon's interior could exceed the amount of water in the Great Lakes 
here on Earth. 

Scientists at the Carnegie Institution's Geophysical Laboratory in 
Washington, along with other scientists across the nation, determined 
that the water was likely present very early in the moon's formation 
history as hot magma started to cool and crystallize. This finding 
means water is native to the moon. 

"For over 40 years we thought the moon was dry," said Francis McCubbin 
of Carnegie and lead author of the report published in Monday's 
Online Early Edition of the Proceedings of the National Academy of 
Sciences. "In our study we looked at hydroxyl, a compound with an 
oxygen atom bound with hydrogen, and apatite, a water-bearing mineral 
in the assemblage of minerals we examined in two Apollo samples and a 
lunar meteorite." 

McCubbin's team utilized tests which detect elements in the parts per 
billion range. Combining their measurements with models that 
characterize how the material crystallized as the moon cooled during 
formation, they found that the minimum water content ranged from 64 
parts per billion to 5 parts per million. The result is at least two 
orders of magnitude greater than previous results from lunar samples 
that estimated water content of the moon to be less than 1 parts per 
billion. 

"In this case, when we talk about water on the moon, we mean water in 
the structural form hydroxyl," said Jim Green, director of the 
Planetary Science Division at NASA Headquarters in Washington. "This 
is a very minor component of the rocks that make up the lunar 
interior." 

The origin of the moon is now commonly believed to be the result of a 
Mars-sized object that impacted the Earth 4.5 billion years ago. This 
impact put a large amount of material into Earth's orbit that 
ultimately compacted to form the moon. The lunar magma ocean that is 
thought to have formed at some point during the compacting process, 
began to cool. During this cooling, water either escaped or was 
preserved as hydroxyl molecules in the crystallizing minerals. 

Previous studies found evidence of water both on the lunar surface and 
inside the moon by using respectively, remote sensing data from the 
Indian spacecraft Chandrayaan-1 and other lunar sample analysis. 
Carnegie researchers looked within crystalline rocks called KREEP (K 
for potassium; REE, for rare Earth elements; and P for phosphorus). 
These rocks are a component of some lunar impact melt and basaltic 
rocks. 

"Since water is insoluble in the main silicates that crystallized, we 
believed that it should have concentrated in those rocks," said 
Andrew Steele of Carnegie and co-author of the report. "That's why we 
selected KREEP to analyze." 

The identification of water from multiple types of lunar rocks that 
display a range of incompatible trace element signatures indicates 
that water may be at low concentrations but ubiquitous within the 
moon's interior, potentially as early as the time of lunar formation 
and magma ocean crystallization. 

"It is gratifying to see this proof of the hydroxyl contents in lunar 
apatite," said lunar scientist Bradley Jolliff of Washington 
University in St. Louis. "The concentrations are very low and, 
accordingly, they have been until recently nearly impossible to 
detect. We can now finally begin to consider the implications - and 
the origin - of water in the interior of the moon." 

The research was funded by the NASA Astrobiology, Mars Fundamental 
Research, and the Lunar Advanced Science and Exploration Research 
programs in NASA's Planetary Division in Washington. 

For more information on NASA science programs, visit: 

http://www.nasa.gov 
	
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