Scientists at Brown University found super-tiny melt inclusions in lunar soil samples that opened the door for measurements that revealed the magnitude of water inside the moon.
There is water inside the moon – so much, in fact, that in some places it rivals the amount of water found within the Earth.
finding from a scientific team including Brown University comes from
the first-ever measurements of water in lunar melt inclusions. Those
measurements show that some parts of the lunar mantle have as much water
as the Earth’s upper mantle.
melt inclusions are tiny globules of molten rock trapped within
crystals that are found in volcanic glass deposits formed during
explosive eruptions. The new finding, published this week in Science Express, shows lunar magma water contents 100 times higher than previous studies have suggested.
result is the culmination of years of investigation by the team
searching for water and other volatiles in volcanic glasses returned by
NASA Apollo missions in the late 1960s and early 1970s. In a paper in
Nature in 2008, the same team led by Alberto Saal, associate professor
of geological sciences at Brown, reported the first evidence for the
presence of water and used models to estimate how much water was
originally in the magmas before eruption.
bottom line,” said Saal, an author on the Science Express paper and the
principal investigator on the research grants, “is that in 2008, we
said the primitive water content in the lunar magmas should be similar
to the water content in lavas coming from the Earth’s depleted upper
mantle. Now, we have proven that is indeed the case.”
new finding got a critical assist from a Brown undergraduate student,
Thomas Weinreich, who found the melt inclusions that allowed the team to
measure the pre-eruption concentration of water in the magma and to
estimate the amount of water in the Moon’s interior. In a classic
needle-in-the-haystack effort, Weinreich searched through thousands of
grains from the famous high-titanium “orange soil” discovered by
astronaut Harrison Schmitt during the Apollo 17 mission before finding
ten that included melt inclusions.
“It just looks like a clear sample with some black specks in it,” said Weinreich, the second author on the paper.
with meteorites, Earth and the other inner planets of our solar system
contain relatively low amounts of water and volatile elements, which
were not abundant in the inner solar system during planet formation. The
even lower quantities of these volatile elements found on the Moon has
long been claimed as evidence that it must have formed following a
high-temperature, catastrophic giant impact. But this new research shows
that aspects of this theory must be reevaluated.
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. “We 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.”
Alberto Saal, associate professor of geological sciences (left) and Thomas Weinreich, undergraduate student, of Brown University.
The research team measured the water content in the inclusions using a state-of-the-art NanoSIMS 50L ion microprobe.
contrast to most volcanic deposits, the 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,” said James Van Orman of Case
Western Reserve University, a member of the science team.
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 it is possible some of
this ice could have come from the water released by eruption of lunar
Rutherford, professor emeritus in geological sciences at Brown, also
contributed to the paper. The NASA LASER and Cosmochemistry programs
funded the research, with additional support provided by the NASA Lunar
Science Institute (NLSI) and the NASA Astrobiology Institute.