Researchers at the Univ.
of Tennessee, Knoxville, continue to chip away at the
mysterious existence of water on the moon—this time by discovering the origin
of lunar water.
Larry Taylor, a distinguished professor in the
Department of Earth and Planetary Sciences, was the one last year to discover
trace amounts of water on the moon. This discovery debunked beliefs held since
the return of the first Apollo rocks that the moon was bone-dry.
Then, he discovered water was actually pretty
abundant and ubiquitous—enough so a human settlement on the moon is not
unquestionable.
Now, Taylor and a team of researchers have
determined the lunar water may have originated from comets smashing into the
moon soon after it formed.
His findings will be posted online, in the article
“Extraterrestrial Hydrogen Isotope Composition of Water in Lunar
Rocks” on the website of Nature Geoscience.
Taylor and his fellow researchers conducted their
study by analyzing rocks brought back from the Apollo mission. Using secondary
ion mass spectrometry, they measured the samples’ “water signatures”,
which tell the possible origin of the water—and made the surprising discovery
that the water on the Earth and moon are different.
“This discovery forces us to go back to
square one on the whole formation of the Earth and moon,” said Taylor. “Before our
research, we thought the Earth and moon had the same volatiles after the Giant
Impact, just at greatly different quantities. Our work brings to light another
component in the formation that we had not anticipated—comets.”
Scientists believe the moon formed by a giant
impact of the nascent Earth with a Mars-sized object called Theia, which caused
a great explosion throwing materials outward to aggregate and create the moon. Taylor’s article
theorizes that at this time, there was a great flux of comets, or “dirty
icebergs,” hitting both the Earth and moon systems. The Earth already
having lots of water and other volatiles did not change much. However, the
moon, being bone-dry, acquired much of its water supply from these comets.
Taylor’s research shows that water has been present throughout
all of the moon’s history—some water being supplied externally by solar winds
and post-formation comets and the other internally during the moon’s original
formation.
“The water we are looking at is
internal,” said Taylor.
“It was put into the moon during its initial formation, where it existed
like a melting pot in space, where cometary materials were added in at small
yet significant amounts.”
To be precise, the lunar water he has found does
not consist of “water”—the molecule H2O—as we know it on
Earth. Rather, it contains the ingredients for water—hydrogen and oxygen—that
when the rocks are heated up, will be liberated to create water. The existence
of hydrogen and oxygen—water—on the moon can literally serve as a launch pad
for further space exploration.
“This water could allow the moon to be a gas station in the sky,”
said Taylor.
“Spaceships use up to 85 percent of their fuel getting away from Earth’s
gravity. This means the moon can act as a stepping stone to other planets.
Missions can fuel up at the moon, with liquid hydrogen and liquid oxygen from
the water, as they head into deeper space, to other places such as Mars.”
