- MOUNTAIN VIEW, Calif. (Reuters) - New information from the Lunar Prospector
spacecraft supports the theory that the Moon was ripped from the Earth
after a massive interplanetary collision, <http://www.nasa.gov NASA
scientists said Tuesday.
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- "This is a critical finding in helping
scientists determine how the Earth and the Moon formed," Dr. Alan
Binder, principal investigator of the Lunar Prospector mission, said in
a news release.
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- The new Lunar Prospector findings, presented
in a series of papers at a scientific meeting in Houston, show that the
lunar core contains less than four percent of the Moon's total mass, a
very small ratio compared with the Earth, which has about 30 percent
of its mass in its iron core.
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- While similarities in mineral composition
suggest that the Moon and the Earth share a common origin, the difference
in their core mass ratio could indicate that the Moon was actually originally
part of the larger planet that was ripped away following a huge collision.
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- "This impact occurred after the
Earth's iron core had formed, ejecting rocky, iron-poor material from
the outer shell into orbit," Binder said, explaining the theory.
"It was this material that collected to form the Moon."
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- The collision theory, which posits that
the Earth was struck by something roughly the size of Mars very early
in its history, has been floated since the 1960s, when scientists first
began collecting information about Earth's nearest neighbor.
-
- The new Lunar Prospector data comes from
gravity measurements which indicate that the Moon's core radius is between
140 and 280 miles.
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- Binder said the $63 million mission,
which is being directed by NASA's Ames Research Center in California,
could provide the data necessary to reach a firmer conclusion as the
small Prospector spacecraft continues to sweep the Moon in a very tight
orbit, mapping and gathering information.
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- "Further analysis of Lunar Prospector
data to refine the exact size of the lunar core and the amounts of elements
like gold, platinum and iridium in lunar rocks - all of which are concentrated
with metallic iron - is required," Binder said.
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- "This will do much to pin down for
good if the 'giant impact' model of the formation of the Moon is correct,
or if the Moon formed in a different manner."
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