Thursday, 25 July 2013

'International Beam Team' Solves Martian Meteorite-Age Puzzle

'International Beam Team' Solves
Martian Meteorite-Age Puzzle

July 24, 2013 — By directing energy
beams at tiny crystals found in a
Martian meteorite, a Western
University-led team of geologists has
proved that the most common group
of meteorites from Mars is almost 4
billion years younger thmany
scientists had believed -- resolving a
long-standing puzzle in Martian
science and painting a much clearer
picture of the Red Planet's evolution
that can now be compared to that of
habitable Earth.
In a paper published today in the
journal Nature , lead author Desmond
Moser, an Earth Sciences professor
from Western's Faculty of Science,
Kim Tait, Curator, Mineralogy, Royal
Ontario Museum, and a team of
Canadian, U.S., and British
collaborators show that a
representative meteorite from the
Royal Ontario Museum (ROM)'s
growing Martian meteorite collection,
started as a 200 million-year-old lava
flow on Mars, and contains an
ancient chemical signature indicating
a hidden layer deep beneath the
surface that is almost as old as the
solar system.
The team, composed of scientists
from ROM, the University of
Wyoming, UCLA, and the University
of Portsmouth, also discovered
crystals that grew while the meteorite
was launched from Mars towards
Earth, allowing them to narrow down
the timing to less than 20 million
years ago while also identifying
possible launch locations on the
flanks of the supervolcanoes at the
Martian equator.
More details can be found in their
paper titled, "Solving the Martian
meteorite age conundrum using
micro-baddeleyite and launch-
generated zircon."
Moser and his group at Western's
Zircon & Accessory Phase Laboratory
(ZAPLab), one of the few electron
nanobeam dating facilities in the
world, determined the growth history
of crystals on a polished surface of
the meteorite. The researchers
combined a long-established dating
method (measuring radioactive
uranium/lead isotopes) with a
recently developed gently-destructive,
mineral grain-scale technique at
UCLA that liberates atoms from the
crystal surface using a focused beam
of oxygen ions.
Moser estimates that there are
roughly 60 Mars rocks dislodged by
meteorite impacts that are now on
Earth and available for study, and
that his group's approach can be
used on these and a much wider
range of heavenly bodies.
"Basically, the inner solar system is
our oyster. We have hundreds of
meteorites that we can apply this
technique to, including asteroids
from beyond Mars to samples from
the Moon," says Moser, who credits
the generosity of the collectors that
identify this material and make it
available for public research.

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