[meteorite-list] Western-led 'International Beam Team' Solves Martian Meteorite Age Puzzle

[Ron Baalke]

http://communications.uwo.ca/media/agepuzzle/

Western-led 'international beam team' solves Martian meteorite age puzzle
Western University
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 than many 
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, comprised 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.

MEDIA CONTACT: Jeff Renaud, Senior Media Relations Officer, 519-661-2111, 
ext. 85165, jrenaud9 at uwo.ca, @jeffrenaud99   

[Photo]
Photo of the NWA 5298 meteorite