Researchers using refined techniques to study minerals from meteorites now believe it took about 20 million years for the Earth to coalesce from the materials already gathered around our sun as the solar system. Recent estimates had pegged the interval closer to 50 million years.

Brigitte Zanda-Hewins, an adjunct member of the graduate faculty at Rutgers department of geological sciences and associate professor at the mineralogy laboratory of the Muséum National d'Histoire Naturelle in Paris, is among a group of researchers publishing its findings in the international journal Science, on Mar. 1.

The group studied radioactive forms of the elements niobium and zirconium found in samples of meteorites. Because meteorites are the oldest objects of our solar system available for study, scientists use their components as a kind of "radioactive chronometer" to help estimate time intervals separating events during the formation of the solar system, including the formation of the Earth.

While recent attempts to use the niobium-zirconium "chronometer" had produced the 50-million-year estimate, Zanda-Hewins said the new 20-million-year figure is the result of performing mineral separations in the samples for the first time, and using extreme precautions to maintain the purity of the samples. Researchers used special processing equipment, anti-contamination air flow and filters, magnetic separation devices and a wide range of chemical separation techniques to avoid any interference by foreign materials.

"We designed an extremely careful approach to separate the minerals and isolate the right ones," she said. The method is described in the article entitled "Niobium-Zirconium Chronometry and Early Solar System Development."

Zanda-Hewins' co-authors are Maria Schönbächler, Mark Rehkämper, Alex N. Halliday and Der-Chuen Lee of ETH Zurich Institute of Isotope Geology and Mineral Resources; Bodo Hattendorf and Detlef Günther of ETH Zurich Laboratory of Inorganic Chemistry; and Michèle Bourot-Denise of the Muséum National d'Histoire Naturelle in Paris.

Besides her work at Rutgers, Zanda-Hewins is well-known as a Paris-based geologist who helps coordinate distribution of meteorite samples for scientific study around the world. She is the author of the 2001 book "Meteorites: Their Impact on Science and History."

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EDITOR'S NOTE: Brigitte Zanda-Hewins may be contacted by phone at 732-445-3232.
Her e-mail address is zandahew@rci.rutgers.edu

Contact: Bill Haduch, 732-932-7084, extension 633
E-mail: bhaduch@ur.rutgers.edu
http://ur.rutgers.edu/medrel

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