Ooops, heading should read 2 million. On Aug 24, 2010, at 12:24 PM, Gary Fujihara wrote:
>> From ASU: http://asunews.asu.edu/20100823_bouvier > > Timescales of early Solar System processes rely on precise, accurate and > consistent ages obtained with radiometric dating. However, recent advances in > instrumentation now allow scientists to make more precise measurements, some > of which are revealing inconsistencies in the ages of samples. Seeking better > constraints on the age of the Solar System, Arizona State University > researchers Audrey Bouvier and Meenakshi Wadhwa analyzed meteorite Northwest > Africa (NWA) 2364 and found that the age of the Solar System predates > previous estimates by up to 1.9 million years. > > By using a dating technique known as lead-lead dating, Bouvier and Wadhwa > were able to calculate the age of a calcium-aluminum-rich inclusion (CAI) > contained within the Northwest Africa 2364 chondritic meteorite. These CAIs > are thought to be the first solids to condense from the cooling > protoplanetary disk during the birth of the Solar System. > > The study’s findings, published online on August 22 in Nature Geoscience, fix > the age of the Solar System at 4.5682 billion years old, between 0.3 and 1.9 > million years older than previous estimates. This relatively small revision > to the currently accepted age of about 4.56 billion years is significant > since some of the most important events that shaped the Solar System occurred > within the first ~10 million years of its formation. > > “This relatively small age adjustment means that there was as much as twice > the amount of iron-60, a certain short-lived isotope of iron, in the early > Solar System than previously determined. This higher initial abundance of > this isotope in the Solar System can only be explained by supernova > injection,” said Bouvier, a faculty research associate in the School of Earth > and Space Exploration (SESE) in ASU’s College of Liberal Arts and Sciences. > “This supernova event, and possibly others, could have triggered the > formation of the Solar System. By studying meteorites and their isotopic > characteristics, we bring new clues about the stellar environment of our Sun > at birth.” > > According to Meenakshi Wadhwa, professor in SESE and director of the Center > for Meteorite Studies, “This work also helps to resolve some long-standing > inconsistencies in early Solar System time scales as obtained by different > high-resolution chronometers. However, there is certainly room for future > studies. In particular, it will be important to conduct high precision > chronologic investigations of CAIs from other pristine meteorites. We also > need to understand the reasons for why the CAIs measured previously from two > other chondritic meteorites, Allende and Efremovka, have yielded younger > ages.” > > One significant aspect of this study is that it is the first published > lead-lead isotopic investigation that takes into account the possible > variation of the uranium isotope composition. Earlier work conducted in > Wadhwa’s laboratory by ASU graduate student Gregory Brennecka, in > collaboration with SESE professor Ariel Anbar, has shown that the uranium > isotope composition of CAIs, long assumed to be constant, can in fact be > highly variable and this has important implications for the calculation of > the precise lead-lead ages of these objects. > > Using the relationship demonstrated by Brennecka and colleagues between the > uranium isotope composition and other geochemical indicators in CAIs, Bouvier > and Wadhwa inferred a uranium isotope composition for the CAI for which they > reported the lead-lead age. Future work at ASU will focus on development of > analytical techniques for the direct measurement of the precise uranium > isotope composition of CAIs for which lead-lead isotopic investigations are > being conducted. > > “Our work can help researchers better understand the sequence of events that > took place within the first few million years of the Solar system formation, > such as the accretion and melting of planetary bodies,” Bouvier said. ”All > these processes happened extremely rapidly, and only by reaching such a > precision on isotopic measurements and chronology can we find out about these > processes of planetary formation.” > > Nikki Staab, [email protected] > 602-710-7169 > School of Earth and Space Exploration > > Gary Fujihara > Big Kahuna Meteorites (IMCA#1693) > 105 Puhili Place, Hilo, Hawai'i 96720 > http://bigkahuna-meteorites.com/ > http://shop.ebay.com/fujmon/m.html > (808) 640-9161 > > ______________________________________________ > Visit the Archives at > http://www.meteoritecentral.com/mailing-list-archives.html > Meteorite-list mailing list > [email protected] > http://six.pairlist.net/mailman/listinfo/meteorite-list Gary Fujihara Big Kahuna Meteorites (IMCA#1693) 105 Puhili Place, Hilo, Hawai'i 96720 http://bigkahuna-meteorites.com/ http://shop.ebay.com/fujmon/m.html (808) 640-9161 ______________________________________________ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list [email protected] http://six.pairlist.net/mailman/listinfo/meteorite-list
