September Geology and GSA Today media ...(ength and became established about 9000 ...)

Date:8/22/2008

ength and became established about 9000 years ago. The record also suggests a second "global" cool phase 8200 years ago that began and ended abruptly. Although packrat midden archives have provided much information on climate in arid regions such as the Grand Canyon, depositional archives are exceedingly rare. Rapid climate changes are difficult to discern without a continuous record, and Wurster et al.'s study shows that guano deposits can provide a wealth of such information, with many like deposits occurring throughout tropical and subtropical regions.

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Koronis asteroid dust within Antarctic ice

Matthew Genge, Dept. of Earth Science and Engineering, Imperial College London, Exhibition Road, London SW7 2AZ, UK; m.genge@imperial.ac.uk. Pages 687-690.

Cosmic dust is everywhereon the streets, in our homes, even on our clothes. Each one of us is never more than a few feet from a dust particle from space. Despite their abundance, however, it is difficult to know exactly from where in space these particles come. Genge reports the discovery that a large proportion of cosmic dust particles found in Antarctic ice, known as micrometeorites, are from the Koronis asteroids of the main asteroid belt between Mars and Jupiter. The source of these dust particles was determined by observations of their mineralogy and chemistry (which closely match a type of meteorite known as ordinary chondrites) and from calculations that show that matching abundances of dust particles are delivered to Earth from Koronis. The Koronis asteroids are a family of rocky bodies formed approximately 2 billion years ago when a much larger asteroid broke into pieces. The most famous of these asteroids is 243 Ida, and its tiny moon Dactyl, which was imaged by the Galileo probe. Genge's work suggests that many micrometeorites are actually tiny pieces of about 20 smaller asteroids known as the Karin asteroid family, within
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Contact: Christa Stratton cstratton@geosociety.org 303-357-1093 Geological Society of America Source:Eurekalert

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