[meteorite-list] NWA 2364 in "Scientific American"
From: Steve Dunklee <steve.dunklee_at_meteoritecentral.com>
Date: Mon, 23 Aug 2010 22:04:22 -0700 (PDT)
I agree that isotope data can give us an estimate to the age when the sun first ignited. But I have a problem with it being considered the age of our solar system. As the solar system condensed to form our sun the solar disc had to at some time reach densities almost as thick as our atmosphere. A cosmic soup teaming with the energy of friction and tempratures conducive to the formation of the chemicals necessary for the formation of life. This solar disc was probably teaming with cyanobacteria and other small organisms possibly found in c chondrites. Then the sun ignited sending out the solar wind which steralized most of it. And allowed life to continue on earth Mars and other places. If you read the piece on cyano bacteria fossils in c chondrites. The fossils were found in material disolved in strong acid. There are not any known surface contaminating bacteria that can survive being disolved in acid. So unless sombody can come up with a method for the
material to form without life. We just dont know!
On Mon Aug 23rd, 2010 7:05 PM EDT Don Giovanni wrote:
>A new analysis of a meteorite shows that an inclusion within the carbonaceous stone is older than any known material in the solar system. The finding pushes back the estimated age of the solar system to 4.568 billion years, older than previous estimates by up to 1.9 million years.
>A piece of the meteorite, known as Northwest Africa 2364, was purchased in 2004 in Morocco and is now part of a collection at Northern Arizona University in Flagstaff, Ariz. About 150 miles south of Flagstaff, two researchers at the Arizona State University Center for Meteorite Studies in Tempe, Audrey Bouvier andMeenakshi Wadhwa, dated an especially primitive piece of the meteorite known as a calcium-aluminum-rich inclusion, or CAI. Their findings appeared online August 22 in Nature Geoscience.
>Bouvier and Wadhwa measured the meteorite's ratio of two lead isotopes, whose relative proportions change on geologic timescales. Each variety of lead is a decay product of uranium, but the two parent uranium isotopes have very different half-lives: uranium 238 decays to lead 206 with a half-life of about 4.5 billion years, whereas uranium 235 decays to lead 207 with a half-life of about 700 million years. So the relative abundances of lead 206 and 207 can be used?along with some calibration for initial uranium abundances?to determine the age of ancient objects.
>The balance of lead isotopes in the Northwest Africa 2364 meteorite point to an age of 4,568,200,000 years, plus or minus a few hundred thousand years. Taking the measurement uncertainties into account, that is between 300,000 and 1.9 million years more ancient than the oldest CAIs found in other meteorites. The lead-derived age of Northwest Africa 2364, Bouvier and Wadhwa write, is "the oldest absolute age yet obtained for any Solar System material and is, therefore, the best estimate for the time of formation of the Solar System."
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Received on Tue 24 Aug 2010 01:04:22 AM PDT