[meteorite-list] ASU recalculates age of solar system/ InterestingAllende CAI details

From: Jeff Kuyken <info_at_meteoritecentral.com>
Date: Sat, 2 Jan 2010 12:29:35 +1100
Message-ID: <577E292531454A73AD4C4E697A3DA25E_at_JeffPC>

Hi all,

>"meaning that the age of the Solar System could be miscalculated by as much
>as several million years."

That doesn't sound like much but as soon as I saw that statement it stood
out... BIG TIME! There has always been speculation with certain meteorites
forming soon after the beginnings of our solar system with the Angrites
being an enigmatic and important one. In fact a recent 2009 paper by T.
Kleine, B. Bourdon, and A. J. Irving concluded that:

"Core formation in the angrite parent body probably occurred within the
first ~2 Myr after CAI formation. This timescale is consistent with a Rb-Sr
model age for separation of the angrite parent body from a hot solar nebula
and with Hf-W model ages for magmatic iron meteorites. Collectively, these
chronological constraints demonstrate that accretion of differentiated
planetesimals predated chondrule formation and accretion of chondrite parent
bodies and that 26Al decay was the dominant heat source for the early
differentiation of meteorite parent bodies. Furthermore, the timescale of
magmatism on the angrite parent body of ~4 to ~10 Myr after CAI formation is
consistent with predictions from thermal models of asteroids that accreted
within the first ~2 Myr after CAI formation."

Cheers,

Jeff


----- Original Message -----
From: "power ofunity" <energylightandlove at yahoo.com>
To: <meteorite-list at meteoritecentral.com>
Sent: Saturday, January 02, 2010 5:55 AM
Subject: [meteorite-list] ASU recalculates age of solar system/
InterestingAllende CAI details


Interesting read from ASU - with supporting details and fascinating info
regarding Allende's CAIs

http://asunews.asu.edu/20091231_brennecka


http://www.sciencemag.org/cgi/content/abstract/science.1180871


Published Online December 31, 2009
Science DOI: 10.1126/science.1180871
Reports
238U/235U Variations in Meteorites: Extant 247Cm and Implications for Pb-Pb
DatingG. A. Brennecka,1, S. Weyer,2, M. Wadhwa,1 P. E. Janney,1 J. Zipfel,3
A. D. Anbar1,4
The 238U/235U isotope ratio has long been considered invariantin meteoritic
materials (i.e., 137.88). This assumption is acornerstone of the
high-precision Pb-Pb dates that define theabsolute age of the Solar System.
Calcium-aluminum-rich inclusionsof the Allende meteorite display variable
238U/235U ratios,ranging between 137.409?0.039 and 137.885?0.009.This range
implies substantial uncertainties in the ages previouslydetermined by Pb-Pb
dating of CAIs, which may be overestimatedby several million years. The
correlation of U isotope ratioswith proxies for Cm/U (i.e., Th/U and Nd/U)
provides strongevidence that the observed variations of 238U/235U in CAIs
wereproduced by the decay of extant 247Cm to 235U in the early SolarSystem,
with an initial 247Cm/235U of ~ 1.1 to 2.4 x 10-4.
1 School of Earth and Space Exploration, Arizona State University, Tempe, AZ
85287, USA.
2 Institut fur Geowissenschaften, Goethe-Universit?t, Frankfurt, Germany.
3 Senckenberg Forschungsinstitut und Naturmuseum, Frankfurt, Germany.
4 Department of Chemistry and Biochemistry, Arizona State University, Tempe,
AZ 85287, USA.
 Current address: Institut f?r Geology und Mineralogie,Universit?t zu K?ln,
Cologne, Germany.
 To whom correspondence should be addressed. E-mail: brennecka at asu.edu
________________________________
Received for publication 20 August 2009. Accepted for publication 11
December 2009.



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Received on Fri 01 Jan 2010 08:29:35 PM PST