TY - JOUR

T1 - Early planetesimal melting from an age of 4.5662 Gyr for differentiated meteorites

AU - Baker, J.

AU - Bizzarro, Martin

AU - Wittig, N.

AU - Haack, H.

AU - Connelly, J.

PY - 2005/8/25

Y1 - 2005/8/25

N2 - Long- and short-lived radioactive isotopes and their daughter products in meteorites are chronometers that can test models for Solar System formation. Differentiated meteorites come from parent bodies that were once molten and separated into metal cores and silicate mantles. Mineral ages for these meteorites, however, are typically younger than age constraints for planetesimal differentiation. Such young ages indicate that the energy required to melt their parent bodies could not have come from the most likely heat source-radioactive decay of short-lived nuclides (Al and Fe) injected from a nearby supernova-because these would have largely decayed by the time of melting. Here we report an age of 4.5662 ± 0.0001 billion years (based on Pb-Pb dating) for basaltic angrites, which is only 1 Myr younger than the currently accepted minimum age of the Solar System and corresponds to a time when Al and Fe decay could have triggered planetesimal melting. Small Mg excesses in bulk angrite samples confirm that Al decay contributed to the melting of their parent body. These results indicate that the accretion of differentiated planetesimals pre-dated that of undifferentiated planetesimals, and reveals the minimum Solar System age to be 4.5695 ± 0.0002 billion years.

AB - Long- and short-lived radioactive isotopes and their daughter products in meteorites are chronometers that can test models for Solar System formation. Differentiated meteorites come from parent bodies that were once molten and separated into metal cores and silicate mantles. Mineral ages for these meteorites, however, are typically younger than age constraints for planetesimal differentiation. Such young ages indicate that the energy required to melt their parent bodies could not have come from the most likely heat source-radioactive decay of short-lived nuclides (Al and Fe) injected from a nearby supernova-because these would have largely decayed by the time of melting. Here we report an age of 4.5662 ± 0.0001 billion years (based on Pb-Pb dating) for basaltic angrites, which is only 1 Myr younger than the currently accepted minimum age of the Solar System and corresponds to a time when Al and Fe decay could have triggered planetesimal melting. Small Mg excesses in bulk angrite samples confirm that Al decay contributed to the melting of their parent body. These results indicate that the accretion of differentiated planetesimals pre-dated that of undifferentiated planetesimals, and reveals the minimum Solar System age to be 4.5695 ± 0.0002 billion years.

UR - http://www.scopus.com/inward/record.url?scp=24144474300&partnerID=8YFLogxK

U2 - 10.1038/nature03882

DO - 10.1038/nature03882

M3 - Journal article

AN - SCOPUS:24144474300

VL - 436

SP - 1127

EP - 1131

JO - Nature

JF - Nature

SN - 0028-0836

IS - 7054

ER -