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Testing accretion mechanisms of the H chondrite parent body utilizing nucleosynthetic anomalies
Author(s) -
Pedersen Søren Grube,
Schiller Martin,
Connelly James N.,
Bizzarro Martin
Publication year - 2019
Publication title -
meteoritics and planetary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.09
H-Index - 100
eISSN - 1945-5100
pISSN - 1086-9379
DOI - 10.1111/maps.13269
Subject(s) - chondrite , meteorite , formation and evolution of the solar system , accretion (finance) , parent body , protoplanetary disk , ordinary chondrite , astrophysics , chondrule , geology , radiogenic nuclide , astrobiology , solar system , asteroid belt , geochemistry , planet , physics , mantle (geology)
Planetary bodies a few hundred kilometers in radii are the precursors to larger planets but it is unclear whether these bodies themselves formed very rapidly or accreted slowly over several millions of years. Ordinary H chondrite meteorites provide an opportunity to investigate the accretion time scale of a small planetary body given that variable degrees of thermal metamorphism present in H chondrites provide a proxy for their stratigraphic depth and, therefore, relative accretion times. We exploit this feature to search for nucleosynthetic isotope variability of 54 Cr, which is a sensitive tracer of spatial and temporal variations in the protoplanetary disk's solids, between 17 H chondrites covering all petrologic types to obtain clues about the parent body accretionary rate. We find no systematic variability in the mass‐biased corrected abundances of 53 Cr or 54 Cr outside of the analytical uncertainties, suggesting very rapid accretion of the H chondrite parent body consistent with turbulent accretion. By utilizing the μ 54 Cr–planetary mass relationship observed between inner solar system planetary bodies, we calculate that the H chondrite accretion occurred at 1.1 ± 0.4 or 1.8 ± 0.2 Myr after the formation of calcium‐aluminum‐rich inclusions ( CAI s), assuming either the initial 26 Al/ 27 Al abundance of inner solar system solids determined from angrite meteorites or CAI s from CV chondrites, respectively. Notably, these ages are in agreement with age estimates based on the parent bodies’ thermal evolution when correcting these calculations to the same initial 26 Al/ 27 Al abundance, reinforcing the idea of a secular evolution in the isotopic composition of inner disk solids.