A unified chronology of dust formation in the early solar system

1Maxime Piralla,1Johan Villeneuve,1Nicolas Schnuriger,1David V.Bekaert,1Yves Marrocchi
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115427]
1Université de Lorraine, CNRS, CRPG, UMR 7358, Nancy, France
Copyright Elsevier

The chronology of dust formation in the early solar system remains controversial. Chondrules are the most abundant high-temperature objects formed during the evolution of the circumsolar disk. Considering chondrule formation, absolute lead‑lead (Pbsingle bondPb) ages and aluminum‑magnesium (26Alsingle bond26Mg) ages relative to calcium‑aluminum-rich inclusions (CAIs) provide inconsistent chronologies, with Pbsingle bondPb ages showing early and protracted chondrule formation episodes whereas 26Alsingle bond26Mg ages suggest that chondrule production was delayed by >1.5 Ma. Here, we develop a new method to precisely determine in situ 26Alsingle bond26Mg ages of spinel-bearing chondrules without being affected by secondary asteroidal processes. Our data demonstrate that 26Alsingle bond26Mg chondrule formation ages are actually 1 Ma older than previously thought and extend over the entire lifetime of the disk. This shift in chondrule formation ages relative to CAIs, however, is not sufficient to reconcile the Pbsingle bondPb and 26Alsingle bond26Mg chronologies. Thus, either chondrules Pbsingle bondPb ages and volcanic achondrites 26Alsingle bond26Mg ages are incorrect or the age of the solar system age should be reevaluated at 4568.7 Ma to ensure consistency between chronometers. We favor the second hypothesis, given that (i) the canonical age of CAIs was determined using only 4 specimens and (ii) older ages of 4568.2 Ma have also been measured. We show that the adoption of 4568.7 Ma as the new canonical age of CAIs and the use of our new spinel-derived 26Alsingle bond26Mg ages enable reconciling the Pbsingle bondPb and 26Alsingle bond26Mg ages of chondrules and achondrites. This new chronology implies the existence of a 0.7–1 Ma gap between the formation of refractory inclusions and chondrules, and supports the homogeneous distribution of 26Al in the circumsolar disk.

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