Evidence from achondrites for a temporal change in Nd nucleosynthetic anomalies within the first 1.5 million years of the inner solar system formation

Half-life and initial Solar System abundance of 146 Sm determined from the oldest andesitic meteorite

“…However, the initial abundance and half-life of the extinct radioactive isotope 146 Sm are still debated, weakening the interpretation of 146 Sm-142 Nd systematics obtained for early planetary processes. Here, we apply the short-lived 26 Al-26 Mg, 146 Sm-142 Nd, and long-lived 147 Sm-143 Sm chronometers to the oldest known andesitic meteorite, Erg Chech 002 (EC 002), to constrain the Solar System initial abundance of 146 Sm. The 26 Al-26 Mg mineral isochron of EC 002 provides a tightly constrained initial δ 26 Mg* of 20.009 ± 0.005 ‰ and ( 26 Al/ 27 Al) 0 of (8.89 ± 0.09) × 10 26 .…”

“…In particular, the different mineral fractions analyzed in Allende Al3S4 CAI exhibit large and variable 148 Nd and 150 Nd anomalies (17), questioning the accuracy of the measured 142 Nd/ 144 Nd ratios and the validity of the deduced initial 146 Sm/ 144 Sm. Erg Chech 002 (EC 002) is a unique silica-rich achondrite recognized as the oldest primordial crust sample discovered to date, with an estimated crystallization age of 2.255 ± 0.013 Myr after CAI formation obtained using in situ secondary ion mass spectrometry (SIMS) 26 Al- 26 Mg measurements (23). The abundance of coarse crystals of pyroxene and plagioclase in EC 002 makes it possible to separate minerals with fractionated Sm/Nd ratios.…”

“…In this study, we report the Sm and Nd isotopic compositions of mineral fractions, leachates, and bulk samples of EC 002, as well as a high-precision internal 26 Al- 26 Mg isochron obtained on the same mineral fractions. A robust crystallization age for EC 002 is constrained by 26…”

Effects of pebble accretion on the growth and composition of planetesimals in the inner Solar System

“…Given the Earth's end-member composition, it has been suggested that a major component of the Earth (∼ 40%) could originate from the most refractory part of the inner Solar System that we do not have samples from (Morbidelli et al 2020;Frossard et al 2021) and later mixed with less thermally-processed planetesimals such as the known achondrite and chondrite parent bodies (Fig. 8).…”

Evidence of a primordial isotopic gradient in the inner region of the solar protoplanetary disc

“…Furthermore, thermal processing could also modify the composition of infalling material from the molecular cloud (Ek et al 2020). This process has also been suggested to explain the temporal change observed in the composition of some elements such as Nd which may be caused by the loss of SiC dust carriers between the time of formation of achondrite and later chondrite parent bodies within the inner solar system (Frossard et al 2021). This does not exclude an existing spatial heterogeneity of massindependent variations which are evident for other elements between achondrite groups whose parent bodies formed within 1.5 million years after the formation of the calcium-aluminium-rich inclusions (CAIs) (e.g.…”