Meteorites have inherited nucleosynthetic anomalies of potassium-40 produced in supernovae

Abstract

Meteorites record processes that occurred before and during the formation of the Solar System in the form of nucleosynthetic anomalies: isotopic compositions that differ from the Solar System patterns. Nucleosynthetic anomalies are rarely seen in volatile elements such as potassium at bulk meteorite scale. We measured potassium isotope ratios in 32 meteorites and identified nucleosynthetic anomalies in the isotope potassium-40. The anomalies are larger and more variable in carbonaceous chondrite (CC) meteorites than in noncarbonaceous (NC) meteorites, indicating that CCs inherited more material produced in supernova nucleosynthesis. The potassium-40 anomaly of Earth is close to that of the NCs, implying that Earth’s potassium was mostly delivered by NCs.

Precise measurement of 40K isotopic anomalies in small samples using a TIMS with a 1013 ohm amplifier

“…The internal precision was reported as the two standard errors (2SE) of the 450 cycles in a single measurement, while the external precision was the 2SE of the 6–13 measurements relative to the average of the standard measurements. The typical internal and external precisions were 0.35 ε and 0.40 ε , respectively, comparable with a recent study 19 (0.40 ε ). The errors from the temperature correction of the gain factors are random errors which could contribute to the internal precision.…”

“…In addition, the smaller signal (signal of 39 K ∼0.35 nA) and the lower filament temperature (∼600 °C) relative to previous studies (3 nA, ∼800 °C (ref. 19, 32 and 33)) would reduce the tailing effect and decrease the ionization of Ca (typically ionized at 1400–1450 °C (ref. 45)), respectively.…”

“…14,15,18 Only recently have the nucleosynthetic anomalies of volatile elements been applied to directly indicate the volatile distribution and migration in the early Solar System. 19,20…”

“…3,4,26–28 Relative to K mass-dependent fractionation, K isotopic anomalies in extraterrestrial samples could provide information directly on the sources of volatiles. 19…”

“…14,15,18 Only recently have the nucleosynthetic anomalies of volatile elements been applied to directly indicate the volatile distribution and migration in the early Solar System. 19,20 As an important volatile element, K (50% Tc = 1006 K (ref. 21)) is widely used to study volatile depletion in terrestrial planets.…”