On the origin of 7Be isotopic records in a Calcium, Aluminium, -rich inclusion

TL;DR

This study investigates the origin of 7Be isotopic records in a Calcium-Aluminium-rich inclusion, suggesting in situ decay from irradiation processes during early Solar System formation, with implications for understanding short-lived nuclide production.

Contribution

It provides evidence for in situ decay of 7Be in CAIs, constraining the irradiation conditions and timing in the early Solar System's evolution.

Findings

Detected excess 7Li/6Li ratios correlated with 9Be/6Li in CAIs.

In situ decay of 7Be indicates multiple irradiation episodes in early Solar System.

Constraints on irradiation sources and timing of CAI formation.

Abstract

A prime question in the formation and early evolution of the Solar system studies is to discern the source(s) of short-lived now extinct nuclides and to determine the ab-initio isotopic composition of our Solar System (ref. 1). The proposed genesis of a short-lived now extinct radionuclide,10Be, by spallation reactions of carbon and oxygen led to the hypothesis of enhanced irradiation in the early Solar system (ref. 2-8). An alternative scenario of production of 10Be (t1/2 =1.386 +- 0.016 million years (ref.9)) by neutrino process in a low mass star (11.8Msun) core collapse supernova has been recently suggested (ref. 10) that can explain the observed abundance of 10Be in the early Solar System. Here, we report well resolved excesses in 7Li/6Li of up to ~21.5 percent in a Type B1 Ca,-Al rich inclusion (CAI) from the Efremovka meteorite that correlate with 9Be/6Li, suggestive of in situ decay of 7Be. The in situ decay of 7Be, with characteristic half-life of 53.12+- 0.07 days (ref. 11) to 7Li, entails multiple episodes of enhanced irradiation in the ESS. The short half-life of 7Be limits its production by interaction of Solar energetic particles with the nebular gas and solids and provides constraints on genealogy and chronology of CAIs. Irradiation of precursor solids/gas of CAIs of Solar composition by a superflare (Lx=10 exp(32) erg/sec) during the terminal phase of class I or II of pre-main sequence stages of the Sun cogently explains the isotopic properties, distinctive petrographic features, and diffusivity constraints in the CAI.