Fossil records of early solar irradiation and cosmolocation of the CAI factory: A reappraisal

Abstract

Calcium-aluminum-rich inclusions (CAIs) in meteorites carry crucial information about the environmental conditions of the nascent Solar System prior to planet formation. Based on models of 50V-10 Be co-production by in-situ irradiation, CAIs are considered to have formed within ~0.1 AU from the proto-Sun. Here, we present vanadium (V) and strontium (Sr) isotopic co-variations in fine-and coarse-grained CAIs and demonstrate that kinetic isotope effects during partial condensation and evaporation best explain V isotope anomalies previously attributed to solar particle irradiation. We also report initial excesses of 10 Be and argue that CV CAIs possess essentially a homogeneous level of 10 Be, inherited during their formation. Based on numerical modeling of 50V-10 Be co-production by irradiation, we show that CAI formation during protoplanetary disk build-up likely occurred at greater heliocentric distances than previously considered, up to planet-forming regions (~1AU), where solar particle fluxes were sufficiently low to avoid substantial in-situ irradiation of CAIs.

Disk transport rates from Ti isotopic signatures of refractory inclusions

“…As indicated by their Ti isotopic and mineralogical signatures, the four WIS CAIs studied here are most consistently related to CAIs found in the more well‐studied carbonaceous chondrite groups (e.g., CM, CV, CR chondrites). This link is important because such regular CAIs are thought to have formed close to the Sun (<1 AU; Bekaert et al., 2021) in a geologically brief window of time (<200,000 years; Connelly et al., 2017; Kawasaki et al., 2019; MacPherson et al., 2012), and their presence in a meteorite that formed distally in the solar system at ~3.5 Myr (Sugiura & Fujiya, 2014) provides some of the first quantitative constraints on the time scales and distances of the transport of millimeter‐scale material in the early solar system. This is consistent with the more recent notion that CAIs were already present in the CC region prior to achondrite (Render et al., 2022) and iron meteorite (Zhang et al., 2022) formation (i.e., <1 Myr after solar system formation).…”

“…The first solids that formed within the solar system are widely thought to have been assemblages of refractory minerals, referred to as Ca-Al-rich inclusions, or CAIs. Due to their atypical mineralogical compositions, these objects must have formed in a high-temperature environment that is often assumed to have existed close (<1 AU) to the young Sun (Bekaert et al [2021] and references therein) and prior to bulk meteorite and planetesimal accretion (Connelly et al, 2017;MacPherson et al, 2012). In this period, the Sun was in a more active pre-main sequence phase that provided the necessary physicochemical conditions for CAI formation for <200,000 years (Cieza et al, 2007).…”

Chondrule-like objects and Ca-Al-rich inclusions in Ryugu may potentially be the oldest Solar System materials

“…Isolated olivine, pyroxene, and spinel grains that are likely to be fragments of chondrules and CAIs and AOA-like porous olivine in the Ryugu samples are also small (<30 µm) 28,40,41 . The Ryugu original parent body formed beyond the H 2 O and CO 2 snow lines in the solar nebula (>3-4 au from the Sun) 28 , while CAIs and AOAs formed near the Sun 6 or planet-forming regions (~1 au) 7 . Radial transport of CAIs and AOAs from the inner regions to the region where the Ryugu original parent body formed is required.…”

“…controlled by the oxygen fugacity of the chondrule-forming environment 4 , and type I chondrules formed under more reducing conditions than type II chondrules 5 . CAIs, composed of Ca-Al-rich minerals including spinel, melilite, perovskite, hibonite, diopside, and anorthite, are condensation products in a gas of approximately solar composition near the Sun 6 or planet-forming regions at ~1 au 7 and the oldest solids in our Solar System with the U-corrected Pb-Pb absolute age of 4567.3 Ma 8,9 . A subset of CAIs experienced melting processes 6 .…”

Review: Vanadium Isotope Geochemistry, Recent Advancements, And Developments In Vanadium Isotopic Analysis By MC-ICP-MS

“…73,74 Similarly, the Anton Paar high-pressure asher can also achieve high pressure (100-110 bar) and temperature (260-320°C) for dissolving insoluble metal oxides. 70,71,99 In addition, microwave digestion system enables samples to absorb microwave radiation and efficiently convert it into thermal energy, resulting in the rapid attainment of high temperature and pressure, facilitating fast digestion of samples including insoluble metal oxides. 17,100 Carbonates.…”