Primitive Stellar Remnants and their Signatures as Probes to the Nascent Solar System

Citation

Marquez, Ren Thomas Caburnay (2024) Primitive Stellar Remnants and their Signatures as Probes to the Nascent Solar System. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/ge1c-kj54. https://resolver.caltech.edu/CaltechTHESIS:06042024-171635742

Abstract

The confluence of eons of alteration, accretion, and a multitude of other planet-building processes present a tremendous challenge in studying the early Solar System through planetary materials. Mainly, pristine records of conditions in the nascent nebula are rare, and often pose significant analytical obstacles. Fine-grained (fg-) calcium-aluminum-rich inclusions (CAIs) offer a unique opportunity to investigate the earliest stages of nebular evolution, as these are (1) the most primitive condensates in the Solar System, and (2) have never seen melting unlike their coarse-grained counterparts. The main difficulty in working with these inclusions is their diminutive size. Central to the work presented here is the development of techniques that enable the analysis of ever-smaller extraterrestrial samples, mainly leachates from fine-grained CAIs, thereby allowing access to information often rendered unintelligable by bulk analysis.

First, I present a new software suite that optimizes mass-dependent isotope measurements on extraterrestrial materials (Chapter 1). This package, dubbed as COSMO, complements existing computational tools for optimizing the double spike technique (i.e., the double spike toolbox) by accounting for analytical artefacts from mass-independent effects (e.g., nucleosynthetic isotope anomalies). Specifically, the software aids in determining the ideal way to split a limited amount of materials between spiked and unspiked measurements. Such a tool should aid in extracting the most amount of information from rare and critical analytes (e.g., unique meteorites and returned samples).

Next, I discuss the nucleosynthetic barium isotope signatures in the various components of fine-grained CAIs (Chapter 3). These samples were derived via step-leaching of fine-grained CAIs from the Allende meteorite, which have previously been demonstrated to exhibit extreme nucleosynthetic ⁸⁴Sr excesses. The barium isotope anomalies in these materials serve to potentially elucidate the stellar source(s) of these signatures, as Sr and Ba are documented to co-vary in known presolar materials and have similar geochemical behavior. However, our analyses revealed that these two elements are decoupled in these refractory leachates, pointing to nucleosynthetic sites that overproduce strontium such as electron-capture supernovae (ECSNe) and core-collapse (Type II) supernovae in massive rotating stars. In addition, the step-leaching procedure also reveals a strong congruence between L1-L3 isotopic variability and the anomalous signatures in presolar SiC grains.

Last, I demonstrate that the extreme strontium isotope anomalies in primitive condensates are hosted in oxides using a new protocol called intra-sample addition (ISA; Chapter 4). This experiment also reveals that ⁸⁴Sr anomalies are heterogeneously distributed in these oxides, which is explained by the nugget effect via the presence of rare but highly anomalous grains. Such grains are interpreted here to be true presolar carriers, which we propose to have served as nucleation seeds of the earliest condensates in the nebula. These results are at-odds with the prevalent notion of a hot and homogeneous nebular gas from which early condensates form, and thus suggest an alternative mechanistic link between disk heterogeneity and the stellar building blocks of the Solar System.

Thesis Files