Recent measurements of silicate and oxide stardust grains have revealed large Mg-isotope anomalies in silicate stardust belonging to group 1, which has challenged the low-mass origins of these grains, among others. In this work, stardust searches were performed in a thin section of the CO3.0 carbonaceous chondrite meteorite Allan Hills (ALHA) 77307 with the NanoSIMS 50L. Several group 1 silicate and oxide grains were subsequently measured for their silicon and magnesium isotopes. Although several group 1 silicate grains were found to fall on the Galactic Chemical Evolution line for both Si and Mg isotopes, a significant fraction do not. These grains are therefore incompatible with their proposed low-mass Red Giant or Asymptotic Giant Branch stellar origins. These observations corroborate recent work and suggest that group 1 grains may have multiple stellar sources which might include pre-supernovae massive stars and supernovae. The silicate stardust abundance calculated from this study is 168 ppm, while the oxide abundance is 18 ppm in ALHA 77307, which is in good agreement with published literature. Additionally, three large silicate stardust grains were found which range in size from 0.8 x 0.6 µm2 to 1.6 x 0.6 µm2 and exhibit unusual “bi-lobed” or “ameboid” shapes. Several C-anomalous presolar grains were also identified in ALHA 77307, many of which were subsequently measured for their N and Si isotopes. These grains are important because in-situ measurements of N and Si isotopes in SiC stardust are rare and N in chemically isolated SiC grains is likely affected by the sample preparation procedure and/or contamination. A majority of SiC grains from this study belong to the “mainstream” group proposed to form in the circumstellar envelopes of low-intermediate mass AGB stars, while two rare SiC AB grains were found with possible origins in J-type carbon stars and/or supernovae. The calculated SiC abundance in ALHA 77307 ranged from 57-148 ppm, the upper limit of which would be the highest presolar SiC abundance so far reported for this meteorite.

Meteorites provide an opportunity to reconstruct the history of the SolarSystem. Differentiated meteorites, also called achondrites, are the result of melting and differentiation processes on their parent body. Stable isotopic compositions of differentiated meteorites and their components have added to the understanding of physical parameters, such as temperature, pressure, and redox conditions relevant to differentiation processes on planetesimals and planets in the early Solar System. In particular, Fe and Si isotopes have proven to be useful in advancing the understanding of physical and chemical processes during planetary accretion and subsequent evolution. In this work, I developed a new method to simultaneously purify Fe and Si from a single aliquot of sample while ensuring consistently high yields and accurate and precise isotopic measurements. I then measured the Fe isotope compositions and Si contents of metals from aubrite meteorites to infer the structure and thermal evolution of their asteroidal parent body. Thereafter, I determined the combined Si and Fe isotope compositions of aubrite metals and the Horse Creek iron meteorite, and compared the magnitude of Si and Fe isotope fractionation factors between metal and silicates for both enstatite chondrites and aubrites to estimate the effect of high-temperature core formation that occurred on the aubrite parent body. I additionally assessed whether correlated Si and Fe isotope systematics can be used to trace core formation and partial melting processes for the aubrite parent body, angrite parent body, Mars, Vesta, Moon, and Earth. Finally, I measured the combined Fe and Si isotope composition of a variety of ungrouped achondrites and brachinites that record different degrees of differentiation under different redox conditions to evaluate the role of differentiation and oxygen fugacity in controlling their Fe and Si isotope compositions. Taken together, this comprehensive dataset reveals the thermal evolution of the aubrite parent body, provides insights into the factors controlling the Fe and Si isotope compositions of various planetary materials, and helps constrain the bulk starting composition of planets and planetesimals.

Short-lived radionuclides (SLRs) once present in the solar nebula can be used to probe the Solar System’s galactic formation environment. Isotopic analyses reveal that the first solids formed in the Solar System, calcium- and aluminum-rich inclusions (CAIs) in chondritic meteorites, formed with the live SLRs 10Be (t1/2 = 1.4 Ma) and 26Al (t1/2 = 0.7 Ma). Beryllium-10 is produced when high-energy ions, solar energetic particles or galactic cosmic rays (GCRs), spall nuclei in gas or dust. The most likely source of Solar System 10Be is inheritance of GCR-irradiated protosolar molecular cloud material, but only if all CAIs recorded the same initial 10Be abundance. The goal of this dissertation is to assess the homogeneity of 10Be by measuring CAIs for 10Be–10B isotope systematics, correlated to 26Al–26Mg and oxygen isotopes.

I synthesized appropriate standards for secondary ion mass spectrometry (SIMS) measurements of 10Be–10B, necessary for accurate determination of the 10Be/9Be ratio. I then analyzed 32 CAIs for 10Be–10B as well as 6 CAIs for 26Al–26Mg and 5 CAIs for oxygen isotopes within this sample set using SIMS. Previous studies analyzed CAIs primarily from CV3 chondrites, which are known to have experienced thermal metamorphism and aqueous alteration. My work included a variety of CAIs (Type A, B, fine-grained, igneous) from CV3oxidized, CV3reduced, CO3, CR2, and CH/CB chondrites. Finally, after evaluating my data and literature data consistently, I statistically tested whether all CAIs belong to a single 10Be population. I find that the majority (~85%) of the normal (i.e., without large isotopic fractionations or anomalies), 26Al-bearing CAIs recorded a single value, 10Be/9Be = (7.0 ± 0.2) × 10-4. Although 6 CAIs recorded higher or lower values, these are plausibly explained by secondary alteration processes. The galaxy-wide average value of 10Be/9Be from GCR interactions 4.56 billion years ago is predicted to be <2 × 10-4; the value I measured is more than 3 times higher. Because GCRs trace supernovae and star formation, my results suggest a similarly enhanced star formation rate in the molecular cloud within ~1 kpc of the Sun, in the ~15 Ma prior to the Sun’s birth.