Understanding dynamics and mixing in the solar nebula, the nature of presolar components present, and origin of rocky bodies including accretion and early differentiation, is fundamental to…

The University of Houston System received a $189,600.63 research grant awarded April 1, 2021, by a civilian federal agency (Shared Services Center) to conduct high-precision isotope measurements investigating the dynamics, mixing, and heterogeneity of the early solar nebula. The research focuses on nucleosynthetic components in presolar materials and chondrite meteorites, specifically examining osmium, molybdenum, ruthenium, and palladium isotopes to understand nebular heterogeneity and the origin of rocky bodies including accretion and early differentiation processes. The project employs newly refined multistatic analytical techniques to analyze isotopic compositions in bulk chondrites and ureilite achondrites, with completion targeted for December 31, 2024. This effort addresses fundamental questions about solar system formation and the distribution of presolar matter with distinct s-process and r-process isotope components across different meteorite groups.

The grant carries no set-aside designation and is classified as a research grant with "other" pricing type. Work is performed at the University of Houston's facility in Houston, Texas. The University of Houston System, a prominent Hispanic Serving Institution, brings substantial expertise in advanced research and development across multiple scientific domains to this project, leveraging its capabilities in materials science and analytical chemistry to address critical questions in planetary science and solar system evolution.

Understanding dynamics and mixing in the solar nebula, the nature of presolar components present, and origin of rocky bodies including accretion and early differentiation, is fundamental to constraining the origin of our solar system and its early evolution. Nucleosynthetic differences are present for CA, TI, CR, NI, SR, ZR, MO, RU, PR, PD, BA, ND, and SM isotopes, indicating nebular heterogeneity at the initial stages of condensation of rocky materials. Recent evidence indicates a dichotomy in nebular isotope components between different groups of chondrites. For example, 95MO versus 94MO in carbonaceous chondrites (CC) show a well-defined trend that is distinct from trends for ordinary (OC), enstatite (EC), and rumurutite (collectively called the NC trend) chondrites. This result has been interpreted that the CC and NC groups were formed in different regions of the solar system with heterogeneous distribution of presolar matter of s- and r-process isotope components. Osmium on the other hand has shown to be largely homogeneous for s- and r-process components in bulk chondrites. Most differences observed in OS isotopic compositions in bulk chondrites have been interpreted as incomplete digestion leaving behind residual s-process pre-solar grains with large isotope leverage for the distinct components. Some variations are observed in fully accessed bulk chondrites and not attributed to incomplete access of OS during digestion. In addition, nucleosynthetic heterogeneity in OS isotopes has been observed in equilibrated ureilite achondrites. This is attributed to melting in the parent body where the s- and r-process components were in distinct materials but could also have resulted from distinctions in the materials which accreted to form the ureilite parent body. In order to examine these issues and their implications to nebular dynamics, mixing, and heterogeneity, we will perform high-precision OS isotope measurements using a newly refined multistatic technique that significantly increases external precision to better delineate subtle differences in sand r-process components. For the first time, on the same fractions that OS is measured, we will measure MO, RU, and PD isotopes to put the nucleosynthetic components observed for OS into the context of the established variability for these elements, to examine potentially additional complexities in coupled variations, and to determine if multiple s- and r-process presolar carriers were extant at nebular condensation. This will be applied to bulk OC s where data are sparse but potentially indicate differences between h and LL group parent bodies and to bulk ureilites showing strong differences in OS isotope nucleosynthetic components. CAI s will be measured to constrain their nucleosynthetic makeup as an important reservoir of refractory elements in the first stages of nebular condensation. Leaching/residue-combustion experiments will be performed on unequilibrated CC, EC, and OC. This examines whether the s- and r-process components for OS, MO, RU, and PD are from the same stellar environments between the chondrite groups or whether multiple nucleosynthetic components were dispersed in the nebula heterogeneously. This will lead to a better understanding of the earliest history of the solar system from the seeding of nucleosynthetic components, nebular condensation, accretion into terrestrial bodies and their early differentiation. This research is consistent with the scope of the emerging worlds program. Our new data will provide transformational insights into how the solar system formed and evolved from protoplanetary disk formation and evolution, chemical and physical processing of nebular dust, bulk properties of solar system bodies, formation, accretion, early thermal and chemical processing, and global differentiation of solar system bodies. Such data will also help in planning for missions that will target specific bodies in our solar system.