Atomic-scale Evidence for Open-system Thermodynamics in the Early Solar Nebula

Abstract

We report a new integrated framework that combines atomic-length-scale characterization via aberration-corrected scanning transmission electron microscopy with first-principles-driven thermodynamic modeling and dust-transport models to probe the origins of some of the first-formed solids in the solar system. We find that within one of the first solids that formed in our solar system, spinel, nominally MgAl2O4, occurs as a twinned inclusion within perovskite, CaTiO3, and contains vanadium segregated to its twin boundary as atomic columns. Our results support a scenario in which spinel condensed at 1435 K in the midplane of the solar protoplanetary disk and was later transported inward to a hotter region where perovskite condensed around it at 1681 K. The spinel became twinned as a result of a displacive phase transition in the perovskite after which it was later transported to cooler regions of the disk and incorporated into its parent asteroid. The condensation, transport, and phase transformation can all be explained within the developed self-consistent framework that reproduces the observed phase assemblage and atomic-scale structure. This framework suggests that planetary materials evolved within a thermodynamically open system and, moving forward, motivates such an approach in order to understand the thermodynamic landscape on which planetary materials formed.

A petrologic and microstructural study of a compact type A calcium‐aluminum‐rich inclusion from the Northwest Africa 5028 CR2 chondrite: Implications for nebular and parent‐body processes

“…Similarities between the spinel inclusion within the perovskite in RS#1 and that studied by Zega et al. (2021) suggest that open‐system condensation is a plausible explanation for the origin of the assemblage we observe here in the rim of this CTA. Nonetheless, below we explore melt solidification as an alternative to condensation, for the formation of this assemblage.…”

“…For example, Zega et al. (2021) examined a twinned spinel inclusion inside of perovskite within an FTA CAI identified in the Allende CV3 chondrite. Combining density‐functional theory with thermodynamic and transport models, they proposed a scenario in which spinel condensed under equilibrium in one location in the solar protoplanetary disk and was subsequently transported inward to a higher temperature region where perovskite condensed around it.…”

“…While the exact dynamical history of CAIs remains unknown, they likely experienced varied thermodynamic environments during their histories in the solar protoplanetary disk, for example, Zega et al. (2021).…”

The Unrestrained Use of Python Libraries for Bridging the Gap Between Planetary and Material Sciences

“…A significant part of the mass constituting this solar nebula experienced high temperatures and evaporated [1]. The first stages of the gas cooling were marked by the condensation of the most refractory solid materials [2,3]. This time-temperature sequence gave rise to the calcium aluminum rich inclusions (CAIs) found in primitive meteorites.…”

“…This time-temperature sequence gave rise to the calcium aluminum rich inclusions (CAIs) found in primitive meteorites. Such CAIs mark time zero for our solar system [4,5] and analysis of their detailed crystal structures and chemistry can provide new insights into the conditions of formation of our solar system [2]. Here I show how the use of python libraries has facilitated the manipulation and the processing of data at the interface between physical sciences and computational thermodynamics.…”