Mixing and transport of dust in the early solar nebula as inferred from titanium isotope variations among chondrules

TL;DR

This study uses titanium isotope variations in chondrules to infer dust mixing and transport processes in the early solar nebula, revealing localized formation regions and limited large-scale chondrule transport.

Contribution

It demonstrates that titanium isotopic variations in chondrules can be explained by local incorporation of CAI-like material, challenging the need for extensive nebular transport.

Findings

Carbonaceous chondrite chondrules show highly variable 50Ti compositions.

Enstatite and ordinary chondrite chondrules have small 50Ti variations.

Isotopic differences support localized formation regions in the protoplanetary disk.

Abstract

Chondrules formed by the melting of dust aggregates in the solar protoplanetary disk and as such provide unique insights into how solid material was transported and mixed within the disk. Here we show that chondrules from enstatite and ordinary chondrites show only small 50Ti variations and scatter closely around the 50Ti composition of their host chondrites. By contrast, chondrules from carbonaceous chondrites have highly variable 50Ti compositions, which, relative to the terrestrial standard, range from the small 50Ti deficits measured for enstatite and ordinary chondrite chondrules to the large 50Ti excesses known from Ca-Al-rich inclusions (CAIs). These 50Ti variations can be attributed to the addition of isotopically heterogeneous CAI-like material to enstatite and ordinary chondrite-like chondrule precursors. The new Ti isotopic data demonstrate that isotopic variations among carbonaceous chondrite chondrules do not require formation over a wide range of orbital distances, but can instead be fully accounted for by the incorporation of isotopically anomalous nuggets into chondrule precursors. As such, these data obviate the need for disk-wide transport of chondrules prior to chondrite parent body accretion and are consistent with formation of chondrules from a given chondrite group in localized regions of the disk. Lastly, the ubiquitous presence of 50Ti-enriched material in carbonaceous chondrites, and the lack of this material in the non-carbonaceous chondrites support the idea that these two meteorite groups derive from areas of the disk that remained isolated from each other through the formation of Jupiter.