Year: 2009
Type: article
Abstract: We measured the titanium (Ti) isotope composition, i.e., 50 Ti/ 47 Ti, 48 Ti/ 47 Ti, and 46 Ti/ 47 Ti, in five calcium-rich–aluminum-rich refractory inclusions (CAIs) from the oxidized CV3 chondrite Allende and in two CAIs from the reduced CV3 chondrite Efremovka. Our data indicate that CAIs are enriched in 50 Ti/ 47 Ti and 46 Ti/ 47 Ti and are slightly depleted in 48 Ti/ 47 Ti compared to normal Ti defined by ordinary chondrites, eucrites, ureilites, mesosiderites, Earth, Moon, and Mars. Some CAIs have an additional 50 Ti excess of ∼8ε relative to bulk carbonaceous chondrites, which are enriched in 50 Ti by ∼2ε relative to terrestrial values, leading to a total excess of ∼10ε. This additional 50 Ti excess is correlated with nucleosynthetic anomalies found in 62 Ni and 96 Zr, all indicating an origin from a neutron-rich stellar source. Bulk carbonaceous chondrites show a similar trend, however, the extent of the anomalies is either less than or similar to the smallest anomalies seen in CAIs. Mass balance calculations suggest that bulk Allende Ti possibly consists of a mixture of at least two Ti components, anomalous Ti located in CAIs and a normal component possibly for matrix and chondrules. This argues for a heterogeneous distribution of Ti isotopes in the solar system. The finding that anomalous Ti is concentrated in CAIs suggests that CAIs formed in a specific region of the solar system and were, after their formation, not homogeneously redistributed within the solar system. Combining the CAI data with improved model predictions for early solar system irradiation effects indicates that a local production scenario for the relatively short lived radionuclides can be excluded, because the production of, e.g., 10 Be, 26 Al, and 41 Ca, would result in a significant collateral shift in Ti isotopes, which is not seen in the measured data.
Source: The Astrophysical Journal
Institutions: University of Bern, University of Manchester, University of Oxford
Language: English
Topic: Astro and Planetary Science
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
Awards: G4020495542, G4651385716, G7883655584
OpenAlex ID: W1965583000