A light carbon isotope composition for the Sun.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 29500355.
- Also identified by DOI 10.1038/s41467-018-03093-3 and PMC identifier 5834507.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Measurements by the Genesis mission have shown that solar wind oxygen is depleted in the rare isotopes, 17O and 18O, by approximately 80 and 100‰, respectively, relative to Earth's oceans, with inferred photospheric values of about -60‰ for both isotopes. Direct astronomical measurements of CO absorption lines in the solar photosphere have previously yielded a wide range of O isotope ratios. Here, we reanalyze the line strengths for high-temperature rovibrational transitions in photospheric CO from ATMOS FTS data, and obtain an 18O depletion of δ18O = -50 ± 11‰ (1σ). From the same analysis we find a carbon isotope ratio of δ13C = -48 ± 7‰ (1σ) for the photosphere. This implies that the primary reservoirs of carbon on the terrestrial planets are enriched in 13C relative to the bulk material from which the solar system formed, possibly as a result of CO self-shielding or inheritance from the parent cloud.