A light carbon isotope composition for the Sun

作者：Lyons James R; Gharib Nezhad Ehsan; Ayres Thomas R

来源：Nature Communications, 2018, 9(1): 908.

DOI：10.1038/s41467-018-03093-3

<jats:title>Abstract</jats:title><jats:p>Measurements by the Genesis mission have shown that solar wind oxygen is depleted in the rare isotopes, <jats:sup>17</jats:sup>O and <jats:sup>18</jats:sup>O, 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 <jats:sup>18</jats:sup>O depletion of <jats:italic>δ</jats:italic><jats:sup>18</jats:sup>O = −50 ± 11‰ (1<jats:italic>σ</jats:italic>). From the same analysis we find a carbon isotope ratio of <jats:italic>δ</jats:italic><jats:sup>13</jats:sup>C = −48 ± 7‰ (1<jats:italic>σ</jats:italic>) for the photosphere. This implies that the primary reservoirs of carbon on the terrestrial planets are enriched in <jats:sup>13</jats:sup>C 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.</jats:p>

• 出版日期2018-3-2