Polycyclic aromatic hydrocarbons in samples of Ryugu formed in the interstellar medium.
basic_science · Level V
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- Record sourced from PubMed, PMID 38127762.
- Also identified by DOI 10.1126/science.adg6304.
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Abstract
Polycyclic aromatic hydrocarbons (PAHs) contain ≲20% of the carbon in the interstellar medium. They are potentially produced in circumstellar environments (at temperatures ≳1000 kelvin), by reactions within cold (~10 kelvin) interstellar clouds, or by processing of carbon-rich dust grains. We report isotopic properties of PAHs extracted from samples of the asteroid Ryugu and the meteorite Murchison. The doubly-<sup>13</sup>C substituted compositions (Δ2×<sup>13</sup>C values) of the PAHs naphthalene, fluoranthene, and pyrene are 9 to 51‰ higher than values expected for a stochastic distribution of isotopes. The Δ2×<sup>13</sup>C values are higher than expected if the PAHs formed in a circumstellar environment, but consistent with formation in the interstellar medium. By contrast, the PAHs phenanthrene and anthracene in Ryugu samples have Δ2×<sup>13</sup>C values consistent with formation by higher-temperature reactions.