image: Scanning electron micrograph of a dated presolar silicon carbide grain. The grain is ~8 micrometers in its longest dimension. view more
Credit: Image courtesy of Janaína N. Ávila
Researchers report a method for obtaining ages of interstellar dust particles as well as insights into the presolar histories of such particles. Interstellar dust, a small but important fraction of matter in space, cannot be dated by astronomical observation or radioactive decay, leaving information on the ages and longevity of interstellar dust particles unknown. Philipp R. Heck and colleagues analyzed 40 grains of silicon carbide, incorporated into the Murchison CM2 meteorite 4.6 billion years ago, for neon isotopes produced by interactions with cosmic rays. Rates of formation of such cosmogenic isotopes can be used to date the particles. Sixty percent of the particles returned ages of less than 300 million years before the formation of the Solar System, compatible with estimates of interstellar lifetimes of 100-200 million years. However, particles with ages more than 1 billion years before the formation of the Solar System suggest that these grains were shielded in dense clumps that helped the particles survive supernova shockwaves in the interstellar medium. Some of the grains' histories may have included aggregates, including mantles of ices or organic compounds. According to the authors, cosmogenic neon dating used in the study is a viable method for obtaining galactic information prior to the formation of the Sun.
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Article #19-04573: "Lifetimes of interstellar dust from cosmic ray exposure ages of presolar silicon carbide," by Philipp R. Heck et al.
MEDIA CONTACTS: Kate Golembiewski, Field Museum of Natural History, Chicago, IL; tel: 312-665-7202; e-mail: <kgolembiewski@fieldmuseum.org>; Philipp R. Heck, Field Museum of Natural History, Chicago, IL; tel: 312-665-7655; e-mail: <prheck@fieldmuseum.org>
Journal
Proceedings of the National Academy of Sciences