image: This is an electron micrograph of an interplanetary dust particle of likely cometary origin. view more
Credit: Hope Ishii
Researchers report that certain interplanetary dust particles (IDPs) represent dust remnants from the initial formation of the Solar System. The interstellar dust from which the Solar System was formed consisted primarily of amorphous silicate and organic carbon. However, the process of Solar System formation would have reworked most of this dust, altering the structure and composition of individual grains. To better understand the composition of presolar interstellar dust, Hope Ishii and colleagues analyzed the composition of comet-derived IDPs. Presolar dust is most likely to have survived in comets, which are small, cold, and formed from the outer protoplanetary disk. Comet-derived IDPs contain amorphous silicate grains known as GEMS (glass with embedded metal and sulfides), but the carbon content of these grains is unclear. Spectroscopic analyses revealed mantles of organic carbon surrounding both GEMS and silicate subgrains within GEMS. The organic carbon in these mantles decomposes at temperatures above 450K, suggesting that the GEMS could not have formed in the hot inner solar nebula, and instead formed in a cold, radiation-rich environment, such as the outer solar nebula or presolar molecular cloud. According to the authors, the results suggest that GEMS represent surviving presolar interstellar dust that formed the original building blocks of the Solar System.
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Article #17-20167: "Multiple generations of grain aggregation in different environments preceded solar system body formation," by Hope A. Ishii et al.
MEDIA CONTACT: Hope A. Ishii, University of Hawaii at Manoa, Honolulu, HI; tel: 808-956-7755, 650-224-2368; e-mail: <hope.ishii@hawaii.edu>
Journal
Proceedings of the National Academy of Sciences