Abstract
The solar system formed from interstellar dust and gas in a molecular cloud. Astronomical observations show that typical interstellar dust consists of amorphous (a-) silicate and organic carbon. Bona fide physical samples for laboratory studies would yield unprecedented insight about solar system formation, but they were largely destroyed. The most likely repositories of surviving presolar dust are the least altered extraterrestrial materials, interplanetary dust particles (IDPs) with probable cometary origins. Cometary IDPs contain abundant submicrona-silicate grains called GEMS (glass with embedded metal and sulfides), believed to be carbon-free. Some have detectable isotopically anomalousa-silicate components from other stars, proving they are preserved dust inherited from the interstellar medium. However, it is debated whether the majority of GEMS predate the solar system or formed in the solar nebula by condensation of high-temperature (>1,300 K) gas. Here, we map IDP compositions with single nanometer-scale resolution and find that GEMS contain organic carbon. Mapping reveals two generations of grain aggregation, the key process in growth from dust grains to planetesimals, mediated by carbon. GEMS grains, some witha-silicate subgrains mantled by organic carbon, comprise the earliest generation of aggregates. These aggregates (and other grains) are encapsulated in lower-density organic carbon matrix, indicating a second generation of aggregation. Since this organic carbon thermally decomposes above ∼450 K, GEMS cannot have accreted in the hot solar nebula, and formed, instead, in the cold presolar molecular cloud and/or outer protoplanetary disk. We suggest that GEMS are consistent with surviving interstellar dust, condensed in situ, and cycled through multiple molecular clouds.
Funder
National Aeronautics and Space Administration
Publisher
Proceedings of the National Academy of Sciences
Reference49 articles.
1. The stardust abundance in the local interstellar cloud at the birth of the solar system;Hoppe;Nature Astron,2017
2. Evolution of interstellar dust and dust in the solar neighborhood;Zhukovska;Astron Astrophys,2008
3. Jones AP Köhler M Ysard N Bocchio M Verstraete L (2017) The global dust modeling framework THEMIS12. Gail H-P and Hoppe P (2010) the origins of protoplanetary dust and the formation of accretion disks. Protoplanetary Dust, eds Apai D Lauretta DS (Cambridge Univ Press, New York), pp 27–65.
4. Mantle formation, coagulation, and the origin of cloud/core shine. II. Comparison with observations. (2016);Ysard;Astron Astrophys,2016
5. Jones A (2014) The physical and compositional properties of dust: What do we really know? Proceedings of the Life Cycle of Dust in the Universe: Observations, Theory, and Laboratory Experiments–LCDU 18-22 November 2013 (Proceedings Sci, Taipei, Taiwan), 20 p.
Cited by
34 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献