Lifetimes of interstellar dust from cosmic ray exposure ages of presolar silicon carbide.

Heck PR; Greer J; Kööp L; Trappitsch R; Gyngard F; Busemann H; Maden C; Ávila JN; Davis AM; Wieler R

doi:10.1073/pnas.1904573117

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Journal article

Lifetimes of interstellar dust from cosmic ray exposure ages of presolar silicon carbide.

Heck PR Robert A. Pritzker Center for Meteoritics and Polar Studies, The Field Museum of Natural History, Chicago, IL 60605; prheck@fieldmuseum.org.
Greer J Robert A. Pritzker Center for Meteoritics and Polar Studies, The Field Museum of Natural History, Chicago, IL 60605.
Kööp L Robert A. Pritzker Center for Meteoritics and Polar Studies, The Field Museum of Natural History, Chicago, IL 60605.
Trappitsch R Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, CA 94550.
Gyngard F Physics Department, Washington University, St. Louis, MO 63130.
Busemann H Institute of Geochemistry and Petrology, ETH Zürich, 8092 Zürich, Switzerland.
Maden C Institute of Geochemistry and Petrology, ETH Zürich, 8092 Zürich, Switzerland.
Ávila JN Research School of Earth Sciences, The Australian National University, Canberra, ACT 2601, Australia.
Davis AM Robert A. Pritzker Center for Meteoritics and Polar Studies, The Field Museum of Natural History, Chicago, IL 60605.
Wieler R Institute of Geochemistry and Petrology, ETH Zürich, 8092 Zürich, Switzerland.

2020-01-15

Published in:

Proceedings of the National Academy of Sciences of the United States of America. - 2020

English We determined interstellar cosmic ray exposure ages of 40 large presolar silicon carbide grains extracted from the Murchison CM2 meteorite. Our ages, based on cosmogenic Ne-21, range from 3.9 ± 1.6 Ma to ∼3 ± 2 Ga before the start of the Solar System ∼4.6 Ga ago. A majority of the grains have interstellar lifetimes of <300 Ma, which is shorter than theoretical estimates for large grains. These grains condensed in outflows of asymptotic giant branch stars <4.9 Ga ago that possibly formed during an episode of enhanced star formation ∼7 Ga ago. A minority of the grains have ages >1 Ga. Longer lifetimes are expected for large grains. We determined that at least 12 of the analyzed grains were parts of aggregates in the interstellar medium: The large difference in nuclear recoil loss of cosmic ray spallation products 3He and 21Ne enabled us to estimate that the irradiated objects in the interstellar medium were up to 30 times larger than the analyzed grains. Furthermore, we estimate that the majority of the grains acquired the bulk of their cosmogenic nuclides in the interstellar medium and not by exposure to an enhanced particle flux of the early active sun.

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