TY - JOUR
T1 - The retention of dust in protoplanetary disks
T2 - Evidence from agglomeratic olivine chondrules from the outer Solar System
AU - Schrader, Devin
AU - Nagashima, Kazuhide
AU - Waitukaitis, Scott R.
AU - Davidson, Jemma
AU - McCoy, Timothy J.
AU - Connolly, Harold C.
AU - Lauretta, Dante S.
N1 - Funding Information:
For supplying the samples that were necessary for this work, the authors would like to thank: the Smithsonian Institution, the members of the Meteorite Working Group, Cecilia Satterwhite and Kevin Righter (NASA, Johnson Space Center), the National Institute of Polar Research (NIPR), Jack Schrader, and Michael Farmer. US Antarctic meteorite samples are recovered by the Antarctic Search for Meteorites (ANSMET) program, which has been funded by NSF and NASA, and characterized and curated by the Department of Mineral Sciences of the Smithsonian Institution and Astromaterials Curation Office at NASA Johnson Space Center. We thank Diane Johnson and Ian Franchi for the use of, and assistance with, the SEM at the Open University. We are grateful to Tim Gooding and Adam Mansur for assistance with the SEM at SI, Ken Domanik for assistance with EPMA at UA, Axel Wittmann for assistance with EPMA at ASU, and Tim Rose, Emma Bullock, and Steve Lynton for assistance with EPMA at SI. We are also grateful to Daisuke Nakashima, two anonymous reviewers, and Associate Editor Sara Russell, whose constructive comments improved the quality of the manuscript. This research was funded in part by the Arizona State University Center for Meteorite Studies, NASA grant (NNX15AH44H, KN PI), and the Smithsonian Institution.
Publisher Copyright:
© 2017 Elsevier Ltd
PY - 2018/2/15
Y1 - 2018/2/15
N2 - By investigating the in situ chemical and O-isotope compositions of olivine in lightly sintered dust agglomerates from the early Solar System, we constrain their origins and the retention of dust in the protoplanetary disk. The grain sizes of silicates in these agglomeratic olivine (AO) chondrules indicate that the grain sizes of chondrule precursors in the Renazzo-like carbonaceous (CR) chondrites ranged from <1 to 80 µm. We infer this grain size range to be equivalent to the size range for dust in the early Solar System. AO chondrules may contain, but are not solely composed of, recycled fragments of earlier formed chondrules. They also contain 16O-rich olivine related to amoeboid olivine aggregates and represent the best record of chondrule-precursor materials. AO chondrules contain one or more large grains, sometimes similar to FeO-poor (type I) and/or FeO-rich (type II) chondrules, while others contain a type II chondrule core. These morphologies are consistent with particle agglomeration by electrostatic charging of grains during collision, a process that may explain solid agglomeration in the protoplanetary disk in the micrometer size regime. The petrographic, isotopic, and chemical compositions of AO chondrules are consistent with chondrule formation by large-scale shocks, bow shocks, and current sheets. The petrographic, isotopic, and chemical similarities between AO chondrules in CR chondrites and chondrule-like objects from comet 81P/Wild 2 indicate that comets contain AO chondrules. We infer that these AO chondrules likely formed in the inner Solar System and migrated to the comet forming region at least 3 Ma after the formation of the first Solar System solids. Observations made in this study imply that the protoplanetary disk retained a dusty disk at least ∼3.7 Ma after the formation of the first Solar System solids, longer than half of the dusty accretion disks observed around other stars.
AB - By investigating the in situ chemical and O-isotope compositions of olivine in lightly sintered dust agglomerates from the early Solar System, we constrain their origins and the retention of dust in the protoplanetary disk. The grain sizes of silicates in these agglomeratic olivine (AO) chondrules indicate that the grain sizes of chondrule precursors in the Renazzo-like carbonaceous (CR) chondrites ranged from <1 to 80 µm. We infer this grain size range to be equivalent to the size range for dust in the early Solar System. AO chondrules may contain, but are not solely composed of, recycled fragments of earlier formed chondrules. They also contain 16O-rich olivine related to amoeboid olivine aggregates and represent the best record of chondrule-precursor materials. AO chondrules contain one or more large grains, sometimes similar to FeO-poor (type I) and/or FeO-rich (type II) chondrules, while others contain a type II chondrule core. These morphologies are consistent with particle agglomeration by electrostatic charging of grains during collision, a process that may explain solid agglomeration in the protoplanetary disk in the micrometer size regime. The petrographic, isotopic, and chemical compositions of AO chondrules are consistent with chondrule formation by large-scale shocks, bow shocks, and current sheets. The petrographic, isotopic, and chemical similarities between AO chondrules in CR chondrites and chondrule-like objects from comet 81P/Wild 2 indicate that comets contain AO chondrules. We infer that these AO chondrules likely formed in the inner Solar System and migrated to the comet forming region at least 3 Ma after the formation of the first Solar System solids. Observations made in this study imply that the protoplanetary disk retained a dusty disk at least ∼3.7 Ma after the formation of the first Solar System solids, longer than half of the dusty accretion disks observed around other stars.
KW - Agglomeratic olivine chondrule
KW - Asteroid
KW - CR chondrite
KW - Comet Wild 2
KW - Oxygen isotopes
KW - Protoplanetary disk
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U2 - 10.1016/j.gca.2017.12.014
DO - 10.1016/j.gca.2017.12.014
M3 - Article
AN - SCOPUS:85040075037
SN - 0016-7037
VL - 223
SP - 405
EP - 421
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
ER -