TY - JOUR
T1 - A water-ice rich minor body from the early Solar System
T2 - The CR chondrite parent asteroid
AU - Schrader, Devin L.
AU - Davidson, Jemma
AU - Greenwood, Richard C.
AU - Franchi, Ian A.
AU - Gibson, Jenny M.
N1 - Funding Information:
We are grateful for the thorough and constructive comments by Neyda Abreu, Corentin Le Guillou, an anonymous reviewer, and the Associate Editor Bernard Marty. For supplying the many samples that were necessary for this work, the authors would like to thank: the members of the Meteorite Working Group, and Cecilia Satterwhite and Kevin Righter (NASA, Johnson Space Center). 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. The authors also thank Michael Farmer, Eric Olson, and Gary Fujihara for samples. We are grateful to Tim Gooding for assistance with the SEM. This research was funded in part by the Science and Technology Facilities Council Grant ST/1001964/1 (RCG and IAF).
Publisher Copyright:
© 2014 Elsevier B.V.
PY - 2014/12/1
Y1 - 2014/12/1
N2 - To better understand the effects of aqueous alteration in the Renazzo-like carbonaceous (CR) chondrite parent asteroid, a minor body in the early Solar System, we studied the petrology and O-isotope compositions of fine-grained matrix from 14 different CR chondrites. The O-isotope compositions of matrix from Queen Alexandra Range 99177 confirm that this sample is the least aqueously altered CR chondrite, provides the best approximation of the primary anhydrous matrix, and suggests matrix is not a byproduct of chondrule formation. Matrix O-isotope compositions within individual CR chondrites are heterogeneous, varying up to ~5‰ in both δO18 and δO17, as a result of the heterogeneous nature of the matrix and diverse range of aqueous alteration recorded by each sample. Aqueous alteration resulted in matrix that is progressively more 16O-depleted and Ca-carbonate rich. Due to the fine-grained nature of matrix its O-isotope composition is a more sensitive indicator of a chondrite's overall degree of aqueous alteration than whole-rock O-isotope compositions, which are typically dominated by the compositions of type I (FeO-poor) chondrule phenocrysts. Petrographic signatures correlate with the degree of aqueous alteration and the wide range of matrix O-isotope compositions indicate that some regions of the CR chondrite parent asteroid were relatively dry, while others were heavily hydrated with water. The O-isotope composition of aqueously altered matrix is consistent with asteroidal water being near δO17~0‰, which suggests an inner Solar System origin for the water. The diverse range of aqueous alteration recorded by a single asteroid has a range of implications for spectral studies of the asteroid belt, and the arrival of Dawn at 1 Ceres, Hayabusa-2 at 162173 1999 JU3, and OSIRIS-REx at 101955 Bennu.
AB - To better understand the effects of aqueous alteration in the Renazzo-like carbonaceous (CR) chondrite parent asteroid, a minor body in the early Solar System, we studied the petrology and O-isotope compositions of fine-grained matrix from 14 different CR chondrites. The O-isotope compositions of matrix from Queen Alexandra Range 99177 confirm that this sample is the least aqueously altered CR chondrite, provides the best approximation of the primary anhydrous matrix, and suggests matrix is not a byproduct of chondrule formation. Matrix O-isotope compositions within individual CR chondrites are heterogeneous, varying up to ~5‰ in both δO18 and δO17, as a result of the heterogeneous nature of the matrix and diverse range of aqueous alteration recorded by each sample. Aqueous alteration resulted in matrix that is progressively more 16O-depleted and Ca-carbonate rich. Due to the fine-grained nature of matrix its O-isotope composition is a more sensitive indicator of a chondrite's overall degree of aqueous alteration than whole-rock O-isotope compositions, which are typically dominated by the compositions of type I (FeO-poor) chondrule phenocrysts. Petrographic signatures correlate with the degree of aqueous alteration and the wide range of matrix O-isotope compositions indicate that some regions of the CR chondrite parent asteroid were relatively dry, while others were heavily hydrated with water. The O-isotope composition of aqueously altered matrix is consistent with asteroidal water being near δO17~0‰, which suggests an inner Solar System origin for the water. The diverse range of aqueous alteration recorded by a single asteroid has a range of implications for spectral studies of the asteroid belt, and the arrival of Dawn at 1 Ceres, Hayabusa-2 at 162173 1999 JU3, and OSIRIS-REx at 101955 Bennu.
KW - Aqueous alteration
KW - Asteroid
KW - CR-chondrite
KW - Matrix
KW - O-isotope
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U2 - 10.1016/j.epsl.2014.09.030
DO - 10.1016/j.epsl.2014.09.030
M3 - Article
AN - SCOPUS:84907952514
SN - 0012-821X
VL - 407
SP - 48
EP - 60
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
ER -