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Direct evidence of volcanic outgassing of Na and K on the Moon from Apollo orange beads

Liu, Yang and Ma, Chi (2022) Direct evidence of volcanic outgassing of Na and K on the Moon from Apollo orange beads. Icarus, 382 . Art. No. 115044. ISSN 0019-1035. doi:10.1016/j.icarus.2022.115044.

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We report the first discovery of a pervasive Na-K-sulfate formed from vapor condensed Na-K-S on the surface of Apollo 74220 orange beads. The molar (Na + K)/S values (A) of different grains range between 1.3 and 2.3, indicating that the original condensates comprise Na-K-sulfides with possible excess native S (for A < 2) or excess Na and K (for A > 2). Together with the previous report of the Zn-Na-S-Cl condensates that contain mostly metallic Zn, our observations show that Na(g) and K(g) condense as sulfides before Zn(g) condenses in its native state. Both thermochemical calculations of lunar volcanic gas and direct observations are inconsistent with the common assumption that moderately volatile elements vaporize and condense as chlorides. The textural relationship of Na-K-S condensates underlying Zn-Na-S-Cl condensates suggests Na-K-S was deposited before Zn-Na-S-Cl, which depleted sulfur from volcanic gas and inhibited the formation of ZnS. These forms of condensates require the volcanic gas that carried 74220 orange beads to be highly reducing (made of mostly H₂) with a sufficient partial pressure of S₂(g) or H₂S(g) to enable interactions between Na and K with S.

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Ma, Chi0000-0002-1828-7033
Additional Information:© 2022 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license ( Received 22 July 2021, Revised 15 April 2022, Accepted 17 April 2022, Available online 20 April 2022, Version of Record 26 April 2022. We are grateful to the NASA Johnson Space Center curatorial staff for the provision of samples and detailed processing history of the allocated samples. A portion of the work was performed at Jet Propulsion Laboratory, which is managed by the California Institute of Technology (Caltech) under a contract with NASA. We thank two anonymous reviewers for detailed and constructive comments. SEM and EDS analyses were carried out at the Caltech GPS Division Analytical Facility, which is supported, in part, by NSF Grants EAR-0318518 and DMR-0080065. All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. Samples used in this study upon completion of the project will be returned to the lunar curation office at Johnson Space Center. Additional SEM images of volcanic beads related to this paper may be requested from the authors.
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Subject Keywords:Vapor condensates; Na-K-sulfate; Volcanic outgassing; The Moon
Record Number:CaltechAUTHORS:20220511-989976300
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Official Citation:Yang Liu, Chi Ma, Direct evidence of volcanic outgassing of Na and K on the Moon from Apollo orange beads, Icarus, Volume 382, 2022, 115044, ISSN 0019-1035,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:114674
Deposited By: Tony Diaz
Deposited On:11 May 2022 21:24
Last Modified:20 Jul 2022 17:16

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