In situ analysis of opal in Gale crater, Mars
Abstract
Silica enrichments resulting in up to ~90 wt% SiO_2 have been observed by the Curiosity rover's instruments in Gale crater, Mars, within the Murray and Stimson formations. Samples acquired by the rover drill revealed a significant abundance of an X‐ray amorphous silica phase. Laser‐induced breakdown spectroscopy (LIBS) highlights an overall correlation of the hydrogen signal with silica content for these Si‐enriched targets. The increased hydration of the high‐silica rocks compared to the surrounding bedrock is also confirmed by active neutron spectroscopy. Laboratory LIBS experiments have been performed to calibrate the hydrogen signal and show that the correlation observed on Mars is consistent with a silica phase containing on average 6.3 ± 1.4 wt% water. X‐ray diffraction and LIBS measurements indicate that opal‐A, amorphous hydrated silica, is the most likely phase containing this water in the rocks. Pyrolysis experiments were also performed on drilled samples by the Sample Analysis at Mars (SAM) instrument to measure volatile content, but the data suggests that most of the water was released during handling prior to pyrolysis. The inferred low‐temperature release of water helps constrain the nature of the opal. Given the geological context and the spatial association with other phases such as calcium sulfates, the opal was likely formed from multiple diagenetic fluid events and possibly represents the latest significant water‐rock interaction in these sedimentary rocks.
Additional Information
© 2018 The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. Received 9 NOV 2017; Accepted 12 JUN 2018; Accepted article online 3 JUL 2018; Published online 4 AUG 2018. The research was funded at Caltech by the Division of Geological and Planetary Sciences Postdoctoral Fellowship and supported by a NASA MSL Participating Scientist Program grant to B. L. Ehlmann. The work performed at Université Paul Sabatier was part of a PhD thesis (Rapin, 2016), and laboratory LIBS experiments were conducted at Institut de Recherche en Astrophysique et Planétologie (IRAP) with support from CNES. MSL/ChemCam U.S. operations were funded by the NASA Mars Exploration Program. Funding for ChemCam operations in France was provided by CNES. The authors gratefully acknowledge the support of all of the people at NASA‐JPL involved in making MSL a successful mission. We also thank two anonymous reviewers for their helpful comments. We acknowledge the Agence Nationale de la Recherche (ANR) under the program ANR‐16‐CE31‐0012 entitled "Mars‐Prime" for helping collaborative efforts in this study. The authors thankfully recognize the help of Paul Thomas, from the University of Technology, Sydney, for TGA on opals. A. C. M. thanks NASA's MSL Participating Scientist program for supporting this effort. All data collected on Mars by MSL/Curiosity used in this study are available on the PDS (Planetary Data System) at pds.nasa.gov. Data shown in Figures 1 and 2 are accessible in the supporting information.Attached Files
Published - Rapin_et_al-2018-Journal_of_Geophysical_Research__Planets.pdf
Supplemental Material - jgre20976-sup-0001-data_set_s01.xlsx
Supplemental Material - jgre20976-sup-0002-data_set_s02.xlsx
Supplemental Material - jgre20976-sup-0003-table_s01.docx
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Additional details
- Eprint ID
- 87542
- DOI
- 10.1029/2017JE005483
- Resolver ID
- CaltechAUTHORS:20180705-070817027
- Caltech
- NASA
- Centre National d'Études Spatiales (CNES)
- Agence Nationale pour la Recherche (ANR)
- ANR-16-CE31-0012
- Created
-
2018-07-05Created from EPrint's datestamp field
- Updated
-
2021-11-15Created from EPrint's last_modified field
- Caltech groups
- Astronomy Department, Division of Geological and Planetary Sciences (GPS)