Mars-Analog Calcium Sulfate Veins Record Evidence of Ancient Subsurface Life

S. McMahon; J. Parnell; P. B. R. Reekie

doi:10.1089/ast.2019.2172

Mars-Analog Calcium Sulfate Veins Record Evidence of Ancient Subsurface Life

S. McMahon^*, J. Parnell, P. B. R. Reekie

^*Corresponding author for this work

Geology and Geophysics

University of Edinburgh

Research output: Contribution to journal › Article › peer-review

3 Citations (Scopus)

Abstract

Ancient veins of calcium sulfate minerals (anhydrite, bassanite, and gypsum) deposited by subsurface aqueous fluids crosscut fluviolacustrine sedimentary rocks at multiple localities on Mars. Although these veins have been considered an attractive target for astrobiological investigation, their potential to preserve biosignatures is poorly understood. Here, we report the presence of biogenic authigenic pyrite in a fibrous gypsum vein of probable Cenozoic emplacement age from Permian lacustrine rocks in Northwest England. Pyrite occurs at the vein margins and displays a complex interfingering boundary with the surrounding gypsum suggestive of replacive authigenic growth. Gypsum-entombed carbonaceous material of probable organic origin was also identified by Raman spectroscopic microscopy in close proximity to the pyrite. Spatially resolved ion microprobe (SIMS) measurements reveal that the pyrite sulfur isotope composition is consistently very light (delta S-34(VCDT) = -30.7 parts per thousand). Comparison with the sulfate in the vein gypsum (delta S-34(VCDT) = +8.5 parts per thousand) indicates a fractionation too large to be explained by nonbiological (thermochemical) sulfate reduction. We infer that the pyrite was precipitated by microorganisms coupling the reduction of vein-derived sulfate with the oxidation of wall-derived organic matter. This is the first evidence that such veins can incorporate biosignatures that remain stable over geological time, which could be detected in samples returned from Mars.

Original language	English
Pages (from-to)	1212-1223
Number of pages	12
Journal	Astrobiology
Volume	20
Issue number	10
Early online date	24 Sept 2020
DOIs	https://doi.org/10.1089/ast.2019.2172
Publication status	Published - 9 Oct 2020

Bibliographical note

Funding Information:
This work was funded by the European Union’s Horizon 2020 Research and Innovation Programme under Marie Skłodowska-Curie grant agreement 747877. We acknowledge the Natural Environment Research Council for supporting the NERC Ion Microprobe Facility in Edinburgh and for supporting P.B.R.R.’s PhD studentship. The authors sincerely thank Mike Hall and John Craven for generous assistance with sample preparation and the operation of the ion microprobe; Alison McDonald and Andrey Gromov for technical assistance with Raman microscopy and analysis; Connor Brolly for assistance with the TOC analysis; and Stephen Phillips for originally collecting the vein sample. We also thank Diana Marosi for bibliographic assistance. We thank Tim Lyons and an anonymous reviewer for helpful comments that improved the manuscript.

Publisher Copyright:
© 2020 Mary Ann Liebert, Inc., publishers.

Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.

Keywords

Mars
Sulfate
Mineral veins
Gypsum
Preservation
Biosignature
SULFUR ISOTOPE FRACTIONATIONS
GALE CRATER
REDUCTION
MICROFOSSILS
METHANE
SEARCH
BIOSIGNATURES
PRESERVATION
MUDSTONE
DEPOSITS
Biosignature. Astrobiology 20, 1212–1223

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Cite this

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title = "Mars-Analog Calcium Sulfate Veins Record Evidence of Ancient Subsurface Life",

abstract = "Ancient veins of calcium sulfate minerals (anhydrite, bassanite, and gypsum) deposited by subsurface aqueous fluids crosscut fluviolacustrine sedimentary rocks at multiple localities on Mars. Although these veins have been considered an attractive target for astrobiological investigation, their potential to preserve biosignatures is poorly understood. Here, we report the presence of biogenic authigenic pyrite in a fibrous gypsum vein of probable Cenozoic emplacement age from Permian lacustrine rocks in Northwest England. Pyrite occurs at the vein margins and displays a complex interfingering boundary with the surrounding gypsum suggestive of replacive authigenic growth. Gypsum-entombed carbonaceous material of probable organic origin was also identified by Raman spectroscopic microscopy in close proximity to the pyrite. Spatially resolved ion microprobe (SIMS) measurements reveal that the pyrite sulfur isotope composition is consistently very light (delta S-34(VCDT) = -30.7 parts per thousand). Comparison with the sulfate in the vein gypsum (delta S-34(VCDT) = +8.5 parts per thousand) indicates a fractionation too large to be explained by nonbiological (thermochemical) sulfate reduction. We infer that the pyrite was precipitated by microorganisms coupling the reduction of vein-derived sulfate with the oxidation of wall-derived organic matter. This is the first evidence that such veins can incorporate biosignatures that remain stable over geological time, which could be detected in samples returned from Mars.",

keywords = "Mars, Sulfate, Mineral veins, Gypsum, Preservation, Biosignature, SULFUR ISOTOPE FRACTIONATIONS, GALE CRATER, REDUCTION, MICROFOSSILS, METHANE, SEARCH, BIOSIGNATURES, PRESERVATION, MUDSTONE, DEPOSITS, Biosignature. Astrobiology 20, 1212–1223",

author = "S. McMahon and J. Parnell and Reekie, {P. B. R.}",

note = "Funding Information: This work was funded by the European Union{\textquoteright}s Horizon 2020 Research and Innovation Programme under Marie Sk{\l}odowska-Curie grant agreement 747877. We acknowledge the Natural Environment Research Council for supporting the NERC Ion Microprobe Facility in Edinburgh and for supporting P.B.R.R.{\textquoteright}s PhD studentship. The authors sincerely thank Mike Hall and John Craven for generous assistance with sample preparation and the operation of the ion microprobe; Alison McDonald and Andrey Gromov for technical assistance with Raman microscopy and analysis; Connor Brolly for assistance with the TOC analysis; and Stephen Phillips for originally collecting the vein sample. We also thank Diana Marosi for bibliographic assistance. We thank Tim Lyons and an anonymous reviewer for helpful comments that improved the manuscript. Publisher Copyright: {\textcopyright} 2020 Mary Ann Liebert, Inc., publishers. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.",

year = "2020",

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doi = "10.1089/ast.2019.2172",

language = "English",

volume = "20",

pages = "1212--1223",

journal = "Astrobiology",

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publisher = "Mary Ann Liebert Inc.",

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T1 - Mars-Analog Calcium Sulfate Veins Record Evidence of Ancient Subsurface Life

AU - McMahon, S.

AU - Parnell, J.

AU - Reekie, P. B. R.

N1 - Funding Information: This work was funded by the European Union’s Horizon 2020 Research and Innovation Programme under Marie Skłodowska-Curie grant agreement 747877. We acknowledge the Natural Environment Research Council for supporting the NERC Ion Microprobe Facility in Edinburgh and for supporting P.B.R.R.’s PhD studentship. The authors sincerely thank Mike Hall and John Craven for generous assistance with sample preparation and the operation of the ion microprobe; Alison McDonald and Andrey Gromov for technical assistance with Raman microscopy and analysis; Connor Brolly for assistance with the TOC analysis; and Stephen Phillips for originally collecting the vein sample. We also thank Diana Marosi for bibliographic assistance. We thank Tim Lyons and an anonymous reviewer for helpful comments that improved the manuscript. Publisher Copyright: © 2020 Mary Ann Liebert, Inc., publishers. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.

PY - 2020/10/9

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N2 - Ancient veins of calcium sulfate minerals (anhydrite, bassanite, and gypsum) deposited by subsurface aqueous fluids crosscut fluviolacustrine sedimentary rocks at multiple localities on Mars. Although these veins have been considered an attractive target for astrobiological investigation, their potential to preserve biosignatures is poorly understood. Here, we report the presence of biogenic authigenic pyrite in a fibrous gypsum vein of probable Cenozoic emplacement age from Permian lacustrine rocks in Northwest England. Pyrite occurs at the vein margins and displays a complex interfingering boundary with the surrounding gypsum suggestive of replacive authigenic growth. Gypsum-entombed carbonaceous material of probable organic origin was also identified by Raman spectroscopic microscopy in close proximity to the pyrite. Spatially resolved ion microprobe (SIMS) measurements reveal that the pyrite sulfur isotope composition is consistently very light (delta S-34(VCDT) = -30.7 parts per thousand). Comparison with the sulfate in the vein gypsum (delta S-34(VCDT) = +8.5 parts per thousand) indicates a fractionation too large to be explained by nonbiological (thermochemical) sulfate reduction. We infer that the pyrite was precipitated by microorganisms coupling the reduction of vein-derived sulfate with the oxidation of wall-derived organic matter. This is the first evidence that such veins can incorporate biosignatures that remain stable over geological time, which could be detected in samples returned from Mars.

AB - Ancient veins of calcium sulfate minerals (anhydrite, bassanite, and gypsum) deposited by subsurface aqueous fluids crosscut fluviolacustrine sedimentary rocks at multiple localities on Mars. Although these veins have been considered an attractive target for astrobiological investigation, their potential to preserve biosignatures is poorly understood. Here, we report the presence of biogenic authigenic pyrite in a fibrous gypsum vein of probable Cenozoic emplacement age from Permian lacustrine rocks in Northwest England. Pyrite occurs at the vein margins and displays a complex interfingering boundary with the surrounding gypsum suggestive of replacive authigenic growth. Gypsum-entombed carbonaceous material of probable organic origin was also identified by Raman spectroscopic microscopy in close proximity to the pyrite. Spatially resolved ion microprobe (SIMS) measurements reveal that the pyrite sulfur isotope composition is consistently very light (delta S-34(VCDT) = -30.7 parts per thousand). Comparison with the sulfate in the vein gypsum (delta S-34(VCDT) = +8.5 parts per thousand) indicates a fractionation too large to be explained by nonbiological (thermochemical) sulfate reduction. We infer that the pyrite was precipitated by microorganisms coupling the reduction of vein-derived sulfate with the oxidation of wall-derived organic matter. This is the first evidence that such veins can incorporate biosignatures that remain stable over geological time, which could be detected in samples returned from Mars.

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KW - SULFUR ISOTOPE FRACTIONATIONS

KW - GALE CRATER

KW - REDUCTION

KW - MICROFOSSILS

KW - METHANE

KW - SEARCH

KW - BIOSIGNATURES

KW - PRESERVATION

KW - MUDSTONE

KW - DEPOSITS

KW - Biosignature. Astrobiology 20, 1212–1223

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U2 - 10.1089/ast.2019.2172

DO - 10.1089/ast.2019.2172

M3 - Article

SN - 1531-1074

VL - 20

SP - 1212

EP - 1223

JO - Astrobiology

JF - Astrobiology

IS - 10

ER -

Mars-Analog Calcium Sulfate Veins Record Evidence of Ancient Subsurface Life

Abstract

Bibliographical note

Keywords

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