Detecting Kerogen as a Biosignature Using Colocated UV Time-Gated Raman and Fluorescence Spectroscopy

Svetlana Shkolyar; Evan J. Eshelman; Jack Farmer; David Hamilton; Michael G. Daly; Cody Youngbull

doi:10.1089/ast.2017.1716

Detecting Kerogen as a Biosignature Using Colocated UV Time-Gated Raman and Fluorescence Spectroscopy

Svetlana Shkolyar, Evan J. Eshelman, Jack Farmer, David Hamilton, Michael G. Daly, Cody Youngbull

Research output: Contribution to journal › Review article › peer-review

33 Scopus citations

Abstract

The Mars 2020 mission will analyze samples in situ and identify any that could have preserved biosignatures in ancient habitable environments for later return to Earth. Highest priority targeted samples include aqueously formed sedimentary lithologies. On Earth, such lithologies can contain fossil biosignatures as aromatic carbon (kerogen). In this study, we analyzed nonextracted kerogen in a diverse suite of natural, complex samples using colocated UV excitation (266 nm) time-gated (UV-TG) Raman and laser-induced fluorescence spectroscopies. We interrogated kerogen and its host matrix in samples to (1) explore the capabilities of UV-TG Raman and fluorescence spectroscopies for detecting kerogen in high-priority targets in the search for possible biosignatures on Mars; (2) assess the effectiveness of time gating and UV laser wavelength in reducing fluorescence in Raman spectra; and (3) identify sample-specific issues that could challenge rover-based identifications of kerogen using UV-TG Raman spectroscopy. We found that ungated UV Raman spectroscopy is suited to identify diagnostic kerogen Raman bands without interfering fluorescence and that UV fluorescence spectroscopy is suited to identify kerogen. These results highlight the value of combining colocated Raman and fluorescence spectroscopies, similar to those obtainable by SHERLOC on Mars 2020, to strengthen the confidence of kerogen detection as a potential biosignature in complex natural samples.

Original language	English (US)
Pages (from-to)	431-453
Number of pages	23
Journal	Astrobiology
Volume	18
Issue number	4
DOIs	https://doi.org/10.1089/ast.2017.1716
State	Published - Apr 2018

Keywords

Biosignatures
Kerogen
Laser-induced fluorescence spectroscopy
Mars 2020 mission
Mars Sample Return
Raman spectroscopy

ASJC Scopus subject areas

Agricultural and Biological Sciences (miscellaneous)
Space and Planetary Science

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10.1089/ast.2017.1716

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title = "Detecting Kerogen as a Biosignature Using Colocated UV Time-Gated Raman and Fluorescence Spectroscopy",

abstract = "The Mars 2020 mission will analyze samples in situ and identify any that could have preserved biosignatures in ancient habitable environments for later return to Earth. Highest priority targeted samples include aqueously formed sedimentary lithologies. On Earth, such lithologies can contain fossil biosignatures as aromatic carbon (kerogen). In this study, we analyzed nonextracted kerogen in a diverse suite of natural, complex samples using colocated UV excitation (266 nm) time-gated (UV-TG) Raman and laser-induced fluorescence spectroscopies. We interrogated kerogen and its host matrix in samples to (1) explore the capabilities of UV-TG Raman and fluorescence spectroscopies for detecting kerogen in high-priority targets in the search for possible biosignatures on Mars; (2) assess the effectiveness of time gating and UV laser wavelength in reducing fluorescence in Raman spectra; and (3) identify sample-specific issues that could challenge rover-based identifications of kerogen using UV-TG Raman spectroscopy. We found that ungated UV Raman spectroscopy is suited to identify diagnostic kerogen Raman bands without interfering fluorescence and that UV fluorescence spectroscopy is suited to identify kerogen. These results highlight the value of combining colocated Raman and fluorescence spectroscopies, similar to those obtainable by SHERLOC on Mars 2020, to strengthen the confidence of kerogen detection as a potential biosignature in complex natural samples.",

keywords = "Biosignatures, Kerogen, Laser-induced fluorescence spectroscopy, Mars 2020 mission, Mars Sample Return, Raman spectroscopy",

author = "Svetlana Shkolyar and Eshelman, {Evan J.} and Jack Farmer and David Hamilton and Daly, {Michael G.} and Cody Youngbull",

note = "Funding Information: This work was supported, in part, by a NASA Astrobiology Institute (NAI) Early Career Collaboration Award, the NASA Mars exploration Program, and the Natural Sciences and Engineering Research Council of Canada (NSERC), and the Postdoctoral Fellowship at Carnegie Institution for Science. The use of facilities within the LeRoy Eyring Center for Solid State Science at Arizona State University is gratefully acknowledged. Emily Matys (MIT) is thanked for prompt assistance providing the kerogen standard. Marc Neveu (NASA HQ/USRA) is thanked for assistance with editing. Andrew Steele (Carnegie Institution for Science) is thanked for very helpful discussion and for assistance with the WITec Raman system. Two anonymous reviewers are thanked for their reviews that greatly improved this article. Publisher Copyright: {\textcopyright} Copyright 2018, Mary Ann Liebert, Inc. 2018.",

year = "2018",

month = apr,

doi = "10.1089/ast.2017.1716",

language = "English (US)",

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T1 - Detecting Kerogen as a Biosignature Using Colocated UV Time-Gated Raman and Fluorescence Spectroscopy

AU - Shkolyar, Svetlana

AU - Eshelman, Evan J.

AU - Farmer, Jack

AU - Hamilton, David

AU - Daly, Michael G.

AU - Youngbull, Cody

N1 - Funding Information: This work was supported, in part, by a NASA Astrobiology Institute (NAI) Early Career Collaboration Award, the NASA Mars exploration Program, and the Natural Sciences and Engineering Research Council of Canada (NSERC), and the Postdoctoral Fellowship at Carnegie Institution for Science. The use of facilities within the LeRoy Eyring Center for Solid State Science at Arizona State University is gratefully acknowledged. Emily Matys (MIT) is thanked for prompt assistance providing the kerogen standard. Marc Neveu (NASA HQ/USRA) is thanked for assistance with editing. Andrew Steele (Carnegie Institution for Science) is thanked for very helpful discussion and for assistance with the WITec Raman system. Two anonymous reviewers are thanked for their reviews that greatly improved this article. Publisher Copyright: © Copyright 2018, Mary Ann Liebert, Inc. 2018.

PY - 2018/4

Y1 - 2018/4

N2 - The Mars 2020 mission will analyze samples in situ and identify any that could have preserved biosignatures in ancient habitable environments for later return to Earth. Highest priority targeted samples include aqueously formed sedimentary lithologies. On Earth, such lithologies can contain fossil biosignatures as aromatic carbon (kerogen). In this study, we analyzed nonextracted kerogen in a diverse suite of natural, complex samples using colocated UV excitation (266 nm) time-gated (UV-TG) Raman and laser-induced fluorescence spectroscopies. We interrogated kerogen and its host matrix in samples to (1) explore the capabilities of UV-TG Raman and fluorescence spectroscopies for detecting kerogen in high-priority targets in the search for possible biosignatures on Mars; (2) assess the effectiveness of time gating and UV laser wavelength in reducing fluorescence in Raman spectra; and (3) identify sample-specific issues that could challenge rover-based identifications of kerogen using UV-TG Raman spectroscopy. We found that ungated UV Raman spectroscopy is suited to identify diagnostic kerogen Raman bands without interfering fluorescence and that UV fluorescence spectroscopy is suited to identify kerogen. These results highlight the value of combining colocated Raman and fluorescence spectroscopies, similar to those obtainable by SHERLOC on Mars 2020, to strengthen the confidence of kerogen detection as a potential biosignature in complex natural samples.

AB - The Mars 2020 mission will analyze samples in situ and identify any that could have preserved biosignatures in ancient habitable environments for later return to Earth. Highest priority targeted samples include aqueously formed sedimentary lithologies. On Earth, such lithologies can contain fossil biosignatures as aromatic carbon (kerogen). In this study, we analyzed nonextracted kerogen in a diverse suite of natural, complex samples using colocated UV excitation (266 nm) time-gated (UV-TG) Raman and laser-induced fluorescence spectroscopies. We interrogated kerogen and its host matrix in samples to (1) explore the capabilities of UV-TG Raman and fluorescence spectroscopies for detecting kerogen in high-priority targets in the search for possible biosignatures on Mars; (2) assess the effectiveness of time gating and UV laser wavelength in reducing fluorescence in Raman spectra; and (3) identify sample-specific issues that could challenge rover-based identifications of kerogen using UV-TG Raman spectroscopy. We found that ungated UV Raman spectroscopy is suited to identify diagnostic kerogen Raman bands without interfering fluorescence and that UV fluorescence spectroscopy is suited to identify kerogen. These results highlight the value of combining colocated Raman and fluorescence spectroscopies, similar to those obtainable by SHERLOC on Mars 2020, to strengthen the confidence of kerogen detection as a potential biosignature in complex natural samples.

KW - Biosignatures

KW - Kerogen

KW - Laser-induced fluorescence spectroscopy

KW - Mars 2020 mission

KW - Mars Sample Return

KW - Raman spectroscopy

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AN - SCOPUS:85045849893

SN - 1531-1074

VL - 18

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JO - Astrobiology

JF - Astrobiology

IS - 4

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Detecting Kerogen as a Biosignature Using Colocated UV Time-Gated Raman and Fluorescence Spectroscopy

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