1
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Jakubek RS, Bhartia R, Uckert K, Asher SA, Czaja AD, Fries MD, Hand K, Haney NC, Razzell Hollis J, Minitti M, Sharma SK, Sharma S, Siljeström S. Calibration of Raman Bandwidths on the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) Deep Ultraviolet Raman and Fluorescence Instrument Aboard the Perseverance Rover. APPLIED SPECTROSCOPY 2023:37028231210885. [PMID: 37964538 DOI: 10.1177/00037028231210885] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2023]
Abstract
In this work, we derive a simple method for calibrating Raman bandwidths for the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument onboard NASA's Perseverance rover. Raman bandwidths and shapes reported by an instrument contain contributions from both the intrinsic Raman band (IRB) and instrumental artifacts. To directly correlate bandwidth to sample properties and to compare bandwidths across instruments, the IRB width needs to be separated from instrumental effects. Here, we use the ubiquitous bandwidth calibration method of modeling the observed Raman bands as a convolution of a Lorentzian IRB and a Gaussian instrument slit function. Using calibration target data, we calculate that SHERLOC has a slit function width of 34.1 cm-1. With a measure of the instrument slit function, we can deconvolve the IRB from the observed band, providing the width of the Raman band unobscured by instrumental artifact. We present the correlation between observed Raman bandwidth and intrinsic Raman bandwidth in table form for the quick estimation of SHERLOC Raman intrinsic bandwidths. We discuss the limitations of using this model to calibrate Raman bandwidth and derive a quantitative method for calculating the errors associated with the calibration. We demonstrate the utility of this method of bandwidth calibration by examining the intrinsic bandwidths of SHERLOC sulfate spectra and by modeling the SHERLOC spectrum of olivine.
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Affiliation(s)
| | - Rohit Bhartia
- Photon Systems Incorporated, Covina, California, USA
| | - Kyle Uckert
- Jet Propulsion Laboratory, California Institution of Technology, Pasadena, California, USA
| | - Sanford A Asher
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Andrew D Czaja
- Department of Geology, University of Cincinnati, Cincinnati, Ohio, USA
| | | | - Kevin Hand
- Jet Propulsion Laboratory, California Institution of Technology, Pasadena, California, USA
| | | | | | | | - Shiv K Sharma
- Hawaii Institute of Geophysics and Planetology, University of Hawaii, Honolulu, Hawaii, USA
| | - Sunanda Sharma
- Jet Propulsion Laboratory, California Institution of Technology, Pasadena, California, USA
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3
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Razzell Hollis J, Sharma S, Abbey W, Bhartia R, Beegle L, Fries M, Hein JD, Monacelli B, Nordman AD. A Deep Ultraviolet Raman and Fluorescence Spectral Library of 51 Organic Compounds for the SHERLOC Instrument Onboard Mars 2020. ASTROBIOLOGY 2023; 23:1-23. [PMID: 36367974 PMCID: PMC9810352 DOI: 10.1089/ast.2022.0023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 08/01/2022] [Indexed: 06/16/2023]
Abstract
We report deep ultraviolet (DUV) Raman and Fluorescence spectra obtained on a SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals) analog instrument for 51 pure organic compounds, including 5 carboxylic acids, 10 polycyclic aromatic hydrocarbons, 24 amino acids, 6 nucleobases, and 6 different grades of macromolecular carbon from humic acid to graphite. Organic mixtures were not investigated. We discuss how the DUV fluorescence and Raman spectra exhibited by different organic compounds allow for detection, classification, and identification of organics by SHERLOC. We find that 1- and 2-ring aromatic compounds produce detectable fluorescence within SHERLOC's spectral range (250-355 nm), but fluorescence spectra are not unique enough to enable easy identification of particular compounds. However, both aromatic and aliphatic compounds can be identified by their Raman spectra, with the number of Raman peaks and their positions being highly specific to chemical structure, within SHERLOC's reported spectral uncertainty of ±5 cm-1. For compounds that are not in the Library, classification is possible by comparing the general number and position of dominant Raman peaks with trends for different kinds of organic compounds.
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Affiliation(s)
- Joseph Razzell Hollis
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
- Department of Life Sciences, The Natural History Museum, London, United Kingdom
| | - Sunanda Sharma
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | - William Abbey
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | | | - Luther Beegle
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | - Marc Fries
- NASA Johnson Space Center, Houston, Texas, USA
| | - Jeffrey D. Hein
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | - Brian Monacelli
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | - Austin D. Nordman
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
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4
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Scheller EL, Razzell Hollis J, Cardarelli EL, Steele A, Beegle LW, Bhartia R, Conrad P, Uckert K, Sharma S, Ehlmann BL, Abbey WJ, Asher SA, Benison KC, Berger EL, Beyssac O, Bleefeld BL, Bosak T, Brown AJ, Burton AS, Bykov SV, Cloutis E, Fairén AG, DeFlores L, Farley KA, Fey DM, Fornaro T, Fox AC, Fries M, Hickman-Lewis K, Hug WF, Huggett JE, Imbeah S, Jakubek RS, Kah LC, Kelemen P, Kennedy MR, Kizovski T, Lee C, Liu Y, Mandon L, McCubbin FM, Moore KR, Nixon BE, Núñez JI, Rodriguez Sanchez-Vahamonde C, Roppel RD, Schulte M, Sephton MA, Sharma SK, Siljeström S, Shkolyar S, Shuster DL, Simon JI, Smith RJ, Stack KM, Steadman K, Weiss BP, Werynski A, Williams AJ, Wiens RC, Williford KH, Winchell K, Wogsland B, Yanchilina A, Yingling R, Zorzano MP. Aqueous alteration processes in Jezero crater, Mars-implications for organic geochemistry. Science 2022; 378:1105-1110. [PMID: 36417498 DOI: 10.1126/science.abo5204] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The Perseverance rover landed in Jezero crater, Mars, in February 2021. We used the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument to perform deep-ultraviolet Raman and fluorescence spectroscopy of three rocks within the crater. We identify evidence for two distinct ancient aqueous environments at different times. Reactions with liquid water formed carbonates in an olivine-rich igneous rock. A sulfate-perchlorate mixture is present in the rocks, which probably formed by later modifications of the rocks by brine. Fluorescence signatures consistent with aromatic organic compounds occur throughout these rocks and are preserved in minerals related to both aqueous environments.
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Affiliation(s)
- Eva L Scheller
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA.,Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Joseph Razzell Hollis
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA.,The Natural History Museum, London, UK
| | - Emily L Cardarelli
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Andrew Steele
- Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, USA
| | - Luther W Beegle
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | | | - Pamela Conrad
- Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, USA
| | - Kyle Uckert
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Sunanda Sharma
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Bethany L Ehlmann
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA.,NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - William J Abbey
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Sanford A Asher
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, USA
| | - Kathleen C Benison
- Department of Geology and Geography, West Virginia University, Morgantown, WV, USA
| | - Eve L Berger
- Texas State University, San Marcos, TX, USA.,Jacobs Johnson Space Center Engineering, Technology and Science Contract, Houston, TX, USA.,NASA Johnson Space Center, Houston, TX, USA
| | - Olivier Beyssac
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Centre National de la Recherche Scientifique, Sorbonne Université, Muséum National d'Histoire Naturelle, 75005 Paris, France
| | | | - Tanja Bosak
- Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
| | | | | | - Sergei V Bykov
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, USA
| | - Ed Cloutis
- Geography, The University of Winnipeg, Winnipeg, MB, Canada
| | - Alberto G Fairén
- Centro de Astrobiología, Consejo Superior de Investigaciones Cientificas-Instituto Nacional de Tecnica Aeroespacial, Madrid, Spain.,Department of Astronomy, Cornell University, Ithaca, NY, USA
| | - Lauren DeFlores
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Kenneth A Farley
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
| | | | - Teresa Fornaro
- Astrophysical Observatory of Arcetri, Istituto Nazionale di Astrofisica, Florence, Italy
| | | | - Marc Fries
- NASA Johnson Space Center, Houston, TX, USA
| | - Keyron Hickman-Lewis
- Department of Earth Sciences, The Natural History Museum, London, UK.,Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università di Bologna, Bologna, Italy
| | | | | | | | | | - Linda C Kah
- Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN, USA
| | - Peter Kelemen
- Lamont Doherty Earth Observatory, Columbia University, Palisades, NY, USA
| | | | - Tanya Kizovski
- Department of Earth Sciences, Brock University, St. Catharines, ON L2S 3A1, Canada
| | - Carina Lee
- Lunar and Planetary Institute, Universities Space Research Association, Houston, TX, USA
| | - Yang Liu
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Lucia Mandon
- Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique, Observatoire de Paris, Centre National de la Recherche Scientifique, Sorbonne Université, Université Paris Diderot, 92195 Meudon, France
| | | | - Kelsey R Moore
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | | | - Jorge I Núñez
- Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
| | | | - Ryan D Roppel
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, USA
| | - Mitchell Schulte
- Mars Exploration Program, NASA Headquarters, Washington, DC, USA
| | - Mark A Sephton
- Earth Science and Engineering, South Kensington Campus, Imperial College London, SW7 2AZ London, UK
| | - Shiv K Sharma
- Hawaii Institute of Geophysics and Planetology, University of Hawaii at Manoa, Honolulu, HI, USA
| | | | - Svetlana Shkolyar
- Department of Astronomy, University of Maryland, College Park, MD, USA.,NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - David L Shuster
- Earth and Planetary Science, University of California Berkeley, Berkeley, CA, USA
| | | | - Rebecca J Smith
- Department of Geosciences, Stony Brook University, Stony Brook, NY, USA
| | - Kathryn M Stack
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Kim Steadman
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | - Benjamin P Weiss
- Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
| | | | - Amy J Williams
- Department of Geological Sciences, University of Florida, Gainesville, FL, USA
| | - Roger C Wiens
- Los Alamos National Laboratory, Los Alamos, NM, USA.,Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN, USA
| | - Kenneth H Williford
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA.,Blue Marble Space Institute of Science, Seattle, WA, USA
| | | | - Brittan Wogsland
- Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN, USA
| | | | | | - Maria-Paz Zorzano
- Centro de Astrobiología, Consejo Superior de Investigaciones Cientificas-Instituto Nacional de Tecnica Aeroespacial, Madrid, Spain
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5
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Osterhout JT, Schopf JW, Kudryavtsev AB, Czaja AD, Williford KH. Deep-UV Raman Spectroscopy of Carbonaceous Precambrian Microfossils: Insights into the Search for Past Life on Mars. ASTROBIOLOGY 2022; 22:1239-1254. [PMID: 36194869 DOI: 10.1089/ast.2021.0135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The current strategy for detecting evidence of ancient life on Mars-a primary goal of NASA's ongoing Mars 2020 mission-is based largely on knowledge of Precambrian life and of its preservation in Earth's early rock record. The fossil record of primitive microorganisms consists mainly of stromatolites and other microbially influenced sedimentary structures, which occasionally preserve microfossils or other geochemical traces of life. Raman spectroscopy is an invaluable tool for identifying such signs of life and is routinely performed on Precambrian microfossils to help establish their organic composition, degree of thermal maturity, and biogenicity. The Mars 2020 rover, Perseverance, is equipped with a deep-ultraviolet (UV) Raman spectrometer as part of the SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals) instrument, which will be used in part to characterize the preservation of organic matter in the ancient sedimentary rocks of Jezero crater and therein search for possible biosignatures. To determine the deep-UV Raman spectra characteristic of ancient microbial fossils, this study analyzes individual microfossils from 14 Precambrian cherts using deep-UV (244 nm) Raman spectroscopy. Spectra obtained were measured and calibrated relative to a graphitic standard and categorized according to the morphology and depositional environment of the fossil analyzed and its Raman-indicated thermal maturity. All acquired spectra of the fossil kerogens include a considerably Raman-enhanced and prominent first-order Raman G-band (∼1600 cm-1), whereas its commonly associated D-band (∼1350 cm-1) is restricted to specimens of lower thermal maturity (below greenschist facies) that thus have the less altered biosignature indicative of relatively well-preserved organic matter. If comparably preserved, similar characteristics would be expected to be exhibited by microfossils or ancient organic matter in rock samples collected and cached on Mars in preparation for future sample return to Earth.
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Affiliation(s)
- Jeffrey T Osterhout
- Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, California, USA
- Center for the Study of Evolution and the Origin of Life, University of California, Los Angeles, California, USA
| | - J William Schopf
- Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, California, USA
- Center for the Study of Evolution and the Origin of Life, University of California, Los Angeles, California, USA
| | - Anatoliy B Kudryavtsev
- Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, California, USA
- Center for the Study of Evolution and the Origin of Life, University of California, Los Angeles, California, USA
| | - Andrew D Czaja
- Department of Geology, University of Cincinnati, Cincinnati, Ohio, USA
| | - Kenneth H Williford
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
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6
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Demaret L, Hutchinson IB, Eppe G, Malherbe C. Quantitative analysis of binary and ternary organo-mineral solid dispersions by Raman spectroscopy for robotic planetary exploration missions on Mars. Analyst 2021; 146:7306-7319. [PMID: 34755725 DOI: 10.1039/d1an01514a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The Mars 2020 and ExoMars 2022, rover-based missions are specifically dedicated to the search for evidence of life and will both utilise Raman spectrometers on the surface of Mars. Raman spectroscopy is indeed a valuable analytical technique for planetary exploration that enables in situ characterisation of rocks and soils collected directly from the surface or retrieved as cores and subsequently crushed when extracted from the subsurface with a drill. On Mars, the miniaturised spectrometers will interrogate ancient geological deposits, in order to try and identify hydrated or aqueously altered minerals and organic matter to assess the habitability of Mars. While the identification of relevant hydrous minerals and organic components is the primary analytical objective of the missions, quantifying their abundances would be of particular significance for interpreting past geological conditions (e.g. formation or alteration processes) and for ascertaining the putative presence of biosignatures. Therefore, we have developed quantitative models that enable the quantification of both mineral proportions from crushed mixtures of geological components and spiked mixtures containing organic analytes dispersed in mineral matrices. Based on data normalisation with appropriate standards (internal and external), we demonstrate that robust quantitative models can be (1) applied for solid dispersions of various complexities relevant to planetary exploration; and (2) applied to different Raman set-ups, including an instrument representative of the ExoMars Raman Laser Spectrometer. With important Raman-active minerals (calcite, gypsum, baryte, quartz), we demonstrate that using a correction factor Fϕ2/ϕ1, based on the ratio of apparent Raman scattering coefficients, the relative proportion of minerals in binary mixtures can be accurately determined. Regarding the organics, evaluated in clay-rich sediments (Fe-smectite) and crushed rocks of coarse-grained fraction (>100μm), we establish calibration curves in the concentration range 2-20 wt% for non-resonant compounds (L-cysteine, phthalic acid, adenine) and even lower (<1 wt%) for pre-resonant anthracene. Despite large levels of heterogeneity, the Raman analyses of these solid dispersions verify that quantitative Raman analyses can be performed in the context of robotic exploration studies.
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Affiliation(s)
- L Demaret
- Mass Spectrometry Laboratory, MolSys Research Unit, University of Liège, Liège, Belgium. .,Early Life Traces & Evolution Laboratory, UR Astrobiology, University of Liège, Liège, Belgium
| | - I B Hutchinson
- Department of Physics and Astronomy, University of Leicester, Leicester, UK
| | - G Eppe
- Mass Spectrometry Laboratory, MolSys Research Unit, University of Liège, Liège, Belgium.
| | - C Malherbe
- Mass Spectrometry Laboratory, MolSys Research Unit, University of Liège, Liège, Belgium. .,Early Life Traces & Evolution Laboratory, UR Astrobiology, University of Liège, Liège, Belgium.,Department of Physics and Astronomy, University of Leicester, Leicester, UK
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7
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Uckert K, Bhartia R, Beegle LW, Monacelli B, Asher SA, Burton AS, Bykov SV, Davis K, Fries MD, Jakubek RS, Hollis JR, Roppel RD, Wu YH. Calibration of the SHERLOC Deep Ultraviolet Fluorescence-Raman Spectrometer on the Perseverance Rover. APPLIED SPECTROSCOPY 2021; 75:763-773. [PMID: 33876994 DOI: 10.1177/00037028211013368] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We describe the wavelength calibration of the spectrometer for the scanning of habitable environments with Raman and luminescence for organics and chemicals (SHERLOC) instrument onboard NASA's Perseverance Rover. SHERLOC utilizes deep ultraviolet Raman and fluorescence (DUV R/F) spectroscopy to enable analysis of samples from the Martian surface. SHERLOC employs a 248.6 nm deep ultraviolet laser to generate Raman-scattered photons and native fluorescence emission photons from near-surface material to detect and classify chemical and mineralogical compositions. The collected photons are focused on a charge-coupled device and the data are returned to Earth for analysis. The compact DUV R/F spectrometer has a spectral range from 249.9 nm to 353.6 nm (∼200 cm-1 to 12 000 cm-1) (with a spectral resolution of 0.296 nm (∼40 cm-1)). The compact spectrometer uses a custom design to project a high-resolution Raman spectrum and a low-resolution fluorescence spectrum on a single charge-coupled device. The natural spectral separation enabled by deep ultraviolet excitation enables wavelength separation of the Raman/fluorescence spectra. The SHERLOC spectrometer was designed to optimize the resolution of the Raman spectral region and the wavelength range of the fluorescence region. The resulting illumination on the charge-coupled device is curved, requiring a segmented, nonlinear wavelength calibration in order to understand the mineralogy and chemistry of Martian materials.
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Affiliation(s)
- Kyle Uckert
- Jet Propulsion Laboratory California Institution of Technology, Pasadena, CA, USA
| | | | - Luther W Beegle
- Jet Propulsion Laboratory California Institution of Technology, Pasadena, CA, USA
| | - Brian Monacelli
- Jet Propulsion Laboratory California Institution of Technology, Pasadena, CA, USA
| | - Sanford A Asher
- University of Pittsburgh Chemistry Department, Pittsburgh, PA, USA
| | | | - Sergei V Bykov
- University of Pittsburgh Chemistry Department, Pittsburgh, PA, USA
| | | | - Marc D Fries
- 43834NASA Johnson Space Center, Houston, TX, USA
| | | | | | - Ryan D Roppel
- University of Pittsburgh Chemistry Department, Pittsburgh, PA, USA
| | - Yen-Hung Wu
- Jet Propulsion Laboratory California Institution of Technology, Pasadena, CA, USA
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8
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Razzell Hollis J, Fornaro T, Rapin W, Wade J, Vicente-Retortillo Á, Steele A, Bhartia R, Beegle LW. Detection and Degradation of Adenosine Monophosphate in Perchlorate-Spiked Martian Regolith Analog, by Deep-Ultraviolet Spectroscopy. ASTROBIOLOGY 2021; 21:511-525. [PMID: 33493410 DOI: 10.1089/ast.2020.2362] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The search for organic biosignatures on Mars will depend on finding material protected from the destructive ambient radiation. Solar ultraviolet can induce photochemical degradation of organic compounds, but certain clays have been shown to preserve organic material. We examine how the SHERLOC instrument on the upcoming Mars 2020 mission will use deep-ultraviolet (UV) (248.6 nm) Raman and fluorescence spectroscopy to detect a plausible biosignature of adenosine 5'-monophosphate (AMP) adsorbed onto Ca-montmorillonite clay. We found that the spectral signature of AMP is not altered by adsorption in the clay matrix but does change with prolonged exposure to the UV laser over dosages equivalent to 0.2-6 sols of ambient martian UV. For pure AMP, UV exposure leads to breaking of the aromatic adenine unit, but in the presence of clay the degradation is limited to minor alteration with new Raman peaks and increased fluorescence consistent with formation of 2-hydroxyadenosine, while 1 wt % Mg perchlorate increases the rate of degradation. Our results confirm that clays are effective preservers of organic material and should be considered high-value targets, but that pristine biosignatures may be altered within 1 sol of martian UV exposure, with implications for Mars 2020 science operations and sample caching.
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Affiliation(s)
- Joseph Razzell Hollis
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | - Teresa Fornaro
- Carnegie Institution for Science, Washington, District of Columbia, USA
- INAF-Astrophysical Observatory of Arcetri, Florence, Italy
| | - William Rapin
- Department of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
- Sorbonne Université, IMPMC, CNRS, Paris, France
| | - Jessica Wade
- Department of Physics, Imperial College London, London, United Kingdom
| | - Álvaro Vicente-Retortillo
- Department of Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, Michigan, USA
- Centro de Astrobiología (CSIC-INTA), Torrejón de Ardoz, Spain
| | - Andrew Steele
- Carnegie Institution for Science, Washington, District of Columbia, USA
| | | | - Luther W Beegle
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
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