1
|
Sephton MA, Freeman K, Hays L, Thiessen F, Benison K, Carrier B, Dworkin JP, Glamoclija M, Gough R, Onofri S, Peterson R, Quinn R, Russell S, Stüeken EE, Velbel M, Zolotov M. Thresholds of Temperature and Time for Mars Sample Return: Final Report of the Mars Sample Return Temperature-Time Tiger Team. ASTROBIOLOGY 2024; 24:443-488. [PMID: 38768433 DOI: 10.1089/ast.2023.0098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
Affiliation(s)
- Mark A Sephton
- Imperial College London, Earth Science and Engineering, South Kensington Campus, London, UK
| | - Kate Freeman
- The Pennsylvania State University, Geosciences, University Park, Pennsylvania, USA
| | - Lindsay Hays
- NASA Headquarters, Mars Sample Return Program, Washington, DC, USA
| | - Fiona Thiessen
- European Space Research and Technology Centre, Noordwijk, South Holland, Netherlands
| | - Kathleen Benison
- West Virginia University, Department of Geology and Geography, Morgantown, West Virginia, USA
| | - Brandi Carrier
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | - Jason P Dworkin
- NASA Goddard Space Flight Center, Astrochemistry, Greenbelt, Maryland, USA
| | - Mihaela Glamoclija
- Rutgers University Newark College of Arts and Sciences, Earth and Environmental Sciences, Newark, New Jersey, USA
| | - Raina Gough
- University of Colorado, Department of Chemistry and Biochemistry, Boulder, Colorado, USA
| | - Silvano Onofri
- University of Tuscia, Department of Ecological and Biological Sciences, Largo dell'Università snc Viterbo, Italy
| | | | - Richard Quinn
- NASA Ames Research Center, Moffett Field, California, USA
| | - Sara Russell
- Natural History Museum, Department of Earth Sciences, London, UK
| | - Eva E Stüeken
- University of St Andrews, School of Earth and Environmental Sciences, St Andrews, Fife, UK
| | - Michael Velbel
- Michigan State University, Earth and Environmental Sciences, East Lansing, Michigan, USA
- Smithsonian Institution, Department of Mineral Sciences, National Museum of Natural History, Washington, DC, USA
| | - Mikhail Zolotov
- Arizona State University, School of Earth and Space Exploration, Tempe, Arizona, USA
| |
Collapse
|
2
|
Pital A, Bromley M, Dorn M, Kim J, Stockton A. Analysis of Early Iron Sulfide, Carbonate, and Phosphate Mineral Analogues Produced by Flow-Driven Precipitation in a Microchannel. ASTROBIOLOGY 2024; 24:138-150. [PMID: 38393829 DOI: 10.1089/ast.2021.0088] [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: 02/25/2024]
Abstract
Most of the chemical and physical interactions of interest to the astrobiology community are influenced by the mineralogy of the systems under consideration. Often, this mineralogy occurs in sediment or sediment-like aqueous microenvironments in which the early minerals differ dramatically from the mature version that results from a long diagenesis, which are tied to complex interactions of pH, redox state, concentration, and temperature. This interconnectedness is difficult to reproduce in a laboratory setting yet is essential to understanding how the physical and chemical demands of living systems alter and are altered by their geological context. We present a facile means for producing precipitated mineral analogues within a microchannel and demonstrate its analytical efficacy through instrumental and modeling techniques. We show that amorphous, early-stage analogues of iron sulfide, iron carbonate, and iron phosphate can be formed at the boundary between flowing solutions, modeled on the microscale, and analyzed by standard instrumental techniques such as scanning electron microscopy/energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy.
Collapse
Affiliation(s)
- Aaron Pital
- School of Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Megan Bromley
- School of Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Max Dorn
- School of Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Jungkyu Kim
- Department of Mechanical Engineering, University of Utah, Salt Lake City, Utah, USA
| | - Amanda Stockton
- School of Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
| |
Collapse
|
3
|
Tan JSW, Salter TL, Watson JS, Waite JH, Sephton MA. Organic Biosignature Degradation in Hydrothermal and Serpentinizing Environments: Implications for Life Detection on Icy Moons and Mars. ASTROBIOLOGY 2023; 23:1045-1055. [PMID: 37506324 DOI: 10.1089/ast.2022.0144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/30/2023]
Abstract
Evidence of liquid water is a primary indicator of habitability on the icy moons in our outer solar system as well as on terrestrial planets such as Mars. If liquid water-containing environments host life, some of its organic remains can be fossilized and preserved as organic biosignatures. However, inorganic materials may also be present and water-assisted organic-inorganic reactions can transform the organic architecture of biological remains. Our understanding of the fate of these organic remains can be assisted by experimental simulations that monitor the chemical changes that occur in microbial organic matter due to the presence of water and minerals. We performed hydrothermal experiments at temperatures between 100°C and 300°C involving lipid-rich microbes and natural serpentinite mineral mixtures generated by the subaqueous hydrothermal alteration of ultramafic rock. The products reveal what the signals of life may look like when subjected to water-organic-inorganic reactions. Straight- and branched-chain lipids in unaltered samples are joined by cyclization and aromatization products in hydrothermally altered samples. Hydrothermal reactions produce distinct products that are not present in the starting materials, including small, single-ring, heteroatomic, and aromatic compounds such as indoles and phenols. Hydrothermal reactions in the presence of serpentinite minerals lead to significant reduction of these organic structures and their replacement by diketopiperazines (DKPs) and dihydropyrazines (DHPs), which may be compounds that are distinct to organic-inorganic reactions. Given that the precursors of DKPs and DHPs are normally lost during early diagenesis, the presence of these compounds can be an indicator of coexisting recent life and hydrothermal processing in the presence of minerals. However, laboratory experiments reveal that the formation and preservation of these compounds can only occur within a distinct temperature window. Our findings are relevant to life detection missions that aim to access hydrothermal and serpentinizing environments in the subsurfaces of icy moons and Mars.
Collapse
Affiliation(s)
- Jonathan S W Tan
- Impacts and Astromaterials Research Centre, Department of Earth Science and Engineering, Imperial College London, London, United Kingdom
| | - Tara L Salter
- Impacts and Astromaterials Research Centre, Department of Earth Science and Engineering, Imperial College London, London, United Kingdom
| | - Jonathan S Watson
- Impacts and Astromaterials Research Centre, Department of Earth Science and Engineering, Imperial College London, London, United Kingdom
| | - J Hunter Waite
- Space Science and Engineering Division, Southwest Research Institute, San Antonio, Texas, USA
| | - Mark A Sephton
- Impacts and Astromaterials Research Centre, Department of Earth Science and Engineering, Imperial College London, London, United Kingdom
| |
Collapse
|
4
|
Finkel PL, Carrizo D, Parro V, Sánchez-García L. An Overview of Lipid Biomarkers in Terrestrial Extreme Environments with Relevance for Mars Exploration. ASTROBIOLOGY 2023; 23:563-604. [PMID: 36880883 PMCID: PMC10150655 DOI: 10.1089/ast.2022.0083] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Lipid molecules are organic compounds, insoluble in water, and based on carbon-carbon chains that form an integral part of biological cell membranes. As such, lipids are ubiquitous in life on Earth, which is why they are considered useful biomarkers for life detection in terrestrial environments. These molecules display effective membrane-forming properties even under geochemically hostile conditions that challenge most of microbial life, which grants lipids a universal biomarker character suitable for life detection beyond Earth, where a putative biological membrane would also be required. What discriminates lipids from nucleic acids or proteins is their capacity to retain diagnostic information about their biological source in their recalcitrant hydrocarbon skeletons for thousands of millions of years, which is indispensable in the field of astrobiology given the time span that the geological ages of planetary bodies encompass. This work gathers studies that have employed lipid biomarker approaches for paleoenvironmental surveys and life detection purposes in terrestrial environments with extreme conditions: hydrothermal, hyperarid, hypersaline, and highly acidic, among others; all of which are analogous to current or past conditions on Mars. Although some of the compounds discussed in this review may be abiotically synthesized, we focus on those with a biological origin, namely lipid biomarkers. Therefore, along with appropriate complementary techniques such as bulk and compound-specific stable carbon isotope analysis, this work recapitulates and reevaluates the potential of lipid biomarkers as an additional, powerful tool to interrogate whether there is life on Mars, or if there ever was.
Collapse
Affiliation(s)
- Pablo L Finkel
- Centro de Astrobiología (CAB), CSIC-INTA, Madrid, Spain
- Department of Physics and Mathematics and Department of Automatics, University of Alcalá, Madrid, Spain
| | | | - Victor Parro
- Centro de Astrobiología (CAB), CSIC-INTA, Madrid, Spain
| | | |
Collapse
|
5
|
Salter TL, Watson JS, Waite JH, Sephton MA. Hydrothermal Processing of Microorganisms: Mass Spectral Signals of Degraded Biosignatures for Life Detection on Icy Moons. ACS EARTH & SPACE CHEMISTRY 2022; 6:2508-2518. [PMID: 36303715 PMCID: PMC9589906 DOI: 10.1021/acsearthspacechem.2c00213] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 08/30/2022] [Accepted: 09/12/2022] [Indexed: 06/16/2023]
Abstract
Life detection missions to the outer solar system are concentrating on the icy moons of Jupiter and Saturn and their inferred subsurface oceans. Access to evidence of habitability, and possibly even life, is facilitated by the ejection of subsurface material in plumes and outgassing fissures. Orbiting spacecraft can intersect the plume material or detect past sputtered remnants of outgassed products and analyze the contents using instruments such as mass spectrometers. Hydrothermalism has been proposed for the subsurface environments of icy moons, and the organic remains of any associated life would be expected to suffer some degradation through hydrothermalism, radiolysis, or spacecraft flyby impact fragmentation. Hydrothermalism is treated here for the first time in the context of the Europa Clipper mission. To assess the influence of hydrothermalism on the ability of orbiting mass spectrometers to detect degrading signals of life, we have subjected Earth microorganisms to laboratory hydrothermal processing. The processed microorganism samples were then analyzed using gas chromatography-mass spectrometry (GC-MS), and mass spectra were generated. Certain compound classes, such as carbohydrates and proteins, are significantly altered by hydrothermal processing, resulting in small one-ring and two-ring aromatic compounds such as indoles and phenols. However, lipid fragments, such as fatty acids, retain their fidelity, and their provenance is easily recognized as biological in origin. Our data indicate that mass spectrometry measurements in the plumes of icy moons, using instruments such as the MAss Spectrometer for Planetary Exploration (MASPEX) onboard the upcoming Europa Clipper mission, can reveal the presence of life even after significant degradation by hydrothermal processing has taken place.
Collapse
Affiliation(s)
- Tara L. Salter
- Impacts
and Astromaterials Research Centre, Department of Earth Science and
Engineering, Imperial College London, London SW7 2AZ, United Kingdom
| | - Jonathan S. Watson
- Impacts
and Astromaterials Research Centre, Department of Earth Science and
Engineering, Imperial College London, London SW7 2AZ, United Kingdom
| | - J. Hunter Waite
- Space
Science and Engineering Division, Southwest
Research Institute, San Antonio, Texas 78238, United States
| | - Mark A. Sephton
- Impacts
and Astromaterials Research Centre, Department of Earth Science and
Engineering, Imperial College London, London SW7 2AZ, United Kingdom
| |
Collapse
|
6
|
Demaret L, Hutchinson IB, Ingley R, Edwards HGM, Fagel N, Compere P, Javaux EJ, Eppe G, Malherbe C. Fe-Rich Fossil Vents as Mars Analog Samples: Identification of Extinct Chimneys in Miocene Marine Sediments Using Raman Spectroscopy, X-Ray Diffraction, and Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy. ASTROBIOLOGY 2022; 22:1081-1098. [PMID: 35704291 DOI: 10.1089/ast.2021.0128] [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: 06/15/2023]
Abstract
On Earth, the circulation of Fe-rich fluids in hydrothermal environments leads to characteristic iron mineral deposits, reflecting the pH and redox chemical conditions of the hydrothermal system, and is often associated with chemotroph microorganisms capable of deriving energy from chemical gradients. On Mars, iron-rich hydrothermal sites are considered to be potentially important astrobiological targets for searching evidence of life during exploration missions, such as the Mars 2020 and the ExoMars 2022 missions. In this study, an extinct hydrothermal chimney from the Jaroso hydrothermal system (SE Spain), considered an interesting geodynamic and mineralogical terrestrial analog for Mars, was analyzed using Raman spectroscopy, X-ray diffraction, and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. The sample consists of a fossil vent in a Miocene shallow-marine sedimentary deposit composed of a marl substrate, an iron-rich chimney pipe, and a central space filled with backfilling deposits and vent condensates. The iron crust is particularly striking due to the combined presence of molecular and morphological indications of a microbial colonization, including mineral microstructures (e.g., stalks, filaments), iron oxyhydroxide phases (altered goethite, ferrihydrite), and organic signatures (carotenoids, organopolymers). The clear identification of pigments by resonance Raman spectroscopy and the preservation of organics in association with iron oxyhydroxides by Raman microimaging demonstrate that the iron crust was indeed colonized by microbial communities. These analyses confirm that Raman spectroscopy is a powerful tool for documenting the habitability of such historical hydrothermal environments. Finally, based on the results obtained, we propose that the ancient iron-rich hydrothermal pipes should be recognized as singular terrestrial Mars analog specimens to support the preparatory work for robotic in situ exploration missions to Mars, as well as during the subsequent interpretation of data returned by those missions.
Collapse
Affiliation(s)
- Lucas Demaret
- Mass Spectrometry Laboratory, MolSys Research Unit, University of Liege, Liege, Belgium
- Early Life Traces & Evolution-Astrobiology, UR Astrobiology, University of Liege, Liege, Belgium
| | - Ian B Hutchinson
- Department of Physics and Astronomy, University of Leicester, Leicester, United Kingdom
| | - Richard Ingley
- Department of Physics and Astronomy, University of Leicester, Leicester, United Kingdom
| | - Howell G M Edwards
- Department of Physics and Astronomy, University of Leicester, Leicester, United Kingdom
| | - Nathalie Fagel
- Laboratory Argiles, Géochimie et Environnements Sédimentaires, University of Liege, Liege, Belgium
| | - Philippe Compere
- Laboratory of Functional and Evolutionary Morphology, UR FOCUS, and Centre for Applied Research and Education in Microscopy (CAREM), University of Liege, Liege, Belgium
| | - Emmanuelle J Javaux
- Early Life Traces & Evolution-Astrobiology, UR Astrobiology, University of Liege, Liege, Belgium
| | - Gauthier Eppe
- Mass Spectrometry Laboratory, MolSys Research Unit, University of Liege, Liege, Belgium
| | - Cédric Malherbe
- Mass Spectrometry Laboratory, MolSys Research Unit, University of Liege, Liege, Belgium
- Early Life Traces & Evolution-Astrobiology, UR Astrobiology, University of Liege, Liege, Belgium
- Department of Physics and Astronomy, University of Leicester, Leicester, United Kingdom
| |
Collapse
|
7
|
Carr CE. Resolving the History of Life on Earth by Seeking Life As We Know It on Mars. ASTROBIOLOGY 2022; 22:880-888. [PMID: 35467949 PMCID: PMC9298492 DOI: 10.1089/ast.2021.0043] [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: 05/08/2023]
Abstract
An origin of Earth life on Mars would resolve significant inconsistencies between the inferred history of life and Earth's geologic history. Life as we know it utilizes amino acids, nucleic acids, and lipids for the metabolic, informational, and compartment-forming subsystems of a cell. Such building blocks may have formed simultaneously from cyanosulfidic chemical precursors in a planetary surface scenario involving ultraviolet light, wet-dry cycling, and volcanism. On the inferred water world of early Earth, such an origin would have been limited to volcanic island hotspots. A cyanosulfidic origin of life could have taken place on Mars via photoredox chemistry, facilitated by orders-of-magnitude more sub-aerial crust than early Earth, and an earlier transition to oxidative conditions that could have been involved in final fixation of the genetic code. Meteoritic bombardment may have generated transient habitable environments and ejected and transferred life to Earth. Ongoing and future missions to Mars offer an unprecedented opportunity to confirm or refute evidence consistent with a cyanosulfidic origin of life on Mars, search for evidence of ancient life, and constrain the evolution of Mars' oxidation state over time. We should seek to prove or refute a martian origin for life on Earth alongside other possibilities.
Collapse
Affiliation(s)
- Christopher E. Carr
- Daniel Guggenheim School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
- Address correspondence to: Christopher E. Carr, ESM Building, Room G10, 620 Cherry St NW, Atlanta, GA 30332, USA
| |
Collapse
|
8
|
Royle SH, Salter TL, Watson JS, Sephton MA. Mineral Matrix Effects on Pyrolysis Products of Kerogens Infer Difficulties in Determining Biological Provenance of Macromolecular Organic Matter at Mars. ASTROBIOLOGY 2022; 22:520-540. [PMID: 35171040 DOI: 10.1089/ast.2021.0074] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Ancient martian organic matter is likely to take the form of kerogen-like recalcitrant macromolecular organic matter (MOM), existing in close association with reactive mineral surfaces, especially iron oxides. Detecting and identifying a biological origin for martian MOM will therefore be of utmost importance for life-detection efforts at Mars. We show that Type I and Type IV kerogens provide effective analogues for putative martian MOM of biological and abiological (meteoric) provenances, respectively. We analyze the pyrolytic breakdown products when these kerogens are mixed with mineral matrices highly relevant for the search for life on Mars. We demonstrate that, using traditional thermal techniques as generally used by the Sample Analysis at Mars and Mars Organic Molecule Analyser instruments, even the breakdown products of highly recalcitrant MOM are transformed during analysis in the presence of reactive mineral surfaces, particularly iron. Analytical transformation reduces the diagnostic ability of this technique, as detected transformation products of both biological and abiological MOM may be identical (low molecular weight gas phases and benzene) and indistinguishable. The severity of transformational effects increased through calcite < kaolinite < hematite < nontronite < magnetite < goethite. Due to their representation of various habitable aqueous environments and the preservation potential of organic matter by iron, it is not advisable to completely avoid iron-rich strata. We conclude that hematite-rich localities, with evidence of extensive aqueous alteration of originally reducing phases, such as the Vera Rubin Ridge, may be relatively promising targets for identifying martian biologically sourced MOM.
Collapse
Affiliation(s)
- Samuel H Royle
- Department of Earth Science and Engineering, Imperial College London, London, UK
| | - Tara L Salter
- Department of Earth Science and Engineering, Imperial College London, London, UK
| | - Jonathan S Watson
- Department of Earth Science and Engineering, Imperial College London, London, UK
| | - Mark A Sephton
- Department of Earth Science and Engineering, Imperial College London, London, UK
| |
Collapse
|
9
|
Vasavada AR. Mission Overview and Scientific Contributions from the Mars Science Laboratory Curiosity Rover After Eight Years of Surface Operations. SPACE SCIENCE REVIEWS 2022; 218:14. [PMID: 35399614 PMCID: PMC8981195 DOI: 10.1007/s11214-022-00882-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Accepted: 03/21/2022] [Indexed: 06/14/2023]
Abstract
UNLABELLED NASA's Mars Science Laboratory mission, with its Curiosity rover, has been exploring Gale crater (5.4° S, 137.8° E) since 2012 with the goal of assessing the potential of Mars to support life. The mission has compiled compelling evidence that the crater basin accumulated sediment transported by marginal rivers into lakes that likely persisted for millions of years approximately 3.6 Ga ago in the early Hesperian. Geochemical and mineralogical assessments indicate that environmental conditions within this timeframe would have been suitable for sustaining life, if it ever were present. Fluids simultaneously circulated in the subsurface and likely existed through the dry phases of lake bed exposure and aeolian deposition, conceivably creating a continuously habitable subsurface environment that persisted to less than 3 Ga in the early Amazonian. A diversity of organic molecules has been preserved, though degraded, with evidence for more complex precursors. Solid samples show highly variable isotopic abundances of sulfur, chlorine, and carbon. In situ studies of modern wind-driven sediment transport and multiple large and active aeolian deposits have led to advances in understanding bedform development and the initiation of saltation. Investigation of the modern atmosphere and environment has improved constraints on the timing and magnitude of atmospheric loss, revealed the presence of methane and the crater's influence on local meteorology, and provided measurements of high-energy radiation at Mars' surface in preparation for future crewed missions. Rover systems and science instruments remain capable of addressing all key scientific objectives. Emphases on advance planning, flexibility, operations support work, and team culture have allowed the mission team to maintain a high level of productivity in spite of declining rover power and funding. SUPPLEMENTARY INFORMATION The online version contains supplementary material available at 10.1007/s11214-022-00882-7.
Collapse
Affiliation(s)
- Ashwin R. Vasavada
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA USA
| |
Collapse
|
10
|
Liu D, Kounaves SP. Degradation of Amino Acids on Mars by UV Irradiation in the Presence of Chloride and Oxychlorine Salts. ASTROBIOLOGY 2021; 21:793-801. [PMID: 33787313 DOI: 10.1089/ast.2020.2328] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The degradation of glycine (Gly), proline (Pro), and tryptophan (Trp) was studied under simulated Mars conditions during UV-driven production of oxychlorines and compared under Mars ambient and humid conditions, as films, and with addition of sodium chloride (NaCl), sodium chlorate (NaClO3), and sodium perchlorate (NaClO4) salts. It was shown that glycine sustained no significant destruction in either of the non-salt samples under Mars ambient or humid conditions. However, its degradation increased in the presence of any of the three salts and under both conditions though more under humid conditions. Proline degradation followed the order No Salt > NaCl > NaClO3 > NaClO4 under Mars ambient conditions but the reverse order under Mars humid conditions. A mechanism is proposed to explain how water and silica participate in these degradation reactions and how it is strongly influenced by the identity of the salt and its ability to promote deliquescence. No difference was observed for tryptophan between Mars ambient and humid conditions, or for the different salts, suggesting its degradation mechanism is different compared to glycine and proline. The results reported here will help to better understand the survival of amino acids in the presence of oxychlorines and UV on Mars and thus provide new insights for the detection of organic compounds on future Mars missions.
Collapse
Affiliation(s)
- Dongyu Liu
- Department of Chemistry, Tufts University, Medford, Massachusetts, USA
| | - Samuel P Kounaves
- Department of Chemistry, Tufts University, Medford, Massachusetts, USA
| |
Collapse
|
11
|
Tan JSW, Sephton MA. Quantifying Preservation Potential: Lipid Degradation in a Mars-Analog Circumneutral Iron Deposit. ASTROBIOLOGY 2021; 21:638-654. [PMID: 33835833 DOI: 10.1089/ast.2020.2344] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Comparisons between the preservation potential of Mars-analog environments have historically been qualitative rather than quantitative. Recently, however, laboratory-based artificial maturation combined with kinetic modeling techniques have emerged as a potential means by which the preservation potential of solvent-soluble organic matter can be quantified in various Mars-analog environments. These methods consider how elevated temperatures, pressures, and organic-inorganic interactions influence the degradation of organic biomarkers post-burial. We used these techniques to investigate the preservation potential of deposits from a circumneutral iron-rich groundwater system. These deposits are composed of ferrihydrite (Fe5HO8 · 4H2O), an amorphous iron hydroxide mineral that is a common constituent of rocks found in ancient lacustrine environments on Mars, such as those observed in Gale Crater. Both natural and synthetic ferrihydrite samples were subjected to hydrous pyrolysis to observe the effects of long-term burial on the mineralogy and organic content of the samples. Our experiments revealed that organic-inorganic interactions in the samples are dominated by the transformation of iron minerals. As amorphous ferrihydrite transforms into more crystalline species, the decrease in surface area results in the desorption of organic matter, potentially rendering them more susceptible to degradation. We also find that circumneutral iron-rich deposits provide unfavorable conditions for the preservation of solvent-soluble organic matter. Quantitative comparisons between preservation potentials as calculated when using kinetic parameters show that circumneutral iron-rich deposits are ∼25 times less likely to preserve solvent-soluble organic matter compared with acidic, iron-rich environments. Our results suggest that circumneutral iron-rich deposits should be deprioritized in favor of acidic iron- and sulfur-rich deposits when searching for evidence of life with solvent extraction techniques.
Collapse
Affiliation(s)
- Jonathan S W Tan
- Department of Earth Science and Engineering, Impacts and Astromaterials Research Centre, Imperial College London, London, United Kingdom
| | - Mark A Sephton
- Department of Earth Science and Engineering, Impacts and Astromaterials Research Centre, Imperial College London, London, United Kingdom
| |
Collapse
|
12
|
Tan JS, Royle SH, Sephton MA. Artificial Maturation of Iron- and Sulfur-Rich Mars Analogues: Implications for the Diagenetic Stability of Biopolymers and Their Detection with Pyrolysis-Gas Chromatography-Mass Spectrometry. ASTROBIOLOGY 2021; 21:199-218. [PMID: 33226839 PMCID: PMC7876361 DOI: 10.1089/ast.2019.2211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 09/29/2020] [Indexed: 05/04/2023]
Abstract
Acidic iron- and sulfur-rich streams are appropriate analogues for the late Noachian and early Hesperian periods of martian history, when Mars exhibited extensive habitable environments. Any past life on Mars may have left behind diagnostic evidence of life that could be detected at the present day. For effective preservation, these remains must have avoided the harsh radiation flux at the martian surface, survived geological storage for billions of years, and remained detectable within their geochemical environment by analytical instrument suites used on Mars today, such as thermal extraction techniques. We investigated the detectability of organic matter within sulfur stream sediments that had been subjected to artificial maturation by hydrous pyrolysis. After maturation, the samples were analyzed by pyrolysis-gas chromatography-mass spectrometry (py-GC-MS) to determine whether organic matter could be detected with this commonly used technique. We find that macromolecular organic matter can survive the artificial maturation process in the presence of iron- and sulfur-rich minerals but cannot be unambiguously distinguished from abiotic organic matter. However, if jarosite and goethite are present in the sulfur stream environment, they interfere with the py-GC-MS detection of organic compounds in these samples. Clay reduces the obfuscating effect of the oxidizing minerals by providing nondeleterious adsorption sites. We also find that after a simple alkali and acid leaching process that removes oxidizing minerals such as iron sulfates, oxides, and oxyhydroxides, the sulfur stream samples exhibit much greater organic responses during py-GC-MS in terms of both abundance and diversity of organic compounds, such as the detection of hopanes in all leached samples. Our results suggest that insoluble organic matter can be preserved over billions of years of geological storage while still retaining diagnostic organic information, but sample selection strategies must either avoid jarosite- and goethite-rich outcrops or conduct preparative chemistry steps to remove these oxidants prior to analysis by thermal extraction techniques.
Collapse
Affiliation(s)
- Jonathan S.W. Tan
- Impacts and Astromaterials Research Centre, Department of Earth Science and Engineering, Imperial College London, London, UK
| | - Samuel H. Royle
- Impacts and Astromaterials Research Centre, Department of Earth Science and Engineering, Imperial College London, London, UK
| | - Mark A. Sephton
- Impacts and Astromaterials Research Centre, Department of Earth Science and Engineering, Imperial College London, London, UK
| |
Collapse
|