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Chou L, Grefenstette N, Borges S, Caro T, Catalano E, Harman CE, McKaig J, Raj CG, Trubl G, Young A. Chapter 8: Searching for Life Beyond Earth. ASTROBIOLOGY 2024; 24:S164-S185. [PMID: 38498822 DOI: 10.1089/ast.2021.0104] [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: 03/20/2024]
Abstract
The search for life beyond Earth necessitates a rigorous and comprehensive examination of biosignatures, the types of observable imprints that life produces. These imprints and our ability to detect them with advanced instrumentation hold the key to our understanding of the presence and abundance of life in the universe. Biosignatures are the chemical or physical features associated with past or present life and may include the distribution of elements and molecules, alone or in combination, as well as changes in structural components or physical processes that would be distinct from an abiotic background. The scientific and technical strategies used to search for life on other planets include those that can be conducted in situ to planetary bodies and those that could be observed remotely. This chapter discusses numerous strategies that can be employed to look for biosignatures directly on other planetary bodies using robotic exploration including those that have been deployed to other planetary bodies, are currently being developed for flight, or will become a critical technology on future missions. Search strategies for remote observations using current and planned ground-based and space-based telescopes are also described. Evidence from spectral absorption, emission, or transmission features can be used to search for remote biosignatures and technosignatures. Improving our understanding of biosignatures, their production, transformation, and preservation on Earth can enhance our search efforts to detect life on other planets.
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Affiliation(s)
- Luoth Chou
- NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
- Center for Space Sciences and Technology, University of Maryland, Baltimore, Maryland, USA
- Georgetown University, Washington, DC, USA
| | - Natalie Grefenstette
- Santa Fe Institute, Santa Fe, New Mexico, USA
- Blue Marble Space Institute of Science, Seattle, Washington, USA
| | | | - Tristan Caro
- Department of Geological Sciences, University of Colorado Boulder, Boulder, Colorado, USA
| | - Enrico Catalano
- Sant'Anna School of Advanced Studies, The BioRobotics Institute, Pisa, Italy
| | | | - Jordan McKaig
- Georgia Institute of Technology, Atlanta, Georgia, USA
| | | | - Gareth Trubl
- Lawrence Livermore National Laboratory, Livermore, California, USA
| | - Amber Young
- NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
- Northern Arizona University, Flagstaff, Arizona, USA
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Grefenstette N, Chou L, Colón-Santos S, Fisher TM, Mierzejewski V, Nural C, Sinhadc P, Vidaurri M, Vincent L, Weng MM. Chapter 9: Life as We Don't Know It. ASTROBIOLOGY 2024; 24:S186-S201. [PMID: 38498819 DOI: 10.1089/ast.2021.0103] [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: 03/20/2024]
Abstract
While Earth contains the only known example of life in the universe, it is possible that life elsewhere is fundamentally different from what we are familiar with. There is an increased recognition in the astrobiology community that the search for life should steer away from terran-specific biosignatures to those that are more inclusive to all life-forms. To start exploring the space of possibilities that life could occupy, we can try to dissociate life from the chemistry that composes it on Earth by envisioning how different life elsewhere could be in composition, lifestyle, medium, and form, and by exploring how the general principles that govern living systems on Earth might be found in different forms and environments across the Solar System. Exotic life-forms could exist on Mars or Venus, or icy moons like Europa and Enceladus, or even as a shadow biosphere on Earth. New perspectives on agnostic biosignature detection have also begun to emerge, allowing for a broader and more inclusive approach to seeking exotic life with unknown chemistry that is distinct from life as we know it on Earth.
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Affiliation(s)
- Natalie Grefenstette
- Santa Fe Institute, Santa Fe, New Mexico, USA
- Blue Marble Space Institute of Science, Seattle, Washington, USA
| | - Luoth Chou
- NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
- Georgetown University, Washington, DC, USA
| | | | - Theresa M Fisher
- School of Earth and Space Exploration, Arizona State University, Arizona, USA
| | | | - Ceren Nural
- Istanbul Technical University, Istanbul, Turkey
| | - Pritvik Sinhadc
- BEYOND: Center For Fundamental Concepts in Science, Arizona State University, Arizona, USA
- Dubai College, Dubai, United Arab Emirates
| | - Monica Vidaurri
- NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
- Howard University, DC, USA
| | - Lena Vincent
- Wisconsin Institute for Discovery, University of Wisconsin-Madison, Wisconsin, USA
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Wulff JP, Temeyer KB, Tidwell JP, Schlechte KG, Lohmeyer KH, Pietrantonio PV. Periviscerokinin (Cap 2b; CAPA) receptor silencing in females of Rhipicephalus microplus reduces survival, weight and reproductive output. Parasit Vectors 2022; 15:359. [PMID: 36203198 PMCID: PMC9535995 DOI: 10.1186/s13071-022-05457-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 08/24/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The cattle fever tick, Rhipicephalus (Boophilus) microplus, is a vector of pathogens causative of babesiosis and anaplasmosis, both highly lethal bovine diseases that affect cattle worldwide. In Ecdysozoa, neuropeptides and their G-protein-coupled receptors play a critical integrative role in the regulation of all physiological processes. However, the physiological activity of many neuropeptides is still unknown in ticks. Periviscerokinins (CAP2b/PVKs) are neuropeptides associated with myotropic and diuretic activities in insects. These peptides have been identified only in a few tick species, such as Ixodes ricinus, Ixodes scapularis and R. microplus, and their cognate receptor only characterized for the last two. METHODS Expression of the periviscerokinin receptor (Rhimi-CAP2bR) was investigated throughout the developmental stages of R. microplus and silenced by RNA interference (RNAi) in the females. In a first experiment, three double-stranded (ds) RNAs, named ds680-805, ds956-1109 and ds1102-1200, respectively, were tested in vivo. All three caused phenotypic effects, but only the last one was chosen for subsequent experiments. Resulting RNAi phenotypic variables were compared to those of negative controls, both non-injected and dsRNA beta-lactamase-injected ticks, and to positive controls injected with beta-actin dsRNA. Rhimi-CAP2bR silencing was verified by quantitative reverse-transcriptase PCR in whole females and dissected tissues. RESULTS Rhimi-CAP2bR transcript expression was detected throughout all developmental stages. Rhimi-CAP2bR silencing was associated with increased female mortality, decreased weight of surviving females and of egg masses, a delayed egg incubation period and decreased egg hatching (P < 0.05). CONCLUSIONS CAP2b/PVKs appear to be associated with the regulation of female feeding, reproduction and survival. Since the Rhimi-CAP2bR loss of function was detrimental to females, the discovery of antagonistic molecules of the CAP2b/PVK signaling system should cause similar effects. Our results point to this signaling system as a promising target for tick control.
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Affiliation(s)
- Juan P. Wulff
- Department of Entomology, Texas A&M University, College Station, TX 77843-2475 USA
| | - Kevin B. Temeyer
- Knipling-Bushland U.S. Livestock Insects Research Laboratory and Veterinary Pest Genomics Center, United States Department of Agriculture–Agricultural Research Service, 2700 Fredericksburg Road, Kerrville, TX 78028-9184 USA
| | - Jason P. Tidwell
- Cattle Fever Tick Research Laboratory, United States Department of Agriculture–Agricultural Research Service, 22675 N. Moorefield Rd. Building 6419, Edinburg, TX 78541-5033 USA
| | - Kristie G. Schlechte
- Knipling-Bushland U.S. Livestock Insects Research Laboratory and Veterinary Pest Genomics Center, United States Department of Agriculture–Agricultural Research Service, 2700 Fredericksburg Road, Kerrville, TX 78028-9184 USA
| | - Kimberly H. Lohmeyer
- Knipling-Bushland U.S. Livestock Insects Research Laboratory and Veterinary Pest Genomics Center, United States Department of Agriculture–Agricultural Research Service, 2700 Fredericksburg Road, Kerrville, TX 78028-9184 USA
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Wulff JP, Temeyer KB, Tidwell JP, Schlechte KG, Xiong C, Lohmeyer KH, Pietrantonio PV. Pyrokinin receptor silencing in females of the southern cattle tick Rhipicephalus (Boophilus) microplus is associated with a reproductive fitness cost. Parasit Vectors 2022; 15:252. [PMID: 35818078 PMCID: PMC9272880 DOI: 10.1186/s13071-022-05349-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Accepted: 05/28/2022] [Indexed: 12/12/2022] Open
Abstract
Background Rhipicephalusmicroplus is the vector of deadly cattle pathogens, especially Babesia spp., for which a recombinant vaccine is not available. Therefore, disease control depends on tick vector control. However, R.microplus populations worldwide have developed resistance to available acaricides, prompting the search for novel acaricide targets. G protein-coupled receptors (GPCRs) are involved in the regulation of many physiological processes and have been suggested as druggable targets for the control of arthropod vectors. Arthropod-specific signaling systems of small neuropeptides are being investigated for this purpose. The pyrokinin receptor (PKR) is a GPCR previously characterized in ticks. Myotropic activity of pyrokinins in feeding-related tissues of Rhipicephalussanguineus and Ixodesscapularis was recently reported. Methods The R.microplus pyrokinin receptor (Rhimi-PKR) was silenced through RNA interference (RNAi) in female ticks. To optimize RNAi, a dual-luciferase assay was applied to determine the silencing efficiency of two Rhimi-PKR double-stranded RNAs (dsRNA) prior to injecting dsRNA in ticks to be placed on cattle. Phenotypic variables of female ticks obtained at the endpoint of the RNAi experiment were compared to those of control female ticks (non-injected and beta-lactamase dsRNA-injected). Rhimi-PKR silencing was verified by quantitative reverse-transcriptase PCR in whole females and dissected tissues. Results The Rhimi-PKR transcript was expressed in all developmental stages. Rhimi-PKR silencing was confirmed in whole ticks 4 days after injection, and in the tick carcass, ovary and synganglion 6 days after injection. Rhimi-PKR silencing was associated with an increased mortality and decreased weight of both surviving females and egg masses (P < 0.05). Delays in repletion, pre-oviposition and incubation periods were observed (P < 0.05). Conclusions Rhimi-PKR silencing negatively affected female reproductive fitness. The PKR appears to be directly or indirectly associated with the regulation of female feeding and/or reproductive output in R.microplus. Antagonists of the pyrokinin signaling system could be explored for tick control. Graphical abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s13071-022-05349-w.
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Affiliation(s)
- Juan P Wulff
- Department of Entomology, Texas A&M University, College Station, TX, 77843-2475, USA
| | - Kevin B Temeyer
- Knipling-Bushland U.S. Livestock Insects Research Laboratory and Veterinary Pest Genomics Center, United States Department of Agriculture-Agricultural Research Service (USDA-ARS), 2700 Fredericksburg Road, Kerrville, TX, 78028-9184, USA
| | - Jason P Tidwell
- Cattle Fever Tick Research Laboratory, USDA-ARS, 22675 N. Moorefield Rd. Building 6419, Edinburg, TX, 78541-5033, USA
| | - Kristie G Schlechte
- Knipling-Bushland U.S. Livestock Insects Research Laboratory and Veterinary Pest Genomics Center, United States Department of Agriculture-Agricultural Research Service (USDA-ARS), 2700 Fredericksburg Road, Kerrville, TX, 78028-9184, USA
| | - Caixing Xiong
- Department of Entomology, Texas A&M University, College Station, TX, 77843-2475, USA
| | - Kimberly H Lohmeyer
- Knipling-Bushland U.S. Livestock Insects Research Laboratory and Veterinary Pest Genomics Center, United States Department of Agriculture-Agricultural Research Service (USDA-ARS), 2700 Fredericksburg Road, Kerrville, TX, 78028-9184, USA
| | - Patricia V Pietrantonio
- Knipling-Bushland U.S. Livestock Insects Research Laboratory and Veterinary Pest Genomics Center, United States Department of Agriculture-Agricultural Research Service (USDA-ARS), 2700 Fredericksburg Road, Kerrville, TX, 78028-9184, USA.
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Dutta B, Bandopadhyay R. Biotechnological potentials of halophilic microorganisms and their impact on mankind. BENI-SUEF UNIVERSITY JOURNAL OF BASIC AND APPLIED SCIENCES 2022; 11:75. [PMID: 35669848 PMCID: PMC9152817 DOI: 10.1186/s43088-022-00252-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Accepted: 05/08/2022] [Indexed: 11/10/2022] Open
Abstract
Background Halophiles are extremophilic organisms represented by archaea, bacteria and eukaryotes that thrive in hypersaline environment. They apply different osmoadaptation strategies to survive in hostile conditions. Habitat diversity of halophilic microorganisms in hypersaline system provides information pertaining the evolution of life on Earth. Main body The microbiome-gut-brain axis interaction contributes greatly to the neurodegenerative diseases. Gut resident halophilic bacteria are used as alternative medication for chronic brain diseases. Halophiles can be used in pharmaceuticals, drug delivery, agriculture, saline waste water treatment, biodegradable plastic production, metal recovery, biofuel energy generation, concrete crack repair and other sectors. Furthermore, versatile biomolecules, mainly enzymes characterized by broad range of pH and thermostability, are suitable candidate for industrial purposes. Reflectance pattern of halophilic archaeal pigment rhodopsin is considered as potential biosignature for Earth-like planets. Short conclusions This review represents important osmoadaptation strategies acquired by halophilic archaea and bacteria and their potential biotechnological applications to resolve present day challenges. Graphical Abstract
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Affiliation(s)
- Bhramar Dutta
- Department of Botany, The University of Burdwan, Purba Bardhaman, West Bengal 713104 India
| | - Rajib Bandopadhyay
- Department of Botany, The University of Burdwan, Purba Bardhaman, West Bengal 713104 India
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Garcia AK, Cavanaugh CM, Kacar B. The curious consistency of carbon biosignatures over billions of years of Earth-life coevolution. THE ISME JOURNAL 2021; 15:2183-2194. [PMID: 33846565 PMCID: PMC8319343 DOI: 10.1038/s41396-021-00971-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 03/12/2021] [Accepted: 03/25/2021] [Indexed: 11/09/2022]
Abstract
The oldest and most wide-ranging signal of biological activity (biosignature) on our planet is the carbon isotope composition of organic materials preserved in rocks. These biosignatures preserve the long-term evolution of the microorganism-hosted metabolic machinery responsible for producing deviations in the isotopic compositions of inorganic and organic carbon. Despite billions of years of ecosystem turnover, evolutionary innovation, organismic complexification, and geological events, the organic carbon that is a residuum of the global marine biosphere in the rock record tells an essentially static story. The ~25‰ mean deviation between inorganic and organic 13C/12C values has remained remarkably unchanged over >3.5 billion years. The bulk of this record is conventionally attributed to early-evolved, RuBisCO-mediated CO2 fixation that, in extant oxygenic phototrophs, produces comparable isotopic effects and dominates modern primary production. However, billions of years of environmental transition, for example, in the progressive oxygenation of the Earth's atmosphere, would be expected to have accompanied shifts in the predominant RuBisCO forms as well as enzyme-level adaptive responses in RuBisCO CO2-specificity. These factors would also be expected to result in preserved isotopic signatures deviating from those produced by extant RuBisCO in oxygenic phototrophs. Why does the bulk carbon isotope record not reflect these expected environmental transitions and evolutionary innovations? Here, we discuss this apparent discrepancy and highlight the need for greater quantitative understanding of carbon isotope fractionation behavior in extant metabolic pathways. We propose novel, laboratory-based approaches to reconstructing ancestral states of carbon metabolisms and associated enzymes that can constrain isotopic biosignature production in ancient biological systems. Together, these strategies are crucial for integrating the complementary toolsets of biological and geological sciences and for interpretation of the oldest record of life on Earth.
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Affiliation(s)
- Amanda K Garcia
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, USA
| | - Colleen M Cavanaugh
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | - Betul Kacar
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, USA.
- Lunar and Planetary Laboratory and Steward Observatory, University of Arizona, Tucson, AZ, USA.
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Smith HH, Hyde AS, Simkus DN, Libby E, Maurer SE, Graham HV, Kempes CP, Sherwood Lollar B, Chou L, Ellington AD, Fricke GM, Girguis PR, Grefenstette NM, Pozarycki CI, House CH, Johnson SS. The Grayness of the Origin of Life. Life (Basel) 2021; 11:498. [PMID: 34072344 PMCID: PMC8226951 DOI: 10.3390/life11060498] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Revised: 05/22/2021] [Accepted: 05/26/2021] [Indexed: 12/05/2022] Open
Abstract
In the search for life beyond Earth, distinguishing the living from the non-living is paramount. However, this distinction is often elusive, as the origin of life is likely a stepwise evolutionary process, not a singular event. Regardless of the favored origin of life model, an inherent "grayness" blurs the theorized threshold defining life. Here, we explore the ambiguities between the biotic and the abiotic at the origin of life. The role of grayness extends into later transitions as well. By recognizing the limitations posed by grayness, life detection researchers will be better able to develop methods sensitive to prebiotic chemical systems and life with alternative biochemistries.
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Affiliation(s)
- Hillary H. Smith
- Department of Geosciences, The Pennsylvania State University, University Park, PA 16802, USA;
- Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, PA 16802, USA
| | - Andrew S. Hyde
- Department of Geosciences, The Pennsylvania State University, University Park, PA 16802, USA;
- Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, PA 16802, USA
| | - Danielle N. Simkus
- NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA; (D.N.S.); (H.V.G.); (L.C.); (C.I.P.)
- NASA Postdoctoral Program, USRA, Columbia, MD 20146, USA
- Department of Physics, Catholic University of America, Washington, DC 20064, USA
| | - Eric Libby
- Santa Fe Institute, Santa Fe, NM 87501, USA; (E.L.); (C.P.K.); (N.M.G.)
- Department of Mathematics and Mathematical Statistics, Umeå University, 90187 Umeå, Sweden
- Icelab, Umeå University, 90187 Umeå, Sweden
| | - Sarah E. Maurer
- Department of Chemistry and Biochemistry, Central Connecticut State University, New Britain, CT 06050, USA;
| | - Heather V. Graham
- NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA; (D.N.S.); (H.V.G.); (L.C.); (C.I.P.)
- Department of Physics, Catholic University of America, Washington, DC 20064, USA
| | | | | | - Luoth Chou
- NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA; (D.N.S.); (H.V.G.); (L.C.); (C.I.P.)
- NASA Postdoctoral Program, USRA, Columbia, MD 20146, USA
- Department of Biology, Georgetown University, Washington, DC 20057, USA
| | - Andrew D. Ellington
- Department of Molecular Biosciences, College of Natural Sciences, The University of Texas at Austin, Austin, TX 78712, USA;
- Center for Systems and Synthetic Biology, The University of Texas at Austin, Austin, TX 78712, USA
| | - G. Matthew Fricke
- Department of Computer Science, University of New Mexico, Albuquerque, NM 87108, USA;
| | - Peter R. Girguis
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA;
| | - Natalie M. Grefenstette
- Santa Fe Institute, Santa Fe, NM 87501, USA; (E.L.); (C.P.K.); (N.M.G.)
- Blue Marble Space Institute of Science, Seattle, WA 98104, USA
| | - Chad I. Pozarycki
- NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA; (D.N.S.); (H.V.G.); (L.C.); (C.I.P.)
- Department of Biology, Georgetown University, Washington, DC 20057, USA
| | - Christopher H. House
- Department of Geosciences, The Pennsylvania State University, University Park, PA 16802, USA;
- Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, PA 16802, USA
| | - Sarah Stewart Johnson
- Department of Biology, Georgetown University, Washington, DC 20057, USA
- Science, Technology and International Affairs Program, Georgetown University, Washington, DC 20057, USA
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Callefo F, Maldanis L, Teixeira VC, Abans RADO, Monfredini T, Rodrigues F, Galante D. Evaluating Biogenicity on the Geological Record With Synchrotron-Based Techniques. Front Microbiol 2019; 10:2358. [PMID: 31681221 PMCID: PMC6798071 DOI: 10.3389/fmicb.2019.02358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 09/27/2019] [Indexed: 11/17/2022] Open
Abstract
The biogenicity problem of geological materials is one of the most challenging ones in the field of paleo and astrobiology. As one goes deeper in time, the traces of life become feeble and ambiguous, blending with the surrounding geology. Well-preserved metasedimentary rocks from the Archaean are relatively rare, and in very few cases contain structures resembling biological traces or fossils. These putative biosignatures have been studied for decades and many biogenicity criteria have been developed, but there is still no consensus for many of the proposed structures. Synchrotron-based techniques, especially on new generation sources, have the potential for contributing to this field of research, providing high sensitivity and resolution that can be advantageous for different scientific problems. Exploring the X-ray and matter interactions on a range of geological materials can provide insights on morphology, elemental composition, oxidation states, crystalline structure, magnetic properties, and others, which can measurably contribute to the investigation of biogenicity of putative biosignatures. Here, we provide an overview of selected synchrotron-based techniques that have the potential to be applied in different types of questions on the study of biosignatures preserved in the geological record. The development of 3rd and recently 4th generation synchrotron sources will favor a deeper understanding of the earliest records of life on Earth and also bring up potential analytical approaches to be applied for the search of biosignatures in meteorites and samples returned from Mars in the near future.
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Affiliation(s)
- Flavia Callefo
- Brazilian Synchrotron Light Laboratory, Brazilian Center for Research in Energy and Materials, Campinas, Brazil
| | - Lara Maldanis
- Brazilian Synchrotron Light Laboratory, Brazilian Center for Research in Energy and Materials, Campinas, Brazil
- Institute of Physics of São Carlos, University of São Paulo, São Paulo, Brazil
| | - Verônica C. Teixeira
- Brazilian Synchrotron Light Laboratory, Brazilian Center for Research in Energy and Materials, Campinas, Brazil
| | - Rodrigo Adrián de Oliveira Abans
- Brazilian Synchrotron Light Laboratory, Brazilian Center for Research in Energy and Materials, Campinas, Brazil
- Interunits Graduate Program in Biotechnology, University of São Paulo, São Paulo, Brazil
| | - Thiago Monfredini
- Brazilian Synchrotron Light Laboratory, Brazilian Center for Research in Energy and Materials, Campinas, Brazil
| | - Fabio Rodrigues
- Fundamental Chemistry Department, University of São Paulo, São Paulo, Brazil
| | - Douglas Galante
- Brazilian Synchrotron Light Laboratory, Brazilian Center for Research in Energy and Materials, Campinas, Brazil
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Walker SI, Bains W, Cronin L, DasSarma S, Danielache S, Domagal-Goldman S, Kacar B, Kiang NY, Lenardic A, Reinhard CT, Moore W, Schwieterman EW, Shkolnik EL, Smith HB. Exoplanet Biosignatures: Future Directions. ASTROBIOLOGY 2018; 18:779-824. [PMID: 29938538 PMCID: PMC6016573 DOI: 10.1089/ast.2017.1738] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Accepted: 03/13/2018] [Indexed: 05/08/2023]
Abstract
We introduce a Bayesian method for guiding future directions for detection of life on exoplanets. We describe empirical and theoretical work necessary to place constraints on the relevant likelihoods, including those emerging from better understanding stellar environment, planetary climate and geophysics, geochemical cycling, the universalities of physics and chemistry, the contingencies of evolutionary history, the properties of life as an emergent complex system, and the mechanisms driving the emergence of life. We provide examples for how the Bayesian formalism could guide future search strategies, including determining observations to prioritize or deciding between targeted searches or larger lower resolution surveys to generate ensemble statistics and address how a Bayesian methodology could constrain the prior probability of life with or without a positive detection. Key Words: Exoplanets-Biosignatures-Life detection-Bayesian analysis. Astrobiology 18, 779-824.
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Affiliation(s)
- Sara I. Walker
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona
- Beyond Center for Fundamental Concepts in Science, Arizona State University, Tempe, Arizona
- ASU-Santa Fe Institute Center for Biosocial Complex Systems, Arizona State University, Tempe, Arizona
- Blue Marble Space Institute of Science, Seattle, Washington
| | - William Bains
- EAPS (Earth, Atmospheric and Planetary Science), MIT, Cambridge, Massachusetts
- Rufus Scientific Ltd., Royston, United Kingdom
| | - Leroy Cronin
- School of Chemistry, University of Glasgow, Glasgow, United Kingdom
| | - Shiladitya DasSarma
- Department of Microbiology and Immunology, Institute of Marine and Environmental Technology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Sebastian Danielache
- Department of Materials and Life Science, Faculty of Science and Technology, Sophia University, Tokyo, Japan
- Earth Life Institute, Tokyo Institute of Technology, Tokyo, Japan
| | - Shawn Domagal-Goldman
- NASA Goddard Space Flight Center, Greenbelt, Maryland
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, University of Washington, Seattle, Washington
| | - Betul Kacar
- Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts
- NASA Astrobiology Institute, Reliving the Past Team, University of Montana, Missoula, Montana
- Department of Molecular and Cell Biology, University of Arizona, Tucson, Arizona
- Department of Astronomy and Steward Observatory, University of Arizona, Tucson, Arizona
| | - Nancy Y. Kiang
- NASA Goddard Institute for Space Studies, New York, New York
| | - Adrian Lenardic
- Department of Earth Science, Rice University, Houston, Texas
| | - Christopher T. Reinhard
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia
- NASA Astrobiology Institute, Alternative Earths Team, University of California, Riverside, California
| | - William Moore
- Department of Atmospheric and Planetary Sciences, Hampton University, Hampton, Virginia
- National Institute of Aerospace, Hampton, Virginia
| | - Edward W. Schwieterman
- Blue Marble Space Institute of Science, Seattle, Washington
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, University of Washington, Seattle, Washington
- NASA Astrobiology Institute, Alternative Earths Team, University of California, Riverside, California
- Department of Earth Sciences, University of California, Riverside, California
- NASA Postdoctoral Program, Universities Space Research Association, Columbia, Maryland
| | - Evgenya L. Shkolnik
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona
| | - Harrison B. Smith
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona
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10
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Schwieterman EW, Kiang NY, Parenteau MN, Harman CE, DasSarma S, Fisher TM, Arney GN, Hartnett HE, Reinhard CT, Olson SL, Meadows VS, Cockell CS, Walker SI, Grenfell JL, Hegde S, Rugheimer S, Hu R, Lyons TW. Exoplanet Biosignatures: A Review of Remotely Detectable Signs of Life. ASTROBIOLOGY 2018; 18:663-708. [PMID: 29727196 PMCID: PMC6016574 DOI: 10.1089/ast.2017.1729] [Citation(s) in RCA: 110] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Accepted: 12/10/2017] [Indexed: 05/04/2023]
Abstract
In the coming years and decades, advanced space- and ground-based observatories will allow an unprecedented opportunity to probe the atmospheres and surfaces of potentially habitable exoplanets for signatures of life. Life on Earth, through its gaseous products and reflectance and scattering properties, has left its fingerprint on the spectrum of our planet. Aided by the universality of the laws of physics and chemistry, we turn to Earth's biosphere, both in the present and through geologic time, for analog signatures that will aid in the search for life elsewhere. Considering the insights gained from modern and ancient Earth, and the broader array of hypothetical exoplanet possibilities, we have compiled a comprehensive overview of our current understanding of potential exoplanet biosignatures, including gaseous, surface, and temporal biosignatures. We additionally survey biogenic spectral features that are well known in the specialist literature but have not yet been robustly vetted in the context of exoplanet biosignatures. We briefly review advances in assessing biosignature plausibility, including novel methods for determining chemical disequilibrium from remotely obtainable data and assessment tools for determining the minimum biomass required to maintain short-lived biogenic gases as atmospheric signatures. We focus particularly on advances made since the seminal review by Des Marais et al. The purpose of this work is not to propose new biosignature strategies, a goal left to companion articles in this series, but to review the current literature, draw meaningful connections between seemingly disparate areas, and clear the way for a path forward. Key Words: Exoplanets-Biosignatures-Habitability markers-Photosynthesis-Planetary surfaces-Atmospheres-Spectroscopy-Cryptic biospheres-False positives. Astrobiology 18, 663-708.
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Affiliation(s)
- Edward W. Schwieterman
- Department of Earth Sciences, University of California, Riverside, California
- NASA Postdoctoral Program, Universities Space Research Association, Columbia, Maryland
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- NASA Astrobiology Institute, Alternative Earths Team, Riverside, California
- Blue Marble Space Institute of Science, Seattle, Washington
| | - Nancy Y. Kiang
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- NASA Goddard Institute for Space Studies, New York, New York
| | - Mary N. Parenteau
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- NASA Ames Research Center, Exobiology Branch, Mountain View, California
| | - Chester E. Harman
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- NASA Goddard Institute for Space Studies, New York, New York
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York
| | - Shiladitya DasSarma
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland
- Institute of Marine and Environmental Technology, University System of Maryland, Baltimore, Maryland
| | - Theresa M. Fisher
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona
| | - Giada N. Arney
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- Planetary Systems Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland
| | - Hilairy E. Hartnett
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona
- School of Molecular Sciences, Arizona State University, Tempe, Arizona
| | - Christopher T. Reinhard
- NASA Astrobiology Institute, Alternative Earths Team, Riverside, California
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia
| | - Stephanie L. Olson
- Department of Earth Sciences, University of California, Riverside, California
- NASA Astrobiology Institute, Alternative Earths Team, Riverside, California
| | - Victoria S. Meadows
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- Astronomy Department, University of Washington, Seattle, Washington
| | - Charles S. Cockell
- University of Edinburgh School of Physics and Astronomy, Edinburgh, United Kingdom
- UK Centre for Astrobiology, Edinburgh, United Kingdom
| | - Sara I. Walker
- Blue Marble Space Institute of Science, Seattle, Washington
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona
- Beyond Center for Fundamental Concepts in Science, Arizona State University, Tempe, Arizona
- ASU-Santa Fe Institute Center for Biosocial Complex Systems, Arizona State University, Tempe, Arizona
| | - John Lee Grenfell
- Institut für Planetenforschung (PF), Deutsches Zentrum für Luft und Raumfahrt (DLR), Berlin, Germany
| | - Siddharth Hegde
- Carl Sagan Institute, Cornell University, Ithaca, New York
- Cornell Center for Astrophysics and Planetary Science, Cornell University, Ithaca, New York
| | - Sarah Rugheimer
- Department of Earth and Environmental Sciences, University of St. Andrews, St. Andrews, United Kingdom
| | - Renyu Hu
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California
| | - Timothy W. Lyons
- Department of Earth Sciences, University of California, Riverside, California
- NASA Astrobiology Institute, Alternative Earths Team, Riverside, California
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11
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Kiang NY, Domagal-Goldman S, Parenteau MN, Catling DC, Fujii Y, Meadows VS, Schwieterman EW, Walker SI. Exoplanet Biosignatures: At the Dawn of a New Era of Planetary Observations. ASTROBIOLOGY 2018; 18:619-629. [PMID: 29741918 PMCID: PMC6014570 DOI: 10.1089/ast.2018.1862] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Accepted: 03/23/2018] [Indexed: 05/15/2023]
Abstract
The rapid rate of discoveries of exoplanets has expanded the scope of the science possible for the remote detection of life beyond Earth. The Exoplanet Biosignatures Workshop Without Walls (EBWWW) held in 2016 engaged the international scientific community across diverse scientific disciplines, to assess the state of the science and technology in the search for life on exoplanets, and to identify paths for progress. The workshop activities resulted in five major review papers, which provide (1) an encyclopedic review of known and proposed biosignatures and models used to ascertain them (Schwieterman et al., 2018 in this issue); (2) an in-depth review of O2 as a biosignature, rigorously examining the nuances of false positives and false negatives for evidence of life (Meadows et al., 2018 in this issue); (3) a Bayesian framework to comprehensively organize current understanding to quantify confidence in biosignature assessments (Catling et al., 2018 in this issue); (4) an extension of that Bayesian framework in anticipation of increasing planetary data and novel concepts of biosignatures (Walker et al., 2018 in this issue); and (5) a review of the upcoming telescope capabilities to characterize exoplanets and their environment (Fujii et al., 2018 in this issue). Because of the immense content of these review papers, this summary provides a guide to their complementary scope and highlights salient features. Strong themes that emerged from the workshop were that biosignatures must be interpreted in the context of their environment, and that frameworks must be developed to link diverse forms of scientific understanding of that context to quantify the likelihood that a biosignature has been observed. Models are needed to explore the parameter space where measurements will be widespread but sparse in detail. Given the technological prospects for large ground-based telescopes and space-based observatories, the detection of atmospheric signatures of a few potentially habitable planets may come before 2030. Key Words: Exoplanets-Biosignatures-Remote observation-Spectral imaging-Bayesian analysis. Astrobiology 18, 619-626.
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Affiliation(s)
- Nancy Y. Kiang
- NASA Goddard Institute for Space Studies (GISS), New York, New York, USA
- Nexus for Exoplanet System Science, ROCKE-3D Team, NASA GISS, USA
- NASA Astrobiology Institute, Virtual Planetary Laboratory, University of Washington, Seattle, Washington, USA
| | - Shawn Domagal-Goldman
- Nexus for Exoplanet System Science, ROCKE-3D Team, NASA GISS, USA
- NASA Astrobiology Institute, Virtual Planetary Laboratory, University of Washington, Seattle, Washington, USA
- NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
| | - Mary N. Parenteau
- NASA Astrobiology Institute, Virtual Planetary Laboratory, University of Washington, Seattle, Washington, USA
- NASA Ames Research Center, Exobiology Branch, Mountain View, California, USA
| | - David C. Catling
- NASA Astrobiology Institute, Virtual Planetary Laboratory, University of Washington, Seattle, Washington, USA
- Department of Earth and Space Sciences/Astrobiology Program, University of Washington, Seattle, Washington, USA
| | - Yuka Fujii
- Earth-Life Science Institute, Tokyo Institute of Technology, Ookayama, Meguro, Tokyo, Japan
| | - Victoria S. Meadows
- NASA Astrobiology Institute, Virtual Planetary Laboratory, University of Washington, Seattle, Washington, USA
- Astronomy Department, University of Washington, Seattle, Washington, USA
| | - Edward W. Schwieterman
- NASA Astrobiology Institute, Virtual Planetary Laboratory, University of Washington, Seattle, Washington, USA
- Department of Earth Sciences, University of California, Riverside, California, USA
- NASA Postdoctoral Program, Universities Space Research Association, Columbia, Maryland, USA
- Blue Marble Space Institute of Science, Seattle, Washington, USA
| | - Sara I. Walker
- Blue Marble Space Institute of Science, Seattle, Washington, USA
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA
- Beyond Center for Fundamental Concepts in Science, Arizona State University, Tempe, Arizona, USA
- ASU-Santa Fe Institute Center for Biosocial Complex Systems, Arizona State University, Tempe, Arizona, USA
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12
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Cabrol NA. Alien Mindscapes-A Perspective on the Search for Extraterrestrial Intelligence. ASTROBIOLOGY 2016; 16:661-76. [PMID: 27383691 PMCID: PMC5111820 DOI: 10.1089/ast.2016.1536] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2016] [Accepted: 05/23/2016] [Indexed: 05/15/2023]
Abstract
UNLABELLED Advances in planetary and space sciences, astrobiology, and life and cognitive sciences, combined with developments in communication theory, bioneural computing, machine learning, and big data analysis, create new opportunities to explore the probabilistic nature of alien life. Brought together in a multidisciplinary approach, they have the potential to support an integrated and expanded Search for Extraterrestrial Intelligence (SETI (1) ), a search that includes looking for life as we do not know it. This approach will augment the odds of detecting a signal by broadening our understanding of the evolutionary and systemic components in the search for extraterrestrial intelligence (ETI), provide more targets for radio and optical SETI, and identify new ways of decoding and coding messages using universal markers. KEY WORDS SETI-Astrobiology-Coevolution of Earth and life-Planetary habitability and biosignatures. Astrobiology 16, 661-676.
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13
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Vane-Wright RI. What is life? And what might be said of the role of behaviour in its evolution? Biol J Linn Soc Lond 2014. [DOI: 10.1111/bij.12300] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- R. I. Vane-Wright
- Life Sciences Department; Natural History Museum; London SW7 5BD UK
- Durrell Institute of Conservation and Ecology (DICE); University of Kent; Canterbury CT2 7NR UK
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14
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Dalluge JJ, Connell LB. On the potential of mass spectrometry-based metabolite profiling approaches to the study of biochemical adaptation in psychrophilic yeast. Extremophiles 2013; 17:953-61. [PMID: 23989708 DOI: 10.1007/s00792-013-0577-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 07/30/2013] [Indexed: 11/24/2022]
Abstract
To move beyond targeted approaches to the biochemical characterization of psychrophilic yeast and provide a more holistic understanding of the chemistry of physiological adaptation of psychrophiles at the molecular level, ultraperformance liquid chromatography combined with simultaneous acquisition of low- and high-collision energy mass spectra (UPLC/MS(e)) was employed for a preliminary comparative analysis of cell extracts of psychrophilic Antarctic yeasts Cryptococcus vishniacii CBS 10616 and Dioszegia cryoxerica CBS 10919 versus the mesophile Saccharomyces cerevisiae 'cry havoc'. A detailed workflow for providing high-confidence preliminary identifications of psychrophilic yeast-specific molecular features is presented. Preliminary identifications of psychrophile-specific features in C. vishniacii and D. cryoxerica determined with the described method include the glycerophospholipids lysophosphatidylcholine 18:2, lysophosphatidylcholine 18:3, lysophosphatidylethanolamine 18:3, and lysophosphatidylethanolamine 18:2. In addition, levels of guanosine diphosphate appear significantly elevated in cell extracts of the psychrophilic yeasts as compared to Saccharomyces cerevisiae. Finally, five psychrophilic yeast-specific peptides have been discovered. All of these are demonstrated to be glycine- and/or proline-rich, a known structural characteristic of many naturally occurring bioactive peptides. The potential of this untargeted metabolite profiling approach as a tool for knowledge discovery and hypothesis generation in the study of biodiversity and microbial adaptation is highlighted.
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Affiliation(s)
- Joseph J Dalluge
- Department of Chemistry, University of Minnesota, Minneapolis, MN, 55455, USA,
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15
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Vukotić B, Ćirković MM. Astrobiological complexity with probabilistic cellular automata. ORIGINS LIFE EVOL B 2012; 42:347-71. [PMID: 22832998 DOI: 10.1007/s11084-012-9293-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Accepted: 06/14/2012] [Indexed: 11/30/2022]
Abstract
The search for extraterrestrial life and intelligence constitutes one of the major endeavors in science, but has yet been quantitatively modeled only rarely and in a cursory and superficial fashion. We argue that probabilistic cellular automata (PCA) represent the best quantitative framework for modeling the astrobiological history of the Milky Way and its Galactic Habitable Zone. The relevant astrobiological parameters are to be modeled as the elements of the input probability matrix for the PCA kernel. With the underlying simplicity of the cellular automata constructs, this approach enables a quick analysis of large and ambiguous space of the input parameters. We perform a simple clustering analysis of typical astrobiological histories with "Copernican" choice of input parameters and discuss the relevant boundary conditions of practical importance for planning and guiding empirical astrobiological and SETI projects. In addition to showing how the present framework is adaptable to more complex situations and updated observational databases from current and near-future space missions, we demonstrate how numerical results could offer a cautious rationale for continuation of practical SETI searches.
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Affiliation(s)
- Branislav Vukotić
- Astronomical Observatory Belgrade, Volgina 7, 11160 Belgrade-74, Serbia.
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16
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Andrulis ED. Theory of the origin, evolution, and nature of life. Life (Basel) 2011; 2:1-105. [PMID: 25382118 PMCID: PMC4187144 DOI: 10.3390/life2010001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Revised: 12/10/2011] [Accepted: 12/13/2011] [Indexed: 12/22/2022] Open
Abstract
Life is an inordinately complex unsolved puzzle. Despite significant theoretical progress, experimental anomalies, paradoxes, and enigmas have revealed paradigmatic limitations. Thus, the advancement of scientific understanding requires new models that resolve fundamental problems. Here, I present a theoretical framework that economically fits evidence accumulated from examinations of life. This theory is based upon a straightforward and non-mathematical core model and proposes unique yet empirically consistent explanations for major phenomena including, but not limited to, quantum gravity, phase transitions of water, why living systems are predominantly CHNOPS (carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur), homochirality of sugars and amino acids, homeoviscous adaptation, triplet code, and DNA mutations. The theoretical framework unifies the macrocosmic and microcosmic realms, validates predicted laws of nature, and solves the puzzle of the origin and evolution of cellular life in the universe.
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Affiliation(s)
- Erik D Andrulis
- Department of Molecular Biology and Microbiology, Case Western Reserve University School of Medicine, Wood Building, W212, Cleveland, OH 44106, USA.
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17
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Bayesian analysis of the astrobiological implications of life's early emergence on Earth. Proc Natl Acad Sci U S A 2011; 109:395-400. [PMID: 22198766 DOI: 10.1073/pnas.1111694108] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Life arose on Earth sometime in the first few hundred million years after the young planet had cooled to the point that it could support water-based organisms on its surface. The early emergence of life on Earth has been taken as evidence that the probability of abiogenesis is high, if starting from young Earth-like conditions. We revisit this argument quantitatively in a bayesian statistical framework. By constructing a simple model of the probability of abiogenesis, we calculate a bayesian estimate of its posterior probability, given the data that life emerged fairly early in Earth's history and that, billions of years later, curious creatures noted this fact and considered its implications. We find that, given only this very limited empirical information, the choice of bayesian prior for the abiogenesis probability parameter has a dominant influence on the computed posterior probability. Although terrestrial life's early emergence provides evidence that life might be abundant in the universe if early-Earth-like conditions are common, the evidence is inconclusive and indeed is consistent with an arbitrarily low intrinsic probability of abiogenesis for plausible uninformative priors. Finding a single case of life arising independently of our lineage (on Earth, elsewhere in the solar system, or on an extrasolar planet) would provide much stronger evidence that abiogenesis is not extremely rare in the universe.
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18
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Ambily Nath IV, Loka Bharathi PA. Diversity in transcripts and translational pattern of stress proteins in marine extremophiles. Extremophiles 2011; 15:129-53. [DOI: 10.1007/s00792-010-0348-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Accepted: 12/09/2010] [Indexed: 11/28/2022]
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19
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Michalski JR, Poulet F, Loizeau D, Mangold N, Dobrea EN, Bishop JL, Wray JJ, McKeown NK, Parente M, Hauber E, Altieri F, Carrozzo FG, Niles PB. The Mawrth Vallis region of Mars: A potential landing site for the Mars Science Laboratory (MSL) mission. ASTROBIOLOGY 2010; 10:687-703. [PMID: 20950170 DOI: 10.1089/ast.2010.0491] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The primary objective of NASA's Mars Science Laboratory (MSL) mission, which will launch in 2011, is to characterize the habitability of a site on Mars through detailed analyses of the composition and geological context of surface materials. Within the framework of established mission goals, we have evaluated the value of a possible landing site in the Mawrth Vallis region of Mars that is targeted directly on some of the most geologically and astrobiologically enticing materials in the Solar System. The area around Mawrth Vallis contains a vast (>1 × 10⁶ km²) deposit of phyllosilicate-rich, ancient, layered rocks. A thick (>150 m) stratigraphic section that exhibits spectral evidence for nontronite, montmorillonite, amorphous silica, kaolinite, saponite, other smectite clay minerals, ferrous mica, and sulfate minerals indicates a rich geological history that may have included multiple aqueous environments. Because phyllosilicates are strong indicators of ancient aqueous activity, and the preservation potential of biosignatures within sedimentary clay deposits is high, martian phyllosilicate deposits are desirable astrobiological targets. The proposed MSL landing site at Mawrth Vallis is located directly on the largest and most phyllosilicate-rich deposit on Mars and is therefore an excellent place to explore for evidence of life or habitability.
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20
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Poulet F, Beaty DW, Bibring JP, Bish D, Bishop JL, Noe Dobrea E, Mustard JF, Petit S, Roach LH. Key scientific questions and key investigations from the first international conference on Martian phyllosilicates. ASTROBIOLOGY 2009; 9:257-267. [PMID: 19400732 DOI: 10.1089/ast.2009.0335] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Minerals and their occurrences can tell us about the chemistry, pressure, and temperatures of past environments on Mars and thus allow inferences about the potential for habitability. Thanks to recent space exploration, a new vision is emerging wherein Mars hosted environmental conditions of potential astrobiological relevance. This epoch is identified by the presence of phyllosilicate-bearing deposits, which are generally contained in very ancient basement rocks. In October 2008, over 100 planetary scientists representing 11 countries met in Paris to assess and discuss the relevance of martian phyllosilicates. The conference was structured to promote the discussion and debate of key scientific questions and key essential investigations. The purpose of this report is to document the current state of knowledge related to martian phyllosilicates and to ascertain which questions remain to be addressed: What are the basic characteristics of the phyllosilicate minerals on Mars? What are the genetic mechanisms by which phyllosilicate minerals have formed on Mars? What is the relationship between the phyllosilicate minerals observed in martian meteorites and those detected from orbit? What are the implications of phyllosilicate-bearing rocks for the development of prebiotic chemistry and the preservation of biosignatures? The most promising investigations to address these questions are presented.
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Affiliation(s)
- François Poulet
- Institut d'Astrophysique Spatiale, CNRS/Université Paris-Sud, Orsay, France.
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21
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Perry RS, Hartmann WK. Mars primordial crust: unique sites for investigating proto-biologic properties. ORIGINS LIFE EVOL B 2006; 36:533-40. [PMID: 17131091 DOI: 10.1007/s11084-006-9037-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The Martian meteorite collection suggests that intact outcrops or boulder-scale fragments of the 4.5 Ga Martian crust exist within tens of meters of the present day surface of Mars. Mars may be the only planet where such primordial crust samples, representing the first 100 Ma of a planet's environment, are available. The primordial crust has been destroyed on Earth by plate tectonics and other geological phenomena and is buried on the Moon under hundreds or thousands of meters of megaregoltih. Early Mars appears to have been remarkably similar to early Earth, and samples of rock from the first few Ma or first 100 Ma may reveal "missing link" proto-biological forms that could shed light on the transition from abiotic organic chemistry to living cells. Such organic snapshots of nascent life are unlikely to be found on Earth.
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Affiliation(s)
- Randall S Perry
- Department of Earth Science and Engineering, South Kensington Campus, Impacts and Astromaterials Research Centre, Imperial College, London, UK.
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22
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Moisander PH, Shiue L, Steward GF, Jenkins BD, Bebout BM, Zehr JP. Application of a nifH oligonucleotide microarray for profiling diversity of N2-fixing microorganisms in marine microbial mats. Environ Microbiol 2006; 8:1721-35. [PMID: 16958753 DOI: 10.1111/j.1462-2920.2006.01108.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Diazotrophic community structure in microbial mats from Guerrero Negro (GN), Baja California, Mexico, was studied using polymerase chain reaction amplification of the nifH gene and a newly developed nifH oligonucleotide microarray. Ninety-six oligonucleotide probes designed for nifH sequences from cultivated isolates and the environment were printed on glass microarrays. Phylogenetic analysis showed that the probes represented all of the main nifH clusters. Specificity was tested by (i) evaluation of cross hybridization using individual targets, and (ii) comparison of the observed hybridization signals and those predicted from the sequences cloned from microbial mats. Signal intensity had a positive relationship with target concentration and the percentage identity between probe and target. Under moderate stringency and high target concentration, specificity of the probes varied from 77% to 100% with the individual targets tested. At the end of a 7-month long nutrient manipulation experiment in GN microbial mats, no expression of nitrogen fixation under nitrogen loading was detected, although a diverse community of diazotrophs was detected. The diversity in diazotrophic population present was higher than in the population expressing the nifH gene, and there were taxa specific differences in response to nutrients. The nifH microarray is a powerful tool for diazotroph community analysis in the marine environment.
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Affiliation(s)
- Pia H Moisander
- Department of Ocean Sciences, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA.
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23
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Ouzounis CA, Kunin V, Darzentas N, Goldovsky L. A minimal estimate for the gene content of the last universal common ancestor--exobiology from a terrestrial perspective. Res Microbiol 2005; 157:57-68. [PMID: 16431085 DOI: 10.1016/j.resmic.2005.06.015] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2005] [Revised: 06/15/2005] [Accepted: 06/30/2005] [Indexed: 10/25/2022]
Abstract
Using an algorithm for ancestral state inference of gene content, given a large number of extant genome sequences and a phylogenetic tree, we aim to reconstruct the gene content of the last universal common ancestor (LUCA), a hypothetical life form that presumably was the progenitor of the three domains of life. The method allows for gene loss, previously found to be a major factor in shaping gene content, and thus the estimate of LUCA's gene content appears to be substantially higher than that proposed previously, with a typical number of over 1000 gene families, of which more than 90% are also functionally characterized. More precisely, when only prokaryotes are considered, the number varies between 1006 and 1189 gene families while when eukaryotes are also included, this number increases to between 1344 and 1529 families depending on the underlying phylogenetic tree. Therefore, the common belief that the hypothetical genome of LUCA should resemble those of the smallest extant genomes of obligate parasites is not supported by recent advances in computational genomics. Instead, a fairly complex genome similar to those of free-living prokaryotes, with a variety of functional capabilities including metabolic transformation, information processing, membrane/transport proteins and complex regulation, shared between the three domains of life, emerges as the most likely progenitor of life on Earth, with profound repercussions for planetary exploration and exobiology.
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Affiliation(s)
- Christos A Ouzounis
- Computational Genomics Group, The European Bioinformatics Institute, EMBL Cambridge Outstation, Cambridge CB10 1SD, UK.
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24
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Trevors JT, Pollack GH. Hypothesis: the origin of life in a hydrogel environment. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2005; 89:1-8. [PMID: 15826671 DOI: 10.1016/j.pbiomolbio.2004.07.003] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A hypothesis is proposed that the first cell(s) on the Earth assembled in a hydrogel environment. Gel environments are capable of retaining water, oily hydrocarbons, solutes, and gas bubbles, and are capable of carrying out many functions, even in the absence of a membrane. Thus, the gel-like environment may have conferred distinct advantages for the assembly of the first cell(s).
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Affiliation(s)
- Jack T Trevors
- Laboratory of Microbial Technology, Department of Environmental Biology, Ontario Agricultural College, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
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25
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Walker JJ, Spear JR, Pace NR. Geobiology of a microbial endolithic community in the Yellowstone geothermal environment. Nature 2005; 434:1011-4. [PMID: 15846344 DOI: 10.1038/nature03447] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2004] [Accepted: 02/14/2005] [Indexed: 11/09/2022]
Abstract
The endolithic environment, the pore space of rocks, is a ubiquitous habitat for microorganisms on the Earth and is an important target of the search for life elsewhere in the Solar System. Photosynthetic, endolithic microbial communities commonly inhabit the outer millimetres to centimetres of all rocks exposed to the Earth's surface. In the most extreme terrestrial climates, such as hot and cold deserts, endolithic microorganisms are often the main form of life. The endolithic microhabitat gives protection from intense solar radiation and desiccation, and it provides mineral nutrients, rock moisture and growth surfaces. Here we describe the discovery and identification of the constituents of an extremely acidic (pH 1) endolithic microbial community inhabiting the pore space of rocks in the geothermal environment of Yellowstone National Park, USA. Subjected to silica mineralization, such endolithic communities constitute biomarkers that can become fossilized and potentially preserved in the geological record. Remnants of these communities could serve as biosignatures and provide important clues about ancient life associated with geothermal environments on the Earth or elsewhere in the Solar System.
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Affiliation(s)
- Jeffrey J Walker
- Department of Molecular, Cellular and Developmental Biology and the Center for Astrobiology, University of Colorado, Boulder, Colorado 80309-0347, USA
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Zehr JP, Jenkins BD, Short SM, Steward GF. Nitrogenase gene diversity and microbial community structure: a cross-system comparison. Environ Microbiol 2003; 5:539-54. [PMID: 12823187 DOI: 10.1046/j.1462-2920.2003.00451.x] [Citation(s) in RCA: 466] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Biological nitrogen fixation is an important source of fixed nitrogen for the biosphere. Microorganisms catalyse biological nitrogen fixation with the enzyme nitrogenase, which has been highly conserved through evolution. Cloning and sequencing of one of the nitrogenase structural genes, nifH, has provided a large, rapidly expanding database of sequences from diverse terrestrial and aquatic environments. Comparison of nifH phylogenies to ribosomal RNA phylogenies from cultivated microorganisms shows little conclusive evidence of lateral gene transfer. Sequence diversity far outstrips representation by cultivated representatives. The phylogeny of nitrogenase includes branches that represent phylotypic groupings based on ribosomal RNA phylogeny, but also includes paralogous clades including the alternative, non-molybdenum, non-vanadium containing nitrogenases. Only a few alternative or archaeal nitrogenase sequences have as yet been obtained from the environment. Extensive analysis of the distribution of nifH phylotypes among habitats indicates that there are characteristic patterns of nitrogen fixing microorganisms in termite guts, sediment and soil environments, estuaries and salt marshes, and oligotrophic oceans. The distribution of nitrogen-fixing microorganisms, although not entirely dictated by the nitrogen availability in the environment, is non-random and can be predicted on the basis of habitat characteristics. The ability to assay for gene expression and investigate genome arrangements provides the promise of new tools for interrogating natural populations of diazotrophs. The broad analysis of nitrogenase genes provides a basis for developing molecular assays and bioinformatics approaches for the study of nitrogen fixation in the environment.
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Affiliation(s)
- Jonathan P Zehr
- Department of Ocean Sciences, University of California, Santa Cruz, Santa Cruz, CA 95064, USA.
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Staley JT. Astrobiology, the transcendent science: the promise of astrobiology as an integrative approach for science and engineering education and research. Curr Opin Biotechnol 2003; 14:347-54. [PMID: 12849791 DOI: 10.1016/s0958-1669(03)00073-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Astrobiology is rapidly gaining the worldwide attention of scientists, engineers and the public. Astrobiology's captivation is due to its inherently interesting focus on life, its origins and distribution in the Universe. Because of its remarkable breadth as a scientific field, astrobiology touches on virtually all disciplines in the physical, biological and social sciences as well as engineering. The multidisciplinary nature and the appeal of its subject matter make astrobiology ideal for integrating the teaching of science at all levels in educational curricula. The rationale for implementing novel educational programs in astrobiology is presented along with specific research and educational policy recommendations.
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Affiliation(s)
- James T Staley
- Department of Microbiology, NSF Astrobiology IGERT Program, University of Washington, Box 357242, Seattle, WA 98195, USA.
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Visscher PT, Baumgartner LK, Buckley DH, Rogers DR, Hogan ME, Raleigh CD, Turk KA, Des Marais DJ. Dimethyl sulphide and methanethiol formation in microbial mats: potential pathways for biogenic signatures. Environ Microbiol 2003; 5:296-308. [PMID: 12662177 DOI: 10.1046/j.1462-2920.2003.00418.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mechanisms of dimethyl sulphide (DMS) and methanethiol (MT) production and consumption were determined in moderately hypersaline mats, Guerrero Negro, Mexico. Biological pathways regulated the net flux of DMS and MT as revealed by increases in flux resulting from decreased salinity, increased temperature and the removal of oxygen. Dimethylsulphoniopropionate (DMSP) was not present in these microbial mats and DMS and MT are probably formed by the reaction of photosynthetically produced low-molecular weight organic carbon and biogenic hydrogen sulphide derived from sulphate reduction. These observations provide an alternative to the notion that DMSP or S-containing amino acids are the dominant precursors of DMS in intertidal sediment systems. The major sink for DMS in the microbial mats was biological consumption, whereas photochemical oxidation to dimethylsulphoxide was the major sink for DMS in the overlying water column. Diel flux measurements demonstrated that significantly more DMS is released from the system during the night than during the day. The major consumers of DMS in the presence of oxygen were monooxygenase-utilizing bacteria, whereas under anoxic conditions, DMS was predominantly consumed by sulphate-reducing bacteria and methanethiol was consumed by methanogenic bacteria. Aerobic and anaerobic consumption rates of DMS were nearly identical. Mass balance estimates suggest that the consumption in the water column is likely to be smaller than net the flux from the mats. Volatile organic sulphur compounds are thus indicators of high rates of carbon fixation and sulphate reduction in these laminated sediment ecosystems, and atmospheric sulphur can be generated as a biogenic signature of the microbial mat community.
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Affiliation(s)
- Pieter T Visscher
- Department of Marine Sciences, University of Connecticut, Groton, CT 06340, USA.
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Abstract
Most reviews of microbial life in cold environments begin with a lament of how little is known about the psychrophilic (cold-loving) inhabitants or their specific adaptations to the cold. This situation is changing, as research becomes better focused by new molecular genetic (and other) approaches, by awareness of accelerated environmental change in polar regions, and by strong interest in the habitability of frozen environments elsewhere in the solar system. This review highlights recent discoveries in molecular adaptation, biodiversity and microbial dynamics in the cold, along with the concept of eutectophiles, organisms living at the critical interface inherent to the phase change of water to ice.
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Affiliation(s)
- Jody W Deming
- School of Oceanography, Box 357940, University of Washington, Seattle, Washington 98195, USA.
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Des Marais DJ, Harwit MO, Jucks KW, Kasting JF, Lin DNC, Lunine JI, Schneider J, Seager S, Traub WA, Woolf NJ. Remote sensing of planetary properties and biosignatures on extrasolar terrestrial planets. ASTROBIOLOGY 2002; 2:153-81. [PMID: 12469366 DOI: 10.1089/15311070260192246] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The major goals of NASA's Terrestrial Planet Finder (TPF) and the European Space Agency's Darwin missions are to detect terrestrial-sized extrasolar planets directly and to seek spectroscopic evidence of habitable conditions and life. Here we recommend wavelength ranges and spectral features for these missions. We assess known spectroscopic molecular band features of Earth, Venus, and Mars in the context of putative extrasolar analogs. The preferred wavelength ranges are 7-25 microns in the mid-IR and 0.5 to approximately 1.1 microns in the visible to near-IR. Detection of O2 or its photolytic product O3 merits highest priority. Liquid H2O is not a bioindicator, but it is considered essential to life. Substantial CO2 indicates an atmosphere and oxidation state typical of a terrestrial planet. Abundant CH4 might require a biological source, yet abundant CH4 also can arise from a crust and upper mantle more reduced than that of Earth. The range of characteristics of extrasolar rocky planets might far exceed that of the Solar System. Planetary size and mass are very important indicators of habitability and can be estimated in the mid-IR and potentially also in the visible to near-IR. Additional spectroscopic features merit study, for example, features created by other biosignature compounds in the atmosphere or on the surface and features due to Rayleigh scattering. In summary, we find that both the mid-IR and the visible to near-IR wavelength ranges offer valuable information regarding biosignatures and planetary properties; therefore both merit serious scientific consideration for TPF and Darwin.
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