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Schaible MJ, Szeinbaum N, Bozdag GO, Chou L, Grefenstette N, Colón-Santos S, Rodriguez LE, Styczinski MJ, Thweatt JL, Todd ZR, Vázquez-Salazar A, Adams A, Araújo MN, Altair T, Borges S, Burton D, Campillo-Balderas JA, Cangi EM, Caro T, Catalano E, Chen K, Conlin PL, Cooper ZS, Fisher TM, Fos SM, Garcia A, Glaser DM, Harman CE, Hermis NY, Hooks M, Johnson-Finn K, Lehmer O, Hernández-Morales R, Hughson KHG, Jácome R, Jia TZ, Marlow JJ, McKaig J, Mierzejewski V, Muñoz-Velasco I, Nural C, Oliver GC, Penev PI, Raj CG, Roche TP, Sabuda MC, Schaible GA, Sevgen S, Sinhadc P, Steller LH, Stelmach K, Tarnas J, Tavares F, Trubl G, Vidaurri M, Vincent L, Weber JM, Weng MM, Wilpiszeki RL, Young A. Chapter 1: The Astrobiology Primer 3.0. ASTROBIOLOGY 2024; 24:S4-S39. [PMID: 38498816 DOI: 10.1089/ast.2021.0129] [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 Astrobiology Primer 3.0 (ABP3.0) is a concise introduction to the field of astrobiology for students and others who are new to the field of astrobiology. It provides an entry into the broader materials in this supplementary issue of Astrobiology and an overview of the investigations and driving hypotheses that make up this interdisciplinary field. The content of this chapter was adapted from the other 10 articles in this supplementary issue and thus represents the contribution of all the authors who worked on these introductory articles. The content of this chapter is not exhaustive and represents the topics that the authors found to be the most important and compelling in a dynamic and changing field.
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Affiliation(s)
- Micah J Schaible
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Nadia Szeinbaum
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - G Ozan Bozdag
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - 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
| | - Stephanie Colón-Santos
- Wisconsin Institute for Discovery, University of Wisconsin-Madison, Wisconsin, USA
- Department of Botany, University of Wisconsin-Madison, Wisconsin, USA
| | - Laura E Rodriguez
- Lunar and Planetary Institute, Universities Space Research Association, Houston, Texas, USA
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | - M J Styczinski
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
- University of Washington, Seattle, Washington, USA
| | - Jennifer L Thweatt
- Department of Biochemistry and Molecular Biology, Penn State University, University Park, Pennsylvania, USA
| | - Zoe R Todd
- Department of Earth and Space Sciences, University of Washington, Seattle, Washington, USA
| | - Alberto Vázquez-Salazar
- Departamento de Biología Evolutiva, Facultad de Ciencias, Universidad Nacional Autónoma de México, Mexico City, Mexico
- Department of Chemical and Biomolecular Engineering, University of California Los Angeles, California, USA
| | - Alyssa Adams
- Center for Space Sciences and Technology, University of Maryland, Baltimore, Maryland, USA
| | - M N Araújo
- Biochemistry Department, University of São Paulo, São Carlos, Brazil
| | - Thiago Altair
- Institute of Chemistry of São Carlos, Universidade de São Paulo, São Carlos, Brazil
- Department of Chemistry, College of the Atlantic, Bar Harbor, Maine, USA
| | | | - Dana Burton
- Department of Anthropology, George Washington University, Washington DC, USA
| | | | - Eryn M Cangi
- Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, Colorado, 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
| | - Kimberly Chen
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Peter L Conlin
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Z S Cooper
- Department of Earth and Space Sciences, University of Washington, Seattle, Washington, USA
| | - Theresa M Fisher
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA
| | - Santiago Mestre Fos
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Amanda Garcia
- Department of Bacteriology, University of Wisconsin-Madison, Wisconsin, USA
| | - D M Glaser
- Arizona State University, Tempe, Arizona, USA
| | - Chester E Harman
- Departamento de Biología Evolutiva, Facultad de Ciencias, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Ninos Y Hermis
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
- Department of Physics and Space Sciences, University of Granada, Granada, Spain
| | - M Hooks
- NASA Johnson Space Center, Houston, Texas, USA
| | - K Johnson-Finn
- Earth-Life Science Institute, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, Japan
- Rensselaer Polytechnic Institute, Troy, New York, USA
| | - Owen Lehmer
- Department of Earth and Space Sciences, University of Washington, Seattle, Washington, USA
| | - Ricardo Hernández-Morales
- Departamento de Biología Evolutiva, Facultad de Ciencias, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Kynan H G Hughson
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Rodrigo Jácome
- Departamento de Biología Evolutiva, Facultad de Ciencias, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Tony Z Jia
- Blue Marble Space Institute of Science, Seattle, Washington, USA
- Earth-Life Science Institute, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, Japan
| | - Jeffrey J Marlow
- Department of Biology, Boston University, Boston, Massachusetts, USA
| | - Jordan McKaig
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Veronica Mierzejewski
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA
| | - Israel Muñoz-Velasco
- Departamento de Biología Evolutiva, Facultad de Ciencias, Universidad Nacional Autónoma de México, Mexico City, Mexico
- Departamento de Biología Celular, Facultad de Ciencias, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Ceren Nural
- Istanbul Technical University, Istanbul, Turkey
| | - Gina C Oliver
- Department of Geology, San Bernardino Valley College, San Bernardino, California, USA
| | - Petar I Penev
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Chinmayee Govinda Raj
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Tyler P Roche
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Mary C Sabuda
- Department of Earth and Environmental Sciences, University of Minnesota-Twin Cities, Minneapolis, Minnesota, USA
- Biotechnology Institute, University of Minnesota-Twin Cities, St. Paul, Minnesota, USA
| | - George A Schaible
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana, USA
| | - Serhat Sevgen
- Blue Marble Space Institute of Science, Seattle, Washington, USA
- Institute of Marine Sciences, Middle East Technical University, Erdemli, Mersin, Turkey
| | - Pritvik Sinhadc
- BEYOND: Center For Fundamental Concepts in Science, Arizona State University, Arizona, USA
- Dubai College, Dubai, United Arab Emirates
| | - Luke H Steller
- Australian Centre for Astrobiology, and School of Biological, Earth and Environmental Sciences, University of New South Wales, Kensington, Australia
| | - Kamil Stelmach
- Department of Chemistry, University of Virginia, Charlottesville, Virginia, USA
| | - J Tarnas
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | - Frank Tavares
- Space Enabled Research Group, MIT Media Lab, Cambridge, Massachusetts, USA
| | - Gareth Trubl
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California, USA
| | - Monica Vidaurri
- Center for Space Sciences and Technology, University of Maryland, Baltimore, Maryland, USA
- Department of Physics and Astronomy, Howard University, Washington DC, USA
| | - Lena Vincent
- Wisconsin Institute for Discovery, University of Wisconsin-Madison, Wisconsin, USA
| | - Jessica M Weber
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | | | | | - Amber Young
- NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
- Northern Arizona University, Flagstaff, Arizona, USA
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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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3
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Jaiswal B. Specular Reflections from Artificial Surfaces as Technosignature. ASTROBIOLOGY 2023; 23:291-294. [PMID: 36745401 DOI: 10.1089/ast.2022.0101] [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: 06/18/2023]
Abstract
Direct imaging of exoplanets will allow for observation of a planet in reflected light. Such a scenario may eventually allow for the possibility to scan a planetary surface for the presence of artificial structures made by alien civilizations. Detectability of planetary-scale structures, called megastructures, has been previously explored. In this work, we show that it is possible to detect structures of much smaller scale on exoplanetary surfaces by searching for the specular reflection of host starlight from the corresponding structures. As the planet rotates, these reflections can manifest as an optical transient riding atop the rotational light curve of the planet. Due to the directional nature of specular reflection, the reflected signal is very strong, and it is comparable to the planetary flux for surfaces that cover only a few parts per million of the total planetary surface area. By tracking the planet around its orbit, it should be possible to scan the planetary surface for any such structures that cover a size larger than a few parts per million of planetary surface. The proposed method will aid in the search for extraterrestrial intelligence in the era of direct imaging of exoplanets.
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Affiliation(s)
- Bhavesh Jaiswal
- Space Astronomy Group, U R Rao Satellite Centre, Bangalore, India
- Department of Physics, Indian Institute of Science, Bangalore, India
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4
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${\mathtt{s}}{\mathtt{t}}{\mathtt{a}}{\mathtt{r}}{\mathtt{r}}{\mathtt{y}}$: Analytic Occultation Light Curves. ACTA ACUST UNITED AC 2019. [DOI: 10.3847/1538-3881/aae8e5] [Citation(s) in RCA: 126] [Impact Index Per Article: 25.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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5
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Fujii Y, Angerhausen D, Deitrick R, Domagal-Goldman S, Grenfell JL, Hori Y, Kane SR, Pallé E, Rauer H, Siegler N, Stapelfeldt K, Stevenson KB. Exoplanet Biosignatures: Observational Prospects. ASTROBIOLOGY 2018; 18:739-778. [PMID: 29938537 PMCID: PMC6016572 DOI: 10.1089/ast.2017.1733] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Accepted: 03/13/2018] [Indexed: 05/04/2023]
Abstract
Exoplanet hunting efforts have revealed the prevalence of exotic worlds with diverse properties, including Earth-sized bodies, which has fueled our endeavor to search for life beyond the Solar System. Accumulating experiences in astrophysical, chemical, and climatological characterization of uninhabitable planets are paving the way to characterization of potentially habitable planets. In this paper, we review our possibilities and limitations in characterizing temperate terrestrial planets with future observational capabilities through the 2030s and beyond, as a basis of a broad range of discussions on how to advance "astrobiology" with exoplanets. We discuss the observability of not only the proposed biosignature candidates themselves but also of more general planetary properties that provide circumstantial evidence, since the evaluation of any biosignature candidate relies on its context. Characterization of temperate Earth-sized planets in the coming years will focus on those around nearby late-type stars. The James Webb Space Telescope (JWST) and later 30-meter-class ground-based telescopes will empower their chemical investigations. Spectroscopic studies of potentially habitable planets around solar-type stars will likely require a designated spacecraft mission for direct imaging, leveraging technologies that are already being developed and tested as part of the Wide Field InfraRed Survey Telescope (WFIRST) mission. Successful initial characterization of a few nearby targets will be an important touchstone toward a more detailed scrutiny and a larger survey that are envisioned beyond 2030. The broad outlook this paper presents may help develop new observational techniques to detect relevant features as well as frameworks to diagnose planets based on the observables. Key Words: Exoplanets-Biosignatures-Characterization-Planetary atmospheres-Planetary surfaces. Astrobiology 18, 739-778.
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Affiliation(s)
- Yuka Fujii
- NASA Goddard Institute for Space Studies, New York, New York, USA
- Earth-Life Science Institute, Tokyo Institute of Technology, Ookayama, Meguro, Tokyo, Japan
| | - Daniel Angerhausen
- CSH Fellow for Exoplanetary Astronomy, Center for Space and Habitability (CSH), Universität Bern, Bern, Switzerland
- Blue Marble Space Institute of Science, Seattle, Washington, USA
| | - Russell Deitrick
- Department of Astronomy, University of Washington, Seattle, Washington, USA
- NASA Astrobiology Institute's Virtual Planetary Laboratory
| | - Shawn Domagal-Goldman
- NASA Astrobiology Institute's Virtual Planetary Laboratory
- NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
| | - John Lee Grenfell
- Department of Extrasolar Planets and Atmospheres (EPA), Institute of Planetary Research, German Aerospace Centre (DLR), Berlin, Germany
| | - Yasunori Hori
- Astrobiology Center, National Institutes of Natural Sciences (NINS), Mitaka, Tokyo, Japan
| | - Stephen R. Kane
- Department of Earth Sciences, University of California, Riverside, California, USA
| | - Enric Pallé
- Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain
- Departamento de Astrofísica, Universidad de La Laguna, Tenerife, Spain
| | - Heike Rauer
- Department of Extrasolar Planets and Atmospheres (EPA), Institute of Planetary Research, German Aerospace Centre (DLR), Berlin, Germany
- Center for Astronomy and Astrophysics, Berlin Institute of Technology, Berlin, Germany
| | - Nicholas Siegler
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
- NASA Exoplanet Exploration Office
| | - Karl Stapelfeldt
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
- NASA Exoplanet Exploration Office
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6
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Catling DC, Krissansen-Totton J, Kiang NY, Crisp D, Robinson TD, DasSarma S, Rushby AJ, Del Genio A, Bains W, Domagal-Goldman S. Exoplanet Biosignatures: A Framework for Their Assessment. ASTROBIOLOGY 2018; 18:709-738. [PMID: 29676932 PMCID: PMC6049621 DOI: 10.1089/ast.2017.1737] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 12/05/2017] [Indexed: 05/04/2023]
Abstract
Finding life on exoplanets from telescopic observations is an ultimate goal of exoplanet science. Life produces gases and other substances, such as pigments, which can have distinct spectral or photometric signatures. Whether or not life is found with future data must be expressed with probabilities, requiring a framework of biosignature assessment. We present a framework in which we advocate using biogeochemical "Exo-Earth System" models to simulate potential biosignatures in spectra or photometry. Given actual observations, simulations are used to find the Bayesian likelihoods of those data occurring for scenarios with and without life. The latter includes "false positives" wherein abiotic sources mimic biosignatures. Prior knowledge of factors influencing planetary inhabitation, including previous observations, is combined with the likelihoods to give the Bayesian posterior probability of life existing on a given exoplanet. Four components of observation and analysis are necessary. (1) Characterization of stellar (e.g., age and spectrum) and exoplanetary system properties, including "external" exoplanet parameters (e.g., mass and radius), to determine an exoplanet's suitability for life. (2) Characterization of "internal" exoplanet parameters (e.g., climate) to evaluate habitability. (3) Assessment of potential biosignatures within the environmental context (components 1-2), including corroborating evidence. (4) Exclusion of false positives. We propose that resulting posterior Bayesian probabilities of life's existence map to five confidence levels, ranging from "very likely" (90-100%) to "very unlikely" (<10%) inhabited. Key Words: Bayesian statistics-Biosignatures-Drake equation-Exoplanets-Habitability-Planetary science. Astrobiology 18, 709-738.
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Affiliation(s)
- David C. Catling
- Astrobiology Program, Department of Earth and Space Sciences, University of Washington, Seattle, Washington
- Virtual Planetary Laboratory, University of Washington, Seattle, Washington
| | - Joshua Krissansen-Totton
- Astrobiology Program, Department of Earth and Space Sciences, University of Washington, Seattle, Washington
- Virtual Planetary Laboratory, University of Washington, Seattle, Washington
| | - Nancy Y. Kiang
- NASA Goddard Institute for Space Studies, New York, New York
| | - David Crisp
- MS 233-200, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
| | - Tyler D. Robinson
- Department of Astronomy and Astrophysics, University of California, Santa Cruz, California
| | - Shiladitya DasSarma
- Department of Microbiology and Immunology, School of Medicine, and Institute of Marine and Environmental Technology, University of Maryland, Baltimore, Maryland
| | | | | | - William Bains
- Department of Earth, Atmospheric and Planetary Science, Cambridge, Massachusetts
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7
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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: 97] [Impact Index Per Article: 16.2] [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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8
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Meadows VS, Reinhard CT, Arney GN, Parenteau MN, Schwieterman EW, Domagal-Goldman SD, Lincowski AP, Stapelfeldt KR, Rauer H, DasSarma S, Hegde S, Narita N, Deitrick R, Lustig-Yaeger J, Lyons TW, Siegler N, Grenfell JL. Exoplanet Biosignatures: Understanding Oxygen as a Biosignature in the Context of Its Environment. ASTROBIOLOGY 2018; 18:630-662. [PMID: 29746149 PMCID: PMC6014580 DOI: 10.1089/ast.2017.1727] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Accepted: 12/15/2017] [Indexed: 05/04/2023]
Abstract
We describe how environmental context can help determine whether oxygen (O2) detected in extrasolar planetary observations is more likely to have a biological source. Here we provide an in-depth, interdisciplinary example of O2 biosignature identification and observation, which serves as the prototype for the development of a general framework for biosignature assessment. Photosynthetically generated O2 is a potentially strong biosignature, and at high abundance, it was originally thought to be an unambiguous indicator for life. However, as a biosignature, O2 faces two major challenges: (1) it was only present at high abundance for a relatively short period of Earth's history and (2) we now know of several potential planetary mechanisms that can generate abundant O2 without life being present. Consequently, our ability to interpret both the presence and absence of O2 in an exoplanetary spectrum relies on understanding the environmental context. Here we examine the coevolution of life with the early Earth's environment to identify how the interplay of sources and sinks may have suppressed O2 release into the atmosphere for several billion years, producing a false negative for biologically generated O2. These studies suggest that planetary characteristics that may enhance false negatives should be considered when selecting targets for biosignature searches. We review the most recent knowledge of false positives for O2, planetary processes that may generate abundant atmospheric O2 without a biosphere. We provide examples of how future photometric, spectroscopic, and time-dependent observations of O2 and other aspects of the planetary environment can be used to rule out false positives and thereby increase our confidence that any observed O2 is indeed a biosignature. These insights will guide and inform the development of future exoplanet characterization missions. Key Words: Biosignatures-Oxygenic photosynthesis-Exoplanets-Planetary atmospheres. Astrobiology 18, 630-662.
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Affiliation(s)
- Victoria S. Meadows
- Department of Astronomy, University of Washington, Seattle, Washington
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
| | - Christopher T. Reinhard
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia
- NASA Astrobiology Institute, Alternative Earths Team, Riverside, California
| | - Giada N. Arney
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- Planetary Systems Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland
| | - Mary N. Parenteau
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- NASA Ames Research Center, Exobiology Branch, Mountain View, California
| | - Edward W. Schwieterman
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- NASA Astrobiology Institute, Alternative Earths Team, Riverside, California
- Department of Earth Sciences, University of California, Riverside, California
- NASA Postdoctoral Program, Universities Space Research Association, Columbia, Maryland
- Blue Marble Space Institute of Science, Seattle, Washington
| | - Shawn D. Domagal-Goldman
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- Planetary Environments Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland
| | - Andrew P. Lincowski
- Department of Astronomy, University of Washington, Seattle, Washington
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
| | - Karl R. Stapelfeldt
- NASA Exoplanet Exploration Program, Jet Propulsion Laboratory/California Institute of Technology, Pasadena, California
| | - Heike Rauer
- German Aerospace Center, Institute of Planetary Research, Extrasolar Planets and Atmospheres, Berlin, Germany
| | - Shiladitya DasSarma
- Department of Microbiology and Immunology, School of Medicine, University of Maryland, Baltimore, Maryland
- Institute of Marine and Environmental Technology, University System of Baltimore, Maryland
| | - Siddharth Hegde
- Carl Sagan Institute, Cornell University, Ithaca, New York
- Cornell Center for Astrophysics and Planetary Science, Cornell University, Ithaca, New York
| | - Norio Narita
- Department of Astronomy, The University of Tokyo, Tokyo, Japan
- Astrobiology Center, NINS, Tokyo, Japan
- National Astronomical Observatory of Japan, NINS, Tokyo, Japan
| | - Russell Deitrick
- Department of Astronomy, University of Washington, Seattle, Washington
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
| | - Jacob Lustig-Yaeger
- Department of Astronomy, University of Washington, Seattle, Washington
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
| | - Timothy W. Lyons
- NASA Astrobiology Institute, Alternative Earths Team, Riverside, California
- Department of Earth Sciences, University of California, Riverside, California
| | - Nicholas Siegler
- NASA Exoplanet Exploration Program, Jet Propulsion Laboratory/California Institute of Technology, Pasadena, California
| | - J. Lee Grenfell
- German Aerospace Center, Institute of Planetary Research, Extrasolar Planets and Atmospheres, Berlin, Germany
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9
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Meadows VS, Arney GN, Schwieterman EW, Lustig-Yaeger J, Lincowski AP, Robinson T, Domagal-Goldman SD, Deitrick R, Barnes RK, Fleming DP, Luger R, Driscoll PE, Quinn TR, Crisp D. The Habitability of Proxima Centauri b: Environmental States and Observational Discriminants. ASTROBIOLOGY 2018; 18:133-189. [PMID: 29431479 PMCID: PMC5820795 DOI: 10.1089/ast.2016.1589] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 09/04/2017] [Indexed: 05/21/2023]
Abstract
Proxima Centauri b provides an unprecedented opportunity to understand the evolution and nature of terrestrial planets orbiting M dwarfs. Although Proxima Cen b orbits within its star's habitable zone, multiple plausible evolutionary paths could have generated different environments that may or may not be habitable. Here, we use 1-D coupled climate-photochemical models to generate self-consistent atmospheres for several evolutionary scenarios, including high-O2, high-CO2, and more Earth-like atmospheres, with both oxic and anoxic compositions. We show that these modeled environments can be habitable or uninhabitable at Proxima Cen b's position in the habitable zone. We use radiative transfer models to generate synthetic spectra and thermal phase curves for these simulated environments, and use instrument models to explore our ability to discriminate between possible planetary states. These results are applicable not only to Proxima Cen b but to other terrestrial planets orbiting M dwarfs. Thermal phase curves may provide the first constraint on the existence of an atmosphere. We find that James Webb Space Telescope (JWST) observations longward of 10 μm could characterize atmospheric heat transport and molecular composition. Detection of ocean glint is unlikely with JWST but may be within the reach of larger-aperture telescopes. Direct imaging spectra may detect O4 absorption, which is diagnostic of massive water loss and O2 retention, rather than a photosynthetic biosphere. Similarly, strong CO2 and CO bands at wavelengths shortward of 2.5 μm would indicate a CO2-dominated atmosphere. If the planet is habitable and volatile-rich, direct imaging will be the best means of detecting habitability. Earth-like planets with microbial biospheres may be identified by the presence of CH4-which has a longer atmospheric lifetime under Proxima Centauri's incident UV-and either photosynthetically produced O2 or a hydrocarbon haze layer. Key Words: Planetary habitability and biosignatures-Planetary atmospheres-Exoplanets-Spectroscopic biosignatures-Planetary science-Proxima Centauri b. Astrobiology 18, 133-189.
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Affiliation(s)
- Victoria S. Meadows
- Astronomy Department, University of Washington, Seattle, Washington
- NASA Astrobiology Institute—Virtual Planetary Laboratory Lead Team, USA
| | - Giada N. Arney
- Astronomy Department, University of Washington, Seattle, Washington
- NASA Astrobiology Institute—Virtual Planetary Laboratory Lead Team, USA
- Planetary Systems Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland
| | - Edward W. Schwieterman
- Astronomy Department, University of Washington, Seattle, Washington
- NASA Astrobiology Institute—Virtual Planetary Laboratory Lead Team, USA
- NASA Postdoctoral Program, Universities Space Research Association, Columbia, Maryland
- Department of Earth Sciences, University of California at Riverside, Riverside, California
| | - Jacob Lustig-Yaeger
- Astronomy Department, University of Washington, Seattle, Washington
- NASA Astrobiology Institute—Virtual Planetary Laboratory Lead Team, USA
| | - Andrew P. Lincowski
- Astronomy Department, University of Washington, Seattle, Washington
- NASA Astrobiology Institute—Virtual Planetary Laboratory Lead Team, USA
| | - Tyler Robinson
- NASA Astrobiology Institute—Virtual Planetary Laboratory Lead Team, USA
- Department of Astronomy and Astrophysics, University of California, Santa Cruz, California
| | - Shawn D. Domagal-Goldman
- NASA Astrobiology Institute—Virtual Planetary Laboratory Lead Team, USA
- Planetary Environments Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland
| | - Russell Deitrick
- Astronomy Department, University of Washington, Seattle, Washington
- NASA Astrobiology Institute—Virtual Planetary Laboratory Lead Team, USA
| | - Rory K. Barnes
- Astronomy Department, University of Washington, Seattle, Washington
- NASA Astrobiology Institute—Virtual Planetary Laboratory Lead Team, USA
| | - David P. Fleming
- Astronomy Department, University of Washington, Seattle, Washington
- NASA Astrobiology Institute—Virtual Planetary Laboratory Lead Team, USA
| | - Rodrigo Luger
- Astronomy Department, University of Washington, Seattle, Washington
- NASA Astrobiology Institute—Virtual Planetary Laboratory Lead Team, USA
| | - Peter E. Driscoll
- NASA Astrobiology Institute—Virtual Planetary Laboratory Lead Team, USA
- Department of Terrestrial Magnetism, Carnegie Institution for Science, Washington, DC
| | - Thomas R. Quinn
- Astronomy Department, University of Washington, Seattle, Washington
- NASA Astrobiology Institute—Virtual Planetary Laboratory Lead Team, USA
| | - David Crisp
- NASA Astrobiology Institute—Virtual Planetary Laboratory Lead Team, USA
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
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10
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Yang W, Marshak A, Várnai T, Knyazikhin Y. EPIC Spectral Observations of Variability in Earth's Global Reflectance. REMOTE SENSING 2018; 10:254. [PMID: 31632826 PMCID: PMC6800679 DOI: 10.3390/rs10020254] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
NASA's Earth Polychromatic Imaging Camera (EPIC) onboard NOAA's Deep Space Climate Observatory (DSCOVR) satellite observes the entire sunlit Earth every 65 to 110 min from the Sun-Earth Lagrangian L1 point. This paper presents initial EPIC shortwave spectral observations of the sunlit Earth reflectance and analyses of its diurnal and seasonal variations. The results show that the reflectance depends mostly on (1) the ratio between land and ocean areas exposed to the Sun and (2) cloud spatial and temporal distributions over the sunlit side of Earth. In particular, the paper shows that (a) diurnal variations of the Earth's reflectance are determined mostly by periodic changes in the land-ocean fraction of its the sunlit side; (b) the daily reflectance displays clear seasonal variations that are significant even without including the contributions from snow and ice in the polar regions (which can enhance daily mean reflectances by up to 2 to 6% in winter and up to 1 to 4% in summer); (c) the seasonal variations of the sunlit Earth reflectance are mostly determined by the latitudinal distribution of oceanic clouds.
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Affiliation(s)
- Weidong Yang
- Goddard Earth Sciences Technology and Research, Universities Space Research Association, Columbia, MD 21046, USA
- NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
| | | | - Tamás Várnai
- NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
- Joint Center for Earth System Technology, University of Maryland at Baltimore County, Baltimore, MD 21250, USA
| | - Yuri Knyazikhin
- Department of Earth and Environment, Boston University, Boston, MA 02215, USA
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11
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Ryu D, Kim SW, Breault RP. New earth system model for optical performance evaluation of space instruments. OPTICS EXPRESS 2017; 25:4926-4944. [PMID: 28380760 DOI: 10.1364/oe.25.004926] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In this study, a new global earth system model is introduced for evaluating the optical performance of space instruments. Simultaneous imaging and spectroscopic results are provided using this global earth system model with fully resolved spatial, spectral, and temporal coverage of sub-models of the Earth. The sun sub-model is a Lambertian scattering sphere with a 6-h scale and 295 lines of solar spectral irradiance. The atmospheric sub-model has a 15-layer three-dimensional (3D) ellipsoid structure. The land sub-model uses spectral bidirectional reflectance distribution functions (BRDF) defined by a semi-empirical parametric kernel model. The ocean is modeled with the ocean spectral albedo after subtracting the total integrated scattering of the sun-glint scatter model. A hypothetical two-mirror Cassegrain telescope with a 300-mm-diameter aperture and 21.504 mm × 21.504-mm focal plane imaging instrument is designed. The simulated image results are compared with observational data from HRI-VIS measurements during the EPOXI mission for approximately 24 h from UTC Mar. 18, 2008. Next, the defocus mapping result and edge spread function (ESF) measuring result show that the distance between the primary and secondary mirror increases by 55.498 μm from the diffraction-limited condition. The shift of the focal plane is determined to be 5.813 mm shorter than that of the defocused focal plane, and this result is confirmed through the estimation of point spread function (PSF) measurements. This study shows that the earth system model combined with an instrument model is a powerful tool that can greatly help the development phase of instrument missions.
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12
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Schwieterman EW, Robinson TD, Meadows VS, Misra A, Domagal-Goldman S. DETECTING AND CONSTRAINING N2ABUNDANCES IN PLANETARY ATMOSPHERES USING COLLISIONAL PAIRS. ACTA ACUST UNITED AC 2015. [DOI: 10.1088/0004-637x/810/1/57] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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13
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Livengood T, Chin G, Sagdeev R, Mitrofanov I, Boynton W, Evans L, Litvak M, McClanahan T, Sanin A, Starr R, Su J. Moonshine: Diurnally varying hydration through natural distillation on the Moon, detected by the Lunar Exploration Neutron Detector (LEND). ICARUS 2015; 255:100-115. [PMID: 28798496 PMCID: PMC5548521 DOI: 10.1016/j.icarus.2015.04.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The Lunar Exploration Neutron Detector (LEND), on the polar-orbiting Lunar Reconnaissance Orbiter (LRO) spacecraft, has detected suppression in the Moon's naturally-occurring epithermal neutron leakage flux that is consistent with the presence of diurnally varying quantities of hydrogen in the regolith near the equator. Peak hydrogen concentration (neutron flux suppression) is on the dayside of the dawn terminator and diminishes through the dawn-to-noon sector. The minimum concentration of hydrogen is in the late afternoon and dusk sector. The chemical form of hydrogen is not determinable from these measurements, but other remote sensing methods and anticipated elemental availability suggest water molecules or hydroxyl ions. Signal-to-noise ratio at maximum contrast is 5.6σ in each of two detector systems. Volatiles are deduced to collect in or on the cold nightside surface and distill out of the regolith after dawn as rotation exposes the surface to sunlight. Liberated volatiles migrate away from the warm subsolar region toward the nearby cold nightside surface beyond the terminator, resulting in maximum concentration at the dawn terminator. The peak concentration within the upper ~1 m of regolith is estimated to be 0.0125 ± 0.0022 weight-percent water-equivalent hydrogen (wt% WEH) at dawn, yielding an accumulation of 190 ± 30 ml recoverable water per square meter of regolith at each dawn. Volatile transport over the lunar surface in opposition to the Moon's rotation exposes molecules to solar ultraviolet radiation. The short lifetime against photolysis and permanent loss of hydrogen from the Moon requires a resupply rate that greatly exceeds anticipated delivery of hydrogen by solar wind implantation or by meteoroid impacts, suggesting that the surface inventory must be continually resupplied by release from a deep volatile inventory in the Moon. The natural distillation of water from the regolith by sunlight and its capture on the cold night surface may provide energy-efficient access to volatiles for in situ resource utilization (ISRU) by direct capture before volatiles can enter the surface, eliminating the need to actively mine regolith for volatile resource recovery.
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Affiliation(s)
- T.A. Livengood
- CRESST/University of Maryland at Planetary Systems Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771, United States
| | - G. Chin
- Planetary Systems Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771, United States
| | - R.Z. Sagdeev
- Department of Physics, University of Maryland, College Park, MD 20742, United States
| | | | - W.V. Boynton
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, United States
| | - L.G. Evans
- Computer Sciences Corporation, Lanham-Seabrook, MD 20706, United States
| | - M.L. Litvak
- Institute for Space Research, Moscow, Russia
| | - T.P. McClanahan
- Astrochemistry Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771, United States
| | - A.B. Sanin
- Institute for Space Research, Moscow, Russia
| | - R.D. Starr
- Department of Physics, Catholic University of America, Washington, DC 20064, United States
| | - J.J. Su
- Department of Physics, University of Maryland, College Park, MD 20742, United States
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14
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Schwieterman EW, Cockell CS, Meadows VS. Nonphotosynthetic pigments as potential biosignatures. ASTROBIOLOGY 2015; 15:341-61. [PMID: 25941875 PMCID: PMC4442567 DOI: 10.1089/ast.2014.1178] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Previous work on possible surface reflectance biosignatures for Earth-like planets has typically focused on analogues to spectral features produced by photosynthetic organisms on Earth, such as the vegetation red edge. Although oxygenic photosynthesis, facilitated by pigments evolved to capture photons, is the dominant metabolism on our planet, pigmentation has evolved for multiple purposes to adapt organisms to their environment. We present an interdisciplinary study of the diversity and detectability of nonphotosynthetic pigments as biosignatures, which includes a description of environments that host nonphotosynthetic biologically pigmented surfaces, and a lab-based experimental analysis of the spectral and broadband color diversity of pigmented organisms on Earth. We test the utility of broadband color to distinguish between Earth-like planets with significant coverage of nonphotosynthetic pigments and those with photosynthetic or nonbiological surfaces, using both 1-D and 3-D spectral models. We demonstrate that, given sufficient surface coverage, nonphotosynthetic pigments could significantly impact the disk-averaged spectrum of a planet. However, we find that due to the possible diversity of organisms and environments, and the confounding effects of the atmosphere and clouds, determination of substantial coverage by biologically produced pigments would be difficult with broadband colors alone and would likely require spectrally resolved data.
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Affiliation(s)
- Edward W. Schwieterman
- University of Washington Astronomy Department, Seattle, Washington, USA
- NAI Virtual Planetary Laboratory, Seattle, Washington, USA
- University of Washington Astrobiology Program, Seattle, Washington, USA
| | - Charles S. Cockell
- University of Edinburgh School of Physics and Astronomy, Edinburgh, UK
- UK Centre for Astrobiology, Edinburgh, UK
| | - Victoria S. Meadows
- University of Washington Astronomy Department, Seattle, Washington, USA
- NAI Virtual Planetary Laboratory, Seattle, Washington, USA
- University of Washington Astrobiology Program, Seattle, Washington, USA
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15
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Fujii Y, Kimura J, Dohm J, Ohtake M. Geology and photometric variation of solar system bodies with minor atmospheres: implications for solid exoplanets. ASTROBIOLOGY 2014; 14:753-68. [PMID: 25238324 PMCID: PMC4172389 DOI: 10.1089/ast.2014.1165] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Accepted: 07/19/2014] [Indexed: 05/21/2023]
Abstract
A reasonable basis for future astronomical investigations of exoplanets lies in our best knowledge of the planets and satellites in the Solar System. Solar System bodies exhibit a wide variety of surface environments, even including potential habitable conditions beyond Earth, and it is essential to know how they can be characterized from outside the Solar System. In this study, we provide an overview of geological features of major Solar System solid bodies with minor atmospheres (i.e., the terrestrial Moon, Mercury, the Galilean moons, and Mars) that affect surface albedo at local to global scale, and we survey how they influence point-source photometry in the UV/visible/near IR (i.e., the reflection-dominant range). We simulate them based on recent mapping products and also compile observed light curves where available. We show a 5-50% peak-to-trough variation amplitude in one spin rotation associated with various geological processes including heterogeneous surface compositions due to igneous activities, interaction with surrounding energetic particles, and distribution of grained materials. Some indications of these processes are provided by the amplitude and wavelength dependence of variation in combinations of the time-averaged spectra. We also estimate the photometric precision needed to detect their spin rotation rates through periodogram analysis. Our survey illustrates realistic possibilities for inferring the detailed properties of solid exoplanets with future direct imaging observations. Key Words: Planetary environments-Planetary geology-Solar System-Extrasolar terrestrial planets.
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Affiliation(s)
- Yuka Fujii
- Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, Japan
| | - Jun Kimura
- Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, Japan
| | - James Dohm
- The University Museum, The University of Tokyo, Tokyo, Japan
| | - Makiko Ohtake
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Kanagawa, Japan
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16
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von Paris P, Selsis F, Kitzmann D, Rauer H. The dependence of the ice-albedo feedback on atmospheric properties. ASTROBIOLOGY 2013; 13:899-909. [PMID: 24111995 PMCID: PMC3807702 DOI: 10.1089/ast.2013.0993] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Accepted: 07/27/2013] [Indexed: 06/02/2023]
Abstract
Ice-albedo feedback is a potentially important destabilizing effect for the climate of terrestrial planets. It is based on the positive feedback between decreasing surface temperatures, an increase of snow and ice cover, and an associated increase in planetary albedo, which then further decreases surface temperature. A recent study shows that for M stars, the strength of the ice-albedo feedback is reduced due to the strong spectral dependence of stellar radiation and snow/ice albedos; that is, M stars primarily emit in the near IR, where the snow and ice albedo is low, and less in the visible, where the snow/ice albedo is high. This study investigates the influence of the atmosphere (in terms of surface pressure and atmospheric composition) on this feedback, since an atmosphere was neglected in previous studies. A plane-parallel radiative transfer model was used for the calculation of planetary albedos. We varied CO₂ partial pressures as well as the H₂O, CH₄, and O₃ content in the atmosphere for planets orbiting Sun-like and M type stars. Results suggest that, for planets around M stars, the ice-albedo effect is significantly reduced, compared to planets around Sun-like stars. Including the effects of an atmosphere further suppresses the sensitivity to the ice-albedo effect. Atmospheric key properties such as surface pressure, but also the abundance of radiative trace gases, can considerably change the strength of the ice-albedo feedback. For dense CO₂ atmospheres of the order of a few to tens of bar, atmospheric rather than surface properties begin to dominate the planetary radiation budget. At high CO₂ pressures, the ice-albedo feedback is strongly reduced for planets around M stars. The presence of trace amounts of H₂O and CH₄ in the atmosphere also weakens the ice-albedo effect for both stellar types considered. For planets around Sun-like stars, O₃ could also lead to a very strong decrease of the ice-albedo feedback at high CO₂ pressures.
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Affiliation(s)
- P von Paris
- 1 Université Bordeaux , LAB, UMR 5804, F-33270, Floirac, France
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17
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Rugheimer S, Kaltenegger L, Zsom A, Segura A, Sasselov D. Spectral fingerprints of Earth-like planets around FGK stars. ASTROBIOLOGY 2013; 13:251-69. [PMID: 23537136 PMCID: PMC3612284 DOI: 10.1089/ast.2012.0888] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
We present model atmospheres for an Earth-like planet orbiting the entire grid of main sequence FGK stars with effective temperatures ranging from Teff=4250 K to Teff=7000 K in 250 K intervals. We have modeled the remotely detectable spectra of Earth-like planets for clear and cloudy atmospheres at the 1 AU equivalent distance from the VIS to IR (0.4 to 20 μm) to compare detectability of features in different wavelength ranges in accordance with the James Webb Space Telescope and future design concepts to characterize exo-Earths. We have also explored the effect of the stellar UV levels as well as spectral energy distribution on a terrestrial atmosphere, concentrating on detectable atmospheric features that indicate habitability on Earth, namely, H2O, O3, CH4, N2O, and CH3Cl. The increase in UV dominates changes of O3, OH, CH4, N2O, and CH3Cl, whereas the increase in stellar temperature dominates changes in H2O. The overall effect as stellar effective temperatures and corresponding UV increase is a lower surface temperature of the planet due to a bigger part of the stellar flux being reflected at short wavelengths, as well as increased photolysis. Earth-like atmosphere models show more O3 and OH but less stratospheric CH4, N2O, CH3Cl, and tropospheric H2O (but more stratospheric H2O) with increasing effective temperature of main sequence stars. The corresponding detectable spectral features, on the other hand, show different detectability depending on the wavelength observed. We concentrate on directly imaged planets here as a framework to interpret future light curves, direct imaging, and secondary eclipse measurements of atmospheres of terrestrial planets in the habitable zone at varying orbital positions.
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Affiliation(s)
- Sarah Rugheimer
- Harvard Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138, USA.
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18
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Blitz MA, Seakins PW. Laboratory studies of photochemistry and gas phase radical reaction kinetics relevant to planetary atmospheres. Chem Soc Rev 2012; 41:6318-47. [DOI: 10.1039/c2cs35204d] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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