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Bozdag GO, Szeinbaum N, Conlin PL, Chen K, Fos SM, Garcia A, Penev PI, Schaible GA, Trubl G. Chapter 5: Major Biological Innovations in the History of Life on Earth. ASTROBIOLOGY 2024; 24:S107-S123. [PMID: 38498818 PMCID: PMC11071111 DOI: 10.1089/ast.2021.0119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 11/14/2023] [Indexed: 03/20/2024]
Abstract
All organisms living on Earth descended from a single, common ancestral population of cells, known as LUCA-the last universal common ancestor. Since its emergence, the diversity and complexity of life have increased dramatically. This chapter focuses on four key biological innovations throughout Earth's history that had a significant impact on the expansion of phylogenetic diversity, organismal complexity, and ecospace habitation. First is the emergence of the last universal common ancestor, LUCA, which laid the foundation for all life-forms on Earth. Second is the evolution of oxygenic photosynthesis, which resulted in global geochemical and biological transformations. Third is the appearance of a new type of cell-the eukaryotic cell-which led to the origin of a new domain of life and the basis for complex multicellularity. Fourth is the multiple independent origins of multicellularity, resulting in the emergence of a new level of complex individuality. A discussion of these four key events will improve our understanding of the intertwined history of our planet and its inhabitants and better inform the extent to which we can expect life at different degrees of diversity and complexity elsewhere.
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Affiliation(s)
- G. Ozan Bozdag
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Nadia Szeinbaum
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Peter L. Conlin
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Kimberly Chen
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, 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
| | - Petar I. Penev
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - George A. Schaible
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana, USA
| | - Gareth Trubl
- Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California, USA
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Ji A, Kasting JF, Cooke GJ, Marsh DR, Tsigaridis K. Comparison between ozone column depths and methane lifetimes computed by one- and three-dimensional models at different atmospheric O 2 levels. ROYAL SOCIETY OPEN SCIENCE 2023; 10:230056. [PMID: 37153363 PMCID: PMC10154922 DOI: 10.1098/rsos.230056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 04/13/2023] [Indexed: 05/09/2023]
Abstract
Recently, Cooke et al. (Cooke et al. 2022 R. Soc. Open Sci. 9, 211165. (doi:10.1098/rsos.211165)) used a three-dimensional coupled chemistry-climate model (WACCM6) to calculate ozone column depths at varied atmospheric O2 levels. They argued that previous one-dimensional (1-D) photochemical model studies, e.g. Segura et al. (Segura et al. 2003 Astrobiology 3, 689-708. (doi:10.1089/153110703322736024)), may have overestimated the ozone column depth at low pO2, and hence also overestimated the lifetime of methane. We have compared new simulations from an updated version of the Segura et al. model with those from WACCM6, together with some results from a second three-dimensional model. The discrepancy in ozone column depths is probably due to multiple interacting parameters, including H2O in the upper troposphere, lower boundary conditions, vertical and meridional transport rates, and different chemical mechanisms, especially the treatment of O2 photolysis in the Schumann-Runge (SR) bands (175-205 nm). The discrepancy in tropospheric OH concentrations and methane lifetime between WACCM6 and the 1-D model at low pO2 is reduced when absorption from CO2 and H2O in this wavelength region is included in WACCM6. Including scattering in the SR bands may further reduce this difference. Resolving these issues can be accomplished by developing an accurate parametrization for O2 photolysis in the SR bands and then repeating these calculations in the various models.
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Affiliation(s)
- A. Ji
- Department of Geosciences, Penn State University, University Park, PA 16802, USA
| | - J. F. Kasting
- Department of Geosciences, Penn State University, University Park, PA 16802, USA
| | - G. J. Cooke
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK
| | - D. R. Marsh
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK
- National Center for Atmospheric Research, Boulder, CO 80301, USA
| | - K. Tsigaridis
- Center for Climate Systems Research, Columbia University, New York, NY 10025, USA
- NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA
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Sabarathinam C, Mohan Viswanathan P, Senapathi V, Karuppannan S, Samayamanthula DR, Gopalakrishnan G, Alagappan R, Bhattacharya P. SARS-CoV-2 phase I transmission and mutability linked to the interplay of climatic variables: a global observation on the pandemic spread. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2022; 29:72366-72383. [PMID: 35028838 PMCID: PMC8758228 DOI: 10.1007/s11356-021-17481-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Accepted: 11/08/2021] [Indexed: 05/05/2023]
Abstract
The study aims to determine the impact of global meteorological parameters on SARS-COV-2, including population density and initiation of lockdown in twelve different countries. The daily trend of these parameters and COVID-19 variables from February 15th to April 25th, 2020, were considered. Asian countries show an increasing trend between infection rate and population density. A direct relationship between the time-lapse of the first infected case and the period of suspension of movement controls the transmissivity of COVID-19 in Asian countries. The increase in temperature has led to an increase in COVID-19 spread, while the decrease in humidity is consistent with the trend in daily deaths during the peak of the pandemic in European countries. Countries with 65°F temperature and 5 mm rainfall have a negative impact on COVID-19 spread. Lower oxygen availability in the atmosphere, fine droplets of submicron size together with infectious aerosols, and low wind speed have contributed to the increase in total cases and mortality in Germany and France. The onset of the D614G mutation and subsequent changes to D614 before March, later G614 in mid-March, and S943P, A831V, D839/Y/N/E in April were observed in Asian and European countries. The results of the correlation and factor analysis show that the COVID-19 cases and the climatic factors are significantly correlated with each other. The optimum meteorological conditions for the prevalence of G614 were identified. It was observed that the complex interaction of global meteorological factors and changes in the mutational form of CoV-2 phase I influenced the daily mortality rate along with other comorbid factors. The results of this study could help the public and policymakers to create awareness of the COVID-19 pandemic.
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Affiliation(s)
- Chidambaram Sabarathinam
- Water Research Centre, Kuwait Institute for Scientific Research, Safat, P.O. Box 24885, 13109, Kuwait City, Kuwait
- Department of Earth Sciences, Annamalai University, Annamalai Nagar, Chidambaram, Tamilnadu, India
| | - Prasanna Mohan Viswanathan
- Department of Applied Geology, Faculty of Engineering and Science, Curtin University, Malaysia, CDT 250, 98009, Miri, Sarawak, Malaysia
| | - Venkatramanan Senapathi
- Department of Disaster Management, Alagappa University, Karikudi, 630003, Tamil Nadu, India.
| | - Shankar Karuppannan
- Department of Applied Geology, School of Applied Natural Science, Adama Science and Technology University, Adama, Ethiopia
| | - Dhanu Radha Samayamanthula
- Water Research Centre, Kuwait Institute for Scientific Research, Safat, P.O. Box 24885, 13109, Kuwait City, Kuwait
| | - Gnanachandrasamy Gopalakrishnan
- School of Geography and Planning, Sun Yat -Sen University, Guangzhou, 510275, People's Republic of China
- Center for Earth, Environment and Resources, Sun Yat -Sen University, Guangzhou, 510275, People's Republic of China
| | | | - Prosun Bhattacharya
- Department of Sustainable Development, Environmental Science and Engineering, KTH Royal Institute of Technology, Stockholm, Sweden
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Rapid timescale for an oxic transition during the Great Oxidation Event and the instability of low atmospheric O 2. Proc Natl Acad Sci U S A 2022; 119:e2205618119. [PMID: 36067299 PMCID: PMC9477391 DOI: 10.1073/pnas.2205618119] [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] [Indexed: 12/03/2022] Open
Abstract
Understanding the rise of atmospheric oxygen on Earth is important for assessing precursors to complex life and for evaluating potential future detections of oxygen on exoplanets as signs of extraterrestrial biospheres. However, it is unclear whether Earth’s initial rise of O2 was monotonic or oscillatory, and geologic evidence poorly constrains O2 afterward, during the mid-Proterozoic (1.8 billion to 0.8 billion years ago). Here, we used a time-dependent photochemical model to simulate oxygen’s rise and the stability of subsequent O2 levels to perturbations in supply and loss. Results show that large oxygen fluctuations are possible during the initial rise of O2 and that Mesoproterozoic O2 had to exceed 0.01% volume concentration for atmospheric stability. The Great Oxidation Event (GOE), arguably the most important event to occur on Earth since the origin of life, marks the time when an oxygen-rich atmosphere first appeared. However, it is not known whether the change was abrupt and permanent or fitful and drawn out over tens or hundreds of millions of years. Here, we developed a one-dimensional time-dependent photochemical model to resolve time-dependent behavior of the chemically unstable transitional atmosphere as it responded to changes in biogenic forcing. When forced with step-wise changes in biogenic fluxes, transitions between anoxic and oxic atmospheres take between only 102 and 105 y. Results also suggest that O2 between ~10−8 and ~10−4 mixing ratio is unstable to plausible atmospheric perturbations. For example, when atmospheres with these O2 concentrations experience fractional variations in the surface CH4 flux comparable to those caused by modern Milankovich cycling, oxygen fluctuates between anoxic (~10−8) and oxic (~10−4) mixing ratios. Overall, our simulations are consistent with possible geologic evidence of unstable atmospheric O2, after initial oxygenation, which could occasionally collapse from changes in biospheric or volcanic fluxes. Additionally, modeling favors mid-Proterozoic O2 exceeding 10−4 to 10−3 mixing ratio; otherwise, O2 would periodically fall below 10−7 mixing ratio, which would be inconsistent with post-GOE absence of sulfur isotope mass-independent fractionation.
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Cooke GJ, Marsh DR, Walsh C, Black B, Lamarque JF. A revised lower estimate of ozone columns during Earth's oxygenated history. ROYAL SOCIETY OPEN SCIENCE 2022; 9:211165. [PMID: 35070343 PMCID: PMC8728182 DOI: 10.1098/rsos.211165] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Accepted: 11/25/2021] [Indexed: 05/17/2023]
Abstract
The history of molecular oxygen (O2) in Earth's atmosphere is still debated; however, geological evidence supports at least two major episodes where O2 increased by an order of magnitude or more: the Great Oxidation Event (GOE) and the Neoproterozoic Oxidation Event. O2 concentrations have likely fluctuated (between 10-3 and 1.5 times the present atmospheric level) since the GOE ∼2.4 Gyr ago, resulting in a time-varying ozone (O3) layer. Using a three-dimensional chemistry-climate model, we simulate changes in O3 in Earth's atmosphere since the GOE and consider the implications for surface habitability, and glaciation during the Mesoproterozoic. We find lower O3 columns (reduced by up to 4.68 times for a given O2 level) compared to previous work; hence, higher fluxes of biologically harmful UV radiation would have reached the surface. Reduced O3 leads to enhanced tropospheric production of the hydroxyl radical (OH) which then substantially reduces the lifetime of methane (CH4). We show that a CH4 supported greenhouse effect during the Mesoproterozoic is highly unlikely. The reduced O3 columns we simulate have important implications for astrobiological and terrestrial habitability, demonstrating the relevance of three-dimensional chemistry-climate simulations when assessing paleoclimates and the habitability of faraway worlds.
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Affiliation(s)
- G. J. Cooke
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK
| | - D. R. Marsh
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK
- National Center for Atmospheric Research, Boulder, CO 80301, USA
| | - C. Walsh
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK
| | - B. Black
- Department of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ, USA
- Department of Earth and Atmospheric Sciences, CUNY City College, New York, NY, USA
| | - J.-F. Lamarque
- National Center for Atmospheric Research, Boulder, CO 80301, USA
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Triple oxygen isotope constraints on atmospheric O 2 and biological productivity during the mid-Proterozoic. Proc Natl Acad Sci U S A 2021; 118:2105074118. [PMID: 34911756 PMCID: PMC8713798 DOI: 10.1073/pnas.2105074118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/02/2021] [Indexed: 12/16/2022] Open
Abstract
Reconstructing the history of biological productivity and atmospheric oxygen partial pressure (pO2) is a fundamental goal of geobiology. Recently, the mass-independent fractionation of oxygen isotopes (O-MIF) has been used as a tool for estimating pO2 and productivity during the Proterozoic. O-MIF, reported as Δ'17O, is produced during the formation of ozone and destroyed by isotopic exchange with water by biological and chemical processes. Atmospheric O-MIF can be preserved in the geologic record when pyrite (FeS2) is oxidized during weathering, and the sulfur is redeposited as sulfate. Here, sedimentary sulfates from the ∼1.4-Ga Sibley Formation are reanalyzed using a detailed one-dimensional photochemical model that includes physical constraints on air-sea gas exchange. Previous analyses of these data concluded that pO2 at that time was <1% PAL (times the present atmospheric level). Our model shows that the upper limit on pO2 is essentially unconstrained by these data. Indeed, pO2 levels below 0.8% PAL are possible only if atmospheric methane was more abundant than today (so that pCO2 could have been lower) or if the Sibley O-MIF data were diluted by reprocessing before the sulfates were deposited. Our model also shows that, contrary to previous assertions, marine productivity cannot be reliably constrained by the O-MIF data because the exchange of molecular oxygen (O2) between the atmosphere and surface ocean is controlled more by air-sea gas transfer rates than by biological productivity. Improved estimates of pCO2 and/or improved proxies for Δ'17O of atmospheric O2 would allow tighter constraints to be placed on mid-Proterozoic pO2.
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Timing the Evolutionary Advent of Cyanobacteria and the Later Great Oxidation Event Using Gene Phylogenies of a Sunscreen. mBio 2019; 10:mBio.00561-19. [PMID: 31113897 PMCID: PMC6529634 DOI: 10.1128/mbio.00561-19] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The biosynthesis of the unique cyanobacterial (oxyphotobacterial) indole-phenolic UVA sunscreen, scytonemin, is coded for in a conserved operon that contains both core metabolic genes and accessory, aromatic amino acid biosynthesis genes dedicated to supplying scytonemin's precursors. Comparative genomics shows conservation of this operon in many, but not all, cyanobacterial lineages. Phylogenetic analyses of the operon's aromatic amino acid genes indicate that five of them were recruited into the operon after duplication events of their respective housekeeping cyanobacterial cognates. We combined the fossil record of cyanobacteria and relaxed molecular clock models to obtain multiple estimates of these duplication events, setting a minimum age for the evolutionary advent of scytonemin at 2.1 ± 0.3 billion years. The same analyses were used to estimate the advent of cyanobacteria as a group (and thus the appearance of oxygenic photosynthesis), at 3.6 ± 0.2 billion years before present. Post hoc interpretation of 16S rRNA-based Bayesian analyses was consistent with these estimates. Because of physiological constraints on the use of UVA sunscreens in general, and the biochemical constraints of scytonemin in particular, scytonemin's age must postdate the time when Earth's atmosphere turned oxic, known as the Great Oxidation Event (GOE). Indeed, our biological estimate is in agreement with independent geochemical estimates for the GOE. The difference between the estimated ages of oxygenic photosynthesis and the GOE indicates the long span (on the order of a billion years) of the era of "oxygen oases," when oxygen was available locally but not globally.IMPORTANCE The advent of cyanobacteria, with their invention of oxygenic photosynthesis, and the Great Oxidation Event are arguably among the most important events in the evolutionary history of life on Earth. Oxygen is a significant toxicant to all life, but its accumulation in the atmosphere also enabled the successful development and proliferation of many aerobic organisms, especially metazoans. The currently favored dating of the Great Oxidation Event is based on the geochemical rock record. Similarly, the advent of cyanobacteria is also often drawn from the same estimates because in older rocks paleontological evidence is scarce or has been discredited. Efforts to obtain molecular evolutionary alternatives have offered widely divergent estimates. Our analyses provide a novel means to circumvent these limitations and allow us to estimate the large time gap between the two events.
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Triple oxygen isotope evidence for limited mid-Proterozoic primary productivity. Nature 2018; 559:613-616. [PMID: 30022163 DOI: 10.1038/s41586-018-0349-y] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 06/01/2018] [Indexed: 11/08/2022]
Abstract
The global biosphere is commonly assumed to have been less productive before the rise of complex eukaryotic ecosystems than it is today1. However, direct evidence for this assertion is lacking. Here we present triple oxygen isotope measurements (∆17O) from sedimentary sulfates from the Sibley basin (Ontario, Canada) dated to about 1.4 billion years ago, which provide evidence for a less productive biosphere in the middle of the Proterozoic eon. We report what are, to our knowledge, the most-negative ∆17O values (down to -0.88‰) observed in sulfates, except for those from the terminal Cryogenian period2. This observation demonstrates that the mid-Proterozoic atmosphere was distinct from what persisted over approximately the past 0.5 billion years, directly reflecting a unique interplay among the atmospheric partial pressures of CO2 and O2 and the photosynthetic O2 flux at this time3. Oxygenic gross primary productivity is stoichiometrically related to the photosynthetic O2 flux to the atmosphere. Under current estimates of mid-Proterozoic atmospheric partial pressure of CO2 (2-30 times that of pre-anthropogenic levels), our modelling indicates that gross primary productivity was between about 6% and 41% of pre-anthropogenic levels if atmospheric O2 was between 0.1-1% or 1-10% of pre-anthropogenic levels, respectively. When compared to estimates of Archaean4-6 and Phanerozoic primary production7, these model solutions show that an increasingly more productive biosphere accompanied the broad secular pattern of increasing atmospheric O2 over geologic time8.
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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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11
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Keles E, Grenfell JL, Godolt M, Stracke B, Rauer H. The Effect of Varying Atmospheric Pressure upon Habitability and Biosignatures of Earth-like Planets. ASTROBIOLOGY 2018; 18:116-132. [PMID: 29364704 DOI: 10.1089/ast.2016.1632] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Understanding the possible climatic conditions on rocky extrasolar planets, and thereby their potential habitability, is one of the major subjects of exoplanet research. Determining how the climate, as well as potential atmospheric biosignatures, changes under different conditions is a key aspect when studying Earth-like exoplanets. One important property is the atmospheric mass, hence pressure and its influence on the climatic conditions. Therefore, the aim of the present study is to understand the influence of atmospheric mass on climate, hence habitability, and the spectral appearance of planets with Earth-like, that is, N2-O2 dominated, atmospheres orbiting the Sun at 1 AU. This work utilizes a 1D coupled, cloud-free, climate-photochemical atmospheric column model; varies atmospheric surface pressure from 0.5 to 30 bar; and investigates temperature and key species profiles, as well as emission and brightness temperature spectra in a range between 2 and 20 μm. Increasing the surface pressure up to 4 bar leads to an increase in the surface temperature due to increased greenhouse warming. Above this point, Rayleigh scattering dominates, and the surface temperature decreases, reaching surface temperatures below 273 K (approximately at ∼34 bar surface pressure). For ozone, nitrous oxide, water, methane, and carbon dioxide, the spectral response either increases with surface temperature or pressure depending on the species. Masking effects occur, for example, for the bands of the biosignatures ozone and nitrous oxide by carbon dioxide, which could be visible in low carbon dioxide atmospheres. Key Words: Planetary habitability and biosignatures-Atmospheres-Radiative transfer. Astrobiology 18, 116-132.
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Affiliation(s)
- Engin Keles
- 1 Zentrum für Astronomie und Astrophysik, Technische Universität Berlin , Berlin, Germany
| | - John Lee Grenfell
- 2 Institut für Planetenforschung , Deutsches Zentrum für Luft- und Raumfahrt, Berlin, Germany
| | - Mareike Godolt
- 1 Zentrum für Astronomie und Astrophysik, Technische Universität Berlin , Berlin, Germany
| | - Barbara Stracke
- 2 Institut für Planetenforschung , Deutsches Zentrum für Luft- und Raumfahrt, Berlin, Germany
| | - Heike Rauer
- 1 Zentrum für Astronomie und Astrophysik, Technische Universität Berlin , Berlin, Germany
- 2 Institut für Planetenforschung , Deutsches Zentrum für Luft- und Raumfahrt, Berlin, Germany
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Abstract
Oxygenic photosynthesis is Earth's dominant metabolism, having evolved to harvest the largest expected energy source at the surface of most terrestrial habitable zone planets. Using CO2 and H2O-molecules that are expected to be abundant and widespread on habitable terrestrial planets-oxygenic photosynthesis is plausible as a significant planetary process with a global impact. Photosynthetic O2 has long been considered particularly robust as a sign of life on a habitable exoplanet, due to the lack of known "false positives"-geological or photochemical processes that could also produce large quantities of stable O2. O2 has other advantages as a biosignature, including its high abundance and uniform distribution throughout the atmospheric column and its distinct, strong absorption in the visible and near-infrared. However, recent modeling work has shown that false positives for abundant oxygen or ozone could be produced by abiotic mechanisms, including photochemistry and atmospheric escape. Environmental factors for abiotic O2 have been identified and will improve our ability to choose optimal targets and measurements to guard against false positives. Most of these false-positive mechanisms are dependent on properties of the host star and are often strongest for planets orbiting M dwarfs. In particular, selecting planets found within the conservative habitable zone and those orbiting host stars more massive than 0.4 M⊙ (M3V and earlier) may help avoid planets with abundant abiotic O2 generated by water loss. Searching for O4 or CO in the planetary spectrum, or the lack of H2O or CH4, could help discriminate between abiotic and biological sources of O2 or O3. In advance of the next generation of telescopes, thorough evaluation of potential biosignatures-including likely environmental context and factors that could produce false positives-ultimately works to increase our confidence in life detection. Key Words: Biosignatures-Exoplanets-Oxygen-Photosynthesis-Planetary spectra. Astrobiology 17, 1022-1052.
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Affiliation(s)
- Victoria S Meadows
- 1 Department of Astronomy and Astrobiology Program, University of Washington , Seattle, Washington
- 2 NASA Astrobiology Institute-Virtual Planetary Laboratory , USA
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13
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Reinhard CT, Olson SL, Schwieterman EW, Lyons TW. False Negatives for Remote Life Detection on Ocean-Bearing Planets: Lessons from the Early Earth. ASTROBIOLOGY 2017; 17:287-297. [PMID: 28418704 PMCID: PMC5399744 DOI: 10.1089/ast.2016.1598] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Accepted: 01/23/2017] [Indexed: 05/04/2023]
Abstract
Ocean-atmosphere chemistry on Earth has undergone dramatic evolutionary changes throughout its long history, with potentially significant ramifications for the emergence and long-term stability of atmospheric biosignatures. Though a great deal of work has centered on refining our understanding of false positives for remote life detection, much less attention has been paid to the possibility of false negatives, that is, cryptic biospheres that are widespread and active on a planet's surface but are ultimately undetectable or difficult to detect in the composition of a planet's atmosphere. Here, we summarize recent developments from geochemical proxy records and Earth system models that provide insight into the long-term evolution of the most readily detectable potential biosignature gases on Earth-oxygen (O2), ozone (O3), and methane (CH4). We suggest that the canonical O2-CH4 disequilibrium biosignature would perhaps have been challenging to detect remotely during Earth's ∼4.5-billion-year history and that in general atmospheric O2/O3 levels have been a poor proxy for the presence of Earth's biosphere for all but the last ∼500 million years. We further suggest that detecting atmospheric CH4 would have been problematic for most of the last ∼2.5 billion years of Earth's history. More broadly, we stress that internal oceanic recycling of biosignature gases will often render surface biospheres on ocean-bearing silicate worlds cryptic, with the implication that the planets most conducive to the development and maintenance of a pervasive biosphere will often be challenging to characterize via conventional atmospheric biosignatures. Key Words: Biosignatures-Oxygen-Methane-Ozone-Exoplanets-Planetary habitability. Astrobiology 17, 287-297.
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Affiliation(s)
- Christopher T. Reinhard
- NASA Astrobiology Institute
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia
| | - Stephanie L. Olson
- NASA Astrobiology Institute
- Department of Earth Sciences, University of California, Riverside, California
| | - Edward W. Schwieterman
- NASA Astrobiology Institute
- 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
| | - Timothy W. Lyons
- NASA Astrobiology Institute
- Department of Earth Sciences, University of California, Riverside, California
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14
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Gebauer S, Grenfell JL, Stock JW, Lehmann R, Godolt M, von Paris P, Rauer H. Evolution of Earth-like Extrasolar Planetary Atmospheres: Assessing the Atmospheres and Biospheres of Early Earth Analog Planets with a Coupled Atmosphere Biogeochemical Model. ASTROBIOLOGY 2017; 17:27-54. [PMID: 28103105 DOI: 10.1089/ast.2015.1384] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Understanding the evolution of Earth and potentially habitable Earth-like worlds is essential to fathom our origin in the Universe. The search for Earth-like planets in the habitable zone and investigation of their atmospheres with climate and photochemical models is a central focus in exoplanetary science. Taking the evolution of Earth as a reference for Earth-like planets, a central scientific goal is to understand what the interactions were between atmosphere, geology, and biology on early Earth. The Great Oxidation Event in Earth's history was certainly caused by their interplay, but the origin and controlling processes of this occurrence are not well understood, the study of which will require interdisciplinary, coupled models. In this work, we present results from our newly developed Coupled Atmosphere Biogeochemistry model in which atmospheric O2 concentrations are fixed to values inferred by geological evidence. Applying a unique tool (Pathway Analysis Program), ours is the first quantitative analysis of catalytic cycles that governed O2 in early Earth's atmosphere near the Great Oxidation Event. Complicated oxidation pathways play a key role in destroying O2, whereas in the upper atmosphere, most O2 is formed abiotically via CO2 photolysis. The O2 bistability found by Goldblatt et al. ( 2006 ) is not observed in our calculations likely due to our detailed CH4 oxidation scheme. We calculate increased CH4 with increasing O2 during the Great Oxidation Event. For a given atmospheric surface flux, different atmospheric states are possible; however, the net primary productivity of the biosphere that produces O2 is unique. Mixing, CH4 fluxes, ocean solubility, and mantle/crust properties strongly affect net primary productivity and surface O2 fluxes. Regarding exoplanets, different "states" of O2 could exist for similar biomass output. Strong geological activity could lead to false negatives for life (since our analysis suggests that reducing gases remove O2 that masks its biosphere over a wide range of conditions). Key Words: Early Earth-Proterozoic-Archean-Oxygen-Atmosphere-Biogeochemistry-Photochemistry-Biosignatures-Earth-like planets. Astrobiology 16, 27-54.
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Affiliation(s)
- S Gebauer
- 1 Zentrum für Astronomie und Astrophysik (ZAA), Technische Universität Berlin (TUB) , Berlin, Germany
- 2 Institut für Planetenforschung (PF) , Deutsches Zentrum für Luft- und Raumfahrt (DLR), Berlin, Germany
| | - J L Grenfell
- 2 Institut für Planetenforschung (PF) , Deutsches Zentrum für Luft- und Raumfahrt (DLR), Berlin, Germany
| | - J W Stock
- 3 Instituto de Astrofísica de Andalucía-CSIC , Granada, Spain
| | - R Lehmann
- 4 Alfred-Wegener Institut Helmholtz-Zentrum für Polar- und Meeresforschung , Potsdam, Germany
| | - M Godolt
- 2 Institut für Planetenforschung (PF) , Deutsches Zentrum für Luft- und Raumfahrt (DLR), Berlin, Germany
| | - P von Paris
- 5 Université de Bordeaux , LAB, UMR 5804, Floirac, France
- 6 CNRS, LAB , UMR 5804, Floirac, France
| | - H Rauer
- 1 Zentrum für Astronomie und Astrophysik (ZAA), Technische Universität Berlin (TUB) , Berlin, Germany
- 2 Institut für Planetenforschung (PF) , Deutsches Zentrum für Luft- und Raumfahrt (DLR), Berlin, Germany
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15
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Arney G, Domagal-Goldman SD, Meadows VS, Wolf ET, Schwieterman E, Charnay B, Claire M, Hébrard E, Trainer MG. The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth. ASTROBIOLOGY 2016; 16:873-899. [PMID: 27792417 PMCID: PMC5148108 DOI: 10.1089/ast.2015.1422] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Accepted: 07/13/2016] [Indexed: 05/21/2023]
Abstract
Recognizing whether a planet can support life is a primary goal of future exoplanet spectral characterization missions, but past research on habitability assessment has largely ignored the vastly different conditions that have existed in our planet's long habitable history. This study presents simulations of a habitable yet dramatically different phase of Earth's history, when the atmosphere contained a Titan-like, organic-rich haze. Prior work has claimed a haze-rich Archean Earth (3.8-2.5 billion years ago) would be frozen due to the haze's cooling effects. However, no previous studies have self-consistently taken into account climate, photochemistry, and fractal hazes. Here, we demonstrate using coupled climate-photochemical-microphysical simulations that hazes can cool the planet's surface by about 20 K, but habitable conditions with liquid surface water could be maintained with a relatively thick haze layer (τ ∼ 5 at 200 nm) even with the fainter young Sun. We find that optically thicker hazes are self-limiting due to their self-shielding properties, preventing catastrophic cooling of the planet. Hazes may even enhance planetary habitability through UV shielding, reducing surface UV flux by about 97% compared to a haze-free planet and potentially allowing survival of land-based organisms 2.7-2.6 billion years ago. The broad UV absorption signature produced by this haze may be visible across interstellar distances, allowing characterization of similar hazy exoplanets. The haze in Archean Earth's atmosphere was strongly dependent on biologically produced methane, and we propose that hydrocarbon haze may be a novel type of spectral biosignature on planets with substantial levels of CO2. Hazy Archean Earth is the most alien world for which we have geochemical constraints on environmental conditions, providing a useful analogue for similar habitable, anoxic exoplanets. Key Words: Haze-Archean Earth-Exoplanets-Spectra-Biosignatures-Planetary habitability. Astrobiology 16, 873-899.
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Affiliation(s)
- Giada Arney
- Astronomy Department, University of Washington, Seattle, Washington, USA
- NASA Astrobiology Institute Virtual Planetary Laboratory, University of Washington, Seattle, Washington, USA
- Astrobiology Program, University of Washington, Seattle, Washington, USA
- Now at: NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
- Now at: NASA Postdoctoral Program, Universities Space Research Association, Columbia, Maryland, USA
| | - Shawn D. Domagal-Goldman
- NASA Astrobiology Institute Virtual Planetary Laboratory, University of Washington, Seattle, Washington, USA
- NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
| | - Victoria S. Meadows
- Astronomy Department, University of Washington, Seattle, Washington, USA
- NASA Astrobiology Institute Virtual Planetary Laboratory, University of Washington, Seattle, Washington, USA
- Astrobiology Program, University of Washington, Seattle, Washington, USA
| | - Eric T. Wolf
- Department of Atmospheric and Oceanic Sciences, Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, Boulder, Colorado, USA
| | - Edward Schwieterman
- Astronomy Department, University of Washington, Seattle, Washington, USA
- NASA Astrobiology Institute Virtual Planetary Laboratory, University of Washington, Seattle, Washington, USA
- Astrobiology Program, University of Washington, Seattle, Washington, USA
- Now at: NASA Postdoctoral Program, Universities Space Research Association, Columbia, Maryland, USA
- Now at: University of California at Riverside, Riverside, California, USA
- Blue Marble Institute of Science, Seattle, Washington, USA
| | - Benjamin Charnay
- Astronomy Department, University of Washington, Seattle, Washington, USA
- NASA Astrobiology Institute Virtual Planetary Laboratory, University of Washington, Seattle, Washington, USA
- Astrobiology Program, University of Washington, Seattle, Washington, USA
- Now at: Paris-Meudon Observatory, Paris, France
| | - Mark Claire
- NASA Astrobiology Institute Virtual Planetary Laboratory, University of Washington, Seattle, Washington, USA
- Blue Marble Institute of Science, Seattle, Washington, USA
- Department of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK
| | - Eric Hébrard
- NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
- University of Exeter, Exeter, Devon, UK
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16
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Domagal-Goldman SD, Wright KE, Adamala K, Arina de la Rubia L, Bond J, Dartnell LR, Goldman AD, Lynch K, Naud ME, Paulino-Lima IG, Singer K, Walther-Antonio M, Abrevaya XC, Anderson R, Arney G, Atri D, Azúa-Bustos A, Bowman JS, Brazelton WJ, Brennecka GA, Carns R, Chopra A, Colangelo-Lillis J, Crockett CJ, DeMarines J, Frank EA, Frantz C, de la Fuente E, Galante D, Glass J, Gleeson D, Glein CR, Goldblatt C, Horak R, Horodyskyj L, Kaçar B, Kereszturi A, Knowles E, Mayeur P, McGlynn S, Miguel Y, Montgomery M, Neish C, Noack L, Rugheimer S, Stüeken EE, Tamez-Hidalgo P, Imari Walker S, Wong T. The Astrobiology Primer v2.0. ASTROBIOLOGY 2016; 16:561-653. [PMID: 27532777 PMCID: PMC5008114 DOI: 10.1089/ast.2015.1460] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Accepted: 06/06/2016] [Indexed: 05/09/2023]
Affiliation(s)
- Shawn D Domagal-Goldman
- 1 NASA Goddard Space Flight Center , Greenbelt, Maryland, USA
- 2 Virtual Planetary Laboratory , Seattle, Washington, USA
| | - Katherine E Wright
- 3 University of Colorado at Boulder , Colorado, USA
- 4 Present address: UK Space Agency, UK
| | - Katarzyna Adamala
- 5 Department of Genetics, Cell Biology and Development, University of Minnesota , Minneapolis, Minnesota, USA
| | | | - Jade Bond
- 7 Department of Physics, University of New South Wales , Sydney, Australia
| | | | | | - Kennda Lynch
- 10 Division of Biological Sciences, University of Montana , Missoula, Montana, USA
| | - Marie-Eve Naud
- 11 Institute for research on exoplanets (iREx) , Université de Montréal, Montréal, Canada
| | - Ivan G Paulino-Lima
- 12 Universities Space Research Association , Mountain View, California, USA
- 13 Blue Marble Space Institute of Science , Seattle, Washington, USA
| | - Kelsi Singer
- 14 Southwest Research Institute , Boulder, Colorado, USA
| | | | - Ximena C Abrevaya
- 16 Instituto de Astronomía y Física del Espacio (IAFE) , UBA-CONICET, Ciudad Autónoma de Buenos Aires, Argentina
| | - Rika Anderson
- 17 Department of Biology, Carleton College , Northfield, Minnesota, USA
| | - Giada Arney
- 18 University of Washington Astronomy Department and Astrobiology Program , Seattle, Washington, USA
| | - Dimitra Atri
- 13 Blue Marble Space Institute of Science , Seattle, Washington, USA
| | | | - Jeff S Bowman
- 19 Lamont-Doherty Earth Observatory, Columbia University , Palisades, New York, USA
| | | | | | - Regina Carns
- 22 Polar Science Center, Applied Physics Laboratory, University of Washington , Seattle, Washington, USA
| | - Aditya Chopra
- 23 Planetary Science Institute, Research School of Earth Sciences, Research School of Astronomy and Astrophysics, The Australian National University , Canberra, Australia
| | - Jesse Colangelo-Lillis
- 24 Earth and Planetary Science, McGill University , and the McGill Space Institute, Montréal, Canada
| | | | - Julia DeMarines
- 13 Blue Marble Space Institute of Science , Seattle, Washington, USA
| | | | - Carie Frantz
- 27 Department of Geosciences, Weber State University , Ogden, Utah, USA
| | - Eduardo de la Fuente
- 28 IAM-Departamento de Fisica, CUCEI , Universidad de Guadalajara, Guadalajara, México
| | - Douglas Galante
- 29 Brazilian Synchrotron Light Laboratory , Campinas, Brazil
| | - Jennifer Glass
- 30 School of Earth and Atmospheric Sciences, Georgia Institute of Technology , Atlanta, Georgia , USA
| | | | | | - Colin Goldblatt
- 33 School of Earth and Ocean Sciences, University of Victoria , Victoria, Canada
| | - Rachel Horak
- 34 American Society for Microbiology , Washington, DC, USA
| | | | - Betül Kaçar
- 36 Harvard University , Organismic and Evolutionary Biology, Cambridge, Massachusetts, USA
| | - Akos Kereszturi
- 37 Research Centre for Astronomy and Earth Sciences , Hungarian Academy of Sciences, Budapest, Hungary
| | - Emily Knowles
- 38 Johnson & Wales University , Denver, Colorado, USA
| | - Paul Mayeur
- 39 Rensselaer Polytechnic Institute , Troy, New York, USA
| | - Shawn McGlynn
- 40 Earth Life Science Institute, Tokyo Institute of Technology , Tokyo, Japan
| | - Yamila Miguel
- 41 Laboratoire Lagrange, UMR 7293, Université Nice Sophia Antipolis , CNRS, Observatoire de la Côte d'Azur, Nice, France
| | | | - Catherine Neish
- 43 Department of Earth Sciences, The University of Western Ontario , London, Canada
| | - Lena Noack
- 44 Royal Observatory of Belgium , Brussels, Belgium
| | - Sarah Rugheimer
- 45 Department of Astronomy, Harvard University , Cambridge, Massachusetts, USA
- 46 University of St. Andrews , St. Andrews, UK
| | - Eva E Stüeken
- 47 University of Washington , Seattle, Washington, USA
- 48 University of California , Riverside, California, USA
| | | | - Sara Imari Walker
- 13 Blue Marble Space Institute of Science , Seattle, Washington, USA
- 50 School of Earth and Space Exploration and Beyond Center for Fundamental Concepts in Science, Arizona State University , Tempe, Arizona, USA
| | - Teresa Wong
- 51 Department of Earth and Planetary Sciences, Washington University in St. Louis , St. Louis, Missouri, USA
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17
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Schwieterman EW, Meadows VS, Domagal-Goldman SD, Deming D, Arney GN, Luger R, Harman CE, Misra A, Barnes R. IDENTIFYING PLANETARY BIOSIGNATURE IMPOSTORS: SPECTRAL FEATURES OF CO AND O 4 RESULTING FROM ABIOTIC O 2/O 3 PRODUCTION. THE ASTROPHYSICAL JOURNAL. LETTERS 2016; Volume 819:L34. [PMID: 30147857 PMCID: PMC6108182 DOI: 10.3847/2041-8205/819/1/l13] [Citation(s) in RCA: 95] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
O2 and O3 have been long considered the most robust individual biosignature gases in a planetary atmosphere, yet multiple mechanisms that may produce them in the absence of life have been described. However, these abiotic planetary mechanisms modify the environment in potentially identifiable ways. Here we briefly discuss two of the most detectable spectral discriminants for abiotic O2/O3: CO and O4. We produce the first explicit self-consistent simulations of these spectral discriminants as they may be seen by James Webb Space Telescope (JWST). If JWST-NIRISS and/or NIRSpec observe CO (2.35, 4.6 μm) in conjunction with CO2 (1.6, 2.0, 4.3 μm) in the transmission spectrum of a terrestrial planet it could indicate robust CO2 photolysis and suggest that a future detection of O2 or O3 might not be biogenic. Strong O4 bands seen in transmission at 1.06 and 1.27 μm could be diagnostic of a post-runaway O2-dominated atmosphere from massive H-escape. We find that for these false positive scenarios, CO at 2.35 μm, CO2 at 2.0 and 4.3 μm, and O4 at 1.27 μm are all stronger features in transmission than O2/O3 and could be detected with S/Ns ≳ 3 for an Earth-size planet orbiting a nearby M dwarf star with as few as 10 transits, assuming photon-limited noise. O4 bands could also be sought in UV/VIS/NIR reflected light (at 0.345, 0.36, 0.38, 0.445, 0.475, 0.53, 0.57, 0.63, 1.06, and 1.27 μm) by a next generation direct-imaging telescope such as LUVOIR/HDST or HabEx and would indicate an oxygen atmosphere too massive to be biologically produced.
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Affiliation(s)
- Edward W Schwieterman
- Astronomy Department, University of Washington, Box 351580, Seattle, WA 98195, USA
- NASA Astrobiology Institute's Virtual Planetary Laboratory, Seattle, WA 981195, USA
- Astrobiology Program, University of Washington, Seattle, WA 98195, USA
| | - Victoria S Meadows
- Astronomy Department, University of Washington, Box 351580, Seattle, WA 98195, USA
- NASA Astrobiology Institute's Virtual Planetary Laboratory, Seattle, WA 981195, USA
- Astrobiology Program, University of Washington, Seattle, WA 98195, USA
| | - Shawn D Domagal-Goldman
- NASA Astrobiology Institute's Virtual Planetary Laboratory, Seattle, WA 981195, USA
- NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
| | - Drake Deming
- NASA Astrobiology Institute's Virtual Planetary Laboratory, Seattle, WA 981195, USA
- Department of Astronomy, University of Maryland, College Park, MD 20742, USA
| | - Giada N Arney
- Astronomy Department, University of Washington, Box 351580, Seattle, WA 98195, USA
- NASA Astrobiology Institute's Virtual Planetary Laboratory, Seattle, WA 981195, USA
- Astrobiology Program, University of Washington, Seattle, WA 98195, USA
| | - Rodrigo Luger
- Astronomy Department, University of Washington, Box 351580, Seattle, WA 98195, USA
- NASA Astrobiology Institute's Virtual Planetary Laboratory, Seattle, WA 981195, USA
- Astrobiology Program, University of Washington, Seattle, WA 98195, USA
| | - Chester E Harman
- NASA Astrobiology Institute's Virtual Planetary Laboratory, Seattle, WA 981195, USA
- Geosciences Department, Pennsylvania State University, University Park, PA 16802, USA
- Pennsylvania State Astrobiology Research Center, 2217 Earth and Engineering Sciences Building, University Park, PA 16802, USA
- Center for Exoplanets and Habitable Worlds, Pennsylvania State University, University Park, PA 16802, USA
| | - Amit Misra
- Astronomy Department, University of Washington, Box 351580, Seattle, WA 98195, USA
- NASA Astrobiology Institute's Virtual Planetary Laboratory, Seattle, WA 981195, USA
- Astrobiology Program, University of Washington, Seattle, WA 98195, USA
| | - Rory Barnes
- Astronomy Department, University of Washington, Box 351580, Seattle, WA 98195, USA
- NASA Astrobiology Institute's Virtual Planetary Laboratory, Seattle, WA 981195, USA
- Astrobiology Program, University of Washington, Seattle, WA 98195, USA
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18
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Hansen J, Sato M, Russell G, Kharecha P. Climate sensitivity, sea level and atmospheric carbon dioxide. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2013; 371:20120294. [PMID: 24043864 PMCID: PMC3785813 DOI: 10.1098/rsta.2012.0294] [Citation(s) in RCA: 146] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Cenozoic temperature, sea level and CO2 covariations provide insights into climate sensitivity to external forcings and sea-level sensitivity to climate change. Climate sensitivity depends on the initial climate state, but potentially can be accurately inferred from precise palaeoclimate data. Pleistocene climate oscillations yield a fast-feedback climate sensitivity of 3±1(°)C for a 4 W m(-2) CO2 forcing if Holocene warming relative to the Last Glacial Maximum (LGM) is used as calibration, but the error (uncertainty) is substantial and partly subjective because of poorly defined LGM global temperature and possible human influences in the Holocene. Glacial-to-interglacial climate change leading to the prior (Eemian) interglacial is less ambiguous and implies a sensitivity in the upper part of the above range, i.e. 3-4(°)C for a 4 W m(-2) CO2 forcing. Slow feedbacks, especially change of ice sheet size and atmospheric CO2, amplify the total Earth system sensitivity by an amount that depends on the time scale considered. Ice sheet response time is poorly defined, but we show that the slow response and hysteresis in prevailing ice sheet models are exaggerated. We use a global model, simplified to essential processes, to investigate state dependence of climate sensitivity, finding an increased sensitivity towards warmer climates, as low cloud cover is diminished and increased water vapour elevates the tropopause. Burning all fossil fuels, we conclude, would make most of the planet uninhabitable by humans, thus calling into question strategies that emphasize adaptation to climate change.
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Affiliation(s)
- James Hansen
- The Earth Institute, Columbia University, New York, NY 10027, USA
- e-mail:
| | - Makiko Sato
- The Earth Institute, Columbia University, New York, NY 10027, USA
| | - Gary Russell
- NASA Goddard Institute for Space Studies, New York, NY 10027, USA
| | - Pushker Kharecha
- The Earth Institute, Columbia University, New York, NY 10027, USA
- NASA Goddard Institute for Space Studies, New York, NY 10027, USA
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19
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Dynamic model constraints on oxygen-17 depletion in atmospheric O2 after a snowball Earth. Proc Natl Acad Sci U S A 2013; 110:14546-50. [PMID: 23898167 DOI: 10.1073/pnas.1302972110] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A large perturbation in atmospheric CO2 and O2 or bioproductivity will result in a drastic pulse of (17)O change in atmospheric O2, as seen in the Marinoan Oxygen-17 Depletion (MOSD) event in the immediate aftermath of a global deglaciation 635 Mya. The exact nature of the perturbation, however, is debated. Here we constructed a coupled, four-box, and quick-response biosphere-atmosphere model to examine both the steady state and dynamics of the MOSD event. Our model shows that the ultra-high CO2 concentrations proposed by the "snowball' Earth hypothesis produce a typical MOSD duration of less than 10(6) y and a magnitude of (17)O depletion reaching approximately -35‰. Both numbers are in remarkable agreement with geological constraints from South China and Svalbard. Moderate CO2 and low O2 concentration (e.g., 3,200 parts per million by volume and 0.01 bar, respectively) could produce distinct sulfate (17)O depletion only if postglacial marine bioproductivity was impossibly low. Our dynamic model also suggests that a snowball in which the ocean is isolated from the atmosphere by a continuous ice cover may be distinguished from one in which cracks in the ice permit ocean-atmosphere exchange only if partial pressure of atmospheric O2 is larger than 0.02 bar during the snowball period and records of weathering-derived sulfate are available for the very first few tens of thousands of years after the onset of the meltdown. In any case, a snowball Earth is a precondition for the observed MOSD event.
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20
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Goldblatt C, Watson AJ. The runaway greenhouse: implications for future climate change, geoengineering and planetary atmospheres. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2012; 370:4197-4216. [PMID: 22869797 DOI: 10.1098/rsta.2012.0004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The ultimate climate emergency is a 'runaway greenhouse': a hot and water-vapour-rich atmosphere limits the emission of thermal radiation to space, causing runaway warming. Warming ceases only after the surface reaches approximately 1400 K and emits radiation in the near-infrared, where water is not a good greenhouse gas. This would evaporate the entire ocean and exterminate all planetary life. Venus experienced a runaway greenhouse in the past, and we expect that the Earth will in around 2 billion years as solar luminosity increases. But could we bring on such a catastrophe prematurely, by our current climate-altering activities? Here, we review what is known about the runaway greenhouse to answer this question, describing the various limits on outgoing radiation and how climate will evolve between these. The good news is that almost all lines of evidence lead us to believe that is unlikely to be possible, even in principle, to trigger full a runaway greenhouse by addition of non-condensible greenhouse gases such as carbon dioxide to the atmosphere. However, our understanding of the dynamics, thermodynamics, radiative transfer and cloud physics of hot and steamy atmospheres is weak. We cannot therefore completely rule out the possibility that human actions might cause a transition, if not to full runaway, then at least to a much warmer climate state than the present one. High climate sensitivity might provide a warning. If we, or more likely our remote descendants, are threatened with a runaway greenhouse, then geoengineering to reflect sunlight might be life's only hope. Injecting reflective aerosols into the stratosphere would be too short-lived, and even sunshades in space might require excessive maintenance. In the distant future, modifying Earth's orbit might provide a sustainable solution. The runaway greenhouse also remains relevant in planetary sciences and astrobiology: as extrasolar planets smaller and nearer to their stars are detected, some will be in a runaway greenhouse state.
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Affiliation(s)
- Colin Goldblatt
- School of Earth and Ocean Sciences, University of Victoria, PO Box 3065, STN CSC, Victoria, British Columbia, Canada V8W 3V6.
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21
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Catling DC, Claire MW, Zahnle KJ, Quinn RC, Clark BC, Hecht MH, Kounaves S. Atmospheric origins of perchlorate on Mars and in the Atacama. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2009je003425] [Citation(s) in RCA: 192] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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23
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Cockell CS, Horneck G. The History of the UV Radiation Climate of the Earth-Theoretical and Space-based Observations¶. Photochem Photobiol 2007. [DOI: 10.1562/0031-8655(2001)0730447thotur2.0.co2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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24
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Harfoot MBJ, Beerling DJ, Lomax BH, Pyle JA. A two-dimensional atmospheric chemistry modeling investigation of Earth's Phanerozoic O3and near-surface ultraviolet radiation history. ACTA ACUST UNITED AC 2007. [DOI: 10.1029/2006jd007372] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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26
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Goldblatt C, Lenton TM, Watson AJ. Bistability of atmospheric oxygen and the Great Oxidation. Nature 2006; 443:683-6. [PMID: 17036001 DOI: 10.1038/nature05169] [Citation(s) in RCA: 204] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2006] [Accepted: 08/14/2006] [Indexed: 11/09/2022]
Abstract
The history of the Earth has been characterized by a series of major transitions separated by long periods of relative stability. The largest chemical transition was the 'Great Oxidation', approximately 2.4 billion years ago, when atmospheric oxygen concentrations rose from less than 10(-5) of the present atmospheric level (PAL) to more than 0.01 PAL, and possibly to more than 0.1 PAL. This transition took place long after oxygenic photosynthesis is thought to have evolved, but the causes of this delay and of the Great Oxidation itself remain uncertain. Here we show that the origin of oxygenic photosynthesis gave rise to two simultaneously stable steady states for atmospheric oxygen. The existence of a low-oxygen (less than 10(-5) PAL) steady state explains how a reducing atmosphere persisted for at least 300 million years after the onset of oxygenic photosynthesis. The Great Oxidation can be understood as a switch to the high-oxygen (more than 5 x 10(-3) PAL) steady state. The bistability arises because ultraviolet shielding of the troposphere by ozone becomes effective once oxygen levels exceed 10(-5) PAL, causing a nonlinear increase in the lifetime of atmospheric oxygen. Our results indicate that the existence of oxygenic photosynthesis is not a sufficient condition for either an oxygen-rich atmosphere or the presence of an ozone layer, which has implications for detecting life on other planets using atmospheric analysis and for the evolution of multicellular life.
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Affiliation(s)
- Colin Goldblatt
- School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK.
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Catling DC, Glein CR, Zahnle KJ, McKay CP. Why O2 is required by complex life on habitable planets and the concept of planetary "oxygenation time". ASTROBIOLOGY 2005; 5:415-38. [PMID: 15941384 DOI: 10.1089/ast.2005.5.415] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Life is constructed from a limited toolkit: the Periodic Table. The reduction of oxygen provides the largest free energy release per electron transfer, except for the reduction of fluorine and chlorine. However, the bonding of O2 ensures that it is sufficiently stable to accumulate in a planetary atmosphere, whereas the more weakly bonded halogen gases are far too reactive ever to achieve significant abundance. Consequently, an atmosphere rich in O2 provides the largest feasible energy source. This universal uniqueness suggests that abundant O2 is necessary for the high-energy demands of complex life anywhere, i.e., for actively mobile organisms of approximately 10(-1)-10(0) m size scale with specialized, differentiated anatomy comparable to advanced metazoans. On Earth, aerobic metabolism provides about an order of magnitude more energy for a given intake of food than anaerobic metabolism. As a result, anaerobes do not grow beyond the complexity of uniseriate filaments of cells because of prohibitively low growth efficiencies in a food chain. The biomass cumulative number density, n, at a particular mass, m, scales as n (> m) proportional to m(-1) for aquatic aerobes, and we show that for anaerobes the predicted scaling is n proportional to m (-1.5), close to a growth-limited threshold. Even with aerobic metabolism, the partial pressure of atmospheric O2 (P(O2)) must exceed approximately 10(3) Pa to allow organisms that rely on O2 diffusion to evolve to a size approximately 10(3) m x P(O2) in the range approximately 10(3)-10(4) Pa is needed to exceed the threshold of approximately 10(2) m size for complex life with circulatory physiology. In terrestrial life, O(2) also facilitates hundreds of metabolic pathways, including those that make specialized structural molecules found only in animals. The time scale to reach P(O(2)) approximately 10(4) Pa, or "oxygenation time," was long on the Earth (approximately 3.9 billion years), within almost a factor of 2 of the Sun's main sequence lifetime. Consequently, we argue that the oxygenation time is likely to be a key rate-limiting step in the evolution of complex life on other habitable planets. The oxygenation time could preclude complex life on Earth-like planets orbiting short-lived stars that end their main sequence lives before planetary oxygenation takes place. Conversely, Earth-like planets orbiting long-lived stars are potentially favorable habitats for complex life.
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Affiliation(s)
- David C Catling
- Department of Atmospheric Sciences and Astrobiology Program, University of Washington, Seattle, Washington, USA.
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Mangum C. Precambrian oxygen levels, the sulfide biosystem, and the origin of the metazoa. ACTA ACUST UNITED AC 2005. [DOI: 10.1002/jez.1402600105] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Farquhar J, Wing BA. The terrestrial record of stable sulphur isotopes: a review of the implications for evolution of Earth’s sulphur cycle. ACTA ACUST UNITED AC 2005. [DOI: 10.1144/gsl.sp.2005.248.01.09] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
AbstractThe observation of anomalous (non mass-dependent) sulphur isotope compositions in Archaean and early Proterozoic rocks but not in rocks younger than approximately 2 Ga has been interpreted to reflect fundamental change in the terrestrial sulphur cycle, in atmospheric chemistry, and in atmospheric oxygen content. Similar non mass-dependent sulphur isotope compositions in present-day samples (atmospheric aerosols and ice-core horizons containing remnants of stratosphere-piercing volcanic eruptions) are interpreted to carry information about modern atmospheric chemistry and transport. The interpretation of these observations hinges on our understanding of the processes that produce non mass-dependent sulphur isotope compositions, the processes that transport and transfer the isotopic signals throughout the sulphur cycle, and the processes that act to preserve or erase these isotopic signals once they are established. The growing dataset and hypotheses related to non mass-dependent sulphur are evaluated, emphasizing that which remains to be learned about the evolution of the record, the compositions of key reservoirs, and the transfer of the signal from the atmosphere to the surface and ultimately to the deep Earth.
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Affiliation(s)
- James Farquhar
- Earth System Science Interdisciplinary Center and Department of Geology, University of Maryland
College Park, Maryland 20742
| | - Boswell A. Wing
- Earth System Science Interdisciplinary Center and Department of Geology, University of Maryland
College Park, Maryland 20742
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Segura A, Krelove K, Kasting JF, Sommerlatt D, Meadows V, Crisp D, Cohen M, Mlawer E. Ozone concentrations and ultraviolet fluxes on Earth-like planets around other stars. ASTROBIOLOGY 2003; 3:689-708. [PMID: 14987475 DOI: 10.1089/153110703322736024] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Coupled radiative-convective/photochemical modeling was performed for Earth-like planets orbiting different types of stars (the Sun as a G2V, an F2V, and a K2V star). O(2) concentrations between 1 and 10(-5) times the present atmospheric level (PAL) were simulated. The results were used to calculate visible/near-IR and thermal-IR spectra, along with surface UV fluxes and relative dose rates for erythema and DNA damage. For the spectral resolution and sensitivity currently planned for the first generation of terrestrial planet detection and characterization missions, we find that O(2) should be observable remotely in the visible for atmospheres containing at least 10(-2) PAL of O(2). O(3) should be visible in the thermal-IR for atmospheres containing at least 10(-3) PAL of O(2). CH(4) is not expected to be observable in 1 PAL O(2) atmospheres like that of modern Earth, but it might be observable at thermal-IR wavelengths in "mid-Proterozoic-type" atmospheres containing approximately 10(-1) PAL of O(2). Thus, the simultaneous detection of both O(3) and CH(4) - considered to be a reliable indication of life - is within the realm of possibility. High-O(2) planets orbiting K2V and F2V stars are both better protected from surface UV radiation than is modern Earth. For the F2V case the high intrinsic UV luminosity of the star is more than offset by the much thicker ozone layer. At O(2) levels below approximately 10(-2) PAL, planets around all three types of stars are subject to high surface UV fluxes, with the F2V planet exhibiting the most biologically dangerous radiation environment. Thus, while advanced life is theoretically possible on high-O(2) planets around F stars, it is not obvious that it would evolve as it did on Earth.
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Affiliation(s)
- Antígona Segura
- Department of Geosciences, Pennsylvania State University, State College, Pennsylvania 16803, USA.
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Abstract
Harvesting light to produce energy and oxygen (photosynthesis) is the signature of all land plants. This ability was co-opted from a precocious and ancient form of life known as cyanobacteria. Today these bacteria, as well as microscopic algae, supply oxygen to the atmosphere and churn out fixed nitrogen in Earth's vast oceans. Microorganisms may also have played a major role in atmosphere evolution before the rise of oxygen. Under the more dim light of a young sun cooler than today's, certain groups of anaerobic bacteria may have been pumping out large amounts of methane, thereby keeping the early climate warm and inviting. The evolution of Earth's atmosphere is linked tightly to the evolution of its biota.
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Affiliation(s)
- James F Kasting
- Department of Geosciences, 443 Deike, The Pennsylvania State University, University Park, PA 16802, USA.
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Pavlov AA, Kasting JF. Mass-independent fractionation of sulfur isotopes in Archean sediments: strong evidence for an anoxic Archean atmosphere. ASTROBIOLOGY 2002; 2:27-41. [PMID: 12449853 DOI: 10.1089/153110702753621321] [Citation(s) in RCA: 182] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Mass-independent fractionation (MIF) of sulfur isotopes has been reported in sediments of Archean and Early Proterozoic Age (> 2.3 Ga) but not in younger rocks. The only fractionation mechanism that is consistent with the data on all four sulfur isotopes involves atmospheric photochemical reactions such as SO2 photolysis. We have used a one-dimensional photochemical model to investigate how the isotopic fractionation produced during SO2 photolysis would have been transferred to other gaseous and particulate sulfur-bearing species in both low-O2 and high-O2 atmospheres. We show that in atmospheres with O2 concentrations < 10(-5) times the present atmospheric level (PAL), sulfur would have been removed from the atmosphere in a variety of different oxidation states, each of which would have had its own distinct isotopic signature. By contrast, in atmospheres with O2 concentrations > or = 10(-5) PAL, all sulfur-bearing species would have passed through the oceanic sulfate reservoir before being incorporated into sediments, so any signature of MIF would have been lost. We conclude that the atmospheric O2 concentration must have been < 10(-5) PAL prior to 2.3 Ga.
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Affiliation(s)
- A A Pavlov
- Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO, USA.
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Traub WA, Jucks KW. A possible aeronomy of extrasolar terrestrial planets. ACTA ACUST UNITED AC 2002. [DOI: 10.1029/130gm25] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
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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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Farquhar J, Savarino J, Airieau S, Thiemens MH. Observation of wavelength-sensitive mass-independent sulfur isotope effects during SO2photolysis: Implications for the early atmosphere. ACTA ACUST UNITED AC 2001. [DOI: 10.1029/2000je001437] [Citation(s) in RCA: 370] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Mercer-Smith JA, Raudino A, Mauzerall DC. A model for the origin of photosynthesis--III. The ultraviolet photochemistry of uroporphyrinogen. Photochem Photobiol 2001; 42:239-44. [PMID: 11539651 DOI: 10.1111/j.1751-1097.1985.tb08937.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The photochemical ramifications of the high ultraviolet flux on the primordial earth prior to the formation of the ozone layer have been considered in a study of the ultraviolet photochemistry of uroporphyrinogen (urohexahydroporphyrin), a colorless compound which absorbs strongly at wavelengths less than 220 nanometers. Urohexahydroporphyrin was investigated since it is the first macrocycle formed on the biosynthetic pathway of chlorophyll and can be used to test the hypothesis that the biosynthetic pathway to chlorophyll recapitulates the evolutionary history of photosynthesis. When urohexahydroporphyrin is illuminated in aqueous anaerobic solution, hydrogen gas is produced. More hydrogen gas is produced in the presence of a colloidal platinum catalyst. The products of the photooxidation of urohexahydroporphyrin are urotetrahydroporphyrin (uroporphomethene) and uroporphyrin. This research shows how the oxidation of uroporphyrinogen to uroporphyrin, the first biogenetic porphyrin, could have occurred anaerobically and abiotically on the primordial earth.
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Cockell CS, Horneck G. The history of the UV radiation climate of the earth--theoretical and space-based observations. Photochem Photobiol 2001; 73:447-51. [PMID: 11332042 DOI: 10.1562/0031-8655(2001)073<0447:thotur>2.0.co;2] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In the Archean era (3.8-2.5 Ga ago) the Earth probably lacked a protective ozone column. Using data obtained in the Earth's orbit on the inactivation of Bacillus subtilis spores we quantitatively estimate the potential biological effects of such an environment. We combine this practical data with theoretical calculations to propose a history of the potential UV stress on the surface of the Earth over time. The data suggest that an effective ozone column was established at a pO2 of approximately 5 x 10(-3) present atmospheric level. The improvement in the UV environment on the early Proterozoic Earth might have been a much more rapid event than has previously been supposed, with DNA damage rates dropping by two orders of magnitude in the space of just a few tens of millions of years. We postulate that a coupling between reduced UV stress and increased pO2 production could have contributed toward a positive feedback in the production of ozone in the early Proterozoic atmosphere. This would contribute to the apparent rapidity of the oxidation event. The data provide an evolutionary perspective on present-day Antarctic ozone depletion.
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Affiliation(s)
- C S Cockell
- British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK.
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Kasting JF. Planetary atmosphere evolution: do other habitable planets exist and can we detect them? ASTROPHYSICS AND SPACE SCIENCE 1996; 241:3-24. [PMID: 11542303 DOI: 10.1007/978-94-011-5808-4_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The goal of this conference is to consider whether it is possible within the next few decades to detect Earth-like planets around other stars using telescopes or interferometers on the ground or in space. Implicit in the term "Earth-like" is the idea that such planets might be habitable by Earth-like organisms, or that they might actually be inhabited. Here, I shall address two questions from the standpoint of planetary atmosphere evolution. First, what are the chances that habitable planets exist around other stars? And, second, if inhabited planets exist, what would be the best way to detect them?
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Affiliation(s)
- J F Kasting
- Department of Geosciences, Penn State University, University Park, PA 16802, USA
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Pierson BK, Mitchell HK, Ruff-Roberts AL. Chloroflexus aurantiacus and ultraviolet radiation: Implications for archean shallow-water stromatolites. ORIGINS LIFE EVOL B 1993. [DOI: 10.1007/bf01581902] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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A model of solar-cycle effects on palaeoclimate and its implications for the Elatina Formation. Nature 1987. [DOI: 10.1038/326577a0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Habitability of the early earth: Clues from the physiology of nitrogen fixation and photosynthesis. ORIGINS LIFE EVOL B 1985. [DOI: 10.1007/bf01808171] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Kasting JF, Holland HD, Pinto JP. Oxidant abundances in rainwater and the evolution of atmospheric oxygen. JOURNAL OF GEOPHYSICAL RESEARCH 1985; 90:10497-510. [PMID: 11542000 DOI: 10.1029/jd090id06p10497] [Citation(s) in RCA: 93] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A one-dimensional photochemical model has been used to estimate the flux of dissolved hydrogen peroxide (H2O2) and of other soluble species in rainwater as a function of atmospheric oxygen level. H2O2 should have replaced O2 as the dominant oxidant in rainwater at oxygen levels below 10(-3)-10(-2) times the present atmospheric level (PAL). The exact value of pO2 at which H2O2 becomes more important than O2 depends on the abundance of trace gases such as CO, CH4, and NO. H2O2 was probably an important oxidant even in an O2-free atmosphere, provided that CO2 levels were significant higher than today's. In model atmospheres containing free O2 the concentration of photochemically produced oxidants generally exceeds that of photochemically produced reductants. The oxidizing power of rainwater is therefore greater than that due to dissolved molecular O2 alone. The difference is small at present but becomes important at O2 levels less than 10(-3) PAL. At O2 levels between 10(-4) and 10(-5) PAL the oxidizing power of rainwater is almost independent of pO2. Precambrian soils in which a part or all of the Fe2+ in their source rocks has been oxidized to Fe3+ could therefore have developed in the presence of an atmosphere with very low values of pO2. On the other hand, the upper limit for pO2 during early and mid-Precambrian time suggested by the incomplete oxidation of FeO in soils developed on basaltic rocks is affected only slightly by the presence of photochemical products in rainwater.
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Affiliation(s)
- J F Kasting
- NASA Ames Research Center, Moffett Field, California, USA
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Kasting JF, Pollack JB. Effects of high CO2 levels on surface temperature and atmospheric oxidation state of the early Earth. JOURNAL OF ATMOSPHERIC CHEMISTRY 1984; 1:403-428. [PMID: 11541984 DOI: 10.1007/bf00053803] [Citation(s) in RCA: 86] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
One-dimensional radiative-convective and photochemical models are used to examine the effects of enhanced CO2 concentrations on the surface temperature of the early Earth and the composition of the prebiotic atmosphere. Carbon dioxide concentrations of the order of 100-1000 times the present level are required to compensate for an expected solar luminosity decrease of 25-30%, if CO2 and H2O were the only greenhouse gases present. The primitive stratosphere was cold and dry, with a maximum H2O volume mixing ratio of 10(-6). The atmospheric oxidation state was controlled by the balance between volcanic emission of reduced gases, photo-stimulated oxidation of dissolved Fe+2 in the oceans, escape of hydrogen to space, and rainout of H2O2 and H2CO. At high CO2 levels, production of hydrogen owing to rainout of H2O2 would have kept the H2 mixing ratio above 2x10(-4) and the ground-level O2 mixing ratio below 10(-11), even if no other sources of hydrogen were present. Increased solar UV fluxes could have led to small changes in the ground-level mixing ratios of both O2 and H2.
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Affiliation(s)
- J F Kasting
- NASA Ames Research Center, Moffett Field, CA 94035, USA
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Kasting JF, Pollack JB, Ackerman TP. Response of Earth's atmosphere to increases in solar flux and implications for loss of water from Venus. ICARUS 1984; 57:335-355. [PMID: 11541985 DOI: 10.1016/0019-1035(84)90122-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A one-dimensional radiative-convective model is used to compute temperature and water vapor profiles as functions of solar flux for an Earth-like atmosphere. The troposphere is assumed to be fully saturated, with a moist adiabatic lapse rate, and changes in cloudiness are neglected. Predicted surface temperatures increase monotonically from -1 to 111 degrees C as the solar flux is increased from 0.81 to 1.45 times its present value. Surface temperatures corresponding to high solar fluxes may be underestimated, however, owing to neglect of H2O continuum absorption outside of the 8- to 12-micrometers window region. These results imply that the surface temperature of a primitive water-rich Venus should have been at least 80-100 degrees C and may have been much higher. The existence of liquid water at the surface depends on poorly known aspects of H2O continuum absorption and on uncertainties concerning relative humidity and cloudiness. In any case, water vapor should have been a major atmospheric constituent at all altitudes, leading to the rapid hydrodynamic escape of hydrogen. The oxygen left behind by this process was presumably consumed by reactions with reduced minerals in the crust. Both the loss of oxygen and the presently observed enrichment of the deuterium-to-hydrogen ratio are most easily explained if oceans of liquid water were initially present.
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Affiliation(s)
- J F Kasting
- Space Science Division, NASA Ames Research Center, Moffett Field, California 94035, USA
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Levine JS, Augustsson TR, Natarajan M. The prebiological paleoatmosphere: stability and composition. ORIGINS OF LIFE 1982; 12:245-59. [PMID: 7162799 DOI: 10.1007/bf00926894] [Citation(s) in RCA: 65] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
In the past, it was generally assumed that the early atmosphere of the Earth contained appreciable quantities of methane (CH4) and ammonia (NH3). This was the type of atmosphere believed to be the most suitable environment for chemical evolution, the nonbiological formation of complex organic molecules, the precursors of living systems. Photochemical considerations suggest that a CH4-NH3 dominated early atmosphere was probably very short-lived, if it ever existed at all. Instead, an early atmosphere of carbon dioxide (CO2) and nitrogen (N2) is favored by photochemical as well as geological and geochemical considerations. Photochemical calculations also indicate that the total oxygen column density of the prebiological paleoatmosphere did not exceed 10(-7) of the present atmospheric level.
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Abstract
The ideas of Harold Urey on the origin and evolution of the atmosphere have dominated thinking in this area for 3 decades. Recent progress in this area is reviewed, with particular emphasis on photochemical modeling studies of atmospheric evolution. Research into the paleoatmosphere can be divided into 3 distinct areas: (1) The photochemistry/chemistry of the prebiological paleoatmosphere, (2) the evolution of oxygen and the transition to an oxidizing atmosphere, and (3) the origin and evolution of ozone. Photochemical calculations indicate that the stability of a heavily reducing paleoatmosphere of CH4--NH3 was extremely shortlived, if such a prebiological atmosphere ever existed at all. A more mildly reducing early atmosphere of CO2--N2 is favored by photochemical considerations. Recent calculations of O2 in the prebiological paleoatmosphere vary from less than 10(-14) of present atmospheric level (PAL) to 10(-1) PAL. Clearly, additional work is indicated. The evolution of O3 as a function of O2 level has been investigated with increasingly detailed photochemical models that have included the photochemistry/chemistry of the oxygen, hydrogen, nitrogen, carbon, and chlorine species, as well as the effects of eddy transport, the rainout of water-soluble species, dry deposition and lightning as a source of trace atmospheric gases.
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Canuto VM, Levine JS, Augustsson TR, Imhoff CL. UV radiation from the young Sun and oxygen and ozone levels in the prebiological palaeoatmosphere. Nature 1982. [DOI: 10.1038/296816a0] [Citation(s) in RCA: 140] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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50
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Kinetics of reactions between free radicals and surfaces (aerosols) applicable to atmospheric chemistry. ACTA ACUST UNITED AC 1982. [DOI: 10.1029/gm026p0107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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