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Pajusalu M, Seager S, Huang J, Petkowski JJ. A qualitative assessment of limits of active flight in low density atmospheres. Sci Rep 2024; 14:13823. [PMID: 38879676 PMCID: PMC11180128 DOI: 10.1038/s41598-024-64114-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Accepted: 06/05/2024] [Indexed: 06/19/2024] Open
Abstract
Exoplanet atmospheres are expected to vary significantly in thickness and chemical composition, leading to a continuum of differences in surface pressure and atmospheric density. This variability is exemplified within our Solar System, where the four rocky planets exhibit surface pressures ranging from 1 nPa on Mercury to 9.2 MPa on Venus. The direct effects and potential challenges of atmospheric pressure and density on life have rarely been discussed. For instance, atmospheric density directly affects the possibility of active flight in organisms, a critical factor since without it, dispersing across extensive and inhospitable terrains becomes a major limitation for the expansion of complex life. In this paper, we propose the existence of a critical atmospheric density threshold below which active flight is unfeasible, significantly impacting biosphere development. To qualitatively assess this threshold and differentiate it from energy availability constraints, we analyze the limits of active flight on Earth, using the common fruit fly, Drosophila melanogaster, as a model organism. We subjected Drosophila melanogaster to various atmospheric density scenarios and reviewed previous data on flight limitations. Our observations show that flies in an N2-enriched environment recover active flying abilities more efficiently than those in a helium-enriched environment, highlighting behavioral differences attributable to atmospheric density vs. oxygen deprivation.
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Affiliation(s)
- Mihkel Pajusalu
- Department of Earth, Planetary, and Atmospheric Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA.
- Tartu Observatory, University of Tartu, 61602, Tõravere, Estonia.
| | - Sara Seager
- Department of Earth, Planetary, and Atmospheric Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA
- Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA
- Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA
| | - Jingcheng Huang
- Department of Earth, Planetary, and Atmospheric Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA
| | - Janusz J Petkowski
- Department of Earth, Planetary, and Atmospheric Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA
- JJ Scientific, 02-792, Warsaw, Mazowieckie, Poland
- Faculty of Environmental Engineering, Wroclaw University of Science and Technology, 50-370, Wroclaw, Poland
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Madhusudhan N, Moses JI, Rigby F, Barrier E. Chemical conditions on Hycean worlds. Faraday Discuss 2023; 245:80-111. [PMID: 37530120 DOI: 10.1039/d3fd00075c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/03/2023]
Abstract
Traditionally, the search for life on exoplanets has been predominantly focused on rocky exoplanets. The recently proposed Hycean worlds have the potential to significantly expand and accelerate the search for life elsewhere. Hycean worlds are a class of habitable sub-Neptunes with planet-wide oceans and H2-rich atmospheres. Their broad range of possible sizes and temperatures lead to a wide habitable zone and high potential for discovery and atmospheric characterization using transit spectroscopy. Over a dozen candidate Hycean planets are already known to be transiting nearby M dwarfs, making them promising targets for atmospheric characterization with the James Webb Space Telescope (JWST). In this work, we investigate possible chemical conditions on a canonical Hycean world, focusing on (a) the present and primordial molecular composition of the atmosphere, and (b) the inventory of bioessential elements for the origin and sustenance of life in the ocean. Based on photochemical and kinetic modeling for a range of conditions, we discuss the possible chemical evolution and observable present-day composition of its atmosphere. In particular, for reduced primordial conditions the early atmospheric evolution passes through a phase that is rich in organic molecules that could provide important feedstock for prebiotic chemistry. We investigate avenues for delivering bioessential metals to the ocean, considering the challenging lack of weathering from a rocky surface and the ocean separated from the rocky core by a thick icy mantle. Based on ocean depths from internal structure modelling and elemental estimates for the early Earth's oceans, we estimate the requirements for bioessential metals in such a planet. We find that the requirements can be met for plausible assumptions about impact history and atmospheric sedimentation, and supplemented by other steady state sources. We discuss the observational prospects for atmospheric characterisation of Hycean worlds with JWST and future directions of this new paradigm in the search for life on exoplanets.
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Affiliation(s)
| | | | - Frances Rigby
- Institute of Astronomy, University of Cambridge, Cambridge, UK.
| | - Edouard Barrier
- Institute of Astronomy, University of Cambridge, Cambridge, UK.
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3
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Possibilities for an Aerial Biosphere in Temperate Sub Neptune-Sized Exoplanet Atmospheres. UNIVERSE 2021. [DOI: 10.3390/universe7060172] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The search for signs of life through the detection of exoplanet atmosphere biosignature gases is gaining momentum. Yet, only a handful of rocky exoplanet atmospheres are suitable for observation with planned next-generation telescopes. To broaden prospects, we describe the possibilities for an aerial, liquid water cloud-based biosphere in the atmospheres of sub Neptune-sized temperate exoplanets, those receiving Earth-like irradiation from their host stars. One such planet is known (K2-18b) and other candidates are being followed up. Sub Neptunes are common and easier to study observationally than rocky exoplanets because of their larger sizes, lower densities, and extended atmospheres or envelopes. Yet, sub Neptunes lack any solid surface as we know it, so it is worthwhile considering whether their atmospheres can support an aerial biosphere. We review, synthesize, and build upon existing research. Passive microbial-like life particles must persist aloft in a region with liquid water clouds for long enough to metabolize, reproduce, and spread before downward transport to lower altitudes that may be too hot for life of any kind to survive. Dynamical studies are needed to flesh out quantitative details of life particle residence times. A sub Neptune would need to be a part of a planetary system with an unstable asteroid belt in order for meteoritic material to provide nutrients, though life would also need to efficiently reuse and recycle metals. The origin of life may be the most severe limiting challenge. Regardless of the uncertainties, we can keep an open mind to the search for biosignature gases as a part of general observational studies of sub Neptune exoplanets.
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Abstract
The habitable zone (HZ) is the circular region around a star(s) where standing bodies of water could exist on the surface of a rocky planet. Space missions employ the HZ to select promising targets for follow-up habitability assessment. The classical HZ definition assumes that the most important greenhouse gases for habitable planets orbiting main-sequence stars are CO2 and H2O. Although the classical HZ is an effective navigational tool, recent HZ formulations demonstrate that it cannot thoroughly capture the diversity of habitable exoplanets. Here, I review the planetary and stellar processes considered in both classical and newer HZ formulations. Supplementing the classical HZ with additional considerations from these newer formulations improves our capability to filter out worlds that are unlikely to host life. Such improved HZ tools will be necessary for current and upcoming missions aiming to detect and characterize potentially habitable exoplanets.
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Walker SI, Bains W, Cronin L, DasSarma S, Danielache S, Domagal-Goldman S, Kacar B, Kiang NY, Lenardic A, Reinhard CT, Moore W, Schwieterman EW, Shkolnik EL, Smith HB. Exoplanet Biosignatures: Future Directions. ASTROBIOLOGY 2018; 18:779-824. [PMID: 29938538 PMCID: PMC6016573 DOI: 10.1089/ast.2017.1738] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Accepted: 03/13/2018] [Indexed: 05/08/2023]
Abstract
We introduce a Bayesian method for guiding future directions for detection of life on exoplanets. We describe empirical and theoretical work necessary to place constraints on the relevant likelihoods, including those emerging from better understanding stellar environment, planetary climate and geophysics, geochemical cycling, the universalities of physics and chemistry, the contingencies of evolutionary history, the properties of life as an emergent complex system, and the mechanisms driving the emergence of life. We provide examples for how the Bayesian formalism could guide future search strategies, including determining observations to prioritize or deciding between targeted searches or larger lower resolution surveys to generate ensemble statistics and address how a Bayesian methodology could constrain the prior probability of life with or without a positive detection. Key Words: Exoplanets-Biosignatures-Life detection-Bayesian analysis. Astrobiology 18, 779-824.
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Affiliation(s)
- Sara I. Walker
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona
- Beyond Center for Fundamental Concepts in Science, Arizona State University, Tempe, Arizona
- ASU-Santa Fe Institute Center for Biosocial Complex Systems, Arizona State University, Tempe, Arizona
- Blue Marble Space Institute of Science, Seattle, Washington
| | - William Bains
- EAPS (Earth, Atmospheric and Planetary Science), MIT, Cambridge, Massachusetts
- Rufus Scientific Ltd., Royston, United Kingdom
| | - Leroy Cronin
- School of Chemistry, University of Glasgow, Glasgow, United Kingdom
| | - Shiladitya DasSarma
- Department of Microbiology and Immunology, Institute of Marine and Environmental Technology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Sebastian Danielache
- Department of Materials and Life Science, Faculty of Science and Technology, Sophia University, Tokyo, Japan
- Earth Life Institute, Tokyo Institute of Technology, Tokyo, Japan
| | - Shawn Domagal-Goldman
- NASA Goddard Space Flight Center, Greenbelt, Maryland
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, University of Washington, Seattle, Washington
| | - Betul Kacar
- Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts
- NASA Astrobiology Institute, Reliving the Past Team, University of Montana, Missoula, Montana
- Department of Molecular and Cell Biology, University of Arizona, Tucson, Arizona
- Department of Astronomy and Steward Observatory, University of Arizona, Tucson, Arizona
| | - Nancy Y. Kiang
- NASA Goddard Institute for Space Studies, New York, New York
| | - Adrian Lenardic
- Department of Earth Science, Rice University, Houston, Texas
| | - Christopher T. Reinhard
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia
- NASA Astrobiology Institute, Alternative Earths Team, University of California, Riverside, California
| | - William Moore
- Department of Atmospheric and Planetary Sciences, Hampton University, Hampton, Virginia
- National Institute of Aerospace, Hampton, Virginia
| | - Edward W. Schwieterman
- Blue Marble Space Institute of Science, Seattle, Washington
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, University of Washington, Seattle, Washington
- NASA Astrobiology Institute, Alternative Earths Team, University of California, Riverside, California
- Department of Earth Sciences, University of California, Riverside, California
- NASA Postdoctoral Program, Universities Space Research Association, Columbia, Maryland
| | - Evgenya L. Shkolnik
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona
| | - Harrison B. Smith
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona
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Zhou N, Cheng Y, Xie J, Zhu C. Harnessing sunlight without a photosensitizer for highly efficient consecutive [3+2]/[4+2] annulation to synthesize fused benzobicyclic skeletons. Chem Commun (Camb) 2017; 53:10707-10710. [DOI: 10.1039/c7cc06548e] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
A photosensitizer-free, highly efficient sunlight-promoted tandem [3+2]/[4+2] annulation of unsaturated α-bromocarbonyls with o-alkynylanilines was described, and allowed for convenient synthesis of fused benzobicyclic skeletons.
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Affiliation(s)
- Nengneng Zhou
- State Key Laboratory of Coordination Chemistry
- Jiangsu Key Laboratory of Advanced Organic Material
- School of Chemistry and Chemical Engineering
- Nanjing University
- Nanjing 210023
| | - Yixiang Cheng
- State Key Laboratory of Coordination Chemistry
- Jiangsu Key Laboratory of Advanced Organic Material
- School of Chemistry and Chemical Engineering
- Nanjing University
- Nanjing 210023
| | - Jin Xie
- State Key Laboratory of Coordination Chemistry
- Jiangsu Key Laboratory of Advanced Organic Material
- School of Chemistry and Chemical Engineering
- Nanjing University
- Nanjing 210023
| | - Chengjian Zhu
- State Key Laboratory of Coordination Chemistry
- Jiangsu Key Laboratory of Advanced Organic Material
- School of Chemistry and Chemical Engineering
- Nanjing University
- Nanjing 210023
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8
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The Cosmic Zoo: The (Near) Inevitability of the Evolution of Complex, Macroscopic Life. Life (Basel) 2016; 6:life6030025. [PMID: 27376334 PMCID: PMC5041001 DOI: 10.3390/life6030025] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2016] [Revised: 06/17/2016] [Accepted: 06/22/2016] [Indexed: 12/31/2022] Open
Abstract
Life on Earth provides a unique biological record from single-cell microbes to technologically intelligent life forms. Our evolution is marked by several major steps or innovations along a path of increasing complexity from microbes to space-faring humans. Here we identify various major key innovations, and use an analytical toolset consisting of a set of models to analyse how likely each key innovation is to occur. Our conclusion is that once the origin of life is accomplished, most of the key innovations can occur rather readily. The conclusion for other worlds is that if the origin of life can occur rather easily, we should live in a cosmic zoo, as the innovations necessary to lead to complex life will occur with high probability given sufficient time and habitat. On the other hand, if the origin of life is rare, then we might live in a rather empty universe.
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Horneck G, Walter N, Westall F, Grenfell JL, Martin WF, Gomez F, Leuko S, Lee N, Onofri S, Tsiganis K, Saladino R, Pilat-Lohinger E, Palomba E, Harrison J, Rull F, Muller C, Strazzulla G, Brucato JR, Rettberg P, Capria MT. AstRoMap European Astrobiology Roadmap. ASTROBIOLOGY 2016; 16:201-43. [PMID: 27003862 PMCID: PMC4834528 DOI: 10.1089/ast.2015.1441] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 01/27/2016] [Indexed: 05/07/2023]
Abstract
The European AstRoMap project (supported by the European Commission Seventh Framework Programme) surveyed the state of the art of astrobiology in Europe and beyond and produced the first European roadmap for astrobiology research. In the context of this roadmap, astrobiology is understood as the study of the origin, evolution, and distribution of life in the context of cosmic evolution; this includes habitability in the Solar System and beyond. The AstRoMap Roadmap identifies five research topics, specifies several key scientific objectives for each topic, and suggests ways to achieve all the objectives. The five AstRoMap Research Topics are • Research Topic 1: Origin and Evolution of Planetary Systems • Research Topic 2: Origins of Organic Compounds in Space • Research Topic 3: Rock-Water-Carbon Interactions, Organic Synthesis on Earth, and Steps to Life • Research Topic 4: Life and Habitability • Research Topic 5: Biosignatures as Facilitating Life Detection It is strongly recommended that steps be taken towards the definition and implementation of a European Astrobiology Platform (or Institute) to streamline and optimize the scientific return by using a coordinated infrastructure and funding system.
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Affiliation(s)
- Gerda Horneck
- European Astrobiology Network Association
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Köln, Germany
| | | | - Frances Westall
- Centre National de la Recherche Scientifique–Centre de Biophysique Moléculaire, Orleans, France
| | - John Lee Grenfell
- Institute for Planetary Research, German Aerospace Center (DLR), Berlin, Germany
| | - William F. Martin
- Institute of Molecular Evolution, Heinrich-Heine University of Düsseldorf, Düsseldorf, Germany
| | - Felipe Gomez
- INTA Centre for Astrobiology, Torrejón de Ardoz, Madrid, Spain
| | - Stefan Leuko
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Köln, Germany
| | - Natuschka Lee
- Department of Ecology and Environmental Science, Umeå University, Umeå, Sweden
- Department of Microbiology, Technical University München, München, Germany
| | - Silvano Onofri
- Department of Ecological and Biological Sciences, University of Tuscia, Viterbo, Italy
| | - Kleomenis Tsiganis
- Department of Physics, Section of Astrophysics, Astronomy and Mechanics, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Raffaele Saladino
- Department of Agrobiology and Agrochemistry, University of Tuscia, Viterbo, Italy
| | | | - Ernesto Palomba
- INAF–Institute for Space Astrophysics and Planetology, Rome, Italy
| | - Jesse Harrison
- Department of Microbiology and Ecosystem Science, University of Vienna, Vienna, Austria
| | - Fernando Rull
- Department of Condensed Matter Physics, Crystallography and Mineralogy, Valladolid University, Valladolid, Spain
| | | | | | | | - Petra Rettberg
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Köln, Germany
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McKay CP. Titan as the Abode of Life. Life (Basel) 2016; 6:life6010008. [PMID: 26848689 PMCID: PMC4810239 DOI: 10.3390/life6010008] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2015] [Revised: 01/27/2016] [Accepted: 01/28/2016] [Indexed: 12/28/2022] Open
Abstract
Titan is the only world we know, other than Earth, that has a liquid on its surface. It also has a thick atmosphere composed of nitrogen and methane with a thick organic haze. There are lakes, rain, and clouds of methane and ethane. Here, we address the question of carbon-based life living in Titan liquids. Photochemically produced organics, particularly acetylene, in Titan’s atmosphere could be a source of biological energy when reacted with atmospheric hydrogen. Light levels on the surface of Titan are more than adequate for photosynthesis, but the biochemical limitations due to the few elements available in the environment may lead only to simple ecosystems that only consume atmospheric nutrients. Life on Titan may make use of the trace metals and other inorganic elements produced by meteorites as they ablate in its atmosphere. It is conceivable that H2O molecules on Titan could be used in a biochemistry that is rooted in hydrogen bonds in a way that metals are used in enzymes by life on Earth. Previous theoretical work has shown possible membrane structures, azotosomes, in Titan liquids, azotosomes, composed of small organic nitrogen compounds, such as acrylonitrile. The search for a plausible information molecule for life in Titan liquids remains an open research topic—polyethers have been considered and shown to be insoluble at Titan temperatures. Possible search strategies for life on Titan include looking for unusual concentrations of certain molecules reflecting biological selection. Homochirality is a special and powerful example of such biology selection. Environmentally, a depletion of hydrogen in the lower atmosphere may be a sign of metabolism. A discovery of life in liquid methane and ethane would be our first compelling indication that the universe is full of diverse and wondrous life forms.
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Affiliation(s)
- Christopher P McKay
- Space Science Division, NASA Ames Research Center, Moffett Field, CA 94035, USA.
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