1
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Poggiali V, Brighi G, Hayes AG, Nicholson PD, MacKenzie S, Lalich DE, Bonnefoy LE, Oudrhiri K, Lorenz RD, Soderblom JM, Tortora P, Zannoni M. Surface properties of the seas of Titan as revealed by Cassini mission bistatic radar experiments. Nat Commun 2024; 15:5454. [PMID: 39013844 PMCID: PMC11252143 DOI: 10.1038/s41467-024-49837-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Accepted: 06/20/2024] [Indexed: 07/18/2024] Open
Abstract
Saturn's moon Titan was explored by the Cassini spacecraft from 2004 to 2017. While Cassini revealed a lot about this Earth-like world, its radar observations could only provide limited information about Titan's liquid hydrocarbons seas Kraken, Ligeia and Punga Mare. Here, we show the results of the analysis of the Cassini mission bistatic radar experiments data of Titan's polar seas. The dual-polarized nature of bistatic radar observations allow independent estimates of effective relative dielectric constant and small-scale roughness of sea surface, which were not possible via monostatic radar data. We find statistically significant variations in effective dielectric constant (i.e., liquid composition), consistent with a latitudinal dependence in the methane-ethane mixing-ratio. The results on estuaries suggest lower values than the open seas, compatible with methane-rich rivers entering seas with higher ethane content. We estimate small-scale roughness of a few millimeters from the almost purely coherent scattering from the sea surface, hinting at the presence of capillary waves. This roughness is concentrated near estuaries and inter-basin straits, perhaps indicating active tidal currents.
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Affiliation(s)
| | - Giancorrado Brighi
- Università di Bologna, Dipartimento di Ingegneria Industriale, Forlì, Italy
| | | | | | | | | | - Léa E Bonnefoy
- Cornell University, Ithaca, NY, USA
- LERMA, Observatoire de Paris, CNRS, Paris, France
| | - Kamal Oudrhiri
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | | | | | - Paolo Tortora
- Università di Bologna, Dipartimento di Ingegneria Industriale, Forlì, Italy
| | - Marco Zannoni
- Università di Bologna, Dipartimento di Ingegneria Industriale, Forlì, Italy
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2
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Nixon CA. The Composition and Chemistry of Titan's Atmosphere. ACS EARTH & SPACE CHEMISTRY 2024; 8:406-456. [PMID: 38533193 PMCID: PMC10961852 DOI: 10.1021/acsearthspacechem.2c00041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 11/02/2023] [Accepted: 02/02/2024] [Indexed: 03/28/2024]
Abstract
In this review I summarize the current state of knowledge about the composition of Titan's atmosphere and our current understanding of the suggested chemistry that leads to that observed composition. I begin with our present knowledge of the atmospheric composition, garnered from a variety of measurements including Cassini-Huygens, the Atacama Large Millimeter/submillimeter Array, and other ground- and space-based telescopes. This review focuses on the typical vertical profiles of gases at low latitudes rather than global and temporal variations. The main body of the review presents a chemical description of how complex molecules are believed to arise from simpler species, considering all known "stable" molecules-those that have been uniquely identified in the neutral atmosphere. The last section of the review is devoted to the gaps in our present knowledge of Titan's chemical composition and how further work may fill those gaps.
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Affiliation(s)
- Conor A. Nixon
- Planetary Systems Laboratory, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, Maryland 20771, United
States
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3
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Styczinski MJ, Cooper ZS, Glaser DM, Lehmer O, Mierzejewski V, Tarnas J. Chapter 7: Assessing Habitability Beyond Earth. ASTROBIOLOGY 2024; 24:S143-S163. [PMID: 38498826 DOI: 10.1089/ast.2021.0097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/20/2024]
Abstract
All known life on Earth inhabits environments that maintain conditions between certain extremes of temperature, chemical composition, energy availability, and so on (Chapter 6). Life may have emerged in similar environments elsewhere in the Solar System and beyond. The ongoing search for life elsewhere mainly focuses on those environments most likely to support life, now or in the past-that is, potentially habitable environments. Discussion of habitability is necessarily based on what we know about life on Earth, as it is our only example. This chapter gives an overview of the known and presumed requirements for life on Earth and discusses how these requirements can be used to assess the potential habitability of planetary bodies across the Solar System and beyond. We first consider the chemical requirements of life and potential feedback effects that the presence of life can have on habitable conditions, and then the planetary, stellar, and temporal requirements for habitability. We then review the state of knowledge on the potential habitability of bodies across the Solar System and exoplanets, with a particular focus on Mars, Venus, Europa, and Enceladus. While reviewing the case for the potential habitability of each body, we summarize the most prominent and impactful studies that have informed the perspective on where habitable environments are likely to be found.
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Affiliation(s)
- M J Styczinski
- University of Washington, Seattle, Washington, USA
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | - Z S Cooper
- University of Washington, Seattle, Washington, USA
| | - D M Glaser
- School of Molecular Sciences, Arizona State University, Tempe, Arizona, USA
| | - O Lehmer
- NASA Ames Research Center, Moffett Field, California, USA
| | - V Mierzejewski
- School of Earth and Space Exploration, Arizona State University, Arizona, USA
| | - J Tarnas
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
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4
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Farnsworth KK, Soto A, Chevrier VF, Steckloff JK, Soderblom JM. Floating Liquid Droplets on the Surface of Cryogenic Liquids: Implications for Titan Rain. ACS EARTH & SPACE CHEMISTRY 2023; 7:439-448. [PMID: 36824999 PMCID: PMC9940721 DOI: 10.1021/acsearthspacechem.2c00311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 12/23/2022] [Accepted: 01/09/2023] [Indexed: 06/18/2023]
Abstract
Saturn's moon, Titan, has a hydrocarbon-based hydrologic cycle with methane and ethane rainfall. Because of Titan's low gravity, "floating liquid droplets" (coherent droplets of liquid hydrocarbons that float upon a liquid surface) may form on the surface of Titan's hydrocarbon lakes and seas during rainfall. Floating liquid droplets, however, have not been investigated in the laboratory under conditions appropriate for the surface of Titan (cryogenic, hydrocarbon, liquids). We conducted a set of experiments to simulate methane and ethane rainfall under Titan surface conditions (89-94 K, 1.5 bar nitrogen atmosphere) and find that floating ethane droplets form in a wide range of bulk liquid compositions, yet floating methane droplets only form in a narrow compositional range and impact velocity. We find droplet formation is independent of the liquid density and hypothesize that dissolved atmospheric nitrogen in the bulk liquid may repel liquid ethane droplets at the surface. We propose that liquid droplets will form in Titan's methane-rich lakes and seas during ethane rainfall with a droplet radius of ≤3 mm and an impact velocity of ≤0.7 m/s. The presence of these droplets on Titan's lakes may result in a liquid surface layer that is dominated in rainfall composition.
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Affiliation(s)
- Kendra K. Farnsworth
- NASA
Postdoctoral Program Fellow, NASA Goddard
Space Flight Center, 8800 Greenbelt Rd, Greenbelt, Maryland20771, United States
- Center
for Space and Planetary Sciences, University
of Arkansas, 332 N. Arkansas
Ave., Fayetteville, Arkansas72701, United States
| | - Alejandro Soto
- Southwest
Research Institute, 1050 Walnut Street, Suite 300, Boulder, Colorado80302, United States
| | - Vincent F. Chevrier
- Center
for Space and Planetary Sciences, University
of Arkansas, 332 N. Arkansas
Ave., Fayetteville, Arkansas72701, United States
| | - Jordan K. Steckloff
- Planetary
Science Institute, 1700 East Fort Lowell, Suite 106, Tucson, Arizona85719, United States
- Department
of Aerospace Engineering and Engineering Mechanics, W.R. Woolrich
Laboratories, C0600, University of Texas
at Austin, 201 East 24th
Street, Austin, Texas78712, United States
| | - Jason M. Soderblom
- Department
of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, Massachusetts02139, United States
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5
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Royer C, Pilorget C, Hamm V, Bibring JP, Poulet F. A new concept of acousto-optic tunable filter-based near-infrared hyperspectral imager for planetary surface exploration. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:044501. [PMID: 35489938 DOI: 10.1063/5.0075256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Accepted: 03/10/2022] [Indexed: 06/14/2023]
Abstract
In the past two decades, near-infrared (NIR) hyperspectral imaging instruments have revolutionized our conception of planetary surfaces in terms of evolution, geology, mineralogy, and alteration processes. The cornerstone of this remote analysis technique is the synergy between imagery, giving the geomorphological context of the observations, and NIR spectroscopy whose spectral range is sensitive to the main absorption features of most of the minerals present on planetary surfaces. The development of a generation of space instrument based on Acousto-Optic Tunable Filters (AOTFs) increases the capacity of these spectrometers to be set up in a variety of space probes. The ExoCam concept, developed at Institut d'Astrophysique Spatiale and profiting from the lab's previous experience (MicrOmega onboard Phobos-Grunt, Hayabusa 2 and ExoMars), thus, proposes for the first time to do hyperspectral imagery through a wide aperture AOTF (15 × 15 mm2) in the 0.95-3.6 µm spectral range. The characterization of this instrumental concept, led on a representative breadboard built for this purpose, showed that the acousto-optic diffraction preserves the image quality up to the diffraction/resolution limit over the whole field of view. The spectral resolution (from 2 to 25 nm over the spectral range) and accuracy of the instrument are also consistent with the identification of planetary surface minerals. This paper describes the ExoCam concept and objectives, the setup of an optical breadboard representative of a space instrument based on this concept, and the results of performance characterizations realized on the breadboard.
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Affiliation(s)
- Clément Royer
- Université Paris-Saclay, CNRS, Institut d'Astrophysique Spatiale, 91405 Orsay, France
| | - C Pilorget
- Université Paris-Saclay, CNRS, Institut d'Astrophysique Spatiale, 91405 Orsay, France
| | - V Hamm
- Université Paris-Saclay, CNRS, Institut d'Astrophysique Spatiale, 91405 Orsay, France
| | - J-P Bibring
- Université Paris-Saclay, CNRS, Institut d'Astrophysique Spatiale, 91405 Orsay, France
| | - F Poulet
- Université Paris-Saclay, CNRS, Institut d'Astrophysique Spatiale, 91405 Orsay, France
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6
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Thompson B, Burt K, Lee A, Lingard K, Maurer SE. Partitioning of amino acids and proteins into decanol using phase transfer agents towards understanding life in non-polar liquids. Sci Rep 2019; 9:17750. [PMID: 31780746 PMCID: PMC6882823 DOI: 10.1038/s41598-019-54322-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Accepted: 10/17/2019] [Indexed: 11/21/2022] Open
Abstract
Water has many roles in the context of life on Earth, however throughout the universe, other liquids may be able to support the emergence of life. We looked at the ability of amino acids, peptides, a depsipeptide, and proteins to partition into a non-polar decanol phase, with and without the addition of a phase transfer agent. Partitioning evaluated using UV detection, or with HPLC coupled to either charged aerosol detection or ESI-MS. For amino acids and short peptides, phase transfer agents were used to move the biomolecules to the decanol phase, and this transfer was pH dependent. For larger molecules, phase transfer agents did not seem to affect the transfer. Both the depsipetide, valinomycin, and the protein Taq DNA polymerase had solubility in the decanol phase. Additionally, valinomycin appeared to retain its biological ability to bind to potassium ions. These results show that most terrestrial biological molecules are not compatible with non-polar solvents, but it is possible to find and perhaps evolve polymers that are functional in such phases.
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Affiliation(s)
- Brooke Thompson
- Department of Chemistry and Biochemistry, Central Connecticut State University, New Britain, CT, 06050, USA
| | - Kayla Burt
- Department of Chemistry and Biochemistry, Central Connecticut State University, New Britain, CT, 06050, USA
| | - Andrew Lee
- Department of Chemistry and Biochemistry, Central Connecticut State University, New Britain, CT, 06050, USA
| | - Kyle Lingard
- Department of Chemistry and Biochemistry, Central Connecticut State University, New Britain, CT, 06050, USA
| | - Sarah E Maurer
- Department of Chemistry and Biochemistry, Central Connecticut State University, New Britain, CT, 06050, USA.
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7
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Dual Frequency Orbiter-Radar System for the Observation of Seas and Tides on Titan: Extraterrestrial Oceanography from Satellite. REMOTE SENSING 2019. [DOI: 10.3390/rs11161898] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Saturn’s largest moon, Titan, is believed to have a ~100 km thick ice shell above a global ocean of liquid water. Organic materials, including liquid hydrocarbon lakes and seas in its polar terrain, cover Titan’s surface, which makes it a world of two oceans. The RADAR instrument on board Cassini, was able to probe lakes and seas during few dedicated altimetric observations, revealing its capability to work as a sounder. Herein, we describe the design of, and scientific motivation for, a dual frequency X/Ka-band radar system that is able to investigate Titan’s subsurface liquid water ocean, as well as the depth and composition of its surface liquid hydrocarbon basins. The proposed system, which could take advantage of the telecommunications dish, can operate as a sounder, as Synthetic Aperture Radar (SAR) able to map the surface at tens meters of scale resolution, and when data are acquired from close-adjacent orbits, as a repeat-pass SAR interferometer (InSAR). The instrument, which is based on the architecture of the Cassini RADAR, can also characterize Titan’s interior by using geophysical measurements of the tidal amplitude to derive high accuracy estimates of the Love number h2 from a 1500 km circular orbit.
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8
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Kawai J, Kebukawa Y, McKay CP, Kobayashi K. Nucleic acid bases in Titan tholins and possible genetic systems in the Titan liquidosphere. LIFE SCIENCES IN SPACE RESEARCH 2019; 20:20-29. [PMID: 30797431 DOI: 10.1016/j.lssr.2018.11.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 11/18/2018] [Accepted: 11/26/2018] [Indexed: 06/09/2023]
Abstract
Titan is the largest moon of Saturn and possesses a dense atmosphere composed of nitrogen and methane. Various types of organic compounds (hydrocarbons, nitriles, etc.) have been found on Titan, which were generated by reactions taking place in its atmosphere. These reactions are considered to provide crucial evidence for chemical reactions which may have occurred in the atmosphere of primitive Earth. Cassini discovered several lakes of liquid methane and ethane on Titan's surface; in addition, the presence of ammonia water in its sub-surface was implied. In order to simulate the chemical reactions in Titan's atmosphere, gas mixtures of nitrogen and methane have been exposed to plasma discharges to synthesize complex organic matters. In this study, we focused on the formation of nucleic acid bases and related compounds recovered from synthesized Titan tholins. The five nucleic acid bases that terrestrial life uses (adenine, cytosine, thymine, guanine, and uracil) have already been reported to be present in synthesized Titan tholins. Purines and pyrimidines, including the five aforementioned nucleic acid bases, were extracted from synthesized Titan tholins and analyzed by HPLC and LC/MS. As a result, the pyrimidine bases of isocytosine and 2, 4-diaminopyrimidine were detected together with the terrestrial nucleic acid bases of adenine, uracil, and cytosine. The results obtained in conjunction with those from previous studies show that some nucleic acid bases and related pyrimidine bases are found in synthesized Titan tholins, suggesting that chemical evolutions toward xenogenetic systems could occur in Titan's environment.
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Affiliation(s)
- Jun Kawai
- High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki, 305-0801, Japan.
| | - Yoko Kebukawa
- Yokohama National University, 79-1 Tokiwadai, Hodogaya-ku, Yokohama, 240-8501, Japan.
| | | | - Kensei Kobayashi
- Yokohama National University, 79-1 Tokiwadai, Hodogaya-ku, Yokohama, 240-8501, Japan.
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9
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Hendrix AR, Hurford TA, Barge LM, Bland MT, Bowman JS, Brinckerhoff W, Buratti BJ, Cable ML, Castillo-Rogez J, Collins GC, Diniega S, German CR, Hayes AG, Hoehler T, Hosseini S, Howett CJ, McEwen AS, Neish CD, Neveu M, Nordheim TA, Patterson GW, Patthoff DA, Phillips C, Rhoden A, Schmidt BE, Singer KN, Soderblom JM, Vance SD. The NASA Roadmap to Ocean Worlds. ASTROBIOLOGY 2019; 19:1-27. [PMID: 30346215 PMCID: PMC6338575 DOI: 10.1089/ast.2018.1955] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Accepted: 09/21/2018] [Indexed: 05/20/2023]
Abstract
In this article, we summarize the work of the NASA Outer Planets Assessment Group (OPAG) Roadmaps to Ocean Worlds (ROW) group. The aim of this group is to assemble the scientific framework that will guide the exploration of ocean worlds, and to identify and prioritize science objectives for ocean worlds over the next several decades. The overarching goal of an Ocean Worlds exploration program as defined by ROW is to "identify ocean worlds, characterize their oceans, evaluate their habitability, search for life, and ultimately understand any life we find." The ROW team supports the creation of an exploration program that studies the full spectrum of ocean worlds, that is, not just the exploration of known ocean worlds such as Europa but candidate ocean worlds such as Triton as well. The ROW team finds that the confirmed ocean worlds Enceladus, Titan, and Europa are the highest priority bodies to target in the near term to address ROW goals. Triton is the highest priority candidate ocean world to target in the near term. A major finding of this study is that, to map out a coherent Ocean Worlds Program, significant input is required from studies here on Earth; rigorous Research and Analysis studies are called for to enable some future ocean worlds missions to be thoughtfully planned and undertaken. A second finding is that progress needs to be made in the area of collaborations between Earth ocean scientists and extraterrestrial ocean scientists.
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Affiliation(s)
- Amanda R. Hendrix
- Planetary Science Institute, Tucson, Arizona
- Address correspondence to: Amanda R. Hendrix, Planetary Science Institute, 1700 East Fort Lowell, Suite 106, Tucson, AZ 85719
| | | | - Laura M. Barge
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
| | - Michael T. Bland
- Astrogeology Science Center, U.S. Geological Survey, Flagstaff, Arizona
| | - Jeff S. Bowman
- Scripps Institution of Oceanography, La Jolla, California
| | | | - Bonnie J. Buratti
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
| | - Morgan L. Cable
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
| | - Julie Castillo-Rogez
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
| | | | - Serina Diniega
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
| | | | - Alexander G. Hayes
- Cornell Center for Astrophysics and Planetary Science, Cornell University, Ithaca, New York
| | - Tori Hoehler
- NASA Ames Research Center, Mountain View, California
| | - Sona Hosseini
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
| | | | - Alfred S. McEwen
- Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona
| | - Catherine D. Neish
- Planetary Science Institute, Tucson, Arizona
- Department of Earth Sciences, The University of Western Ontario, London, Ontario, Canada
| | - Marc Neveu
- NASA HQ/Universities Space Association, Washington, District of Columbia
| | - Tom A. Nordheim
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
| | | | | | - Cynthia Phillips
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
| | | | - Britney E. Schmidt
- School of Earth & Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia
| | | | - Jason M. Soderblom
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Steven D. Vance
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
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10
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Mahjoub A, Choukroun M, Hodyss R, Sotin C, Beauchamp P, Barmatz M. Titan Lakes Simulation System (TiLSS): A cryogenic experimental setup to simulate Titan's liquid hydrocarbon surfaces. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:124502. [PMID: 30599566 DOI: 10.1063/1.5053126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Accepted: 11/18/2018] [Indexed: 06/09/2023]
Abstract
Titan's hydrocarbon lakes play an important role in the chemistry, geomorphology, and climate of the satellite. Our knowledge of their composition relies mainly on thermodynamic modeling and assumptions based on Cassini Radar and VIMS (Visible and Infrared Mapping Spectrometer) data. Several thermodynamic models have been used to calculate the composition of these lakes, and their results on even the major lake components (methane, ethane, propane, and nitrogen) exhibit large discrepancies. Recent Cassini radar observations revealed an echo from the lake's bottom. A low loss factor of attenuation is needed within the lakes to interpret these observations, and it has been suggested that the lakes are dominated by methane. Cassini VIMS data obtained on the North Pole lakes at three-year intervals showed no detectable surface level change, which is consistent with ethane being their primary constituent. This additional discrepancy between thermodynamic models and Cassini data strongly shows the need for experimental measurements under realistic Titan conditions in order to better constrain the thermodynamic models. We designed and built a cryogenic experimental platform allowing the simulation of Titan's lakes. This facility, named Titan Lakes Simulation System (TiLSS), produces liquid hydrocarbons in equilibrium with a gas phase mimicking Titan's atmosphere. Samples of the condensed liquid are injected directly into a gas chromatograph allowing the direct measurement of its chemical components and their abundances. To test the overall operation of the system, a gas mixture of methane and ethane was condensed under 1.5 bar of nitrogen and analyzed. Results from this proof of concept test are in good agreement with experimental studies previously published.
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Affiliation(s)
- Ahmed Mahjoub
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA
| | - Mathieu Choukroun
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA
| | - Robert Hodyss
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA
| | - Christophe Sotin
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA
| | - Patricia Beauchamp
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA
| | - Martin Barmatz
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA
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11
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Kobayashi K, Geppert WD, Carrasco N, Holm NG, Mousis O, Palumbo ME, Waite JH, Watanabe N, Ziurys LM. Laboratory Studies of Methane and Its Relationship to Prebiotic Chemistry. ASTROBIOLOGY 2017; 17:786-812. [PMID: 28727932 DOI: 10.1089/ast.2016.1492] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
To examine how prebiotic chemical evolution took place on Earth prior to the emergence of life, laboratory experiments have been conducted since the 1950s. Methane has been one of the key molecules in these investigations. In earlier studies, strongly reducing gas mixtures containing methane and ammonia were used to simulate possible reactions in the primitive atmosphere of Earth, producing amino acids and other organic compounds. Since Earth's early atmosphere is now considered to be less reducing, the contribution of extraterrestrial organics to chemical evolution has taken on an important role. Such organic molecules may have come from molecular clouds and regions of star formation that created protoplanetary disks, planets, asteroids, and comets. The interstellar origin of organics has been examined both experimentally and theoretically, including laboratory investigations that simulate interstellar molecular reactions. Endogenous and exogenous organics could also have been supplied to the primitive ocean, making submarine hydrothermal systems plausible sites of the generation of life. Experiments that simulate such hydrothermal systems where methane played an important role have consequently been conducted. Processes that occur in other Solar System bodies offer clues to the prebiotic chemistry of Earth. Titan and other icy bodies, where methane plays significant roles, are especially good targets. In the case of Titan, methane is both in the atmosphere and in liquidospheres that are composed of methane and other hydrocarbons, and these have been studied in simulation experiments. Here, we review the wide range of experimental work in which these various terrestrial and extraterrestrial environments have been modeled, and we examine the possible role of methane in chemical evolution. Key Words: Methane-Interstellar environments-Submarine hydrothermal systems-Titan-Origin of life. Astrobiology 17, 786-812.
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Affiliation(s)
- Kensei Kobayashi
- 1 Department of Chemistry, Yokohama National University , Yokohama, Japan
| | - Wolf D Geppert
- 2 Department of Geological Sciences, Stockholm University , Stockholm, Sweden
| | - Nathalie Carrasco
- 3 LATMOS, Université Versailles St-Quentin , UPMC, CNRS, Guyancourt, France
| | - Nils G Holm
- 2 Department of Geological Sciences, Stockholm University , Stockholm, Sweden
| | - Olivier Mousis
- 4 Aix Marseille Université , CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, Marseille, France
| | | | - J Hunter Waite
- 6 Southwest Research Institute , San Antonio, Texas, USA
| | - Naoki Watanabe
- 7 Institute of Low Temperature Science, Hokkaido University , Sapporo, Japan
| | - Lucy M Ziurys
- 8 Department of Astronomy, Department of Chemistry and Biochemistry, and Steward Observatory, University of Arizona , Tucson, Arizona, USA
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12
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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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13
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14
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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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15
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Hargreaves RJ, Buzan E, Dulick M, Bernath PF. High-resolution absorption cross sections of C2H6 at elevated temperatures. ACTA ACUST UNITED AC 2015. [DOI: 10.1016/j.molap.2015.09.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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16
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Heller R, Williams D, Kipping D, Limbach MA, Turner E, Greenberg R, Sasaki T, Bolmont É, Grasset O, Lewis K, Barnes R, Zuluaga JI. Formation, habitability, and detection of extrasolar moons. ASTROBIOLOGY 2014; 14:798-835. [PMID: 25147963 PMCID: PMC4172466 DOI: 10.1089/ast.2014.1147] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Accepted: 06/05/2014] [Indexed: 06/03/2023]
Abstract
The diversity and quantity of moons in the Solar System suggest a manifold population of natural satellites exist around extrasolar planets. Of peculiar interest from an astrobiological perspective, the number of sizable moons in the stellar habitable zones may outnumber planets in these circumstellar regions. With technological and theoretical methods now allowing for the detection of sub-Earth-sized extrasolar planets, the first detection of an extrasolar moon appears feasible. In this review, we summarize formation channels of massive exomoons that are potentially detectable with current or near-future instruments. We discuss the orbital effects that govern exomoon evolution, we present a framework to characterize an exomoon's stellar plus planetary illumination as well as its tidal heating, and we address the techniques that have been proposed to search for exomoons. Most notably, we show that natural satellites in the range of 0.1-0.5 Earth mass (i) are potentially habitable, (ii) can form within the circumplanetary debris and gas disk or via capture from a binary, and (iii) are detectable with current technology.
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Affiliation(s)
- René Heller
- Origins Institute, Department of Physics and Astronomy, McMaster University, Hamilton, Canada
| | - Darren Williams
- The Behrend College School of Science, Penn State Erie, Erie, Pennsylvania, USA
| | - David Kipping
- Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA
| | - Mary Anne Limbach
- Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey, USA
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey, USA
| | - Edwin Turner
- Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey, USA
- The Kavli Institute for the Physics and Mathematics of the Universe, The University of Tokyo, Kashiwa, Japan
| | - Richard Greenberg
- Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
| | | | - Émeline Bolmont
- Université de Bordeaux, LAB, UMR 5804, Floirac, France
- CNRS, LAB, UMR 5804, Floirac, France
| | - Olivier Grasset
- Planetology and Geodynamics, University of Nantes, CNRS, Nantes, France
| | - Karen Lewis
- Earth and Planetary Sciences, Tokyo Institute of Technology, Tokyo, Japan
| | - Rory Barnes
- Astronomy Department, University of Washington, Seattle, Washington, USA
- NASA Astrobiology Institute—Virtual Planetary Laboratory Lead Team, USA
| | - Jorge I. Zuluaga
- FACom—Instituto de Física—FCEN, Universidad de Antioquia, Medellín, Colombia
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17
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Barnes JW, Sotin C, Soderblom JM, Brown RH, Hayes AG, Donelan M, Rodriguez S, Mouélic SL, Baines KH, McCord TB. Cassini/VIMS observes rough surfaces on Titan's Punga Mare in specular reflection. ACTA ACUST UNITED AC 2014; 3:3. [PMID: 27512619 PMCID: PMC4959132 DOI: 10.1186/s13535-014-0003-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Accepted: 06/19/2014] [Indexed: 11/28/2022]
Abstract
Cassini/VIMS high-phase specular observations of Titan’s north pole during the T85 flyby show evidence for isolated patches of rough liquid surface within the boundaries of the sea Punga Mare. The roughness shows typical slopes of 6°±1°. These rough areas could be either wet mudflats or a wavy sea. Because of their large areal extent, patchy geographic distribution, and uniform appearance at low phase, we prefer a waves interpretation. Applying theoretical wave calculations based on Titan conditions our slope determination allows us to infer winds of 0.76±0.09 m/s and significant wave heights of \documentclass[12pt]{minimal}
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$2^{+2}_{-1}$
\end{document}2−1+2 cm at the time and locations of the observation. If correct, these would represent the first waves seen on Titan’s seas, and also the first extraterrestrial sea-surface waves in general.
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Affiliation(s)
- Jason W Barnes
- Department of Physics, University of Idaho, Moscow, 83844-0903 Idaho USA
| | - Christophe Sotin
- Jet Propulsion Laboratory, Caltech, Pasadena, 91109 California USA
| | - Jason M Soderblom
- Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, 02141 MA USA
| | - Robert H Brown
- Lunar and Planetary Laboratory, University of Arizona, Tucson, 85721 Arizona USA
| | | | | | - Sebastien Rodriguez
- Laboratoire AIM, Université Paris Diderot/CEA Irfu/CNRS, Centre de l'orme des Mérisiers, bât. 709, Gif/Yvette Cedex, 91191 France
| | - Stéphane Le Mouélic
- Laboratoire de Planétologie et Géodynamique, CNRS UMR6112, Université de Nantes, Nantes, France
| | - Kevin H Baines
- Space Science and Engineering Center, University of Wisconsin, Madison, 53706 WI USA
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18
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Vu TH, Gloesener E, Choukroun M, Ibourichene A, Hodyss R. Experimental Study on the Effect of Ammonia on the Phase Behavior of Tetrahydrofuran Clathrates. J Phys Chem B 2014; 118:13371-7. [DOI: 10.1021/jp5042487] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tuan Hoang Vu
- NASA
Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak
Grove Drive, Pasadena, California 91109, United States
| | - Elodie Gloesener
- Observatoire Royal de Belgique, Avenue
Circulaire 3, 1180 Uccle, Belgium
| | - Mathieu Choukroun
- NASA
Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak
Grove Drive, Pasadena, California 91109, United States
| | | | - Robert Hodyss
- NASA
Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak
Grove Drive, Pasadena, California 91109, United States
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19
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Vu TH, Cable ML, Choukroun M, Hodyss R, Beauchamp P. Formation of a New Benzene–Ethane Co-Crystalline Structure Under Cryogenic Conditions. J Phys Chem A 2014; 118:4087-94. [DOI: 10.1021/jp501698j] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Tuan Hoang Vu
- NASA Jet
Propulsion Laboratory, California Institute of Technology, 4800 Oak
Grove Drive, Pasadena, California 91109, United States
| | - Morgan L. Cable
- NASA Jet
Propulsion Laboratory, California Institute of Technology, 4800 Oak
Grove Drive, Pasadena, California 91109, United States
| | - Mathieu Choukroun
- NASA Jet
Propulsion Laboratory, California Institute of Technology, 4800 Oak
Grove Drive, Pasadena, California 91109, United States
| | - Robert Hodyss
- NASA Jet
Propulsion Laboratory, California Institute of Technology, 4800 Oak
Grove Drive, Pasadena, California 91109, United States
| | - Patricia Beauchamp
- NASA Jet
Propulsion Laboratory, California Institute of Technology, 4800 Oak
Grove Drive, Pasadena, California 91109, United States
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20
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Arvelo J, Lorenz R. Plumbing the depths of Ligeia: considerations for depth sounding in Titan's hydrocarbon seas. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2013; 134:4335. [PMID: 25669245 DOI: 10.1121/1.4824908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Saturn's moon Titan is the only satellite in this solar system with a dense atmosphere and hydrocarbon seas. The Titan Mare Explorer (TiME) mission would splashdown a capsule to float for 3 months on Ligeia Mare, a several-hundred-kilometer wide sea near Titan's north pole. Among TiME's scientific goals is the determination of the depth of Ligeia, to be achieved with an acoustic depth sounder. Since Titan's surface temperature is known to vary around 92 K, all instruments must be ruggedized to operate at cryogenic temperatures. This paper's contributions include an approach to infer key acoustic properties of this remote environment and the extraterrestrial environment's influence on the development of a cryogenic depth sounder. Additionally, an approach is formulated to infer the transducer's response, sensitivity, and performance when in situ calibration is impossible or when replicating key environmental conditions is too costly.
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Affiliation(s)
- Juan Arvelo
- The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland 20723
| | - Ralph Lorenz
- The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland 20723
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21
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Telling J, Lacrampe-Couloume G, Sherwood Lollar B. Carbon and hydrogen isotopic composition of methane and C2+ alkanes in electrical spark discharge: implications for identifying sources of hydrocarbons in terrestrial and extraterrestrial settings. ASTROBIOLOGY 2013; 13:483-490. [PMID: 23683048 DOI: 10.1089/ast.2012.0915] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The low-molecular-weight alkanes--methane, ethane, propane, and butane--are found in a wide range of terrestrial and extraterrestrial settings. The development of robust criteria for distinguishing abiogenic from biogenic alkanes is essential for current investigations of Mars' atmosphere and for future exobiology missions to other planets and moons. Here, we show that alkanes synthesized during gas-phase radical recombination reactions in electrical discharge experiments have values of δ(2)H(methane)>δ(2)H(ethane)>δ(2)H(propane), similar to those of the carbon isotopes. The distribution of hydrogen isotopes in gas-phase radical reactions is likely due to kinetic fractionations either (i) from the preferential incorporation of (1)H into longer-chain alkanes due to the more rapid rate of collisions of the smaller (1)H-containing molecules or (ii) by secondary ion effects. Similar δ(13)C(C1-C2+) and δ(2)H(C1-C2+) patterns may be expected in a range of extraterrestrial environments where gas-phase radical reactions dominate, including interstellar space, the atmosphere and liquid hydrocarbon lakes of Saturn's moon Titan, and the outer atmospheres of Jupiter, Saturn, Neptune, and Uranus. Radical recombination reactions at high temperatures and pressures may provide an explanation for the combined reversed δ(13)C(C1-C2+) and δ(2)H(C1-C2+) patterns of terrestrial alkanes documented at a number of high-temperature/pressure crustal sites.
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Affiliation(s)
- Jon Telling
- Department of Earth Sciences, University of Toronto, Toronto, Canada.
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22
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Barnes JW, Buratti BJ, Turtle EP, Bow J, Dalba PA, Perry J, Brown RH, Rodriguez S, Mouélic SL, Baines KH, Sotin C, Lorenz RD, Malaska MJ, McCord TB, Clark RN, Jaumann R, Hayne PO, Nicholson PD, Soderblom JM, Soderblom LA. Precipitation-induced surface brightenings seen on Titan by Cassini VIMS and ISS. ACTA ACUST UNITED AC 2013. [DOI: 10.1186/2191-2521-2-1] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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23
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Mastrapa RME, Grundy WM, Gudipati MS. Amorphous and Crystalline H2O-Ice. THE SCIENCE OF SOLAR SYSTEM ICES 2013. [DOI: 10.1007/978-1-4614-3076-6_11] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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24
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Cornet T, Bourgeois O, Le Mouélic S, Rodriguez S, Sotin C, Barnes JW, Brown RH, Baines KH, Buratti BJ, Clark RN, Nicholson PD. Edge detection applied to Cassini images reveals no measurable displacement of Ontario Lacus' margin between 2005 and 2010. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/2012je004073] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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25
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Possible tropical lakes on Titan from observations of dark terrain. Nature 2012; 486:237-9. [PMID: 22699614 DOI: 10.1038/nature11165] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Accepted: 04/26/2012] [Indexed: 11/08/2022]
Abstract
Titan has clouds, rain and lakes--like Earth--but composed of methane rather than water. Unlike Earth, most of the condensable methane (the equivalent of 5 m depth globally averaged) lies in the atmosphere. Liquid detected on the surface (about 2 m deep) has been found by radar images only poleward of 50° latitude, while dune fields pervade the tropics. General circulation models explain this dichotomy, predicting that methane efficiently migrates to the poles from these lower latitudes. Here we report an analysis of near-infrared spectral images of the region between 20° N and 20° S latitude. The data reveal that the lowest fluxes in seven wavelength bands that probe Titan's surface occur in an oval region of about 60 × 40 km(2), which has been observed repeatedly since 2004. Radiative transfer analyses demonstrate that the resulting spectrum is consistent with a black surface, indicative of liquid methane on the surface. Enduring low-latitude lakes are best explained as supplied by subterranean sources (within the last 10,000 years), which may be responsible for Titan's methane, the continual photochemical depletion of which furnishes Titan's organic chemistry.
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26
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Cable ML, Hörst SM, Hodyss R, Beauchamp PM, Smith MA, Willis PA. Titan Tholins: Simulating Titan Organic Chemistry in the Cassini-Huygens Era. Chem Rev 2011; 112:1882-909. [DOI: 10.1021/cr200221x] [Citation(s) in RCA: 165] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Morgan L. Cable
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, United States
| | - Sarah M. Hörst
- Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado 80309, United States
| | - Robert Hodyss
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, United States
| | - Patricia M. Beauchamp
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, United States
| | - Mark A. Smith
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721, United States
- College of Natural Sciences and Mathematics, University of Houston, Houston, Texas 77004, United States
| | - Peter A. Willis
- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, United States
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27
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Abstract
The Cassini-Huygens mission discovered an active "hydrologic cycle" on Saturn's giant moon Titan, in which methane takes the place of water. Shrouded by a dense nitrogen-methane atmosphere, Titan's surface is blanketed in the equatorial regions by dunes composed of solid organics, sculpted by wind and fluvial erosion, and dotted at the poles with lakes and seas of liquid methane and ethane. The underlying crust is almost certainly water ice, possibly in the form of gas hydrates (clathrate hydrates) dominated by methane as the included species. The processes that work the surface of Titan resemble in their overall balance no other moon in the solar system; instead, they are most like that of the Earth. The presence of methane in place of water, however, means that in any particular planetary system, a body like Titan will always be outside the orbit of an Earth-type planet. Around M-dwarfs, planets with a Titan-like climate will sit at 1 AU--a far more stable environment than the approximately 0.1 AU where Earth-like planets sit. However, an observable Titan-like exoplanet might have to be much larger than Titan itself to be observable, increasing the ratio of heat contributed to the surface atmosphere system from internal (geologic) processes versus photons from the parent star.
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Affiliation(s)
- Jonathan I Lunine
- Dipartimento di Fisica, University of Rome "Tor Vergata", Rome, Italy 00133.
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28
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Clark RN, Curchin JM, Barnes JW, Jaumann R, Soderblom L, Cruikshank DP, Brown RH, Rodriguez S, Lunine J, Stephan K, Hoefen TM, Le Mouélic S, Sotin C, Baines KH, Buratti BJ, Nicholson PD. Detection and mapping of hydrocarbon deposits on Titan. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2009je003369] [Citation(s) in RCA: 134] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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29
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Hayes AG, Wolf AS, Aharonson O, Zebker H, Lorenz R, Kirk RL, Paillou P, Lunine J, Wye L, Callahan P, Wall S, Elachi C. Bathymetry and absorptivity of Titan's Ontario Lacus. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2009je003557] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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30
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Jacovi R, Laufer D, Dimitrov V, Bar-Nun A. Chemical composition of simulated Titan's midatmospheric aerosols. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2010je003585] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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31
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Wilson EH, Atreya SK. Titan’s Carbon Budget and the Case of the Missing Ethane. J Phys Chem A 2009; 113:11221-6. [DOI: 10.1021/jp905535a] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Eric H. Wilson
- Jet Propulsion Laboratory, 4800 Oak Grove Drive M/S 169-237, Pasadena, California 91109-8099, Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, Michigan 48109-2143
| | - Sushil K. Atreya
- Jet Propulsion Laboratory, 4800 Oak Grove Drive M/S 169-237, Pasadena, California 91109-8099, Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, Michigan 48109-2143
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Abstract
Methane clouds, lakes and most fluvial features on Saturn's moon Titan have been observed in the moist high latitudes, while the tropics have been nearly devoid of convective clouds and have shown an abundance of wind-carved surface features like dunes. The presence of small-scale channels and dry riverbeds near the equator observed by the Huygens probe at latitudes thought incapable of supporting convection (and thus strong rain) has been suggested to be due to geological seepage or other mechanisms not related to precipitation. Here we report the presence of bright, transient, tropospheric clouds in tropical latitudes. We find that the initial pulse of cloud activity generated planetary waves that instigated cloud activity at other latitudes across Titan that had been cloud-free for at least several years. These observations show that convective pulses at one latitude can trigger short-term convection at other latitudes, even those not generally considered capable of supporting convection, and may also explain the presence of methane-carved rivers and channels near the Huygens landing site.
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33
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Loakes D, Holliger P. Darwinian chemistry: towards the synthesis of a simple cell. MOLECULAR BIOSYSTEMS 2009; 5:686-94. [PMID: 19562107 DOI: 10.1039/b904024b] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The total synthesis of a simple cell is in many ways the ultimate challenge in synthetic biology. Outlined eight years ago in a visionary article by Szostak et al. (J. W. Szostak, D. P. Bartel and P. L. Luisi, Nature, 2001, 409, 387), the chances of success seemed remote. However, recent progress in nucleic acid chemistry, directed evolution and membrane biophysics have brought the prospect of a simple synthetic cell with life-like properties such as growth, division, heredity and evolution within reach. Success in this area will not only revolutionize our understanding of abiogenesis but provide a fertile test-bed for models of prebiotic chemistry and early evolution. Last but not least, a robust "living" protocell may provide a versatile and safe chassis for embedding synthetic devices and systems.
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Affiliation(s)
- David Loakes
- Medical Research Council, Laboratory of Molecular Biology, Hills Road, Cambridge, CB2 0QH, UK
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34
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Shapiro R, Schulze-Makuch D. The search for alien life in our solar system: strategies and priorities. ASTROBIOLOGY 2009; 9:335-343. [PMID: 19355818 DOI: 10.1089/ast.2008.0281] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
With the assumption that future attempts to explore our Solar System for life will be limited by economic constraints, we have formulated a series of principles to guide future searches: (1) the discovery of life that has originated independently of our own would have greater significance than evidence for panspermia; (2) an unambiguous identification of living beings (or the fully preserved, intact remains of such beings) is more desirable than the discovery of markers or fossils that would inform us of the presence of life but not its composition; (3) we should initially seek carbon-based life that employs a set of monomers and polymers substantially different than our own, which would effectively balance the need for ease of detection with that of establishing a separate origin; (4) a "follow-the-carbon" strategy appears optimal for locating such alternative carbon-based life. In following this agenda, we judge that an intensive investigation of a small number of bodies in our Solar System is more likely to succeed than a broad-based survey of a great number of worlds. Our priority for investigation is (1) Titan, (2) Mars, (3) Europa. Titan displays a rich organic chemistry and offers several alternative possibilities for the discovery of extant life or the early stages that lead to life. Mars has already been subjected to considerable study through landers and orbiters. Although only small amounts of methane testify to the inventory of reduced carbon on the planet, a number of other indicators suggest that the presence of microbial life is a possibility. Care will be needed, of course, to distinguish indigenous life from that which may have spread by panspermia. Europa appears to contain a subsurface ocean with the possibility of hydrothermal vents as an energy source. Its inventory of organic carbon is not yet known.
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Affiliation(s)
- Robert Shapiro
- Department of Chemistry, New York University , New York, New York 10003, USA.
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Griffith CA. Storms, polar deposits and the methane cycle in Titan's atmosphere. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2009; 367:713-728. [PMID: 19073459 DOI: 10.1098/rsta.2008.0245] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
In Titan's atmosphere, the second most abundant constituent, methane, exists as a gas, liquid and solid, and cycles between the atmosphere and the surface. Similar to the Earth's hydrological cycle, Titan sports clouds, rain and lakes. Yet, Titan's cycle differs dramatically from its terrestrial counterpart, and reveals the workings of weather in an atmosphere that is 10 times thicker than the Earth's atmosphere, that is two orders of magnitude less illuminated, and that involves a different condensable. While ongoing measurements by the Cassini-Huygens mission are revealing the intricacies of the moon's weather, circulation, lake coverage and geology, knowledge is still limited by the paucity of observations. This review of Titan's methane cycle therefore focuses on measured characteristics of the lower atmosphere and surface that appear particularly perplexing or alien.
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Affiliation(s)
- Caitlin Ann Griffith
- Department of Planetary Sciences, University of Arizona, 1629 East University Boulevard, Tucson, AZ 85721, USA.
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