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Kleimeier NF, Liu Y, Turner AM, Young LA, Chin CH, Yang T, He X, Lo JI, Cheng BM, Kaiser RI. Excited state photochemically driven surface formation of benzene from acetylene ices on Pluto and in the outer solar system. Phys Chem Chem Phys 2022; 24:1424-1436. [PMID: 34982080 DOI: 10.1039/d1cp04959c] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
NASA's New Horizons mission unveiled a diverse landscape of Pluto's surface with massive regions being neutral in color, while others like Cthulhu Macula range from golden-yellow to reddish comprising up to half of Pluto's carbon budget. Here, we demonstrate in laboratory experiments merged with electronic structure calculations that the photolysis of solid acetylene - the most abundant precipitate on Pluto's surface - by low energy ultraviolet photons efficiently synthesizes benzene and polycyclic aromatic hydrocarbons via excited state photochemistry thus providing critical molecular building blocks for the colored surface material. Since low energy photons deliver doses to Pluto's surface exceeding those from cosmic rays by six orders of magnitude, these processes may significantly contribute to the coloration of Pluto's surface and of hydrocarbon-covered surfaces of Solar System bodies such as Triton in general. This discovery critically enhances our perception of the distribution of aromatic molecules and carbon throughout our Solar System.
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Affiliation(s)
- N Fabian Kleimeier
- W. M. Keck Research Laboratory in Astrochemistry, University of Hawaii at Manoa, Honolulu, HI 96822, USA. .,Department of Chemistry, University of Hawaii at Manoa, Honolulu, HI 96822, USA
| | - Yiwei Liu
- State Key Laboratory of Precision Spectroscopy, Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, P. R. China.
| | - Andrew M Turner
- W. M. Keck Research Laboratory in Astrochemistry, University of Hawaii at Manoa, Honolulu, HI 96822, USA. .,Department of Chemistry, University of Hawaii at Manoa, Honolulu, HI 96822, USA
| | - Leslie A Young
- Southwest Research Institute, Department of Space Studies, Boulder, CO 80302, USA
| | - Chih-Hao Chin
- State Key Laboratory of Precision Spectroscopy, Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, P. R. China.
| | - Tao Yang
- State Key Laboratory of Precision Spectroscopy, Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, P. R. China. .,Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, P. R. China
| | - Xiao He
- State Key Laboratory of Precision Spectroscopy, Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, P. R. China. .,New York University - East China Normal University Center for Computational Chemistry, New York University, Shanghai 200062, P. R. China.
| | - Jen-Iu Lo
- Department of Medical Research, Hualien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Hualien City 970, Taiwan
| | - Bing-Ming Cheng
- Department of Medical Research, Hualien Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Hualien City 970, Taiwan.,Tzu-Chi University of Science and Technology, Hualien City 970, Taiwan
| | - Ralf I Kaiser
- W. M. Keck Research Laboratory in Astrochemistry, University of Hawaii at Manoa, Honolulu, HI 96822, USA. .,Department of Chemistry, University of Hawaii at Manoa, Honolulu, HI 96822, USA
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2
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Fan S, Gao P, Zhang X, Adams DJ, Kutsop NW, Bierson CJ, Liu C, Yang J, Young LA, Cheng AF, Yung YL. A bimodal distribution of haze in Pluto's atmosphere. Nat Commun 2022; 13:240. [PMID: 35017491 PMCID: PMC8752795 DOI: 10.1038/s41467-021-27811-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 11/22/2021] [Indexed: 11/24/2022] Open
Abstract
Pluto, Titan, and Triton make up a unique class of solar system bodies, with icy surfaces and chemically reducing atmospheres rich in organic photochemistry and haze formation. Hazes play important roles in these atmospheres, with physical and chemical processes highly dependent on particle sizes, but the haze size distribution in reducing atmospheres is currently poorly understood. Here we report observational evidence that Pluto’s haze particles are bimodally distributed, which successfully reproduces the full phase scattering observations from New Horizons. Combined with previous simulations of Titan’s haze, this result suggests that haze particles in reducing atmospheres undergo rapid shape change near pressure levels ~0.5 Pa and favors a photochemical rather than a dynamical origin for the formation of Titan’s detached haze. It also demonstrates that both oxidizing and reducing atmospheres can produce multi-modal hazes, and encourages reanalysis of observations of hazes on Titan and Triton. Pluto’s haze is revealed to have two types of particles: small spherical organic haze particles and micron-size fluffy aggregates. The persistence of these two populations has important implications for haze formation and properties on icy worlds.
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Affiliation(s)
- Siteng Fan
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, 91125, USA. .,LMD/IPSL, Sorbonne Université, PSL Research University, École Normale Supérieure, École Polytechnique, CNRS, Paris, 75005, France.
| | - Peter Gao
- Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, 20015, USA
| | - Xi Zhang
- Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, CA, 95064, USA
| | - Danica J Adams
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, 91125, USA
| | | | - Carver J Bierson
- Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, CA, 95064, USA.,School of Earth and Space Exploration, Arizona State University, Tempe, AZ, 85281, USA
| | - Chao Liu
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, 91125, USA.,Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration, School of Atmospheric Physics, Nanjing University of Information Science & Technology, Nanjing, 210044, China
| | - Jiani Yang
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, 91125, USA
| | | | - Andrew F Cheng
- Johns Hopkins University Applied Physics Laboratory, Laurel, MD, 20723, USA
| | - Yuk L Yung
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, 91125, USA.,Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, 91109, USA
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Zhan Z, Seager S, Petkowski JJ, Sousa-Silva C, Ranjan S, Huang J, Bains W. Assessment of Isoprene as a Possible Biosignature Gas in Exoplanets with Anoxic Atmospheres. ASTROBIOLOGY 2021; 21:765-792. [PMID: 33798392 DOI: 10.1089/ast.2019.2146] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The search for possible biosignature gases in habitable exoplanet atmospheres is accelerating, although actual observations are likely years away. This work adds isoprene, C5H8, to the roster of biosignature gases. We found that isoprene geochemical formation is highly thermodynamically disfavored and has no known abiotic false positives. The isoprene production rate on Earth rivals that of methane (CH4; ∼500 Tg/year). Unlike methane, on Earth isoprene is rapidly destroyed by oxygen-containing radicals. Although isoprene is predominantly produced by deciduous trees, isoprene production is ubiquitous to a diverse array of evolutionary distant organisms, from bacteria to plants and animals-few, if any, volatile secondary metabolites have a larger evolutionary reach. Although non-photochemical sinks of isoprene may exist, such as degradation of isoprene by life or other high deposition rates, destruction of isoprene in an anoxic atmosphere is mainly driven by photochemistry. Motivated by the concept that isoprene might accumulate in anoxic environments, we model the photochemistry and spectroscopic detection of isoprene in habitable temperature, rocky exoplanet anoxic atmospheres with a variety of atmosphere compositions under different host star ultraviolet fluxes. Limited by an assumed 10 ppm instrument noise floor, habitable atmosphere characterization when using James Webb Space Telescope (JWST) is only achievable with a transit signal similar or larger than that for a super-Earth-sized exoplanet transiting an M dwarf star with an H2-dominated atmosphere. Unfortunately, isoprene cannot accumulate to detectable abundance without entering a run-away phase, which occurs at a very high production rate, ∼100 times the Earth's production rate. In this run-away scenario, isoprene will accumulate to >100 ppm, and its spectral features are detectable with ∼20 JWST transits. One caveat is that some isoprene spectral features are hard to distinguish from those of methane and also from other hydrocarbons containing the isoprene substructure. Despite these challenges, isoprene is worth adding to the menu of potential biosignature gases.
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Affiliation(s)
- Zhuchang Zhan
- Department of Earth, Atmospheric, and Planetary Sciences, MIT, Cambridge, Massachusetts, USA
| | - Sara Seager
- Department of Earth, Atmospheric, and Planetary Sciences, MIT, Cambridge, Massachusetts, USA
- Department of Physics, MIT, Cambridge, Massachusetts, USA
- Department of Aeronautics and Astronautics, and MIT, Cambridge, Massachusetts, USA
| | - Janusz Jurand Petkowski
- Department of Earth, Atmospheric, and Planetary Sciences, MIT, Cambridge, Massachusetts, USA
| | - Clara Sousa-Silva
- Department of Earth, Atmospheric, and Planetary Sciences, MIT, Cambridge, Massachusetts, USA
| | - Sukrit Ranjan
- Department of Earth, Atmospheric, and Planetary Sciences, MIT, Cambridge, Massachusetts, USA
| | | | - William Bains
- Department of Earth, Atmospheric, and Planetary Sciences, MIT, Cambridge, Massachusetts, USA
- Rufus Scientific, Royston, United Kingdom
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Brown OCF, Vrinceanu D, Kharchenko V, Sadeghpour HR. Formation of argon cluster with proton seeding. Mol Phys 2020. [DOI: 10.1080/00268976.2020.1767813] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- O. C. F. Brown
- ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA
- Department of Physics and Astronomy, University of Southampton, Southampton, UK
| | - D. Vrinceanu
- Department of Physics, Texas Southern University, Houston, TX, USA
| | - V. Kharchenko
- ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA
- Department of Physics, University of Connecticut, Storrs, CT, USA
| | - H. R. Sadeghpour
- ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA
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Affiliation(s)
- Robert A West
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA
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Witze A. Hazy skies cool down Pluto. Nature 2017. [DOI: 10.1038/nature.2017.22996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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