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McDonald GD, Méndez Harper J, Ojha L, Corlies P, Dufek J, Ewing RC, Kerber L. Aeolian sediment transport on Io from lava-frost interactions. Nat Commun 2022; 13:2076. [PMID: 35440556 PMCID: PMC9018742 DOI: 10.1038/s41467-022-29682-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Accepted: 03/22/2022] [Indexed: 11/30/2022] Open
Abstract
Surface modification on Jupiter’s volcanically active moon, Io, has to date been attributed almost exclusively to lava emplacement and volcanic plume deposits. Here we demonstrate that wind-blown transport of sediment may also be altering the Ionian surface. Specifically, shallow subsurface interactions between lava and Io’s widespread sulfur dioxide (SO2) frost can produce localized sublimation vapor flows with sufficient gas densities to enable particle saltation. We calculate anticipated outgassing velocities from lava–SO2 frost interactions, and compare these to the saltation thresholds predicted when accounting for the tenuous nature of the sublimated vapor. We find that saltation may occur if frost temperatures surpass 155 K. Finally we make the first measurements of the dimensions of linear features in images from the Galileo probe, previously termed “ridges”, which demonstrate certain similarities to dunes on other planetary bodies. Io joins a growing list of bodies with tenuous and transient atmospheres where aeolian sediment transport may be an important control on the landscape. Dunes may form on Jupiter’s moon Io. Despite a tenuous atmosphere, interactions between widespread lava and sulfur dioxide frost may produce vapor flows dense enough to mobilize sand grains. Ridge-like features may be evidence of this phenomenon.
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Affiliation(s)
- George D McDonald
- Department of Earth and Planetary Sciences, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.
| | | | - Lujendra Ojha
- Department of Earth and Planetary Sciences, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
| | - Paul Corlies
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Josef Dufek
- Department of Earth Sciences, University of Oregon, Eugene, OR, USA
| | - Ryan C Ewing
- Department of Geology and Geophysics, Texas A&M University, College Station, TX, USA
| | - Laura Kerber
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
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2
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Emtiaz SM, Toriello F, He J, Vidali G. Infrared Spectroscopic Study of Methane Ice, Pure and in Mixtures with Polar (H 2O) and Nonpolar (N 2) Molecules. J Phys Chem A 2022; 126:1973-1979. [PMID: 35302374 PMCID: PMC8978181 DOI: 10.1021/acs.jpca.2c00287] [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] [Indexed: 11/30/2022]
Abstract
Mid-infrared studies of fundamental modes of ices of pure CH4 and its mixtures with polar (H2O) and nonpolar (e.g., N2) molecules are essential in order to learn the state of aggregation and thermal history of ices present in the interstellar medium and outer solar system bodies. Such data will be useful in the interpretation of observational data from the James Webb Space Telescope. Using an ultrahigh vacuum apparatus, we conducted reflection-absorption infrared spectroscopy measurements in the mid-IR range of pure methane ice and methane-containing ice mixtures of interest to interstellar and solar system ice chemistry, e.g., with H2O and N2 molecules. We found that nuclear spin conversion (NSC) in solid methane and its crystalline structures is affected─in different ways─by the presence of H2O and N2. Specifically, we found a relationship between the thickness and the solid-state ordering transformation in methane thin films. This new study of the NSC of pure CH4 ice and of the CH4:H2O ice mixture at 7 K is carried out in relation to the segregation of H2O using the ν1 and ν2 IR inactive modes of methane. The diffusion of N2 and CH4 in the CH4:N2 ice mixture with temperature cycling has been studied to obtain the relationship between IR features and the state of aggregation of the ice.
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Affiliation(s)
- Shahnewaz M Emtiaz
- Physics Department, Syracuse University, Syracuse, New York 13244, United States
| | - Francis Toriello
- Physics Department, Syracuse University, Syracuse, New York 13244, United States
| | - Jiao He
- Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany
| | - Gianfranco Vidali
- Physics Department, Syracuse University, Syracuse, New York 13244, United States
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3
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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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4
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Preud'homme N, Lumay G, Vandewalle N, Opsomer E. Numerical measurement of flow fluctuations to quantify cohesion in granular materials. Phys Rev E 2022; 104:064901. [PMID: 35030871 DOI: 10.1103/physreve.104.064901] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 11/18/2021] [Indexed: 11/07/2022]
Abstract
The flow of cohesive granular materials in a two-dimensional rotating drum is investigated using discrete element method simulations. Contacts between particles are modeled based on the widely used model of the spring-dashpot and Coulomb's friction law. A simplified model of intermediate range attraction between grains (i.e., cohesion) has been used in order to reproduce the flow of electrostatic or wet granular materials. Granular flow is generated by means of a rotating drum and the effect of the rotation speed, the friction between the grains, and the cohesion are studied. Significantly different flow behaviors are observed when cohesion is added. Plug flow appears in the rotating drum for a wide range of rotation speeds when cohesion becomes sufficiently strong. We propose a measurement of surface flow fluctuations to quantify the strength of cohesion, inspired by the previous observation of plug flow. Then, we make use of the results to include the effect of cohesion into a theoretical flow model. A good agreement is obtained between theory and numerical measurements of the granular bed's dynamic angle of repose, which allows us to propose a method for estimating the microscopic cohesion between grains based on the measurement of surface fluctuations.
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Affiliation(s)
| | | | | | - Eric Opsomer
- GRASP, University of Liège, B-4000 Liège, Belgium
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5
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Qin Y, Zhang S, Zhang S, Tucker MG, Keen DA, Cai G, Phillips AE, Dove MT. Orientational order and phase transitions in deuterated methane: a neutron total scattering and reverse Monte Carlo study. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 34:015401. [PMID: 34619662 DOI: 10.1088/1361-648x/ac2db8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2021] [Accepted: 10/07/2021] [Indexed: 06/13/2023]
Abstract
We report a study of the orientational order and phase transitions in crystalline deuterated methane, carried out using neutron total scattering and the reverse Monte Carlo method. The resultant atomic configurations are consistent with the average structures obtained from Rietveld refinement of the powder diffraction data, but additionally enable us to determine the C-D bond orientational distribution functions (ODF) for the disordered molecules in the high-temperature phase, and for both ordered and disordered molecules in the intermediate-temperature phase. We show that this approach gives more accurate information than can been obtained from fitting a bond ODF to diffraction data. Given the resurgence of interest in orientationally-disordered crystals, we argue that the approach of total scattering with the RMC method provides a unique quantification of orientational order and disorder.
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Affiliation(s)
- Yinze Qin
- College of Physics, Sichuan University, Chengdu, Sichuan 610065, People's Republic of China
| | - Shidong Zhang
- College of Physics, Sichuan University, Chengdu, Sichuan 610065, People's Republic of China
| | - Sijie Zhang
- College of Physics, Sichuan University, Chengdu, Sichuan 610065, People's Republic of China
| | - Matthew G Tucker
- Oak Ridge National Laboratory, Neutron Scattering Division, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831, United States of America
| | - David A Keen
- ISIS Facility, Harwell Campus, Chilton, Didcot, OX11 0QX, United Kingdom
| | - Guanqun Cai
- School of Physical and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
| | - Anthony E Phillips
- School of Physical and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
| | - Martin T Dove
- College of Computer Science, Sichuan University, Chengdu, Sichuan 610065, People's Republic of China
- Department of Physics, School of Sciences, Wuhan University of Technology, 205 Luoshi Road, Hongshan district, Wuhan, Hubei, 430070, People's Republic of China
- School of Mechanical Engineering Dongguan University of Technology, 1st Daxue Road, Songhan Lake, Dongguan, Guangdong 523000, People's Republic of China
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6
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An expression for the angle of repose of dry cohesive granular materials on Earth and in planetary environments. Proc Natl Acad Sci U S A 2021; 118:2107965118. [PMID: 34518227 PMCID: PMC8463844 DOI: 10.1073/pnas.2107965118] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/06/2021] [Indexed: 11/23/2022] Open
Abstract
The angle between the sloping side of a heap of particles and the horizontal, called angle of repose, is often used to characterize the flowability of granular materials on Earth and planetary environments, such as sand, dust aerosols, and powders. In planetary research, this angle provides an excellent proxy for particle size. The smaller the particle is, the larger the effect of attractive forces between atoms and molecules on the surface of the particles relative to particle weight, the less flowable the material, and the steeper, thus, the angle of repose. We present a model that accurately predicts the angle of repose as a function of particle size, both on Earth and under extraterrestrial gravity. The angle of repose—i.e., the angle θr between the sloping side of a heap of particles and the horizontal—provides one of the most important observables characterizing the packing and flowability of a granular material. However, this angle is determined by still poorly understood particle-scale processes, as the interactions between particles in the heap cause resistance to roll and slide under the action of gravity. A theoretical expression that predicts θr as a function of particle size and gravity would have impact in the engineering, environmental, and planetary sciences. Here we present such an expression, which we have derived from particle-based numerical simulations that account for both sliding and rolling resistance, as well as for nonbonded attractive particle–particle interactions (van der Waals). Our expression is simple and reproduces the angle of repose of experimental conical heaps as a function of particle size, as well as θr obtained from our simulations with gravity from 0.06 to 100 times that of Earth. Furthermore, we find that heaps undergo a transition from conical to irregular shape when the cohesive to gravitational force ratio exceeds a critical value, thus providing a proxy for particle-scale interactions from heap morphology.
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7
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Abstract
Modern dune fields are valuable sources of information for the large-scale analysis of terrestrial and planetary environments and atmospheres, but their study relies on understanding the small-scale dynamics that constantly generate new dunes and reshape older ones. Here, we designed a landscape-scale experiment at the edge of the Gobi desert, China, to quantify the development of incipient dunes under the natural action of winds. High-resolution topographic data documenting 42 mo of bedform dynamics are examined to provide a spectral analysis of dune pattern formation. We identified two successive phases in the process of dune growth, from the initial flat sand bed to a meter-high periodic pattern. We focus on the initial phase, when the linear regime of dune instability applies, and measure the growth rate of dunes of different wavelengths. We identify the existence of a maximum growth rate, which readily explains the mechanism by which dunes select their size, leading to the prevalence of a 15-m wavelength pattern. We quantitatively compare our experimental results with the prediction of the dune instability theory using transport and flow parameters independently measured in the field. The remarkable agreement between theory and observations demonstrates that the linear regime of dune growth is permanently expressed on low-amplitude bed topography, before larger regular patterns and slip faces eventually emerge. Our experiment underpins existing theoretical models for the early development of eolian dunes, which can now be used to provide reliable insights into atmospheric and surface processes on Earth and other planetary bodies.
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8
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Yin X, Huang N, Jiang C, Parteli EJ, Zhang J. Splash function for the collision of sand-sized particles onto an inclined granular bed, based on discrete-element-simulations. POWDER TECHNOL 2021. [DOI: 10.1016/j.powtec.2020.10.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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9
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Emtiaz SM, Toriello F, He J, Vidali G. Infrared Spectroscopic Study of Solid Methane: Nuclear Spin Conversion of Stable and Metastable Phases. J Phys Chem A 2020; 124:552-559. [PMID: 31891499 DOI: 10.1021/acs.jpca.9b10643] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Infrared spectroscopy was employed to study thin films of solid methane at low temperatures. We report new measurements of temporal changes of infrared spectra of methane ice in the ν3 and ν4 bands due to nuclear spin conversion upon rapid cooling from 30 to 6.0-11.0 K. The relaxation rates of the nuclear spin were found to be a function of temperature. The activation energy associated with the relaxation has been determined over an extended temperature range. We also found a new metastable phase of methane ice upon deposition at T < 7 K. After the deposition at 6 K and annealed to a higher temperature, a phase transition from the metastable phase to a stable crystalline phase takes place. We found that the relaxation has different activation energies below and above 8.5 K. From a quantitative analysis of the ν3 and ν4 IR bands, we suggest that the metastable phase is a crystalline phase with a degree of orientational disorder between the two known stable solid phases.
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Affiliation(s)
- Shahnewaz M Emtiaz
- Physics Department , Syracuse University , Syracuse , New York 13244 , United States
| | - Francis Toriello
- Physics Department , Syracuse University , Syracuse , New York 13244 , United States
| | - Jiao He
- Laboratory for Astrophysics, Leiden Observatory , Leiden University , 2300 RA Leiden , Netherlands
| | - Gianfranco Vidali
- Physics Department , Syracuse University , Syracuse , New York 13244 , United States
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10
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Nakao-Kusune S, Sakaue T, Nishimori H, Nakanishi H. Stabilization of a straight longitudinal dune under bimodal wind with large directional variation. Phys Rev E 2020; 101:012903. [PMID: 32069671 DOI: 10.1103/physreve.101.012903] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2019] [Indexed: 11/07/2022]
Abstract
It has been observed that the direction in which a sand dune extends its crest line depends on seasonal variation of wind direction; when the variation is small, the crest line develops more or less perpendicularly to the mean wind direction to form a transverse dune with some undulation. In the case of bimodal wind with a large relative angle, however, the dune extends its crest along the mean wind direction and evolves into an almost straight longitudinal dune. Motivated by these observations, we investigate the dynamical stability of isolated dunes using the crest line model, where the dune dynamics is represented by its crest line motion. First, we extend the previous linear stability analysis under the unidirectional wind to the case with nonzero slant angle between the wind direction and the normal direction of the crest line, and show that the stability diagram does not depend on the slant angle. Second, we examine how the linear stability is affected by the seasonal changes of wind direction in the case of bimodal wind with equal strength and duration. For the transverse dune, we find that the stability is virtually the same with that for the unidirectional wind as long as the dune evolution during a season is small. On the other hand, in the case of the longitudinal dune, the dispersions of the growth rates for the perturbation are drastically different from those of the unidirectional wind, and we find that the largest growth rate is always located at k=0. This is because the growth of the perturbation with k≠0 is canceled by the alternating wind from opposite sides of the crest line even though it grows during each duration period of the bimodal wind. For a realistic parameter set, the system is in the wavy unstable regime of the stability diagram for the unidirectional wind, thus the straight transverse dune is unstable to develop undulation and eventually evolves into a string of barchans when the seasonal variation of wind direction is small, but the straight longitudinal dune is stabilized under the large variation of bimodal wind direction. We also perform numerical simulations on the crest line model, and find that the results are consistent with our linear analysis and the previous reports that show that the longitudinal dunes tend to have a straight ridge elongating over time.
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Affiliation(s)
| | - Takahiro Sakaue
- Department of Physics and Mathematics, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258, Japan
| | - Hiraku Nishimori
- Department of Mathematical and Life Sciences, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
| | - Hiizu Nakanishi
- Department of Physics, Kyushu University, Fukuoka 819-0395, Japan
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11
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Ning WX, Liu XY, Wang ZT. An analytical model for the growth and migration of a transverse dune. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2019; 42:42. [PMID: 30945008 DOI: 10.1140/epje/i2019-11804-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Accepted: 03/05/2019] [Indexed: 06/09/2023]
Abstract
The growth and migration speed formulae for a 2-d transverse dune are derived under the assumptions of shape similarity, the near surface airflow independent of height, and the 100% sand trapping efficiency of lee face during dune evolution. Although very simple, this analytical model can quantificationally reflect the field investigations of barchan migrations and the chronological data of mega-dune growth.
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Affiliation(s)
- Wen-Xiao Ning
- Northwest Institute of Eco-Environment and Resources, CAS, 730000, Lanzhou, P.R. China
| | - Xu-Yang Liu
- Northwest Institute of Eco-Environment and Resources, CAS, 730000, Lanzhou, P.R. China
| | - Zhen-Ting Wang
- Northwest Institute of Eco-Environment and Resources, CAS, 730000, Lanzhou, P.R. China.
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12
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Marston JO, Pacheco-Vázquez F. Millimetric granular craters from pulsed laser ablation. Phys Rev E 2019; 99:030901. [PMID: 30999424 DOI: 10.1103/physreve.99.030901] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Indexed: 11/07/2022]
Abstract
This Rapid Communication reports on an experimental study of granular craters formed by a mechanism, namely, optical energy, via a pulsed laser focused onto the surface of a granular bed. This represents an insight into granular cratering for two reasons; first, there is no physical contact between the initiation mechanism and the granular media (as typical for impact or explosion craters). Second, the resulting craters are millimetric in scale, which facilitates a test of energy scalings down to a previously unobserved lengthscale. Indeed, we observe a range of energy scalings conforming to D_{c}∼E^{β} with β≈0.31-0.43 depending on the characteristics of the granular media.
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Affiliation(s)
- J O Marston
- Department of Chemical Engineering, Texas Tech University, Lubbock, Texas 79409, USA
| | - F Pacheco-Vázquez
- Insituto de Fisica, Benemerita Universidad Autonoma de Puebla, Puebla 72570, Mexico
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13
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Abplanalp MJ, Góbi S, Kaiser RI. On the formation and the isomer specific detection of methylacetylene (CH 3CCH), propene (CH 3CHCH 2), cyclopropane (c-C 3H 6), vinylacetylene (CH 2CHCCH), and 1,3-butadiene (CH 2CHCHCH 2) from interstellar methane ice analogues. Phys Chem Chem Phys 2019; 21:5378-5393. [PMID: 30221272 DOI: 10.1039/c8cp03921f] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Pure methane (CH4) ices processed by energetic electrons under ultra-high vacuum conditions to simulate secondary electrons formed via galactic cosmic rays (GCRs) penetrating interstellar ice mantles have been shown to produce an array of complex hydrocarbons with the general formulae: CnH2n+2 (n = 4-8), CnH2n (n = 3-9), CnH2n-2 (n = 3-9), CnH2n-4 (n = 4-9), and CnH2n-6 (n = 6-7). By monitoring the in situ chemical evolution of the ice combined with temperature programmed desorption (TPD) studies and tunable single photon ionization coupled to a reflectron time-of-flight mass spectrometer, specific isomers of C3H4, C3H6, C4H4, and C4H6 were probed. These experiments confirmed the synthesis of methylacetylene (CH3CCH), propene (CH3CHCH2), cyclopropane (c-C3H6), vinylacetylene (CH2CHCCH), 1-butyne (HCCC2H5), 2-butyne (CH3CCCH3), 1,2-butadiene (H2CCCH(CH3)), and 1,3-butadiene (CH2CHCHCH2) with yields of 2.17 ± 0.95 × 10-4, 3.7 ± 1.5 × 10-3, 1.23 ± 0.77 × 10-4, 1.28 ± 0.65 × 10-4, 4.01 ± 1.98 × 10-5, 1.97 ± 0.98 × 10-4, 1.90 ± 0.84 × 10-5, and 1.41 ± 0.72 × 10-4 molecules eV-1, respectively. Mechanistic studies exploring the formation routes of methylacetylene, propene, and vinylacetylene were also conducted, and revealed the additional formation of the 1,2,3-butatriene isomer. Several of the above isomers, methylacetylene, propene, vinylacetylene, and 1,3-butadiene, have repeatedly been shown to be important precursors in the formation of polycyclic aromatic hydrocarbons (PAHs), but until now their interstellar synthesis has remained elusive.
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Affiliation(s)
- Matthew J Abplanalp
- W. M. Keck Research Laboratory in Astrochemistry, University of Hawaii at Manoa, Honolulu, HI 96822, USA.
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14
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Abstract
Despite a very thin atmosphere, dunes may form on Pluto
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Affiliation(s)
- Alexander G Hayes
- Spacecraft Planetary Imaging Facility, Cornell University, 412 Space Science Building, Ithaca, NY 14853-6801, USA.
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