DOCSLIB.ORG

Radiolytic H2 Production in Martian Environments Mary Dzaugis University of Rhode Island, [email protected]

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Radiolytic H2 Production in Martian Environments Mary Dzaugis University of Rhode Island, Mdzaugis@Uri.Edu University of Rhode Island DigitalCommons@URI Graduate School of Oceanography Faculty Graduate School of Oceanography Publications 2018 Radiolytic H2 Production in Martian Environments Mary Dzaugis university of rhode island, [email protected] Arthur J. Spivack University of Rhode Island, [email protected] See next page for additional authors Creative Commons License This work is licensed under a Creative Commons Attribution 4.0 License. Follow this and additional works at: https://digitalcommons.uri.edu/gsofacpubs Citation/Publisher Attribution Dzaugis, M., Spivack, A.J., D'Hondt, S. Radiolytic H2 production in martian environments (2018) Astrobiology, 18(9), pp. 1137-1146. DOI: 10.1089/ast.2017.1654 This Article is brought to you for free and open access by the Graduate School of Oceanography at DigitalCommons@URI. It has been accepted for inclusion in Graduate School of Oceanography Faculty Publications by an authorized administrator of DigitalCommons@URI. For more information, please contact [email protected]. Authors Mary Dzaugis, Arthur J. Spivack, and Steven D’Hondt This article is available at DigitalCommons@URI: https://digitalcommons.uri.edu/gsofacpubs/429 ASTROBIOLOGY Volume 18, Number 9, 2018 Mary Ann Liebert, Inc. DOI: 10.1089/ast.2017.1654 Radiolytic H2 Production in Martian Environments Mary Dzaugis, Arthur J. Spivack, and Steven D’Hondt Abstract Hydrogen, produced by water radiolysis, has been suggested to support microbial communities on Mars. We quantitatively assess the potential magnitude of radiolytic H2 production in wet martian environments (the ancient surface and the present subsurface) based on the radionuclide compositions of (1) eight proposed Mars 2020 landing sites, and (2) three sites that individually yield the highest or lowest calculated radiolytic H2 production rates on Mars. For the proposed landing sites, calculated H2 production rates vary by a factor of *1.6, while the three comparison sites differ by a factor of *6. Rates in wet martian sediment and micro- fractured rock are comparable with rates in terrestrial environments that harbor low concentrations of microbial life (e.g., subseafloor basalt). Calculated H2 production rates for low-porosity (<35%), fine-grained martian sediment (0.12–1.2 nM/year) are mostly higher than rates for South Pacific subseafloor basalt (*0.02–0.6 nM/ year). Production rates in martian high-porosity sediment (>35%) and microfractured (1 mm) hard rock (0.03 to <0.71 nM/year) are generally similar to rates in South Pacific basalt, while yields for larger martian fractures (1 and 10 cm) are one to two orders of magnitude lower (<0.01 nM/year). If minerals or brine that amplify radiolytic H2 production rates are present, H2 yields exceed the calculated rates. Key Words: Mars—Water radiolysis—Habitability—Hydrogen—Geochemistry—Mars 2020. Astrobiology 18, 1137–1146. 1. Introduction Previous studies suggested that radiolysis might support life on Mars (i.e.,Linet al., 2005b; Sherwood Lollar et al., he search for extraterrestrial life has prompted >20 2007; Lefticariu et al., 2010; Tu¨rke et al., 2015). However, Tsurface and orbital missions to Mars (Walter, 2015). few studies quantified radiolysis rates. To better under- Many of these missions have focused on identifying past and stand the origin of the subsurface methane flux on Mars, present aqueous environments, as water is necessary for life Onstott et al. (2006) investigated the diffusion of He, H2, as we know it. However, it is not the only requirement for life. and CH4 through the martian crust. They calculated ra- Habitable environments must also provide biologically har- diolytic production rates for the deep subsurface crust vestable energy. A variety of geochemical processes produce based on the chemical composition of martian meteorites chemical species that can be metabolized by microorganisms and a 6.6 km-thick crustal profile of estimated porosity. In for energy. Several studies have proposed that some sub- contrast to their global approach, we calculate specific surface microbial communities on Earth rely on molecular rates for a broad range of lithologies, including both water- hydrogen (H2) as their primary electron donor (i.e., Stevens saturated rock and sediment, based on compositional data and McKinley, 1995; Pedersen, 2000). In terrestrial subsur- at 11 specific sites on Mars. face environments, H2 is abiologically produced by water These 11 sites include the three currently proposed Mars radiolysis (i.e., Pedersen, 2000; Lin et al., 2005a; Blair et al., 2020 Rover landing sites (Witze, 2017), five other sites that 2007; Tu¨rke et al., 2015; Dzaugis et al., 2016), rock weath- were previously under consideration for the Mars 2020 ering (i.e., Stevens and McKinley, 1995; Pedersen, 2000), mission (Ono et al., 2016), and three sites with minimum or and serpentinization (i.e., Kelley et al., 2001, 2005). These maximum mean martian rates of radiolytic H2 production chemolithotrophic communities serve as models for life on (based on radionuclide concentrations). Our purpose of se- other planets, such as Mars (McCollom and Seewald, 2013). lecting these sites is to quantify (1) the magnitude of ra- Here we quantify the potential for radiolytic production of H2 diolytic H2 production in the wet martian past at potential in water-saturated environments, such as the ancient martian Mars 2020 landing sites, and (2) the range of H2 production surface or the present subsurface. rates in present-day martian subsurface groundwater. Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island. Ó Mary Dzaugis et al., 2018; Published by Mary Ann Liebert, Inc. This Open Access article is distributed under the terms of the Creative Commons License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. 1137 1138 DZAUGIS ET AL. Identification of past and present habitable environments eration, as all eight sites may have once harbored liquid water, is one of the main objectives of Mars Exploration missions and potentially H2-oxidizing life (Ono et al., 2016). (Mustard et al., 2013). Because oxidative H2 respiration is a Finally, we chose three additional locations, based on source of chemical energy for microbial life, estimates of their radioisotope compositions, to evaluate minimum and past H2 production rates based on the radioisotope compo- maximum radiolytic H2 production rates on the past martian sitions of proposed Mars 2020 sites are important for un- surface and in the present subsurface: Acidalia Planitia derstanding the ancient habitability of the sites. (maximum rate), the northern pole (minimum rate for an Eight sites were originally considered as the possible ice-covered region), and Promethei Terra (minimum rate for landing sites for the Mars 2020 mission (Mustard et al., a region without ice cover). The locations of the 11 sites are 2013). Many of these locations have similar geological and shown in Figure 1. topographic features, in part because the final site must be Martian surface material ranges from loose, fine-grained safe for rovers to land and travel (Mustard et al., 2013). The regolith to large pieces of fractured rock. To account for this eight candidate sites were narrowed to three based on the heterogeneity, we calculate H2 production rates using two following criteria: an ancient environment likely to have been different radiolysis models. One model is for fractured hard- habitable, accessible rocks with potential for biosignature rock aquifers (Dzaugis et al., 2015, 2016), the other is for preservation, and geological materials that may answer water-saturated fine-grained sediment (Blair et al., 2007). questions about planetary evolution (Witze, 2017). The three sites currently under consideration for the 2. Methods Mars 2020 landing site are as follows: Jezero Crater, an In this section, we describe the radiolysis models and ancient lake that has both deltaic and lacustrine deposits discuss the variables used in our calculations: fractured rock with well-defined stratigraphy (Schon et al., 2012; Witze, composition, sediment porosity, radioactivity, density, and 2017); NE Syrtis Major which was once volcanically ac- H yield per 100 eV absorbed (G-value). Lithologies of the tive, with widespread evidence of past liquid-water activity 2 11 localities are described in Table 1, and calculated H and a variety of interesting environments, including a 2 production rates are given in Table 2. banded olivine-carbonate unit and a crater-retaining cap of mafic rock (Hiesinger and Head, 2004; Ono et al., 2016); 2.1. Fractured hard-rock model and Columbia Hills, where Mars Exploration rover Spirit provided evidence of ancient hydrothermal activity and/or We previously used this model to calculate production rates hot springs (Squyres et al., 2008). in terrestrial oceanic basaltic aquifers (Dzaugis et al., 2016). In In addition to these three locations, we evaluate radiolytic H2 this study, we use parameter values appropriate for Mars. production for five other sites originally under consideration Within hard-rock aquifers, ionizing radiation produced for Mars 2020: Eberswalde Crater, Holden Crater, Nili Fossae, during the decay of radioactive elements in the rock decom- Mawrth Vallis, and SW Melas Chasma. We include these sites poses water molecules and leads to production of hydrogen as points of comparison for the three sites still under consid- molecules
Load more

Recommended publications
  • Imaginative Geographies of Mars: the Science and Significance of the Red Planet, 1877 - 1910
    Copyright by Kristina Maria Doyle Lane 2006 The Dissertation Committee for Kristina Maria Doyle Lane Certifies that this is the approved version of the following dissertation: IMAGINATIVE GEOGRAPHIES OF MARS: THE SCIENCE AND SIGNIFICANCE OF THE RED PLANET, 1877 - 1910 Committee: Ian R. Manners, Supervisor Kelley A. Crews-Meyer Diana K. Davis Roger Hart Steven D. Hoelscher Imaginative Geographies of Mars: The Science and Significance of the Red Planet, 1877 - 1910 by Kristina Maria Doyle Lane, B.A.; M.S.C.R.P. Dissertation Presented to the Faculty of the Graduate School of The University of Texas at Austin in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy The University of Texas at Austin August 2006 Dedication This dissertation is dedicated to Magdalena Maria Kost, who probably never would have understood why it had to be written and certainly would not have wanted to read it, but who would have been very proud nonetheless. Acknowledgments This dissertation would have been impossible without the assistance of many extremely capable and accommodating professionals. For patiently guiding me in the early research phases and then responding to countless followup email messages, I would like to thank Antoinette Beiser and Marty Hecht of the Lowell Observatory Library and Archives at Flagstaff. For introducing me to the many treasures held deep underground in our nation’s capital, I would like to thank Pam VanEe and Ed Redmond of the Geography and Map Division of the Library of Congress in Washington, D.C. For welcoming me during two brief but productive visits to the most beautiful library I have seen, I thank Brenda Corbin and Gregory Shelton of the U.S.
    [Show full text]
  • Mawrth Vallis, Mars: a Fascinating Place for Future in Situ Exploration
    Mawrth Vallis, Mars: a fascinating place for future in situ exploration François Poulet1, Christoph Gross2, Briony Horgan3, Damien Loizeau1, Janice L. Bishop4, John Carter1, Csilla Orgel2 1Institut d’Astrophysique Spatiale, CNRS/Université Paris-Sud, 91405 Orsay Cedex, France 2Institute of Geological Sciences, Planetary Sciences and Remote Sensing Group, Freie Universität Berlin, Germany 3Purdue University, West Lafayette, USA. 4SETI Institute/NASA-ARC, Mountain View, CA, USA Corresponding author: François Poulet, IAS, Bâtiment 121, CNRS/Université Paris-Sud, 91405 Orsay Cedex, France; email: [email protected] Running title: Mawrth: a fascinating place for exploration 1 Abstract After the successful landing of the Mars Science Laboratory rover, both NASA and ESA initiated a selection process for potential landing sites for the Mars2020 and ExoMars missions, respectively. Two ellipses located in the Mawrth Vallis region were proposed and evaluated during a series of meetings (3 for Mars2020 mission and 5 for ExoMars). We describe here the regional context of the two proposed ellipses as well as the framework of the objectives of these two missions. Key science targets of the ellipses and their astrobiological interests are reported. This work confirms the proposed ellipses contain multiple past Martian wet environments of subaerial, subsurface and/or subaqueous character, in which to probe the past climate of Mars, build a broad picture of possible past habitable environments, evaluate their exobiological potentials and search for biosignatures in well-preserved rocks. A mission scenario covering several key investigations during the nominal mission of each rover is also presented, as well as descriptions of how the site fulfills the science requirements and expectations of in situ martian exploration.
    [Show full text]
  • 1 Orbital Evidence for Clay and Acidic Sulfate Assemblages on Mars Based on 2 Mineralogical Analogs from Rio Tinto, Spain 3 4 Hannah H
    1 Orbital Evidence for Clay and Acidic Sulfate Assemblages on Mars Based on 2 Mineralogical Analogs from Rio Tinto, Spain 3 4 Hannah H. Kaplan1*, Ralph E. Milliken1, David Fernández-Remolar2, Ricardo Amils3, 5 Kevin Robertson1, and Andrew H. Knoll4 6 7 Authors: 8 9 1 Department of Earth, Environmental and Planetary Sciences, Brown University, 10 Providence, RI, 02912 USA. 11 12 2British Geological Survey, Nicker Hill, Keyworth, NG12 5GG, UK. 13 14 3 Centro de Astrobiologia (INTA-CSIC), Ctra Ajalvir km 4, Torrejon de Ardoz, 28850, 15 Spain. 16 17 4 Department of Organismic and Evolutionary Biology, Harvard University, 18 Çambridge, MA, USA. 19 20 *Corresponding author: [email protected] 1 21 Abstract 22 23 Outcrops of hydrated minerals are widespread across the surface of Mars, 24 with clay minerals and sulfates being commonly identified phases. Orbitally-based 25 reflectance spectra are often used to classify these hydrated components in terms of 26 a single mineralogy, although most surfaces likely contain multiple minerals that 27 have the potential to record local geochemical conditions and processes. 28 Reflectance spectra for previously identified deposits in Ius and Melas Chasma 29 within the Valles Marineris, Mars, exhibit an enigmatic feature with two distinct 30 absorptions between 2.2 – 2.3 µm. This spectral ‘doublet’ feature is proposed to 31 result from a mixture of hydrated minerals, although the identity of the minerals has 32 remained ambiguous. Here we demonstrate that similar spectral doublet features 33 are observed in airborne, field, and laboratory reflectance spectra of rock and 34 sediment samples from Rio Tinto, Spain.
    [Show full text]
  • Martian Crater Morphology
    ANALYSIS OF THE DEPTH-DIAMETER RELATIONSHIP OF MARTIAN CRATERS A Capstone Experience Thesis Presented by Jared Howenstine Completion Date: May 2006 Approved By: Professor M. Darby Dyar, Astronomy Professor Christopher Condit, Geology Professor Judith Young, Astronomy Abstract Title: Analysis of the Depth-Diameter Relationship of Martian Craters Author: Jared Howenstine, Astronomy Approved By: Judith Young, Astronomy Approved By: M. Darby Dyar, Astronomy Approved By: Christopher Condit, Geology CE Type: Departmental Honors Project Using a gridded version of maritan topography with the computer program Gridview, this project studied the depth-diameter relationship of martian impact craters. The work encompasses 361 profiles of impacts with diameters larger than 15 kilometers and is a continuation of work that was started at the Lunar and Planetary Institute in Houston, Texas under the guidance of Dr. Walter S. Keifer. Using the most ‘pristine,’ or deepest craters in the data a depth-diameter relationship was determined: d = 0.610D 0.327 , where d is the depth of the crater and D is the diameter of the crater, both in kilometers. This relationship can then be used to estimate the theoretical depth of any impact radius, and therefore can be used to estimate the pristine shape of the crater. With a depth-diameter ratio for a particular crater, the measured depth can then be compared to this theoretical value and an estimate of the amount of material within the crater, or fill, can then be calculated. The data includes 140 named impact craters, 3 basins, and 218 other impacts. The named data encompasses all named impact structures of greater than 100 kilometers in diameter.
    [Show full text]
  • Columbus Crater HLS2 Hangout: Exploration Zone Briefing
    Columbus Crater HLS2 Hangout: Exploration Zone Briefing Kennda Lynch1,2, Angela Dapremont2, Lauren Kimbrough2, Alex Sessa2, and James Wray2 1Lunar and Planetary Institute/Universities Space Research Association 2Georgia Institute of Technology Columbus Crater: An Overview • Groundwater-fed paleolake located in northwest region of Terra Sirenum • ~110 km in diameter • Diversity of Noachian & Hesperian aged deposits and outcrops • High diversity of aqueous mineral deposits • Estimated 1.5 km depth of sedimentary and/or volcanic infill • High Habitability and Biosignature Preservation Potential LZ & Field Station Latitude: 194.0194 E Longitude: 29.2058 S Altitude: +910 m SROI #1 RROI #1 LZ/HZ SROI #4 SROI #2 SROI #5 22 KM HiRISE Digital Terrain Model (DTM) • HiRISE DTMs are made from two images of the same area on the ground, taken from different look angles (known as a stereo-pair) • DTM’s are powerful research tools that allow researchers to take terrain measurements and model geological processes • For our traversability analysis of Columbus: • The HiRISE DTM was processed and completed by the University of Arizona HiRISE Operations Center. • DTM data were imported into ArcMap 10.5 software and traverses were acquired and analyzed using the 3D analyst tool. • A slope map was created in ArcMap to assess slope values along traverses as a supplement to topography observations. Slope should be ≤30°to meet human mission requirements. Conclusions Traversability • 9 out of the 17 traverses analyzed met the slope criteria for human missions. • This region of Columbus Crater is traversable and allows access to regions of astrobiological interest. It is also a possible access point to other regions of Terra Sirenum.
    [Show full text]
  • NASA Mars Exploration Strategy: “Follow the Water”
    Gullies on Mars -- Water or Not? Allan H. Treiman NASA Mars Exploration Strategy: “Follow the Water” Life W Climate A T Geology E Resources R Evidence of Water on Mars Distant Past Crater Degradation and Valley Networks ‘River’ Channels Flat Northern Lowlands Meteorites Carbonate in ALH84001 Clay in nakhlites MER Rover Sites Discoveries Hydrous minerals: jarosite! Fe2O3 from water (blueberries etc.) Silica & sulfate & phosphate deposits Recent Past (Any liquid?) Clouds & Polar Ice Ground Ice Valley Networks and Degraded Craters 1250 km River Channels - Giant Floods! 225 km 10 km craters River Channels - ‘Normal’ Flows 14 km 1 km River Channels from Rain? 700 km Science, July 2, 2004 19 km Ancient Martian Meteorite ALH84001 MER Opportunity - Heatshield and parachute. Jarosite - A Water-bearing Mineral Formed in Groundwater 3+ KFe3 (SO4)2(OH)6 2 Jarosite = K2SO4 + 3 Fe2O3 + 3 H2SO4 Hematite is in “Blueberries,” which still suggest water. Stone Mountain MER Spirit: Columbia Hills H2O Now: Clouds & Polar Caps Ground Ice – Mars Orbiter GRS Water abundances within a few meters depth of the Martian surface. Wm. Feldman. AAAS talk & Los Alamos Nat’l. Lab. Press Release, 15 Feb. 2003. (SPACE.com report, 16 Feb. 2003) So, Water on Mars !! So? Apparently, Mars has/had lots of water. Lots of evidence for ancient liquid water (> ~2 billion years ago), both surface and underground. Martian Gullies - Liquid Water or Not? Material flows down steep slopes, most commonly interpreted as water-bearing debris flows [Malin and Edgett (2000) Science 288, 2330]. Liquid water is difficult to produce and maintain near Mars’ surface, now.
    [Show full text]
  • Downselection of Landing Sites Proposed for the Mars 2020 Rover Mission
    47th Lunar and Planetary Science Conference (2016) 2324.pdf DOWNSELECTION OF LANDING SITES PROPOSED FOR THE MARS 2020 ROVER MISSION. M. P. Golombek1, J. A. Grant2, K. A. Farley3, K. Williford1, A. Chen1, R. E. Otero1, and J. W. Ashley1, 1Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109; 2Smithsonian Institution, Center for Earth and Planetary Sciences, Washington, D.C. 20560, 3Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125. Introduction: The Mars 2020 mission would ex- suitable for addressing key planetary evolution ques- plore a site likely to have been habitable, seek signs of tions if and when they are returned to Earth. past life, prepare a returnable cache with the most Results of the voting were presented as the compelling samples, take the first steps towards in-situ weighted average (assigning 5 points to each green resource utilization on Mars, and demonstrate technol- vote, 3 to each yellow vote, and 1 to each red vote that ogy needed for future human and robotic exploration were then summed and divided by the total number of of Mars. The first landing site workshop identified and votes) and the mode (color receiving the most votes). prioritized 27 landing sites proposed by the science This ensured that participants could not skew the re- community according to science objectives that also sults by withholding votes from some sites. Both met the engineering constraints [1]. This abstract de- methods yield similar results and reveal a fall-off in scribes the downselection of landing sites that occurred support for sites ranked lower than the top nine or ten at the second landing site workshop and associated based on mode and average, respectively [2].
    [Show full text]
  • Refereed Articles in 2020
    Refereed articles in 2020 [1] R. Brunetto, C. Lantz, T. Nakamura, D. Baklouti, T. Le Pivert-Jolivet, S. Kobayashi, and F. Borondics. Characterizing irradiated surfaces using IR spectroscopy. Icarus, 345:113722, July 2020. [2] G. Cremonese, F. Capaccioni, M. T. Capria, A. Doressoundiram, P. Palumbo, M. Vincendon, M. Massironi, S. Debei, M. Zusi, F. Altieri, M. Amoroso, G. Aroldi, M. Baroni, A. Barucci, G. Bellucci, J. Benkhoff, S. Besse, C. Bettanini, M. Blecka, D. Borrelli, J. R. Brucato, C. Carli, V. Carlier, P. Cerroni, A. Cicchetti, L. Colangeli, M. Dami, V. Da Deppo, V. Della Corte, M. C. De Sanctis, S. Erard, F. Esposito, D. Fantinel, L. Fer- ranti, F. Ferri, I. Ficai Veltroni, G. Filacchione, E. Flamini, G. Forlani, S. Fornasier, O. Forni, M. Fulchignoni, V. Galluzzi, K. Gwinner, W. Ip, L. Jorda, Y. Langevin, L. Lara, F. Leblanc, C. Leyrat, Y. Li, S. Marchi, L. Marinangeli, F. Marzari, E. Mazzotta Epifani, M. Mendillo, V. Men- nella, R. Mugnuolo, K. Muinonen, G. Naletto, R. Noschese, E. Palomba, R. Paolinetti, D. Perna, G. Piccioni, R. Politi, F. Poulet, R. Ragaz- zoni, C. Re, M. Rossi, A. Rotundi, G. Salemi, M. Sgavetti, E. Simioni, N. Thomas, L. Tommasi, A. Turella, T. Van Hoolst, L. Wilson, F. Zam- bon, A. Aboudan, O. Barraud, N. Bott, P. Borin, G. Colombatti, M. El Yazidi, S. Ferrari, J. Flahaut, L. Giacomini, L. Guzzetta, A. Lucchetti, E. Martellato, M. Pajola, A. Slemer, G. Tognon, and D. Turrini. SIMBIO- SYS: Scientific Cameras and Spectrometer for the BepiColombo Mission. Space Sci. Rev., 216(5):75, June 2020. [3] Pierre Guiot, Mathieu Vincendon, John Carter, Yves Langevin, and Alain Carapelle.
    [Show full text]
  • Ganymede Science Questions and Future Exploration
    Planetary Science Decadal Survey Community White Paper Ganymede science questions and future exploration Geoffrey C. Collins, Wheaton College, Norton, Massachusetts [email protected] Claudia J. Alexander, Jet Propulsion Laboratory Edward B. Bierhaus, Lockheed Martin Michael T. Bland, Washington University in St. Louis Veronica J. Bray, University of Arizona John F. Cooper, NASA Goddard Space Flight Center Frank Crary, Southwest Research Institute Andrew J. Dombard, University of Illinois at Chicago Olivier Grasset, University of Nantes Gary B. Hansen, University of Washington Charles A. Hibbitts, Johns Hopkins University Applied Physics Laboratory Terry A. Hurford, NASA Goddard Space Flight Center Hauke Hussmann, DLR, Berlin Krishan K. Khurana, University of California, Los Angeles Michelle R. Kirchoff, Southwest Research Institute Jean-Pierre Lebreton, European Space Agency Melissa A. McGrath, NASA Marshall Space Flight Center William B. McKinnon, Washington University in St. Louis Jeffrey M. Moore, NASA Ames Research Center Robert T. Pappalardo, Jet Propulsion Laboratory G. Wesley Patterson, Johns Hopkins University Applied Physics Laboratory Louise M. Prockter, Johns Hopkins University Applied Physics Laboratory Kurt Retherford, Southwest Research Institute James H. Roberts, Johns Hopkins University Applied Physics Laboratory Paul M. Schenk, Lunar and Planetary Institute David A. Senske, Jet Propulsion Laboratory Adam P. Showman, University of Arizona Katrin Stephan, DLR, Berlin Federico Tosi, Istituto Nazionale di Astrofisica, Rome Roland J. Wagner, DLR, Berlin Introduction Ganymede is a planet-sized (larger than Mercury) moon of Jupiter with unique characteristics, such as being the largest satellite in the solar system, the most centrally condensed solid body in the solar system, and the only solid body in the outer solar system known to posses an internally generated magnetic field.
    [Show full text]
  • A Comparative View of Radiation, Xa9745787 Photo and Photocatalytically Induced Oxidation of Water Pollutants
    A COMPARATIVE VIEW OF RADIATION, XA9745787 PHOTO AND PHOTOCATALYTICALLY INDUCED OXIDATION OF WATER POLLUTANTS N. GETOFF Institute for Theoretical Chemistry and Radiation Chemistry, University of Vienna, Vienna, Austria Abstract Water resources are presently overloaded with biologically resistant (refractory) pollutants. Several oxidation methods have been developed for their degradation, the most efficient of which is iradiation treatment, particularly that based on e-beam processing in the presence of Q/O3. The next-best method is photoinduced pollutant oxidation with VUV- and/or UV-light, using HjO2 or H2O2/O3 as an additional source of OH radicals. The photocatalytic method, using e.g. TiQ as a catalyst in combination with oxidation agents such as If Oj or H2O2/O3, is also recommended. The suitability of these three methods is illustrated by examples and they are briefly discussed and compared on the basis of theirenergy consumption and efficiency. Other methods, such as ozone treatment, the photo-Fenton process, ultrasonic and elctrochemical treatments, as well as the well known biological process and thermal oxidation of refractory pollutants, are briefly mentioned. 1. INTRODUCTION Current water resources are strongly overloaded with biologically resistant pollutants, as a result of global population growth and the development of certain industries in the past few decades. The disposal of chemical waste in rivers, seas and oceans has contributed to possibly-irrepairable destruction of marine life. The application of fertilizers, pesticides etc. in modern agriculture has exacerbated the situation. Hence, urgent measures are necessary for remediation of water resources. For the degradation of water pollutants, a number of oxidation methods, based on processes initiated by ionizing radiation, UV- and visible light, photocatalytic induced reactions, as well as combinations of these, have been developed.
    [Show full text]
  • Grid Mapping of Ice-Related Landforms in Acidalia Planitia, Mars
    Grid mapping of ice-related landforms in Acidalia Planitia, Mars Ernst Hauber1 Csilla Orgel2 Dennis Reiss3 Stephan van Gasselt4 Andreas Johnsson5 1German Aerospace Center (DLR), Institute of Planetary Research, Berlin, [email protected] 2Institut für Geowissenschaften, FU Berlin, [email protected] 3Institut für Planetologie, WWU Münster, [email protected] 4National Chengchi University, Taipei, [email protected] 5Dept.of Earth Sciences, University of Gothenburg, [email protected] Abstract Many young landforms in mid- and high-latitudes on Mars are probably related to ice, but their exact distribution and origin are still poorly understood. In an attempt to determine their extent and identify possible spatial relationships and genetic links between them, we mapped their distribution across a N-S traverse across Acidalia Planitia, following a grid-mapping approach. The general characteristics of Acidalia are similar to that of Utopia Planitia and Arcadia Planitia, which are known to host large water ice reservoirs. Keywords: Mars; permafrost; landforms; ice; climate; grid mapping. Introduction patterned ground in Utopia Planitia; Séjourné et al., 2011). Large quantities of excess water ice reside in the upper parts of the Martian crust in the northern hemisphere We aim at a better understanding of the distribution of (e.g., Plaut et al., 2009; Stuurman et al., 2016; Bramson et possibly ice-related landforms in Acidalia Planitia, the al., 2015). Although it is believed that this ice was third major lowland basin. Our goal is to identify deposited during phases of different obliquities (e.g., latitude-dependencies of such landforms and their Madeleine et al., 2009), it does survive over geological relation to each other as well as to external parameters time under current conditions (Bramson et al., 2017) and such as topography, and thermal inertia.
    [Show full text]
  • Investigations of Moon-Magnetosphere Interactions by the Europa Clipper Mission
    EPSC Abstracts Vol. 13, EPSC-DPS2019-366-1, 2019 EPSC-DPS Joint Meeting 2019 c Author(s) 2019. CC Attribution 4.0 license. Investigations of Moon-Magnetosphere Interactions by the Europa Clipper Mission Haje Korth (1), Robert T. Pappalardo (2), David A. Senske (2), Sascha Kempf (3), Margaret G. Kivelson (4,5), Kurt Retherford (6), J. Hunter Waite (6), Joseph H. Westlake (1), and the Europa Clipper Science Team (1) Johns Hopkins University Applied Physics Laboratory, Maryland, USA, (2) Jet Propulsion Laboratory, California, USA, (3) University of Colorado, Colorado, USA, (4) University of Michigan, Michigan, USA, (5) University of California, California, USA, (6) Southwest Research Institute, Texas, USA. ([email protected]) 1. Introduction magnetic fields inducing eddy currents in the ocean. By measuring the induced field response at multiple The influence of the Jovian space environment on frequencies, the ice shell thickness and the ocean Europa is multifaceted, and observations of moon- layer thickness and conductivity can be uniquely magnetosphere interaction by the Europa Clipper will determined. The ECM consists of four fluxgate provide an understanding of the satellite’s interior sensors mounted on a 5-m-long boom and a control structure and compositional makeup among others. electronics hosted in a vault shielding it from The variability of Jupiter’s magnetic field at Europa radiation damage. The use of four sensors allows for induces electric currents within the moon’s dynamic removal of higher-order spacecraft- conducting ocean layer, the magnitude of which generated magnetic fields on a boom that is short depends on the ocean’s location, extent, and compared with the spacecraft dimensions.
    [Show full text]