DOCSLIB.ORG

Problem Set 5

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Problem Set 5 Problem Set 5 Formation of the moon In our global warming lecture we discussed the fact that the Earth itself was once a `runaway greenhouse', because its entire surface was molten rock. The Earth was probably molten just after it formed (because of the gravitational energy it gained while forming). But, as we saw in the moon formation movies, the Earth was probably also molten just after the moon forming impact. We're going to use this fact to estimate the mass of the moon-forming impactor. The energy of the impactor was all kinetic energy: 1 E = m v2 2 imp (E is kinetic energy, mimp is the mass of the impactor, and v is the velocity of the impactor). A lot of this energy was converted into heat, which caused the Earth to melt. The energy required to cause the entire Earth to get to the melting point is: E = mEarthcpTmelt (E is energy, mEarth is the mass of the Earth, cp is called specific heat, and is different for different materials, Tmelt is the melting temperature). To find out how big the impactor needed to be to melt the Earth, we equate the two expressions above and solve for mimp to find m c T m = Earth p melt imp 1 2 2 v Let T be the melting temperature of rock: 1000 K. Let v be the escape velocity from Earth: 11000 m/s. 3 And let cp be the specific heat of rock: 0.7 ×10 Joules/kg/K. Look up the mass of the Earth (in kg). Calculate the mass of the impactor required to melt the Earth How does the mass of the impactor compare with the mass of the moon, the mass of the Earth, and the mass of Mars? Even after rock becomes hot enough to melt, extra energy is required for the rock to change phase from solid to liquid (this is called the `heat of melting'). Taking this into account, would the impactor mass you estimate be bigger, smaller, or the same? Explain. 1 The impactor could have hit the Earth with a speed faster than the escape speed. Taking this into account, would the impactor mass you estimate be bigger, smaller, or the same? Explain. The specific heat (cp) value we used above is for rock. However, the Earth has a significant amount of metal in its core, and metal has a lower specific heat than rock. Taking this into account, would the impactor mass you estimate be bigger, smaller, or the same? Explain. Come up with at least 2 other reasons why our simple calculation is not exactly correct. (By the way, in case you're curious, researchers believe the mass of the moon-forming impactor was similar to the mass of Mars. Did you come close?) Google Mars Data collected by NASA and other space organizations are always available to the public, but can sometimes be hard to access. However, the web is making a lot of the data more accessible. In this homework set, you'll explore one tool { Google Mars { to learn about Mars's surface. The first step is to pull up a webpage with Google Mars, which is located here: http://www.google.com/mars The first map that appears is an elevation map, created from data taken by the Mars Orbiter Laser Altimeter (MOLA), that surveyed the surface of Mars from 1997-2006. MOLA determined the height of the surface by measuring the time it took a pulse of laser light to leave the spacecraft, reflect off the surface of Mars, and return to the detectors. Zoom out on Mars until you can see the whole planet (a quirk of Google Mars is that the map \wraps" around, so you may see features repeat when you zoom out too much.) Using the MOLA map, answer the following questions: • One of the most noticeable features of the MOLA map is the difference between the northern and southern hemispheres of Mars, called the Martian Dichotomy (that's just a fancy word for something with two different parts). Using the elevation bar on your map, what is the typical elevation of the southern highlands? • What is typical elevation of the northern lowlands? 2 One theory to explain the appearance of the lowlands is that an ocean might have existed there in the past. We're going to make a rough estimate of the volume of water that would be needed to fill the ocean. Let the radius of the ocean be 1000 km, and the depth be the difference in height between the highlands and lowlands. Calculate the volume of the ocean using the equation for the volume of a cylinder: Volume = height × π × radius2 • What are the heights of the polar caps (the swirling features at the top and bottom of the maps)? • Assuming the polar caps are made from water and are 500 km in radius, calculate an approximate volume for the polar caps. • Assuming ice and water have similar densities (which they do) could water from the polar caps have filled our hypothetical ocean? • Besides freezing into ice caps, what else could have happened to water on Mars? • Last week you did a crater counting activity for Mars. Looking at the differences in cratering between the northern and southern hemispheres, what can you say qualitatively about the ages of the surfaces in the two different hemispheres? • Hellas Basin has some of the lowest elevation on Mars. Use the search function to search for "Hellas Basin." What is the elevation in the bottom of the basin? • Do you suspect Hellas Basin was formed by an impact? Why or why not? • Type `Olympus Mons' in the search bar. About how high is Olympus Mons, and how does it compare to the height of Earth's biggest mountain (from base to height), Mauna Kea? 3 • Use the search box to search for \MER Spirit Rover ". This will put you in Gusev Crater. What feature do you think makes scientists believe water once filled this crater? • Use the search box to search for \Valles Marineris". Describe how Valles Marineris is similar to or different from the Gusev Crater water feature. • Do you think water flowed in Valles Marineris? Why or why not? In addition to MOLA (the elevation map) Google provides a visible map and an infrared map as well. The visible map would be similar to what we'd see with our own eyes. The infrared map is the heat emitted by the surface. • Use the search box to search for \Water ice in crater at Martian north pole" and then click on the `Visible' box at the upper right. What do you think is the feature in the center of the crater? • Now click on the `Elevation' box. Does this agree with your hypothesis? Explain. • Now click on the `Infrared' box. What does the feature look like and why? (Remember, infrared light is the heat emitted by the surface) 4.
Load more

Recommended publications
  • Global Structure of the Martian Dichotomy: an Elliptical Impact Basin? J
    Lunar and Planetary Science XXXIX (2008) 1980.pdf GLOBAL STRUCTURE OF THE MARTIAN DICHOTOMY: AN ELLIPTICAL IMPACT BASIN? J. C. Andrews-Hanna1, M. T. Zuber1, and W. B. Banerdt2 (1Dept. of Earth, Atm., and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, [email protected]; 2JPL, Caltech, Pasadena, CA 91109). Introduction: The topography and crustal Tharsis (Figure 2b). Short-wavelength anomalies in the thickness of Mars are dominated by the near- model crustal roots can result from either local density hemispheric dichotomy between the southern anomalies or the spatially- and temporally-variable highlands and northern lowlands. The dichotomy lithosphere thickness during Tharsis construction. boundary can be traced along an apparently irregular Thus, the roots are negative beneath younger portions path around the planet, except where it is buried of the rise that are likely composed of dense lava flows beneath the Tharsis volcanic rise [1]. The isostatic and supported by a thicker lithosphere (e.g., Olympus compensation of the dichotomy [2] and the ancient Mons), and positive beneath older portions that are population of buried impact craters beneath the largely isostatic today (e.g., Tempe Terra). lowlands [3] suggest that the dichotomy is one of the Nevertheless, we are able to map the dichotomy most ancient features on the planet. Early workers boundary both beneath Tharsis and elsewhere (Figure suggested a giant impact origin for the dichotomy [4], 2b). The location of the sub-Tharsis dichotomy but the attempted fit of a circular “Borealis basin” to boundary is largely insensitive to the choice of the irregular dichotomy boundary proved lithosphere thickness.
    [Show full text]
  • MARS DURING the PRE-NOACHIAN. J. C. Andrews-Hanna1 and W. B. Bottke2, 1Lunar and Planetary La- Boratory, University of Arizona
    Fourth Conference on Early Mars 2017 (LPI Contrib. No. 2014) 3078.pdf MARS DURING THE PRE-NOACHIAN. J. C. Andrews-Hanna1 and W. B. Bottke2, 1Lunar and Planetary La- boratory, University of Arizona, Tucson, AZ 85721, [email protected], 2Southwest Research Institute and NASA’s SSERVI-ISET team, 1050 Walnut St., Suite 300, Boulder, CO 80302. Introduction: The surface geology of Mars appar- ing the pre-Noachian was ~10% of that during the ently dates back to the beginning of the Early Noachi- LHB. Consideration of the sawtooth-shaped exponen- an, at ~4.1 Ga, leaving ~400 Myr of Mars’ earliest tially declining impact fluxes both in the aftermath of evolution effectively unconstrained [1]. However, an planet formation and during the Late Heavy Bom- enduring record of the earlier pre-Noachian conditions bardment [5] suggests that the impact flux during persists in geophysical and mineralogical data. We use much of the pre-Noachian was even lower than indi- geophysical evidence, primarily in the form of the cated above. This bombardment history is consistent preservation of the crustal dichotomy boundary, to- with a late heavy bombardment (LHB) of the inner gether with mineralogical evidence in order to infer the Solar System [6] during which HUIA formed, which prevailing surface conditions during the pre-Noachian. followed the planet formation era impacts during The emerging picture is a pre-Noachian Mars that was which the dichotomy formed. less dynamic than Noachian Mars in terms of impacts, Pre-Noachian Tectonism and Volcanism: The geodynamics, and hydrology. crust within each of the southern highlands and north- Pre-Noachian Impacts: We define the pre- ern lowlands is remarkably uniform in thickness, aside Noachian as the time period bounded by two impacts – from regions in which it has been thickened by volcan- the dichotomy-forming impact and the Hellas-forming ism (e.g., Tharsis, Elysium) or thinned by impacts impact.
    [Show full text]
  • Arxiv:2003.06799V2 [Astro-Ph.EP] 6 Feb 2021
    Thomas Ruedas1,2 Doris Breuer2 Electrical and seismological structure of the martian mantle and the detectability of impact-generated anomalies final version 18 September 2020 published: Icarus 358, 114176 (2021) 1Museum für Naturkunde Berlin, Germany 2Institute of Planetary Research, German Aerospace Center (DLR), Berlin, Germany arXiv:2003.06799v2 [astro-ph.EP] 6 Feb 2021 The version of record is available at http://dx.doi.org/10.1016/j.icarus.2020.114176. This author pre-print version is shared under the Creative Commons Attribution Non-Commercial No Derivatives License (CC BY-NC-ND 4.0). Electrical and seismological structure of the martian mantle and the detectability of impact-generated anomalies Thomas Ruedas∗ Museum für Naturkunde Berlin, Germany Institute of Planetary Research, German Aerospace Center (DLR), Berlin, Germany Doris Breuer Institute of Planetary Research, German Aerospace Center (DLR), Berlin, Germany Highlights • Geophysical subsurface impact signatures are detectable under favorable conditions. • A combination of several methods will be necessary for basin identification. • Electromagnetic methods are most promising for investigating water concentrations. • Signatures hold information about impact melt dynamics. Mars, interior; Impact processes Abstract We derive synthetic electrical conductivity, seismic velocity, and density distributions from the results of martian mantle convection models affected by basin-forming meteorite impacts. The electrical conductivity features an intermediate minimum in the strongly depleted topmost mantle, sandwiched between higher conductivities in the lower crust and a smooth increase toward almost constant high values at depths greater than 400 km. The bulk sound speed increases mostly smoothly throughout the mantle, with only one marked change at the appearance of β-olivine near 1100 km depth.
    [Show full text]
  • Análisis Geológico De La Región Oxia Planum En Marte, Sitio Principal De Aterrizaje De La Misión Exomars 2020
    UNIVERSIDAD NACIONAL AUTÓNOMA DE MÉXICO FACULTAD DE INGENIERÍA Análisis geológico de la región Oxia Planum en Marte, sitio principal de aterrizaje de la Misión ExoMars 2020 TESIS Que para obtener el título de Ingeniera Geóloga P R E S E N T A Karen Itzel Reyes Ayala DIRECTOR DE TESIS Dr. Primož Kajdič Ciudad Universitaria, Cd. Mx., 2016. Jurado asignado Presidente: Dr. Jaime Humberto Urrutia Fucugauchi Vocal: Dr. Primož Kajdič Secretario: Dr. Dante Jaime Morán Zenteno Primer suplente: Dr. Héctor Javier Durand Manterola Segundo suplente: Dr. Enrique Alejandro González Torres Director de tesis: Dr. Primož Kajdič Asesores externos: Dr. Jorge L. Vago (European Space Agency) Dr. Olivier Witasse (European Space Agency) A José Anselmo Reyes León Mi más sincero agradecimiento al European Space Research and Technology Centre (ESTEC) de la Agencia Espacial Europea por brindarme la oportunidad de participar en el Third ExoMars 2018 Landing Site Selection Workshop y permitirme el acceso al material disponible para realizar este trabajo. Agradecimientos Tere y Carlos. Soy tan afortunada de tenerlos como padres, gracias por educarme con buenos principios y hacerme la persona que soy en la actualidad. Sus palabras de aliento nunca me dejaron caer, sus grandes sacrificios hoy pueden verse reflejados en este logro. Gracias por sus ejemplos de perseverancia y constancia que los caracterizan y que me han infundado siempre. El orgullo que sienten por mí fue lo que me hizo llegar hasta el final. ¡Los amo! Dr. Primož Kajdič. Gracias por haberme adentrado en el estudio de las Ciencias Espaciales, por creer en mis capacidades y haber hecho posible mi estancia en ESTEC.
    [Show full text]
  • Pre-Mission Insights on the Interior of Mars Suzanne E
    Pre-mission InSights on the Interior of Mars Suzanne E. Smrekar, Philippe Lognonné, Tilman Spohn, W. Bruce Banerdt, Doris Breuer, Ulrich Christensen, Véronique Dehant, Mélanie Drilleau, William Folkner, Nobuaki Fuji, et al. To cite this version: Suzanne E. Smrekar, Philippe Lognonné, Tilman Spohn, W. Bruce Banerdt, Doris Breuer, et al.. Pre-mission InSights on the Interior of Mars. Space Science Reviews, Springer Verlag, 2019, 215 (1), pp.1-72. 10.1007/s11214-018-0563-9. hal-01990798 HAL Id: hal-01990798 https://hal.archives-ouvertes.fr/hal-01990798 Submitted on 23 Jan 2019 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Open Archive Toulouse Archive Ouverte (OATAO ) OATAO is an open access repository that collects the wor of some Toulouse researchers and ma es it freely available over the web where possible. This is an author's version published in: https://oatao.univ-toulouse.fr/21690 Official URL : https://doi.org/10.1007/s11214-018-0563-9 To cite this version : Smrekar, Suzanne E. and Lognonné, Philippe and Spohn, Tilman ,... [et al.]. Pre-mission InSights on the Interior of Mars. (2019) Space Science Reviews, 215 (1).
    [Show full text]
  • 35247, and –40247 Quadrangles, Reull Vallis Region of Mars by Scott C
    Prepared for the National Aeronautics and Space Administration Geologic Map of MTM –30247, –35247, and –40247 Quadrangles, Reull Vallis Region of Mars By Scott C. Mest and David A. Crown Pamphlet to accompany Scientific Investigations Map 3245 65° 65° MC-01 MC-05 MC-07 30° MC-06 30° MC-12 MC-15 MC-13 MC-14 0° 45° 90° 135° 180° 0° 0° MC-21 MC-22 MC-20 MC-23 SIM 3245 -30° MC-28 -30° MC-27 MC-29 MC-30 -65° -65° 2014 U.S. Department of the Interior U.S. Geological Survey Contents Introduction.....................................................................................................................................................1 Physiographic Setting ...................................................................................................................................1 Data .............................................................................................................................................................2 Contact Types .................................................................................................................................................2 Fluvial Features ..............................................................................................................................................2 Waikato Vallis ........................................................................................................................................3 Eridania Planitia ....................................................................................................................................4
    [Show full text]
  • Volcanoes? Analogues to Martian Plumes Feeding the Giant Shield Are Terrestrial Plumes from Motionless Plates
    Downloaded from http://sp.lyellcollection.org/ by guest on February 22, 2014 Geological Society, London, Special Publications Online First Are terrestrial plumes from motionless plates analogues to Martian plumes feeding the giant shield volcanoes? Christine M. Meyzen, Matteo Massironi, Riccardo Pozzobon and Luca Dal Zilio Geological Society, London, Special Publications, first published February 21, 2014; doi 10.1144/SP401.8 Email alerting click here to receive free e-mail alerts when service new articles cite this article Permission click here to seek permission to re-use all or request part of this article Subscribe click here to subscribe to Geological Society, London, Special Publications or the Lyell Collection How to cite click here for further information about Online First and how to cite articles Notes © The Geological Society of London 2014 Downloaded from http://sp.lyellcollection.org/ by guest on February 22, 2014 Are terrestrial plumes from motionless plates analogues to Martian plumes feeding the giant shield volcanoes? CHRISTINE M. MEYZEN1*, MATTEO MASSIRONI1,2, RICCARDO POZZOBON1,3 & LUCA DAL ZILIO1 1Dipartimento di Geoscienze, Universita` degli Studi di Padova, via G. Gradenigo, 6, 35131 Padova, Italy 2INAF, Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy 3IRSPS-DISPUTer, Universita’ G. d’Annunzio, Via Vestini 31, 66013 Chieti, Italy *Corresponding author (e-mail: [email protected]) Abstract: On Earth, most tectonic plates are regenerated and recycled through convection. However, the Nubian and Antarctic plates could be considered as poorly mobile surfaces of various thicknesses that are acting as conductive lids on top of Earth’s deeper convective system. Here, volcanoes do not show any linear age progression, at least not for the last 30 myr, but constitute the sites of persistent, focused, long-term magmatic activity rather than a chain of volcanoes, as observed in fast-moving plate plume environments.
    [Show full text]
  • Investigation of the Global Escarpment, Including the Fretted Terrain, in the Martian Northern Hemisphere
    Investigation of the Global Escarpment, including the Fretted Terrain, in the Martian Northern Hemisphere by Benjamin Chad Harrold A thesis submitted to the Graduate Faculty of Auburn University in partial fulfillment of the requirements for the Degree of Master of Science Auburn, Alabama August 9, 2010 Copyright 2010 by Benjamin Chad Harrold Approved by David T. King Jr., Co-Chair, Professor of Geology Luke J. Marzen, Co-Chair, Associate Professor of Geography Lorraine W. Wolf, Professor of Geology Abstract The global escarpment and associated fretted terrain are located in the Martian northern hemisphere. Two competing hypothesis presently in play explain the origin of Mars’ global escarpment. These hypotheses involve endogenic and exogenic processes and both could help explain the extreme topographic difference between the southern highlands and the northern lowlands. The focus of this study, the fretted terrain area of the global escarpment, is a transition zone of mesa-like features located directly north of the global escarpment. With the use of digital imagery analysis, georeferencing of existing maps, and the interpretation of current models, the most plausible origin of the escarpment proposed herein would be an exogenic process, namely a single, mega-scale impact shortly after formation of the planet. The main lines of evidence supporting this favored hypothesis are the modeled elliptical shaped basin, similarities between crustal thickness and topographic elevations, mineralogy, and the orientation and size distribution of the northern fretted terrain. ii Acknowledgments The author would like to thank the members of his thesis committee, Drs. David King, Luke Marzen, and Lorraine Wolf for their unequivocal support and guidance during this project.
    [Show full text]
  • Global Thermochemical Convection After Mars' Giant Impact: Numerical
    EPSC Abstracts Vol. 13, EPSC-DPS2019-1447-2, 2019 EPSC-DPS Joint Meeting 2019 c Author(s) 2019. CC Attribution 4.0 license. Global Thermochemical Convection after Mars’ Giant Impact: Numerical Models Kar-Wai Cheng (1), Antoine B. Rozel (1), Gregor J. Golabek (2), Harry Ballantyne (3), Martin Jutzi (3), Paul Tackley (1) (1) ETH Zürich, Switzerland, (2) University of Bayreuth, Germany, (3) University of Bern, Switzerland ([email protected]) Abstract both a crustal dichotomy and a long-lived volcanic region as the consequence of a single giant impact To investigate the formation of the martian crustal using thermochemical models. dichotomy and its possible link to Tharsis volcanic region, several sets of numerical simulations are 2. Methods presented. They mainly focus on the effect of various melt and crustal production parameters on the We use the thermochemical convection code StagYY long-term mantle convection subsequent to a giant [11] in 2D spherical annulus and axisymmetric impact. Diagnostics comparable to observational data geometry. Phase changes relevant to Mars and including topography, crustal thickness and surface temperature- and pressure-dependent viscosity are heat flux are computed. considered. 1. Introduction A parametrized impact is imposed as a thermal anomaly, whose size and amplitude follow standard The crustal dichotomy is one of the most prominent methods of impact scaling [12]. Melting of silicates characteristics of Mars, featuring a ≈5.5 km contrast causes compositional buoyancy and can affect in topography and ≈25 km difference in crustal geodynamic processes, and therefore related thickness between the southern highlands and the parameter, such as melt densities, are systematically northern lowlands [1], and is thought to have formed studied.
    [Show full text]
  • Building with Martian Regolith Experimental Research on the Efficient and Sustainable Production Process and Construction Method
    BUILDING WITH MARTIAN REGOLITH EXPERIMENTAL RESEARCH ON THE EFFICIENT AND SUSTAINABLE PRODUCTION PROCESS AND CONSTRUCTION METHOD AGATA MINTUS, 4745523 GRADUATION REPORT BUILDING WITH MARTIAN REGOLITH AGATA MINTUS, 4745523 PERSONAL INFORMATION TELEPHONE NUMBER: EMAIL ADDRESS: STUDIO/TOPIC NAME: Sustainable Design Graduation Studio - Material Science & Structural Design THEME: Experimental research on sustainable production and fabrication of novel material MENTORS: Dr.ir. F.A. Veer (first mentor) 2 Dr. O. Copuroglu (second mentor) Dr.D.P. Peck (third mentor) SUPERVISORS: Layla van Ellen Fernando França de Mendonça Filho GRADUATION PROJECT TITLE: Building with Martian regolith TOPIC: Experimental research on the efficient and sustainable production process and construction method KEYWORDS: Mars | building | ISRU fabrication | sustainability | regolith | efficiency Graduation Report | Agata Mintus PREFACE The main reason for choosing this topic is due to my interest in a hands-on approach and structural design. During my studies, I was developing my skills and knowledge in achieving sustainability in structural design optimization and manufacturing methods. Also, my passion for space architecture pushed me in the direction of experimental research which is possible to perform in the Sustainable Graduation Studio. I didn’t expect at the beginning of thesis studies, that I would be able to propose my own topic for the graduation project, that would be unusual and extreme in terms of the context. The fact, that I was able to focus on my passion and interest towards more scientific aspects like material science during this research made the work enjoyable, challenging and exciting. Therefore I would like to express my gratitude to everyone who helped me accomplish this goal and individual growth.
    [Show full text]
  • Lithospheric Flexure and the Evolution of the Dichotomy Boundary on Mars Thomas R
    GEOPHYSICAL RESEARCH LETTERS, VOL. 33, L08S05, doi:10.1029/2005GL024325, 2006 Lithospheric flexure and the evolution of the dichotomy boundary on Mars Thomas R. Watters Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, Washington, D. C., USA Patrick J. McGovern Lunar and Planetary Institute, Houston, Texas, USA Received 5 August 2005; revised 7 October 2005; accepted 28 October 2005; published 1 February 2006. [1] The boundary of the Martian crustal dichotomy in the boundary suggests that tectonism played a role in its eastern hemisphere is one of the most striking topographic formation and/or modification. A population of subdued features on the planet. The long wavelength topography of circular depressions in the northern lowlands revealed in much of the boundary is expressed by a broad rise and an Mars Orbiter Laser Altimeter (MOLA) data interpreted to arched ramp that slopes downward from the southern be ancient buried impact basins suggests that the northern highlands into the northern lowlands and often ends in a lowlands crust and the crustal dichotomy formed in the steep scarp. Lithospheric flexure of the southern highlands Early Noachian [Frey et al., 2002; Frey, 2006]. This for both a continuous and broken plate boundary with the suggests that the present-day boundary has evolved from northern lowlands lithosphere is modeled. We find that the an ancient dichotomy boundary modified by tectonism, long wavelength topography of the boundary is best fit by a volcanism, deposition and erosion [Watters, 2003a, lithospheric deflection profile of a broken lithosphere for 2003b; Irwin et al., 2004]. reasonable values of the flexural parameter.
    [Show full text]
  • Complementarity of Seismological and Electromagnetic Sounding Methods for Constraining the Structure of the Martian Mantle Antoine Mocqueta;∗ , Michel Menvielleb;C
    Planetary and Space Science 48 (2000) 1249–1260 www.elsevier.nl/locate/planspasci Complementarity of seismological and electromagnetic sounding methods for constraining the structure of the Martian mantle Antoine Mocqueta;∗ , Michel Menvielleb;c aUMR-CNRS 6112 Laboratoire de Planetologieà et Geodynamique,à Faculteà des Sciences et des Techniques, 2 rue de la Houssiniere, BP 92208, 44322 Nantes Cedex 3, France bCETP, UMR CNRS=UVSQ 8639-Observatoire de Saint-Maur, 4 Avenue de Neptune, 94107 Saint-Maur-des-Fosses,à France cDepartementà des Sciences de la Terre, Universiteà Paris-Sud, France Received 31 May 1999; received in revised form 17 December 1999; accepted 12 April 2000 Abstract The complementarity of seismological and electromagnetic sounding methods for the thermodynamical characterization of the Martian mantle is discussed by illustrating the observational constraints and limitations of both methods. The increase of temperature within a few hundreds of kilometers thick Martian outer lid with conductive heat transfer should induce the presence of a seismic low-velocity zone, due to the relatively small increase of pressure within Mars. The depth of minimum velocity will help to constrain the thickness and mean thermal gradient of the lid. These parameters will be strongly constrained by electromagnetic sounding methods. At greater depths, temperature variations of the order of 400 K will be detectable if seismic velocities can be determined with an accuracy better than 2%. An extrapolation of presently available laboratory data to the pressure range of Mars’ mantle predicts that the deep mantle electrical conductivity will be accessible if Mars’ mantle is cold, and mineralogically similar to the Earth’s.
    [Show full text]