Long wavelength folding on Mercury / Talk third bi-weekly / Vis Viva
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Sander van Oers became our first member on April 17th, 2013, when he gave this talk on his work on the geophysics of Mercury. His research was carried out during a placement at UCLA. https://twitter.com/SocietyVisViva https://www.facebook.com/SocietyVisViva http://www.visviva.nl ============== It shall be pointed out that our meetings are about more than just slides—they are about the interaction of our Fellows. Vis Viva offers a forum for the active discussion of space topics, and so our talks are lively get-together with a permanent conversation of the speaker and the audience. Since just slides cannot get this across, we kindly invite you to join one of our bi-weekly activities.
Transcript of Long wavelength folding on Mercury / Talk third bi-weekly / Vis Viva
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Outline
1 Why a Mission to Mercury?
2 The MESSENGER Mission
3 The MESSENGER Spacecraft
4 Long-Wavelength Folding
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Why a Mission to Mercury?Last Visit: Mariner 10 in 1975
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Six Key Outstanding QuestionsWhy is Mercury so Dense?
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Six Key Outstanding QuestionsWhat is the geologic history of Mercury?
Credit: NASA/Johns Hopkins University
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Six Key Outstanding QuestionsWhat is the nature of Mercury’s magnetic field?
Credit: NASA/Johns Hopkins University
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Six Key Outstanding QuestionsWhat is the structure of Mercury’s core?
Credit: NASA/Johns Hopkins University
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Six Key Outstanding QuestionsWhat are the unusual materials at Mercury’s poles?
Credit: NASA/Johns Hopkins University
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Six Key Outstanding QuestionsWhat volatiles are important at Mercury?
Credit: NASA/Johns Hopkins University
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The MESSENGER MissionPrimary Mission
Primary mission at Mercury:Orbit for one Earth year (equivalent to just over four Mercuryyears, or two Mercury solar days), collecting data on thecomposition and structure of Mercurys crust, its topography andgeologic history, the nature of its thin atmosphere and activemagnetosphere, and the makeup of its core and polar materials.
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The MESSENGER MissionQuick Overview
MESSENGER = MErcury Surface, Space ENvironment,GEochemistry and Ranging
Cost $446MLaunch Date August 3, 2004
Launch Vehicle Delta II 7925HFlybys EVVMMMArrival March 2011Status Extended Mission in Progress (!)
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The MESSENGER MissionInterplanetary Trajectory
Credit: NASA/Johns Hopkins University
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The MESSENGER MissionMercury Orbit
Credit: NASA/Johns Hopkins University
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The MESSENGER MissionWebsite - Q & A
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The SpacecraftQuick Overview
Size 1.42 m tall, 1.85 m wide and 1.27 m deepMass 1,107 kg
Dry Mass 507.9 kgPropellant 599.4 kg
Power 640 WPropulsion
Large Maneuvers One Bipropellant ThrusterSmall Maneuvers 16 Monopropellant Thrusters
Instruments 7
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The SpacecraftChallenges of a Mercury Orbiter
Credit: NASA/Johns Hopkins University
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The SpacecraftAssembly
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The SpacecraftLaser Ranging at Interplanetary Distances
Credit: NASA/Goddard Space Flight Center
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The SpacecraftThe Instruments
Credit: NASA/Johns Hopkins University
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The SpacecraftThe Instruments: MLA
Credit: NASA/Johns Hopkins University
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Long-Wavelength FoldingObservations
Credit: NASA/Johns Hopkins University
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Long-Wavelength FoldingObservations
Klimczak et al. (2012)
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Long-Wavelength FoldingObservations
Credit: NASA/Johns Hopkins University
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Long-Wavelength FoldingA Theory
Lithospheric Folding caused by Global Contraction due to Cooling
Observed Amplitude: ∼ 2.5 kmObserved Wavelength: ∼ 1200 km
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Long-Wavelength FoldingFolding Mechanism
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Long-Wavelength FoldingResult Perturbing Flow
Fletcher and Hallet (1983)
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Long-Wavelength FoldingFolding on Earth: Basin and Range Province
Image from Marli Miller, University of Oregon
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Long-Wavelength FoldingAnalogy?
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Long-Wavelength FoldingLinear Stability Analysis
1 Formulate the Basic Flow
2 Add a Small Disturbance
3 Substitute the Sum into the Governing Equations andLinearize
4 Formulate an Eigenvalue Problem
5 Solve the Eigenvalue Problem
The flow is unstable if a solution grows in time.
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Long-Wavelength FoldingGrowth Rate for one Wavelength
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Long-Wavelength FoldingGrowth Rates
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Long-Wavelength FoldingDepth Brittle Layer
Zuber et al. (2010)
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Long-Wavelength FoldingDifferent Creep Laws
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Long-Wavelength FoldingInitial Results For Mercury
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Long-Wavelength FoldingProblems-Depth
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Long-Wavelength FoldingProblems-Wavelength
Radius Mercurius ≈ 2440km, Wavelength = 1200 km
Credit: NASA/Johns Hopkins University
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Long-Wavelength FoldingCompositional Layers
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Long-Wavelength FoldingMulti-Layer
Bassi and Bonnin (1988)
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Long-Wavelength FoldingGrowth Rate for Multiple Layers
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Long-Wavelength FoldingFuture Work
1 Solve Equations for a Spherical Body
2 Distinguish between Single or Mutli Layer Model
3 Incorporate Latest Findings on Mercury
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Future for MercuryMESSENGER
Credit: NASA/Johns Hopkins University
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Future for MercuryBepiColombo
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