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Mars Global Surveyor Magnetometer - PI: M. Acuna

Mars Global Surveyor Magnetometer - PI: M. Acuna. 1. 2. and. 1. 2. Planetary Dynamos. Volume of electrically conducting fluid ... which is convecting ... and rotating. All planetary objects probably have enough rotation - the presence (or not) of a global magnetic field tells us about.

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Mars Global Surveyor Magnetometer - PI: M. Acuna

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  1. Mars Global SurveyorMagnetometer - PI: M. Acuna

  2. 1 2 and 1 2 Planetary Dynamos Volume of electrically conducting fluid ... which is convecting ... and rotating All planetary objects probably have enough rotation - the presence (or not) of a global magnetic field tells us about

  3. No core dynamo today Magnetization of surface rocks

  4. Magnetization only of old, cratered terrain -> Dynamo ceased ~3.5 billion years ago

  5. Ionosphere

  6. Atmospheric Loss Processes Neutral Bulk removal “stripping” Ion Ion pickup Photochemical loss Sputtering

  7. Crustal magnetic sources affect these processes: shielding atmosphere from SW field topology open field lines

  8. MGS Measurements - Implications for Mars’ Atmosphere • Ancient dynamo • -> early protection for atmosphere • Strong crustal magnetization • -> affect atmospheric loss after dynamo turn-off

  9. Solar Wind Interaction Boundary Pressure Balance: obstacle to the solar wind PSolar Wind = P (magnetic)crust + P (thermal)ionosphere David Brain

  10. Mars’Interaction Boundary Response to the Solar Wind

  11. Field Topology Solar wind and magnetic field impinging on Mars’ complex magnetic field Close-up of strong anomaly region David Brain

  12. Changing Topology of Mars’ Magnetic Field

  13. Over a Strong Magnetic Region

  14. Mars Aeronomy Mission • Upper atmosphere • Ionosphere • Magnetic Field • Pick-Up Ions • Solar Wind

  15. 3 scenarios for how the dynamo stopped • Dynamo convection driven by radiogenic / formation heating: Cools down, mantle slows down, core stops convecting • Inner core condensation drives dynamo: Cools down, inner solid core expands to (almost) fill core • Plate tectonics drives dynamo: Cools down, mantle slows down, core slows down

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