1. Mars Global Surveyor Magnetometer - PI: M. Acuna

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 2 1 21 and

3. No core dynamo today Magnetization of surface rocks

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

6. Ionosphere

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

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

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

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

11. Mars’Interaction Boundary Response to the Solar Wind

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

13. Changing Topology of Mars’ Magnetic Field

14. Over a Strong Magnetic Region

15. Mars Aeronomy Mission  Upper atmosphere  Ionosphere  Magnetic Field  Pick-Up Ions  Solar Wind

16. 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