1. C.M. Rodrigue, 2014 Geography, CSULB Mars: First Order Landscapes Geography 441/541 S/14 Dr. Christine M. Rodrigue

2. C.M. Rodrigue, 2014 Geography, CSULB Explanations for the Crustal Dichotomy Endogenous explanations – Degree-1 convection - Planetary accretion - Heat accumulation - Magma ocean - Gravitationally unstable crystal accumulation - Mantle overturn - Initiation of upwelling/downwelling plumes - Sinking of cool mantle material intensifies temperature contrast in outer liquid core - This creates a dynamo/planetary magnetic field

3. C.M. Rodrigue, 2014 Geography, CSULB Explanations for the Crustal Dichotomy Endogenous explanations – Did Mars have plate tectonics? - Upwelling → crustal thinning through tension and ablation (Northern Lowlands?) - Downwelling → compression and thickening (Southern Highlands?) - Cerberus Fossæ a spreading zone rift? - South dipping plate south of Cerberus Fossæ - East dipping plate under Tharsis (volcanic arc?) - Or... could crustal prominence develop above upwelling plume instead?

4. C.M. Rodrigue, 2014 Geography, CSULB Explanations for the Crustal Dichotomy Endogenous explanations – Evidence for plate tectonics? - No trenches - Crustal thickening in Terra Cimmeria/Sirenum? - Banded magnetization: Could these symmetrical changes in remanent magnetization be like the bands on Earth's ocean floors in spreading zones, where new lithosphere records the prevailing magnetic field? - Fault systems - Cerberus Fossæ? - Valles Marineris? - Transform fault-like offsets in magnetic bands in Noachis Terra

5. C.M. Rodrigue, 2014 Geography, CSULB Plate Tectonics: Banded Magnetic Anomalies

6. C.M. Rodrigue, 2014 Geography, CSULB Explanations for the Crustal Dichotomy Endogenous explanations – Other explanations for the magnetic anomalies - Not the roughly symmetrical polarity reversals seen on Earth's ocean floors near spreading zones - Possibly great basaltic dikes that picked up remanent magnetization during solidification as they ascended through joints in country rock - Maybe the accumulation of terranes with distinct magnetization records due to plate tectonic compression over a downwelling

7. C.M. Rodrigue, 2014 Geography, CSULB Explanations for the Crustal Dichotomy Endogenous explanations – Stagnant lid convection - Earth's crust is < 10 km thick on the ocean floors but ~40 km thick under continents (up to 70 km thick under continental compression zones, e.g., Tibet) - Mars' crust averages ~ 50 km thick, ranging from ~25 km thick under the Northern Lowlands and Arabia Terra and up to 75 km thick under the Southern Highlands - Could such a thick crust have prevented Mars' lithosphere breaking into plates and enabling vigorous convection? - Interestingly, a stagnant lid would be capable of drifting as a unit, perhaps explaining why Tharsis is centered on the equator.

8. C.M. Rodrigue, 2014 Geography, CSULB Earth Crustal Thickness: Isopach Map

9. C.M. Rodrigue, 2014 Geography, CSULB Mars Crustal Thickness: Block Diagram

10. C.M. Rodrigue, 2014 Geography, CSULB Mars Crustal Thickness: Hypsometric Isopach Map

11. C.M. Rodrigue, 2014 Geography, CSULB Explanations for the Crustal Dichotomy Exogenous explanations – Impact created the Northern Lowlands basin - Planetary accretion - Heat

12. C.M. Rodrigue, 2014 Geography, CSULB Mars Crustal Thickness MOLA topography Crustal thickness Isostatic root – Andrews-Hanna, Zuber, and Banerdt 2008

13. C.M. Rodrigue, 2014 Geography, CSULB Mars Crustal Thickness MOLA topography Modelled ellipse – Andrews-Hanna, Zuber, Banerdt 2008