Mars: First Order Landscapes The Great Crustal Dichotomy

Mars: First Order Landscapes The Great Crustal Dichotomy
Geography 441/541 S/18 Dr. Christine M. Rodrigue C.M. Rodrigue, 2018 Geography, CSULB

Mars: First Order Landscapes
C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes On Earth, the orders of relief scheme Is sometimes seen in geography textbooks Organizes topographic variation in a scale-dependent manner Geographers often focus on Spatial analysis of particular phenomena Regional synthesis to integrate assemblages of phenomena Scales at which processes and regional patterns operate The interactions among phenomena at different scales C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes Examples of interactions among scales In spatial statistics: the Modifiable Areal Unit Problem (MAUP) In human geography: local cultural and political responses to global economic and political processes Biogeography: alpha, beta, and gamma measures of biodiversity Geomorphology: "megageomorphology" has emerged as remote sensing technology has made the simultaneous examination of form and process at large scale (small map scale) possible C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes For Mars, a handy descriptive scheme for handling the regional variations in Mars’ physical landscapes The “First Order of Relief” = the crustal dichotomy The Northern Lowlands The Southern Highlands If Earth’s oceans evaporated (which they will …), there would remain a crustal dichotomy here Former ocean basins: low elevation, thin crust, basaltic, with a veneer of pelagic sediments Former continents: high elevation, thick crust, granitic rocks and their extrusive igneous, sedimentary, and metamorphic derivatives C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes Northern Lowlands Regional subdivisions: Vastitas Borealis Utopia Planitia Embayments: Acidalia Planitia Chryse Planitia Amazonis Planitia Arcadia Planitia Isidis Planitia Elysium Planitia Mars: First Order Landscapes C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes Northern Lowlands Relatively young surface Smooth with few craters This is exactly what you’d expect if Mars had had an ocean It could be expected to receive sediments from rivers, floods, and coastal processes and create terrigenous sediments nearshore, with some of them dissolving They would be turned into minerals that would eventually precipitate out of the water column onto the abyssal floor The oceans would thus cover the underlying original rock surface, much as pelagic sediments here do C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes Northern Lowlands Further suggestions of an ocean: Drainage of Martian outflow channels and valley networks This is also exactly what you’d expect if Mars had had an ocean to serve as base level for stream networks C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes Northern Lowlands Drainage: Valles Marineris' outflow channels, which drain into Chryse Planitia Nanedis north of Ganges Ares and Aram Chaos Argyre to Aram and Ares C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes Northern Lowlands Even better: Coastlines!? Transition between the southern highlands and the northern lowlands is quite abrupt C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes Northern Lowlands Even better: Coastlines!? Terraces on the Arcadia side of Alba Mons C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes Vastitas Borealis Even better: Coastlines!? Tim Parker’s analysis of Viking imagery C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes Northern Lowlands Even better: Coastlines!? Tim Parker’s analysis of Viking imagery (1994) His and others’ re-analysis using MOC imagery seemed to debunk his argument, which even he admitted in 2001 But it’s as though the new imagery is so fine in resolution that it can’t detect the coarser scale at which this putative ocean’s coastline features might exist MOLA suggests that, in fact, at least one of the “coastlines” is at the same elevation (water seeks a level constant with respect to the geoid) C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes Northern Lowlands Plot complication That "ocean" floor is dominated by andesitic rock (on Earth, it's basalt) Not sediments with minerologies consistent with precipitation out of water. No carbonates! No ocean? C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes Northern Lowlands About those andesites "Surface Type 1" (basalts dominating the southern highlands) "Surface Type 2" (andesites and andesitic basalts dominating the northern lowlands) C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes Northern Lowlands Rampart craters C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes Northern Lowlands Patterned ground C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes Northern Lowlands Thumbprint terrain Rootless cones C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes Northern Lowlands Dunes C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes The Southern Highlands Mostly 1-5 km above the mean martian geoid Versus 0-3 km below for the Northern Lowlands ~1-3 km scarp dividing the two C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes Southern Highlands: Ancient, battered terrain Arabia Terra C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes Southern Highlands: Ancient, battered terrain Thaumasia Highlands: snow-fed channels? C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes Southern Highlands: Ancient, battered terrain Noachis Terra to right Amenthes Planum below Signs of water or fluid C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes Southern Highlands: Ancient, battered terrain Hellas, with Isidis and Utopia from the Northern Lowlands beyond C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes Southern Highlands: Ancient, battered terrain Noachis Terra, Holden Crater, alluvial fan/bajada? (right) Delta, too, from Uzboi Vallis entering from southwest (left) C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes Southern Highlands: Ancient, battered terrain Syrtis Major Planum, volcanic province, basaltic, not dusty C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes Southern Highlands: Ancient, battered terrain Dust devil track Promethei Terra on left Syrtis Major on right C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes Southern Highlands: Ancient, battered terrain Terrain softening at higher latitudes Cimmeria Terra to left Noachis Terra to right C.M. Rodrigue, 2018 Geography, CSULB

The “Orders of Relief” for Martian Landscapes Basalt terrain and dust dominate the Southern Highlands while andesite is quite prevalent in the Northern Lowlands Spectra showing high proportions of basalt shown in the green Andesite shown in the red channel Hæmatite shown in blue (small area) Dust-dominated areas come out brown C.M. Rodrigue, 2018 Geography, CSULB

Mars: First Order Landscapes The Great Crustal Dichotomy

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