C.M. Rodrigue, 2015Geography, CSULB

Geography on Mars:

Third Order of Relief

Los Angeles Geographical Society6 March 2015

Dr. Christine M. RodrigueGeography

California State University, Long Beach

C.M. Rodrigue, 2015Geography, CSULB

Geography on Mars

• Third order of relief and deep time on Mars– Geological periods (actually eons in Earth terms)_ Noachian period: formation of planet 4.6 Ga to tapering off of the

Late Heavy Bombardment of the solar system ~3.75 Ga_ dense cratering of a wide variety of sizes_ planetary magnetic field starts and collapses_ denser atmosphere, possibly warmer_ above water's triple point_ ground and surface water:

• ocean, seas, and lakes• valley networks

_ neutral or alkaline hydrochemistry (phyllosilicate clays)_ volcanic activity starts and then concentrates spatially_ only period potentially friendly to life "as we know it, Jim"

C.M. Rodrigue, 2015Geography, CSULB

Geography on Mars

• Third order of relief and deep time on Mars– Geological periods (actually eons in Earth terms)_ Hesperian period: until ~3.5 to 1.8 Ga; most commonly

thought to fade out around 3.0 Ga_ impacts fewer and smaller_ loss of atmosphere with loss of magnetic field_ surface waters lost to space, permafrost, ice caps_ volcanism (and sulfur dioxide)_ volcanic activity focusses on Tharsis and Elysium_ sulfate hydrochemistry (very acid, hostile to life)_ different mineralogy: sulfates, evaporites_ outwash floods as magma interacts with permafrost

C.M. Rodrigue, 2015Geography, CSULB

Geography on Mars

• Third order of relief and deep time on Mars– Geological periods (actually eons in Earth terms)_ Amazonian period: "young" Mars, from ~3.0 Ga to today_ Cratering low level, low size_ May be dampening of slopes by groundwater seeps_ There is evidence of recent volcanic eruptions but not at Noachian or

Hesperian levels_ Giant outflows may occasionally occur_ Ice ages may occur due to axial and orbital changes_ Wind is the dominant agent, however

• Dust devils are very common• Occasionally, planet-covering dust storms

_ Geochemistry is dominated by oxidation of iron into anhydrous oxides, creating reddish dust

C.M. Rodrigue, 2015Geography, CSULB

Geography on Mars

• Third order of relief and deep time on Mars– Geochemical periods (just to stir the pot)_ Phyllosian period: time of the phyllosilicate clays

• Up to late Noachian, when volcanism took off and pumped out so much sulfuric acid into the atmosphere

• These clays form in neutral or alkaline surface or subsurface waters

_ Theiikian period: time of the sulfates• Late Noachian/much of the Hesperian• Sulfate minerals and evaporites form from a lot of water• Acidic conditions (related to volcanism)• Hydrated sulfates (gypsum, magnesium sulfate)

_ Siderikian: time of iron oxidation• Late Hesperian and the Amazonian• Oxidation of iron-rich rocks

C.M. Rodrigue, 2015Geography, CSULB

Third Order: Deep Time on Mars

C.M. Rodrigue, 2015Geography, CSULB

Third Order: Varying Crater Densities• Noachian Hesperian Amazonian

C.M. Rodrigue, 2015Geography, CSULB

Third Order: Noachian Regions

C.M. Rodrigue, 2015Geography, CSULB

Third Order: Hesperian Regions

C.M. Rodrigue, 2015Geography, CSULB

Third Order: Amazonian Regions