C.M. Rodrigue, 2015 Geography, CSULB Geography on Mars: Third Order of Relief Los Angeles Geographical Society 6 March 2015 Dr. Christine M. Rodrigue Geography California State University, Long Beach

C.M. Rodrigue, 2015 Geography, 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, 2015 Geography, 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, 2015 Geography, 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, 2015 Geography, 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, 2015 Geography, CSULB Third Order: Deep Time on Mars

C.M. Rodrigue, 2015 Geography, CSULB Third Order: Varying Crater Densities Noachian Hesperian Amazonian

C.M. Rodrigue, 2015 Geography, CSULB Third Order: Noachian Regions

C.M. Rodrigue, 2015 Geography, CSULB Third Order: Hesperian Regions

C.M. Rodrigue, 2015 Geography, CSULB Third Order: Amazonian Regions