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