Mars' Third Order of Relief: Regions Differentiated by Age

• Regions not evenly distributed by age or surface coverage:

• Amazonian youngest regions cover about 25% of the planet
• despite being Mars' loooongest period, ~3 billion years
• atmosphere thins out, wind becomes dominant process even so, very localized volcanism, planet dries out other than permafrost and ice caps, chemistry dominated by anhydrous ferric oxides
• smaller regions than Noachian ones; like Hesperian regions, on the planum or planitia scale:
• Amazonis Planitia; Elysium Planitia; Utopia Planitia cover materials; Acidalia Planitia; lavas surrounding Tharsis Montes, Olympus Mons, and Alba Mons; Arcadia Planitia; Planum Boreum under and around the north polar ice cap; Planum Australe under the south polar ice cap