Surface of Mars

• Note the craters.
• Plate tectonics? We see no analogues of the earth's midocean ridges.
• Valles Marineris.
  • Computer generated perspective view of part of Valles Marineris
  • This is interpreted as a crack in the crust. Perhaps the inside expanded as it warmed from radioactive decay after the crust had formed.
• Olympus Mons.
  • Perspective view of Olympus Mons.
  • There are some other volcanos on Mars, but not a lot.
  • All but this one seem to have been extinct for a very long time. How could we know this?