Venus Four Stages of Planetary Development

1
VenusFour Stages of Planetary Development

• Differentiation
• Venus must be differentiated (no direct evidence,
  though)
• Crust Formation and Cratering
• Surface is young
• 300-500 Myr based on craters
• Preserves none of original crust or craters

2
VenusFour Stages of Planetary Development

• Lava Flooding
• Most of surface appears to be solidified lava
• Slow Surface Evolution
• Reprocessed entire surface
• Current reprocessing is slower than on Earth
• No (or special) plate tectonics
• Lots of volcanoes
• Slow erosion because no water on surface

3
Venus Interior

• Because of size, must have been completely molten
  when formed therefore must have differentiated
• Density of 5.2g/cm3 ? must contain iron and
  nickel
• Likely has an iron/nickel core that is only a
  little smaller than Earths

4
Venus Interior

• Magnetic Field
• Venus has no magnetic field
• Either solid iron/nickel core
• OR slow rotation ? dynamo effect does not
  function
• Therefore upper atmosphere directly interacts
  with solar wind

5
Venus Atmosphere

• Composition
• 96 CO2
• 3.5 N2
• traces of
• H20 (water)
• H2S04 (sulfuric acid)
• HCl (hydrochloric acid)
• HF (hydrofluoric acid)
• Sulfuric acid clouds blanket entire planet ?
  surface not visible from space

6
Venus Atmosphere

• Surface pressure much greater than Earths
• atmosphere 90x denser than Earths which is only
  1/10 the density of water

7
Venus Atmosphere

• Evolution
• Closer to its original composition than Earth
• Without oceans, CO2 not trapped in rocks
• Original volatiles (NH3, CH4) decomposed by UV
  sunlight and heat
• H escaped into space
• N2 remained in atmosphere
• C ? CO2
• The sulfur, chlorine and fluorine baked out of
  surface by heat

8
MarsFour Stages of Planetary Development

• Differentiation
• Size between Earth (1/2) and Moon (2x) ?
  differentiation
• Relatively low density ? iron core is small
• Crust Formation and Cratering
• Preserves some original crust (heavily cratered
  in Southern Hemisphere)
• Northern Hemisphere is much younger (1-2 Gyr)
• Less Cratered
• Volcanic origin

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MarsFour Stages of Planetary Development

• Lava Flooding (Maybe Water?)
• Original lava plains probably buried under later
  volcanic activity (Northern Hemisphere)
• May have had early oceans in basins
• Slow Surface Evolution
• Part of surface reprocessed
• No plate tectonics
• Lots of volcanic activity
• Wind and, perhaps, water erosion

10
Mars Interior

• Magnetic Field
• Expect no magnetic field if completely cooled and
  solid
• Mars Global Surveyor detected a remnant magnetic
  field
• Similar to Mercury, a former magnetic filed
  magnetized some iron in Mars

11
Mars Atmosphere

• Composition
• 95 CO2
• 2 N2
• 1.6 Ar
• traces of others (including H2O)
• Very tenuous
• 1 density of Earths
• Has seasonal weather ? large dust storms
• Large amount of airborne dust
• Dust gives the Martian sky a red color when
  viewed from surface

12
Mars Atmosphere

• Used to have much more atmosphere in past but
  most has probably escaped into space
• Retention of atmosphere (kinetic vs. gravity)
• Solar wind and UV light (no ozone) help liberate
  atmosphere
• 1.6 Ar indicates that the atmosphere was denser
  in the past
• Like Earth (1.3) Ar retained while other gases
  were removed

13
Mars Surface

• Volcanoes
• Northern regions contain many extinct volcanoes
• Largest volcano in solar system is Olympus Mons
• Volcanoes on Mars are hot spot volcanoes

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Mars Satellites

• Two small satellites Phobos (25 km) and Deimos
  (12 km)
• Irregular in shape (gravity and spherical shapes)
• Most likely are captured asteroids
• Tidally locked to Mars