History of the Surface of Venus

Spring 2003

Planetary Comparison with Earth

• Mass 0.8 of Earth; .98 in mean density (reduced to same pressure)
• Similar amounts of C; Earth=lithospheric storage, Venus=atmospheric storage
• Earth-Moon System vs. Venus Only

Cratering Age

• Morphological Record < 10^9 years
  McKinnon et al. 1997, Venus II
• Therefore no direct record of most of history

• Continuous, episodic or evolutionary change?

Surface Properties

• Surface temperature difference 288K vs. 730K
  • Therefore Venus dehydrated in atmosphere and probably upper lithosphere at least.
  • Must have experienced a "Runaway Greenhouse" - When? Or, did it start out that way?
  • But did planet dehydrate, or only crust?
• Geographic features

• Thermal modelling suggests significant crustal thickening within last ~10^9 years.

Morphological Features and Distribution

• Lakshmi Planum
• Cratering
  Venus ridged terrain
• Coronae
  • Shield field in corona
  • Idern Kuva Corona
  • Topographic Groups
• Volcanism (Head paper)
  • Shield field and lava flows
  • Global distribution map of shield fields
  • Intermediate volcano
  • Steep-sided domes
  • Circular caldera
  • Lava flood-type flow
  • Global distribution map of lava flow fields
  • Lava channel

Tectonic and regional correlations interior block terrain Beta Regio Beta Regio altimetry

Tanaka paper Geomorphic/geologic map Resurfacing history Terminology

• Extensional deformation
  • impact crater Somerville
  • Diana and Dali Chasmae
• Tessera (Hansen et. al.)
• Geologic sketch map
• Map of typical crustal plateau
• SAR images
• Fracture ribbon models

Planetary Synthesis

• 
• Phillips and Hansen
• 
• Solomon et al.

• But still no good explanation of when and how current Greenhouse atmosphere formed

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Last updated 06/05/2003