Chapter 9 Venus

9.1 Orbital Properties

  • Venus is much brighter than Mercury, and can be farther from the Sun

  • Called morning or evening star, as it is still “tied” to Sun

  • Brightest object in the sky after Sun and Moon

9.2 Physical Properties

  • Radius: 6000km

  • Mass: 4.9 × 1024 kg

  • Density: 5200 kg/m³

  • Rotation period: 243 days, retrograde

9.3 Long-Distance Observations of Venus

  • Dense atmosphere and thick clouds make surface impossible to see

  • Surface temperature is about 730K — hotter than Mercury!

9.4 The Surface of Venus

  • Surface is relatively smooth

  • Two continent-like features: Ishtar Terra and Aphrodite Terra

  • No plate tectonics

  • Mountains, a few craters, many volcanoes and large lava flows

  • Lava has flowed from cracks on the surface

9.5 The Atmosphere of Venus

  • Venus’s atmosphere is very dense

  • Solid cloud bank 50-70 km above surface

  • Atmosphere is mostly carbon dioxide; clouds are sulfuric acid

  • Venus is the victim of a runway greenhouse effect— just kept getting hotter and hotter as infrared radiation is resorbed

9.6 Venus’s Magnetic Field and Internal Structure

  • No magnetic field, probably because rotation is so slow

  • No evidence for plate tectonics

  • Venus resembles a young Earth (1 billion years)