Venus
• Venus’ mass and radius are nearly the
same as Earth.
• Rotation rate is slow and retrograde:
243 Earth days, longer than its year
(225 Earth days). Perhaps caused by
solar tides and atmospheric friction, or
collisional impact.
• Atmosphere is incredibly thick (90 times
Earth’s, equal to 900 m below sea level)
and hot (750 K).
• Highly reflective clouds nearly cancels
Venus’ proximitiy to Sun, so Venus absorbs only 5% more solar energy than
the Earth.
• High temperature caused by Greenhouse effect, raising temperature by
470 K (45 K on the Earth, and 5 K
on Mars, for comparison)
• Surface obscured by sulfuric acid clouds
high in Venus’ atmosphere.
• Near surface, atmosphere is clear, but
density of atmosphere causes peculiar
bending of light so that it looks like
the bottom of a fishbowl.
• Surface explored by radar from Earth
and satellites in orbit around Venus.
Surface is solid, no lakes, and few mountains. Craters and volcanos exist, but
little evidence of plate tectonics, due
to absence of water in planet’s crust.
• Water is now completely lacking from
Venus, but was abundant in past, as
deduced from high deuterium/hydrogen
ratio in atmosphere, 100 times the value
on Earth.
• Lack of tectonics also indicated by lesser
amounts of Ar40 (from decay of K40)
in atmosphere.
• Venus evolved divergently from the Earth
because it is too close to the Sun.