84 Chapter 2 From the Solar System to the Milky Way
Size Approximately 0.95 times the size of Earth (equatorial radius of 3,761 miles,
or 6,052 km)
Mass Approximately 0.82 times the mass of Earth
Surface gravity Approximately 0.91 times the gravity of Earth
Satellites None
Mean distance from the Sun 0.72 AU
Orbital period Approximately 225 days
Rotation period Approximately 243 days
What’s It Like There?
Venus is the closest planet to Earth, and the two planets have many features in common.
The gravity on Venus is practically the same as gravity on Earth. Venus has an atmosphere,
and it also has active volcanic activity that spews out hydrogen sulfide, nitrogen, and sulfu-
rous acid gas.
Since Venus is covered with thick clouds consisting of concentrated sulfuric acid, and
the main component of its atmosphere (approximately 96 percent) is carbon dioxide, its
surface temperature is between 752°F and 932°F (400°C–500°C) because of the intense
greenhouse effect. Also, the atmospheric pressure at the planet’s surface is approximately
92 times the pressure at Earths surface.
Although this is a minor point, the direction of Venus’s rotation is opposite to that of
Earth, so there the Sun rises in the west and sets in the east.

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