(Background) The Magellan robot spacecraft is seen here in artist's conception orbiting Venus in the early 1990s. When close to the veiled planet, its radar system scans the surface; when farther away, it sends data home to Earth.
(Inset A) Each of the insets shows a three-dimensional, computer-enhanced view of surface features on Venus, artificially colored and vertically exaggerated to enhance small-scale structure. This is the volcanic Gula Mons area, with extensive lava flows across otherwise fractured plains.
(Inset B) A distant view of Maat Mons (above rear), an 8-kilometer high volcano, now apparently dormant.
(Inset C) A closer view of Maat Mons, showing clearly more lava flows across the fractured terrain in the foreground.
(Inset D) The Danu Montes comprise a mountain range rising 1 to 3 kilometers above the plains—probably formed ages ago by surface compression, much like the Andes and Appalachian mountain ranges on Earth.
Studying this chapter will enable you to:
Summarize Venus's general orbital and physical properties.
Explain why Venus is hard to observe from Earth and how we have obtained more detailed knowledge of the planet.
Compare the surface features and geology of Venus with those of Earth and the Moon.
Describe the characteristics of Venus's atmosphere and contrast it with that of Earth.
Explain why the greenhouse effect has produced conditions on Venus very different from those on Earth.
Describe Venus's magnetic field and internal structure.
In its bulk properties at least, Venus seems almost a carbon copy of our own world. The two planets are similar in size, density, and chemical composition. They orbit at comparable distances from the Sun. At formation, they must have been almost indistinguishable from each other. Yet they are now about as different as two terrestrial planets can be. Whereas Earth is a vibrant world, teeming with life, Venus is an uninhabitable inferno, with a dense, hot atmosphere of carbon dioxide, lacking any trace of oxygen or water. Somewhere along their respective evolutionary paths, Venus and Earth diverged, and diverged radically. How did this occur? What were the factors leading to Venus's present condition? Why are Venus's surface, atmosphere, and interior so different from Earth's? In answering these questions we will discover that a planet's environment, as well as its composition, can play a critical role in determining its future.
