Overview (The Solar System)
Venus is sometimes referred to as Earth’s twin sister because its size, mass, and density are similar to those of Earth. Venus’s surface conditions, however, definitely make Venus Earth’s “evil” twin sister. Owing to a runaway greenhouse effect from the Carbon dioxide atmosphere, Venus has a surface temperature hot enough to melt lead. The surface Atmospheric pressure is nearly one hundred times what it is on Earth. Thick layers of sulfuric acid clouds veil the surface of Venus. Landers on Mars can last for years, but on Venus they are destroyed by the harsh surface conditions within about an hour. These atmospheric conditions make it impossible to study the surface of Venus using direct optical means or long-term robotic landers. Astronomers must use radar maps rather than optical photographs to study the planet’s surface features. Radar maps from both Earth and Spacecraft have, however, unveiled the surface of our mysterious twin sister.
Radar maps show that volcanic activity has played a major role in shaping the surface of Venus. Volcanic activity includes not only erupting volcanoes but also lava flows and other activity whereby solid, liquid, or gaseous material escapes from the planet’s interior. Volcanic activity is often caused by tectonic activity but can occur independently of tectonic activity. There are more than sixteen hundred large volcanic features on the surface of Venus and possibly as many as...
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Knowledge Gained (The Solar System)
Because thick clouds veil the surface of Venus, astronomers for a long time could only speculate about the planet’s surface. Prior to the space age, speculations varied: The surface was envisioned as hot and steamy by some, as a hot and dry desert by others. With the coming of the space age, astronomers were finally able to gather data on the surface of Venus. They did not, however, suspect just how hot Venus really was.
The first radar maps of Venus from Earth were made using the Arecibo Radio telescope in Puerto Rico, beginning in the late 1970’s. Because of the distance to the planet, these images had a relatively low resolution, on the order of a few kilometers. These Earth-based radar maps did, however, allow planetary scientists to observe the large-scale surface features of Venus.
Earth-based radar maps of Venus can reveal only part of the Venusian surface, because during Venus’s closest approach to Earth only one side faces Earth. Orbiting spacecraft have therefore been sent to map the surface of Venus. Pioneer Venus 1 went into orbit around Venus in late 1978. This mission was the first orbital mission to use radar to map much of the surface of Venus, with a Resolution of about 7 kilometers. In 1990, the Magellan mission went into orbit around Venus. The Magellan orbiter made much more extensive and detailed radar maps of Venus. Because it used a polar rather than an equatorial orbit, Magellan was able...
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Context (The Solar System)
The volcanoes on Venus contribute to its very harsh surface environment. Volcanoes on Earth outgas significant amounts of carbon dioxide gas. Those on Venus and Mars probably do the same. On Earth, biological activity, such as plant respiration, uses the carbon dioxide. Earth therefore has a very small percentage of carbon dioxide in its atmosphere. On Venus, however, the carbon dioxide is still in the atmosphere; 97 percent of Venus’s atmosphere is carbon dioxide. All this carbon dioxide produces a runaway greenhouse effect and surface temperatures greater than 700 kelvins.
Jupiter’s moon Io is also volcanically active. However the volcanoes on Io differ from the volcanoes on Venus and other terrestrial planets. In addition to rock, Io’s composition includes significant amounts of ice.
Venus, Mars, and Earth all have large volcanoes. However, the volcanic and tectonic activity is different on each of these three planets. The differences arise from differences in size and internal heating of the planets. Mars has had the least amount of volcanic activity. Earth’s crust is divided into several tectonic plates. Movement of these plates is an important force in shaping the volcanic activity on Earth. Venus does not have a crust broken into several plates. Hence, Venus has much volcanic activity, but it does not have the types of features formed by crustal plate movement. Understanding how volcanic and tectonic activity...
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Further Reading (The Solar System)
Chaisson, Eric, and Steve McMillan. Astronomy Today. 6th ed. New York: Addison-Wesley, 2008. Chapter 9 of this very readable introductory astronomy textbook covers the planet Venus. There is a good section on the planet’s surface volcanism.
Freedman, Roger A., and William J. Kaufmann III. Universe. 8th ed. New York: W. H. Freeman, 2008. Chapter 11 of this introductory astronomy textbook is a complete and readable overview of Mercury, Venus, and Mars, including volcanic activity.
Hartmann, William K. Moons and Planets. 5th ed. Belmont, Calif.: Thomson Brooks/Cole, 2005. This textbook on the planets and satellites of the solar system summarizes our understanding of volcanic and other tectonic processes on Venus as well as other planets and moons.
Hester, Jeff, et al. Twenty-first Century Astronomy. New York: W. W. Norton, 2007. Chapters 6 and 7 of this well-illustrated astronomy textbook are about the terrestrial planets. Volcanic and tectonic processes are well covered, and the comparison of these processes on different planets is very good.
Morrison, David, Sidney Wolf, and Andrew Fraknoi. Abell’s Exploration of the Universe. 7th ed. Philadelphia: Saunders College Publishing, 1995. Venus is covered in chapter 15 of this classic astronomy textbook.
Zeilik, Michael. Astronomy: The Evolving Universe. 9th ed. New York: Cambridge University...
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