Overview (The Solar System)
The second planet from the Sun and Earth’s immediate inner neighbor, Venus is often called Earth’s twin, because the masses and radii of the two planets are very similar. Venus’s mass is 82 percent that of Earth. Its radius is only 5 percent less than Earth’s. Under ordinary circumstances, no objects in the sky other than the Sun and the Moon surpass Venus in brightness. Viewing Venus with one or more of the other planets also visible in the sky shortly before sunrise or briefly after sunset can be an awe-inspiring sight. In ancient times, since Venus could at times be seen in the morning skies and at other times in the evening skies, the planet was actually thought to be two different objects; they were given the names Phosphoros and Hesperus for the morning and evening star, respectively.
Venus revolves once around the Sun every Earth 224.7 days. It rotates on its axis once every 243.01 days. The inclination of its orbit is about 3.5° with respect to the ecliptic plane. Its orbit, like those of all the other planets, is an ellipse, but it is very close to being a perfect circle. The tilt of Venus’s axis of rotation is about 17.8° , as compared with the Earth’s 23.5° . As a result, any seasonal changes of weather on Venus would be less extreme than on Earth. Remarkably, its rotation is retrograde, backward, as compared with the direction of revolution, or clockwise, as seen from above the ecliptic plane. It is not...
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Methods of Study (The Solar System)
The first attempt to send an interplanetary probe to Venus did not fare well. Mariner 1 launched on July 22, 1962. A software error caused its booster to veer dangerously off course while low in the atmosphere, and it was destroyed on purpose by the range safety personnel at Cape Canaveral.
Mariner 2, a sister Spacecraft to the failed first American Venus probe, launched successfully on August 27, 1962. Fortunately, this probe was able to fly within 34,833 kilometers of the Venusian surface on December 14, 1962. Although it carried no photographic equipment, Mariner 2 provided a treasure trove of new information about the shrouded planet. The spacecraft was outfitted with Geiger tubes, an ion chamber, a Cosmic dust detector, a microwave radiometer, and a Magnetometer experiment. Mariner 2 determined that the Venusian surface temperature was more than 670 kelvins. It detected neither a planetary magnetic field nor any Van Allen-like radiation belts about the planet. It continued to collect data about particles and fields in interplanetary space until contact was lost on January 3, 1963, at a distance of 87 million kilometers from Earth.
Mariner 5 was launched on June 14, 1967, and was sent to fly by Venus. This spacecraft also did not include photographic or television cameras. It was equipped with radio science and ultraviolet experiments as well as particle and magnetic field detectors. Mariner 5 encountered Venus on...
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Context (The Solar System)
Earth’s atmosphere has the potential to become more like that of Venus. There are two ways that such a situation could develop. If Earth moved closer to the Sun, increased solar heat would release more carbon dioxide into the atmosphere. Limestone rock (calcium carbonate) and dissolved carbon dioxide in the oceans provide a tremendous store of trapped carbon dioxide. Under higher temperatures, the rocks and seashells would chemically release carbon dioxide, and the greenhouse mechanism would raise the atmosphere’s temperature. As a result, new carbon dioxide would be released and would speed the greenhouse mechanism. The second way that Earth’s atmosphere could become more like that of Venus involves pollution of the atmosphere to the extent that enough carbon dioxide accelerates the existing greenhouse effect.
More generally, study of Venus’s atmosphere helps scientists to better understand terrestrial weather and climate. Earth has an atmosphere composed mostly of nitrogen. The weather, however, is influenced primarily by water molecules and carbon dioxide molecules. These substances are found in Earth’s atmosphere only in trace amounts; nevertheless, they are responsible for most of the heat transfer around the globe. On Venus, the weather is controlled by the atmosphere’s main constituent, carbon dioxide. The contrasts between weather processes on Venus and those on the Earth have led to a more complete understanding...
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Further Reading (The Solar System)
Beatty, J. Kelly, Carolyn Collins Petersen, and Andrew Chaikin, eds. The New Solar System. 4th ed. Cambridge, Mass.: Sky, 1999. Amply illustrated with color images, diagrams, and informative tables, this book is aimed at a popular audience, but it can also be useful to specialists. Contains an appendix with planetary data tables, a bibliography for each chapter, planetary maps, and an index.
Cattermole, Peter John. Venus: The Geological Story. Baltimore: Johns Hopkins University Press, 1996. Provides a comprehensive presentation of the latest understanding of Venus based on Magellan data.
Elkins-Tanton, Linda T. The Sun, Mercury, and Venus. New York: Chelsea House, 2006. Examines the innermost portion of the solar system and the star, our Sun, which plays such a prominent role in the evolution of both planets. For the general audience with an interest in science.
Esposito, Larry W., Ellen R. Stofan, and Thomas E. Cravens, eds. Exploring Venus as a Terrestrial Planet. New York: American Geophysical Union, 2007. A collection of articles covering all major areas of planetary research on Venus. Technical.
Fimmel, Richard O., Lawrence Colin, and Eric Burgess. Pioneering Venus: A Planet Unveiled. Washington, D.C.: National Aeronautics and Space Administration, 1995. A complete summary of the findings of Pioneer Venus as of 1983. Pioneer Venus orbited Venus and sent...
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