VENUS

Venus with Cupid and a dolphin, classical sculpture; in the Museo Nazionale Romano, Rome ancient Italian goddess associated with cultivated fields and gardens and later identified by the Romans with the Greek goddess of love, Aphrodite. Venus had no worship in Rome in early times, as the scholar Marcus Terentius Varro (11627 BC) shows, attesting that he could find no mention of her name in old records. This is corroborated by the absence of any festival for her in the oldest Roman calendar and by her lack of a flamen (special priest). Her cult among the Latins, however, seems to be immemorial, for she had apparently at least two ancient temples, one at Lavinium, the other at Ardea, at which festivals of the Latin cities were held. Hence, it was no long step to bring her to Rome, apparently from Ardea itself. But how she came to be identified with so important a deity as Aphrodite remains a puzzle. That Venus' identification with Aphrodite took place fairly early is certain. A contributory reason for it is perhaps the date (August 19) of the foundation of one of her Roman temples. August 19 is the Vinalia Rustica, a festival of Jupiter; hence, he and Venus came to be associated, and this facilitated their equation, as father and daughter, with the Greek deities Zeus and Aphrodite. She was, therefore, also a daughter of Dione, was the wife of Vulcan, and was the mother of Cupid. In myth and legend she was famous for her romantic intrigues and affairs with both gods and mortals, and she became associated with many aspects, both positive and negative, of femininity. As Venus Verticordia, she was charged with the protection of chastity in women and girls. But the most important cause of the identification was the reception into Rome of the famous cult of Venus Erycinai.e., of Aphrodite of Eryx (Erice) in Sicilythis cult itself resulting from the identification of an Oriental mother-goddess with the Greek deity. This reception took place during and shortly after the Second Punic War. A temple was dedicated to Venus Erycina on the Capitol in 215 BC and a second outside the Colline gate in 181 BC. The latter developed in a way reminiscent of the temple at Eryx with its harlots, becoming the place of worship of Roman courtesans, hence the title of dies meretricum (prostitutes' day) attached to April 23, the day of its foundation. The importance of the worship of Venus-Aphrodite was increased by the political ambitions of the gens Iulia, the clan of Julius Caesar and, by adoption, of Augustus. They claimed descent from Iulus, the son of Aeneas; Aeneas was the alleged founder of the temple of Eryx and, in some legends, of the city of Rome also. From the time of Homer onward, he was made the son of Aphrodite, so that his descent gave the Iulii divine origin. Others than the Iulii sought to connect themselves with a deity grown so popular and important, notably Gnaeus Pompeius, the triumvir. He dedicated a temple to Venus as Victrix (Bringer of Victory) in 55 BC. Julius Caesar's own temple (46 BC), however, was dedicated to Venus Genetrix, and as Genetrix (Begetting Mother) she was best known until the death of Nero in AD 68. But despite the extinction of the Julio-Claudian line, she remained popular, even with the emperors; Hadrian completed a temple of Venus at Rome in AD 135. The Birth of Venus, oil on canvas by Sandro Botticelli, c. 1485; in the As a native Italian deity, Venus had no myths of her own. She therefore took over those of Aphrodite and, through her, became identified with various foreign goddesses. The most noteworthy result of this development is perhaps the acquisition by the planet Venus of that name. The planet was at first the star of the Babylonian goddess Ishtar and thence of Aphrodite. Because of her association with love and with feminine beauty, the goddess Venus has been a favourite subject in art since ancient times; notable representations include the statue known as the Venus de Milo (c. 150 BC) and the painting The Birth of Venus (c. 1485; see photograph) by Sandro Botticelli. in astronomy, second major planet from the Sun. Named for the Roman goddess of love and beauty, it is, after the Moon, the most brilliant natural object in the nighttime sky. Venus comes closer to the Earth than any other planet, approaching to within about 42,000,000 km (26,100,000 miles) at inferior conjunctioni.e., when Venus comes between the Earth and the Sun. Venus revolves around the Sun at a mean distance of 107,500,000 km (66,650,000 miles) in a nearly circular orbit. As viewed from the Earth, and as it travels around the Sun, Venus undergoes phase changes similar to those of the Moon. It completes one orbital revolution in 225 Earth days but goes through one cycle of phases in 584 days. Venus is a near twin of the Earth in size and mass. Its diameter is about 12,103 km (7,516 miles) as compared to 12,756 km (7,921 miles) for the Earth; and its mass is approximately 0.81 of the latter. The two planets, however, bear little resemblance to one another in other respects. Venus is completely enveloped by a thick layer of clouds consisting chiefly of droplets of concentrated sulfuric acid; this main cloud deck extends from an altitude of about 45 km (28 miles) up to nearly 70 km (43 miles). Thin hazes extend a few kilometres below the deck's lowest layers and about 20 km (12 miles) above its highest ones. Some cloud-top regions appear dark in ultraviolet light, possibly owing to the presence of sulfur dioxide, chlorine, or solid sulfur. The composition of Venus' atmosphere is quite different from that of the terrestrial atmosphere. Spacecraft measurements indicate that carbon dioxide comprises more than 96 percent of the constituent matter, which accounts for the extreme density of the Venusian atmosphere. Nitrogen makes up another 3.5 percent; trace amounts of argon, water vapour, carbon monoxide, helium, and sulfur dioxide are also present. The dense atmosphere, together with the thick cloud cover, traps incoming solar energy so efficiently that Venus has a surface temperature of about 460 C (860 F)the highest of any planet in the solar system. This high temperature is accompanied by an equally high surface pressure of about 90 bars, or 90 times the atmospheric pressure at the Earth's surface. Detailed information on the appearance and composition of Venus' surface was obtained by the Soviet Venera spacecraft in the 1970s and '80s. Photographs revealed plains strewn with flat, slabby rocks as well as a darker, fine-grained soil. The surface composition measured by Venera 13 and 14 suggested a composition similar to basalts found on Earth. Venus, view of the northern hemisphere based on observations made by the Magellan spacecraft. The False-colour perspective view of Ovda Regio, the western section of Aphrodite Terra. The image False-colour image of a shield volcano on Aphrodite Terra, north of Ovda Regio. The summit of the Radar mapping of Venus by the Venera mission as well as by the U.S. Pioneer and Magellan missions has shown a geologically complex and diverse surface topography. Most of the planet consists of gently rolling plains, although there are several lowland areas and two continent-sized highlands: Ishtar Terra and Aphrodite Terra. The Maxwell Montes are a huge mountain chain on eastern Ishtar that rise more than 10 km (6 miles) above the average Venusian surface elevation. Other surface features include impact craters, rift valleys, novae (radiating patterns of faults and fractures atop a topographic rise), coronae (oval patterns of faults, fractures, and ridges, with a raised outer rim and a depressed interior), tesserae (large, elevated regions composed of rugged, complex terrain), shield volcanoes, and long, sinuous lava-flow channels. Many of these features are associated with volcanic activity. Overall, the Venusian topography does not suggest plate-tectonic activity of the kind thought to have shaped much of the Earth's surface. However, there is strong evidence that Venus, like the Earth, is presently a geologically active body. Unlike most of the other planets, Venus rotates in retrograde (from east to west), slowly turning on its axis once every 243 days. The axis itself is tilted only 3 from the plane of the planet's orbit around the Sun. These facts indicate that seasonal changes must be very slight. Solar heating and the slow rotation of Venus result in an atmospheric circulation in which air rises owing to heating at the equator, migrates sluggishly at high altitudes to the poles, descends there as it cools, and then returns toward the equator along the surface. Such a simple pattern would be completely unstable on the rapidly rotating Earth. Even on Venus, remarkable instabilities appear in the form of intense wave patterns and modify the simple picture. Also, the rotation rate of the atmosphere increases with height from the surface to the upper atmosphere. Thus, features in the clouds have been observed to travel completely around Venus' equator in about four Earth days. second planet from the Sun and the planet whose orbit is closest to that of the Earth. Enhanced photograph of Venus, as obtained in February 1979 in ultraviolet light by the Pioneer When visible, Venus, designated in astronomy, is the brightest planet in the sky. Viewed through a telescope, it presents a brilliant, yellow-white, essentially featureless face to the observer. The obscured appearance results because the surface of the planet is hidden from sight by a continuous and permanent cover of clouds. Features in the clouds are difficult to discern and become evident only when the planet is viewed in ultraviolet light. When observed at ultraviolet wavelengths, the clouds of Venus exhibit distinctive dark markings, with complex swirling patterns near the equator and global-scale bright and dark bands that are V-shaped and open to the west. Venus has a mean distance from the Sun of 108 million km. Its distance from the Earth varies from a minimum of about 42 million km to a maximum of about 257 million km. Additional reading The definitive collection of papers summarizing the understanding of Venus that existed prior to the Veneras 15 and 16 and Magellan missions is D.M. Hunten et al. (eds.), Venus (1983); the material on the Venusian surface is now largely out of date, but the many articles dealing with the planet's atmosphere and magnetosphere are still current. A more recent, though still pre-Magellan, overview of the state of Venus' surface is given by Alexander T. Basilevsky and James W. Head III The Geology of Venus, Annual Review of Earth and Planetary Sciences, 16:295317 (1988). Popular-level treatments of Venus, also pre-Magellan, are provided by Garry E. Hunt and Patrick Moore, The Planet Venus (1982); and Eric Burgess, Venus: An Errant Twin (1985). An excellent collection of papers by Soviet scientists in English on Venus is V.L. Barsukov et al. (eds.), Venus Geology, Geochemistry, and Geophysics (1992). The initial results of major spacecraft missions to Venus are reported in several journals: on Pioneer Venus, Journal of Geophysical Research, 85:75738337 (1980); V.L. Barsukov et al., The Geology and Geomorphology of the Venus Surface as Revealed by the Radar Images Obtained by Veneras 15 and 16, Journal of Geophysical Research, pt. B, Solid Earth and Planets, 91(B4):D378D398 (March 30, 1986); a set of 9 articles on the Magellan spacecraft at Venus in Science, 252(5003):247312 (April 12, 1991); and two issues of Journal of Geophysical Research, pt. E, Planets, vol. 97, devoted to detailed Magellan mission results: no. 8 (Aug. 25, 1992); and no. 10 (Oct. 25, 1992). Steven W. Squyres