Venus

Venus

Venus, second planet from the Sun and sixth in the solar system in size and mass. No planet approaches closer to Earth than Venus; at its nearest it is the closest large body to Earth other than the Moon. Because Venus’s orbit is nearer the Sun than Earth’s, the planet is always roughly in the same direction in the sky as the Sun and can be seen only in the hours near sunrise or sunset. When it is visible, it is the most brilliant planet in the sky. Venus is designated by the symbol ♀.

colour-coded global image of the topography of Venus

Venus was one of the five planets—along with Mercury, Mars, Jupiter, and Saturn—known in ancient times, and its motions were observed and studied for centuries prior to the invention of advanced astronomical instruments. Its appearances were recorded by the Babylonians, who equated it with the goddess Ishtar, about 3000 bce, and it also is mentioned prominently in the astronomical records of other ancient civilizations, including those of China, Central America, Egypt, and Greece. Like the planet Mercury, Venus was known in ancient Greece by two different names—Phosphorus (see Lucifer) when it appeared as a morning star and Hesperus when it appeared as an evening star. Its modern name comes from the Roman goddess of love and beauty (the Greek equivalent being Aphrodite), perhaps because of the planet’s luminous jewel-like appearance.

Venus has been called Earth’s twin because of the similarities in their masses, sizes, and densities and their similar relative locations in the solar system. Because they presumably formed in the solar nebula from the same kind of rocky planetary building blocks, they also likely have similar overall chemical compositions. Early telescopic observations of the planet revealed a perpetual veil of clouds, suggestive of a substantial atmosphere and leading to popular speculation that Venus was a warm, wet world, perhaps similar to Earth during its prehistoric age of swampy carboniferous forests and abundant life. Scientists now know, however, that Venus and Earth have evolved surface conditions that could hardly be more different. Venus is extremely hot, dry, and in other ways so forbidding that it is improbable that life as it is understood on Earth could have developed there. One of scientists’ major goals in studying Venus is to understand how its harsh conditions came about, which may hold important lessons about the causes of environmental change on Earth.