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

colour-coded global image of the topography of Venus

Colour-coded global image of the topography of Venus below its obscuring clouds, based on radar data from the Magellan spacecraft with supplemental data from Venera and Pioneer Venus missions and Earth-based radar studies. Violet hues mark the lowest elevations; red and pink hues, the highest ones. The hemisphere shown is centred on 0° longitude; north is at the top. The prominent red and pink region in the far north is the planet's highest terrain, Maxwell Montes.

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.

View of the Andromeda Galaxy (Messier 31, M31).

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Planetary data for Venus

*Time required for the planet to return to the same position in the sky relative to the Sun as seen from Earth.

mean distance from Sun= 108,209,475 km (0.72 AU)

eccentricity of orbit= 0.007

inclination of orbit to ecliptic= 3.4°

Venusian year (sidereal period of revolution)= 224.7 Earth days

maximum visual magnitude= −4.6

mean synodic period*= 584 Earth days

mean orbital velocity= 35 km/sec

radius (mean)= 6,051.8 km

surface area= 4.6 × 108 km2

mass= 4.87 × 1024 kg

mean density= 5.24 g/cm3

mean surface gravity= 887 cm/sec2

escape velocity= 10.4 km/sec

rotation period (Venusian sidereal day)= 243 Earth days (retrograde)

Venusian mean solar day= 116.8 Earth days

inclination of equator to orbit= 177.3°

atmospheric composition carbon dioxide, 96%; molecular nitrogen, 3.5%; water, 0.02%; trace quantities of carbon monoxide, molecular oxygen, sulfur dioxide, hydrogen chloride, and other gases

mean surface temperature= 737 K (867 °F, 464 °C)

surface pressure at mean radius= 95 bars

mean visible cloud temperature= about 230 K (−46 °F, −43 °C)

number of known moons= none .