Venus is the second planet from the Sun. Similar in size and mass to Earth, Venus has no liquid water, and its atmosphere is far thicker and denser than that of any other rocky body in the Solar System. The atmosphere is composed mostly of carbon dioxide and has a thick cloud layer of sulfuric acid that spans the whole planet. At the mean surface level, the atmosphere reaches a temperature of 737 K (464 °C; 867 °F), making it the hottest planet in the solar system and also a pressure 92 times greater than Earth's at sea level, turning the lowest layer of the atmosphere into a supercritical fluid. From Earth, Venus is visible as a star-like point of light, appearing brighter than any other natural point of light in the sky, as either the brightest "morning star" or "evening star". It was also given the poetic name Ēarendel in Old English, meaning "ray of light" along with the two previous epithets. Venus orbits closer to the Sun than the Earth does. The orbits of Venus and Earth make the two planets approach each other in synodic periods of 1.6 years. In the course of this, Venus comes closer to Earth than any other planet. In interplanetary spaceflight from Earth, Venus is frequently used as a waypoint for gravity assists, offering a more economical route allowing spacecraft to save fuel. Venus has no moons and a very slow retrograde rotation about its axis, a result of competing forces of solar tidal locking and differential heating of Venus's massive atmosphere. As a result, a Venusian day is 116.75 Earth days long, about half a Venusian solar year, which is 224.7 Earth days long. Venus has a weak magnetosphere; lacking an internal dynamo, it is induced by the solar wind interacting with the atmosphere. Internally, Venus has a core, a mantle, and a crust. Internal heat escapes through active volcanism, resulting in resurfacing, instead of plate tectonics. Venus may have had liquid surface water early in its history with a habitable environment, before a runaway greenhouse effect evaporated any water and turned Venus into its present state. There are atmospheric conditions at cloud layer altitudes that are the most similar ones to Earth in the Solar System and have been identified as possibly favourable for life on Venus, with potential biomarkers found in 2020, spurring new research and missions to Venus. Throughout history humans across the globe have observed Venus and it has acquired particular importance in many cultures. With telescopes, the phases of Venus became discernible and, by 1613, were presented as decisive evidence disproving the then-dominant geocentric model and supporting the heliocentric model. Venus was visited for the first time in 1961 by Venera 1, which flew past the planet, achieving the first interplanetary spaceflight. The first data from Venus were returned during the second interplanetary mission, Mariner 2, in 1962. In 1967, the first interplanetary impactor, Venera 4, reached Venus, followed by the lander Venera 7 in 1970, with the first images captured by Mariner 10 during its 1974 gravity assist en route to Mercury. As of 2025, Solar Orbiter is on its way to fly by Venus in 2026, and the next mission planned to launch to Venus is the Venus Life Finder, scheduled for 2026 as well.
Physical characteristics
Venus is one of the four terrestrial planets in the Solar System, meaning that it is a rocky body like Earth. It is similar to Earth in size and mass and is often described as Earth's "sister" or "twin". Venus is very close to spherical due to its slow rotation. It has a diameter of 12,103.6 km (7,520.8 mi)—only 638.4 km (396.7 mi) less than Earth's—and its mass is 81.5% of Earth's, making it the third-smallest planet in the Solar System. Conditions on the surface of Venus differ radically from those on Earth because its dense atmosphere is 96.5% carbon dioxide, causing an intense greenhouse effect, with most of the remaining 3.5% being nitrogen. The surface pressure is 9.3 megapascals (93 bars), and the average surface temperature is 737 K (464 °C; 867 °F), above the critical points of both major constituents and making the surface atmosphere a supercritical fluid of mainly supercritical carbon dioxide and some supercritical nitrogen.
Natural history
Formation
The rocky terrestrial planets including Venus are thought to have formed in five stages: dust settling, planetesimal formation, planetary embryos, giant impacts, and finally formation of atmospheres. Limited measurements from Venus have prevented a more detailed analysis of the formation timeline. Venus may have had active plate tectonics during its first billion years, yielding volcanic outgassing leading to the current amount of nitrogen in its atmosphere. As a result, may have had a more habitable environment, possibly one capable of sustaining life. Venus has gained interest as a case for research into the development of Earth-like planets and their habitability. However, analysis of gas decomposition in its current atmosphere shows that Venus's volcanic activity yields too little water to create oceans, indicating that Venus has likely been a inhospitable world for its entire history.
Future Venus is expected to be destroyed, along with Mercury, and possibly the Earth and the Moon, when the Sun becomes a red giant in approximately seven or eight billion years.
Geography
The Venusian surface was a subject of speculation until some of its secrets were revealed by probes in the 20th century. Venera landers in 1975 and 1982 returned images of a surface covered in sediment and relatively angular rocks. The surface was mapped in detail by Magellan in 1990–91. There is evidence of extensive volcanism, and variations in the atmospheric sulphur dioxide may indicate that there are active volcanoes.
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