Venus

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.

[40] The southern continent is called Aphrodite Terra, after the Greek mythological goddess of love, and is the larger of the two highland regions at roughly the size of South America.

[50][51] The stratigraphically oldest tessera terrains have consistently lower thermal emissivity than the surrounding basaltic plains measured by Venus Express and Magellan, indicating a different, possibly a more felsic, mineral assemblage.

[61][62] This massive volcanic activity is fuelled by a hot interior, which models say could be explained by energetic collisions when the planet was young, as well as radioactive decay as in the case of the earth.

Impacts would have had significantly higher velocity than on Earth, both because Venus moves faster due to its closer proximity to the Sun and because high-eccentricity objects colliding with the planet would have high speeds.

[63] In 2008 and 2009, the first direct evidence for ongoing volcanism was observed by Venus Express, in the form of four transient localized infrared hot spots within the rift zone Ganis Chasma,[64][note 1] near the shield volcano Maat Mons.

The number of craters, together with their well-preserved condition, indicates the planet underwent a global resurfacing event 300–600 million years ago,[44][45] followed by a decay in volcanism.

[12][76] The principal difference between the two planets is the lack of evidence for plate tectonics on Venus, possibly because its crust is too strong to subduct without water to make it less viscous.

This erosion process results in a steady loss of low-mass hydrogen, helium, and oxygen ions, whereas higher-mass molecules, such as carbon dioxide, are more likely to be retained.

[4] Because of its runaway greenhouse effect, Venus has been identified by scientists such as Carl Sagan as a warning and research object linked to climate change on Earth.

[98][99] Studies have suggested that billions of years ago, the atmosphere of Venus may have been much more like the one surrounding the early Earth, and there may have been substantial quantities of liquid water on the surface.

[100][101][102] After a period of 600 million to several billion years,[103] the rising luminosity of the Sun and possibly large volcanic resurfacing caused the evaporation of the original water.

[133] Although Venus has no seasons, in 2019 astronomers identified a cyclical variation in sunlight absorption by the atmosphere, possibly caused by opaque, absorbing particles suspended in the upper clouds.

The variation causes observed changes in the speed of Venus's zonal winds and appears to rise and fall in time with the Sun's 11-year sunspot cycle.

Alex Alemi's and David Stevenson's 2006 study of models of the early Solar System at the California Institute of Technology shows Venus likely had at least one moon created by a huge impact event billions of years ago.

[165] About 10 million years later, according to the study, another impact reversed the planet's spin direction and the resulting tidal deceleration caused the Venusian moon gradually to spiral inward until it collided with Venus.

[185] When Venus is sufficiently bright with enough angular distance from the sun, it is easily observed in a clear daytime sky with the naked eye, though most people do not know to look for it.

[196] Nonetheless, a cylinder seal from the Jemdet Nasr period and the Venus tablet of Ammisaduqa from the First Babylonian dynasty indicate that the ancient Sumerians already knew that the morning and evening stars were the same celestial object.

[207][note 4] When the Italian physicist Galileo Galilei first observed the planet with a telescope in the early 17th century, he found it showed phases like the Moon, varying from crescent to gibbous to full and vice versa.

This could be possible only if Venus orbited the Sun, and this was among the first observations to clearly contradict the Ptolemaic geocentric model that the Solar System was concentric and centred on Earth.

[210][211] The 1639 transit of Venus was accurately predicted by Jeremiah Horrocks and observed by him and his friend, William Crabtree, at each of their respective homes, on 4 December 1639 (24 November under the Julian calendar in use at that time).

Later, American astronomer Chester Smith Lyman observed a complete ring around the dark side of the planet when it was at inferior conjunction, providing further evidence for an atmosphere.

[223] Venera 3, launched in 1966, became humanity's first probe and lander to reach and impact another celestial body other than the Moon, but could not return data as it crashed into the surface of Venus.

[226] In 1974, Mariner 10 swung by Venus to bend its path towards Mercury and took ultraviolet photographs of the clouds, revealing the extraordinarily high wind speeds in the Venusian atmosphere.

[236][237][238] Such speculations go back to 1967, when Carl Sagan and Harold J. Morowitz suggested in a Nature article that tiny objects detected in Venus's clouds might be organisms similar to Earth's bacteria (which are of approximately the same size): In August 2019, astronomers led by Yeon Joo Lee reported that long-term pattern of absorbance and albedo changes in the atmosphere of the planet Venus caused by "unknown absorbers", which may be chemicals or even large colonies of microorganisms high up in the atmosphere of the planet, affect the climate.

[240] In September 2020, a team of astronomers led by Jane Greaves from Cardiff University announced the likely detection of phosphine, a gas not known to be produced by any known chemical processes on the Venusian surface or atmosphere, in the upper levels of the planet's clouds.

The discovery prompted NASA administrator Jim Bridenstine to publicly call for a new focus on the study of Venus, describing the phosphine find as "the most significant development yet in building the case for life off Earth".

Though by the Roman era they were recognized as one celestial object, known as "the star of Venus", the traditional two Greek names continued to be used, though usually translated to Latin as Lūcifer and Vesper.

Modern Chinese, Japanese, Korean and Vietnamese cultures refer to the planet literally as the "metal star" (金星), based on the Five elements.

The impenetrable Venusian cloud cover gave science fiction writers free rein to speculate on conditions at its surface; all the more so when early observations showed that not only was it similar in size to Earth, it possessed a substantial atmosphere.

Venus to scale among the Inner Solar System planetary-mass objects , arranged by the order of their orbits outward from the Sun (from left: Mercury , Venus, Earth , the Moon , Mars and Ceres )
Color-coded elevation map, showing the elevated terrae "continents" in yellow and minor features of Venus .
Surface panorama taken by Venera 13
Radar mosaic of two 65 km (40 mi) wide (and less than 1 km (0.62 mi) high) pancake domes in Venus's Eistla region
The plains of Venus
Impact craters on the surface of Venus (false-colour image reconstructed from radar data)
Spherical cross-section of Venus showing the different layers
The differentiated structure of Venus
The atmosphere of Venus appears darker and lined with shadows. The shadows trace the prevailing wind direction.
Cloud structure of the Venusian atmosphere, made visible through ultraviolet imaging
Types of cloud layers, as well as temperature and pressure change by altitude in the atmosphere
Mars circling the Sun further and slower than Earth
Venus is the second planet from the Sun, making a full orbit in about 224 days
Venus and its rotation in respect to its revolution.
A complex, spiral, floral pattern with five loops encircling the middle
Earth is positioned at the centre of the diagram, and the curve represents the direction and distance of Venus as a function of time.
A photograph of the night sky taken from the seashore. A glimmer of sunlight is on the horizon. There are many stars visible. Venus is at the centre, much brighter than any of the stars, and its light can be seen reflected in the ocean.
Venus, pictured centre-right, is always brighter than all other planets or stars at their maximal brightness, as seen from Earth. Jupiter is visible at the top of the image.
Diagram illustrating the phases of Venus
The phases of Venus and evolution of its apparent diameter
venus next to a crescent moon in the blue daytime sky
Venus is often visible to the naked eye in daytime, as seen just prior to the lunar occultation of 7 December 2015
White disk with a small black dot projected on a screen
2012 transit of Venus , projected to a white card by a telescope
Oldest known recording of Venus positions, of the Babylonian Venus tablet of Ammisaduqa (1600 BC).
The Pre-Columbian Mayan Dresden Codex , which calculates appearances of Venus.
A hand-drawn sequence of images showing Venus passing over the edge of the Sun's disk, leaving an illusory drop of shadow behind
The " black drop effect " as recorded during the 1769 transit
First view and first clear 180-degree panorama of Venus's surface as well as any other planet than Earth (1975, Soviet Venera 9 lander). Black-and-white image of barren, black, slate-like rocks against a flat sky. The ground and the probe are the focus.
WISPR of the Parker Solar Probe took this visible light footage of the nightside in 2021, showing the hot faintly glowing surface, and its Aphrodite Terra as large dark patch, through the clouds, which prohibit such observations on the dayside when they are illuminated. [ 233 ] [ 234 ]
Global topographic map of Venus, with all probe landings marked
Artist's rendering of a NASA High Altitude Venus Operational Concept (HAVOC) crewed floating outpost on Venus
The eight-pointed star a symbol used in some cultures for Venus, and sometimes combined into a star and crescent arrangement. Here the eight pointed star is the Star of Ishtar , the Babylonian Venus goddess, alongside the solar disk of her brother Shamash and the crescent moon of their father Sin on a boundary stone of Meli-Shipak II , dating to the twelfth century BC.
Venus is portrayed just to the right of the large cypress tree in Vincent van Gogh 's 1889 painting The Starry Night . [ 282 ] [ 283 ]
The Sun, the planets, their moons, and several trans-Neptunian objects The Sun Mercury Venus The Moon Earth Mars Phobos and Deimos Ceres The main asteroid belt Jupiter Moons of Jupiter Rings of Jupiter Saturn Moons of Saturn Rings of Saturn Uranus Moons of Uranus Rings of Uranus Neptune Moons of Neptune Rings of Neptune Pluto Moons of Pluto Haumea Moons of Haumea Makemake S/2015 (136472) 1 The Kuiper Belt Eris Dysnomia The Scattered Disc The Hills Cloud The Oort Cloud