Introduction :

Venus is the second planet from the Sun. It is named after the Roman goddess of love and beauty. As the brightest natural object in Earth's night sky after the Moon, Venus can cast shadows and can be, on rare occasion, visible to the naked eye in broad daylight. Venus lies within Earth's orbit, and so never appears to venture far from the Sun, either setting in the west just after dusk or rising in the east a little while before dawn. Venus orbits the Sun every 224.7 Earth days. With a rotation period of 243 Earth days, it takes longer to rotate about its axis than any other planet in the Solar System by far, and does so in the opposite direction to all but Uranus (meaning the Sun rises in the west and sets in the east). Venus does not have any moons, a distinction it shares only with Mercury among the planets in the Solar System.

Venus is a terrestrial planet and is sometimes called Earth's "sister planet" because of their similar size, mass, proximity to the Sun, and bulk composition. It is radically different from Earth in other respects. It has the densest atmosphere of the four terrestrial planets, consisting of more than 96% carbon dioxide. The atmospheric pressure at the planet's surface is about 92 times the sea level pressure of Earth, or roughly the pressure at 900 m (3,000 ft) underwater on Earth. Venus has, by far, the hottest surface of any planet in the Solar System, with a mean temperature of 737 K (464 °C; 867 °F), even though Mercury is closer to the Sun. Venus is shrouded by an opaque layer of highly reflective clouds of sulfuric acid, preventing its surface from being seen from space in visible light. It may have had water oceans in the past, but these would have vaporized as the temperature rose due to a runaway greenhouse effect. The water has probably photodissociated, and the free hydrogen has been swept into interplanetary space by the solar wind because of the lack of a planetary magnetic field. Venus' surface is a dry desertscape interspersed with slab-like rocks and is periodically resurfaced by volcanism.

As one of the brightest objects in the sky, Venus has been a major fixture in human culture for as long as records have existed. It has been made sacred to gods of many cultures, and has been a prime inspiration for writers and poets as the "morning star" and "evening star". Venus was the first planet to have its motions plotted across the sky, as early as the second millennium BC.

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Internal Structure of Venus

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Venus Atmosphere

Size and Distance :

With a radius of 3,760 miles (6,052 kilometers), Venus is roughly the same size as Earth — just slightly smaller.

From an average distance of 67 million miles (108 million kilometers), Venus is 0.7 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. It takes sunlight 6 minutes to travel from the Sun to Venus.

Orbit and Rotation :

Venus' rotation and orbit are unusual in several ways. Venus is one of just two planets that rotate from east to west. Only Venus and Uranus have this "backwards" rotation. It completes one rotation in 243 Earth days — the longest day of any planet in our solar system, even longer than a whole year on Venus. But the Sun doesn't rise and set each "day" on Venus like it does on most other planets. On Venus, one day-night cycle takes 117 Earth days because Venus rotates in the direction opposite of its orbital revolution around the Sun.

Venus makes a complete orbit around the Sun (a year in Venusian time) in 225 Earth days or slightly less than two Venusian day-night cycles. Its orbit around the Sun is the most circular of any planet — nearly a perfect circle. Other planet's orbits are more elliptical, or oval-shaped.

With an axial tilt of just 3 degrees, Venus spins nearly upright, and so does not experience noticeable seasons.

Internal structure :

Venus, represented without its atmosphere and showing its internal structure. Based on a false-color global radar view from Magellan.

Without seismic data or knowledge of its moment of inertia, little direct information is available about the internal structure and geochemistry of Venus. The similarity in size and density between Venus and Earth suggests they share a similar internal structure: a core, mantle, and crust. Like that of Earth, the Venusian core is at least partially liquid because the two planets have been cooling at about the same rate The slightly smaller size of Venus means pressures are 24% lower in its deep interior than Earth's. 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 results in reduced heat loss from the planet, preventing it from cooling and providing a likely explanation for its lack of an internally generated magnetic field. Instead, Venus may lose its internal heat in periodic major resurfacing events.

Atmosphere and climate :

Cloud structure in the Venusian atmosphere in 2018, revealed by observations in the two ultraviolet bands by Akatsuki

Planet Venus - viewed by the Parker Solar Probe (July 2020)

Venus has an extremely dense atmosphere composed of 96.5% carbon dioxide, 3.5% nitrogen - both being supercritical fluids at surface, and traces of other gases including sulfur dioxide. The mass of its atmosphere is 93 times that of Earth's, whereas the pressure at its surface is about 92 times that at Earth's—a pressure equivalent to that at a depth of nearly 1 km (5⁄8 mi) under Earth's oceans. The density at the surface is 65 kg/m3, 6.5% that of water or 50 times as dense as Earth's atmosphere at 293 K (20 °C; 68 °F) at sea level. The CO2-rich atmosphere generates the strongest greenhouse effect in the Solar System, creating surface temperatures of at least 735 K (462 °C; 864 °F). This makes Venus' surface hotter than Mercury's, which has a minimum surface temperature of 53 K (−220 °C; −364 °F) and maximum surface temperature of 700 K (427 °C; 801 °F), even though Venus is nearly twice Mercury's distance from the Sun and thus receives only 25% of Mercury's solar irradiance. This temperature is higher than that used for sterilization.

Venus' atmosphere is extremely enriched of primordial noble gases compared to that of Earth. This enrichment indicates an early divergence from Earth in evolution. An unusually large comet impact or accretion of a more massive primary atmosphere from solar nebula have been proposed to explain the enrichment. However, the atmosphere is also depleted of radiogenic argon, a proxy to mantle degassing, suggesting an early shutdown of major magmatism.

Facts about Venus :

  • Venus does not have any moons or rings.

  • Venus is nearly as big as the Earth with a diameter of 12,104 km.

  • Venus is thought to be made up of a central iron core, rocky mantle and silicate crust.

  • A day on the surface of Venus (solar day) would appear to take 117 Earth days.

  • A year on Venus takes 225 Earth days.​

  • The surface temperature on Venus can reach 471 °C.

Some More Facts :

  • A day on Venus lasts longer than a year. 
    It takes 243 Earth days to rotate once on its axis (sidereal day). The planet’s orbit around the Sun takes 225 Earth days, compared to the Earth’s 365. A day on the surface of Venus (solar day) takes 117 Earth days.

  • Venus rotates in the opposite direction to most other planets. 
    This means that Venus is rotating in the opposite direction to the Sun, this is also known as a retrograde rotation. One possible reason for this might be a collision with an asteroid or other object.

  • Venus is the second brightest object in the night sky. 
    Only the Moon is brighter. With a magnitude of between -3.8 to -4.6 Venus is so bright it can be seen during daytime on a clear day.

 

  • Atmospheric pressure on Venus is 92 times greater than the Earth’s. 
    Due to this crushing small asteroids when they enter its atmosphere Venus has not small craters. The pressure felt on Venus’ surface is equivalent to that deep beneath the sea on Earth.

  • Venus is often called the Earth’s sister planet. 

The Earth and Venus are very similar in size with only a 638 km difference in diameter and Venus having 81.5% of the Earth’s mass. Both also have a central core,    a molten mantle and a crust.

  • The same side of Venus always faces the Earth when at their closest.
    It is possible this is due to the Earth’s gravational influence.

  • Venus is also known as the Morning Star and the Evening Star. 
    Early civilisations thought Venus was two different bodies. These were called Phosphorus and Hesperus by the Greeks, and Lucifer and Vesper by the Romans. When Venus’ orbit around the Sun overtakes Earth’s orbit, it changes from being visible after sunset to being visible before sunrise. Mayan astronomers made detailed observations of Venus as early as 650 AD.

  • Venus is the hottest planet in our solar system. 
    The average surface temperature is 462 °C, and because Venus does not tilt on its axis, there is no seasonal variation. The dense atmosphere of around 96.5 percent carbon dioxide traps heat and causes a greenhouse effect.

  • A detailed study of Venus finished in 2015. 
    In 2006, the Venus Express space craft was sent into orbit around Venus by the European Space Agency. Originally planned to last five hundred Earth days, the mission was extended several times before the craft was deorbited in 2015. More than 1,000 volcanoes or volcanic centres larger than 20 km have been found on the surface of Venus.

  • The Russians sent the first mission to Venus. 
    The Venera 1 space probe was launched in 1961, but lost contact with base. The USA also lost their first probe to Venus, Mariner 1, although Mariner 2 was able to take measurements of the planet in 1962. The Soviet Union’s Venera 3 was the first man-made craft to land on Venus in 1966.

 

  • At one point it was thought Venus might be a tropical paradise. 

The dense clouds of sulphuric acid surrounding Venus make it impossible to view its surface from outside its atmosphere. It was only when radio mapping was d        developed in the 1960s that scientists were able to observe the extreme temperatures and hostile environment.

Source: NASA Visualization Technology Applications and Development (VTAD)

3 D Model of Venus

Source Credits : NASA, Wikipedia and Space Facts.