Illuminated crescent Moon and Venus.
Stephen Rahn (Public domain)

Solar System Summer: Venus

  • 26th Jul 2023
  • Author: Elspeth Lewis - Education Presenter
  1. Venus surface taken using RADAR imagery by the spacecraft Magellan.
    NASA/PlanetUser CC BY-SA 4.0

    Because of its similar size to Earth, Venus is sometimes known as Earth’s twin, but with an average surface temperature of 464 degrees Celsius, it is certainly an evil twin!

Early observations

Named after the roman goddess of love and beauty, Venus is the third brightest object in the sky after the Sun and the Moon. One of the earliest surviving astronomical documents is a 21-year record of Venus’ appearances from 1600BC. Venus is usually either visible for a few hours after sunset, or in the morning just before sunrise, giving rise to the names morning star and evening star. Some ancient cultures believed that Venus was in fact two separate objects. The Greek philosopher Pythagoras realised that they were the same object in about 500BC.

Galileo started studying Venus with a telescope in 1610 and found that the planet appeared to go through phases much like the Moon. These phases helped convince Galileo and other scientists that the planets orbited the Sun and not the Earth.

A diagram showing the phases of Venus as seen from Earth.
NASA

Surface features

Although famed for its heat and atmosphere, Venus has many interesting surface features including many volcanoes. Some of these are classed as ‘pancake domes’ which have flat tops and very steep sides, probably formed by very viscous lava and the high atmospheric pressure.

Many of the features on Venus are named after real and mythical women. Venus also has mountains, including its tallest, Skadi Mons which is 11,520 metres above the surface of Venus making it over 2500 metres taller than Mount Everest.


Venus does have craters on its surface, but much fewer than Mercury or Mars, meaning that Venus’ surface is relatively young.

Volcanic domes also known as ‘pancake domes’. The cracks are formed from cooling lava. There is also an impact crater in the top right corner. The image is from the Magellan mission.
NASA/JPL

Fact File

  1. Venus photographed by Mariner 10 as it performed a flyby on its way to Mercury.
    NASA/JPL-Caltech

    Size: Venus has a diameter of 12,104 kilometres across, about 95% of Earth’s. 

    Gravity: The density of Venus is about 95% that of Earth meaning the gravity of Venus is about 90% of Earth’s (due to it's slightly smaller size).

  2. The Solar System including the planets formed from a collapsing cloud of gas and dust called a nebula.
    NASA

    Age: Like the rest of the planets, Venus is about 4.5 billion years old.

    Distance: On average, Venus is 108 million kilometres, or 0.7AU (astronomical units) from the Sun, which is just over two thirds closer to the Sun than Earth.

  3. A sequence of images composited together to show path of Venus across the Sun.
    SDO/NASA

    Transits: As seen from Earth as a small black dot moving across the face of the Sun, the transits of Venus during the eighteenth and nineteenth centuries allowed scientists for the first time to accurately determine a value for the distance between Earth and the Sun, called the 'Astronomical Unit' (AU). The last transit of Venus happened in June 2012 and the next one won't take place until 2117.

  4. Venus size to scale compared to the other terrestrial planets in our Solar System.
    NASA/JHUAPL/Carniegie Institution of Washington/Apollo 17 crew/ESA/MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA

    Composition/Structure: Venus is one of 4 rocky planets in our Solar System. Like Earth it has an iron core covered by a mantle made of hot rock, with a rocky crust on the surface. Scientists think in Venus’ early history there was potentially water on the surface, however this has since evaporated and vented into space.

    Atmosphere: Venus has a very thick atmosphere which is mainly made up of carbon dioxide, with clouds of sulfuric acid. This atmosphere is about 90 times heavier than Earth’s atmosphere, causing an immense pressure which has crushed any missions that have landed on the surface.

  5. Composite map of the complete radar image collection obtained by the Magellan mission.
    NASA/JPL

    Temperature: Venus is the hottest planet in our Solar System, despite Mercury being closer to the Sun. The average surface temperature of Venus is 464°C compared to Mercury’s highest daytime temperature of around 430°C. The carbon dioxide in the atmosphere traps in heat causing a runaway greenhouse effect.

    Rotation: A full rotation on Venus lasts 243 Earth days which is longer than a year on Venus! However, the amount of time it takes for the Sun to appear back in the same place in the sky is only 117 Earth days. Venus and Uranus rotate clockwise unlike all the other planets that rotate anticlockwise.

  6. Venus orbits closer to the sun than Earth. At that closer distance, solar storms may strike the planet so powerfully that the lack of a magnetic field on Venus might not prevent Venus from having aurorae.
    C. Carreau/ESA

    Speed: Venus orbits at 35 km/s, about 5km/s faster than Earth, which means that it takes Venus 225 Earth days to orbit the Sun.

    Moons: Venus has no moons.

    Auroras: Scientists think Venus could potentially have aurora caused by the Sun’s magnetic field stretching out to the planet.

    Rings: Venus has no rings.

    Discovered by: Venus was known to ancient people.

Missions to Venus

There have been 23 successful missions to Venus, 16 failed missions and 7 missions that have performed a flyby of Venus on their way to study another celestial object. Some of the more notable are listed below. 

Mariner 2 – NASA - launched 1962 – flew past Venus on December 14th, 1962, and it was the first successful mission to another planet. There had been 4 previous attempted missions to Venus, however 3 had unsuccessful launches, and although Venera 1 managed to perform a flyby, it had lost communications and so no data was returned. Mariner 2 studied the atmosphere and temperature, finding that Venus was much inhospitable than originally imagined.  

Venera 3- Soviet Union- launched 1966 – became the first space craft to crash on the surface of another planet, but no planetary data was returned. 

Venera 4- Soviet Union - launched 1967- was the first probe to transmit data from the atmosphere of another planet and found that the atmospheric composition was between 90 and 95% carbon dioxide. 

Venera 7- Soviet Union- launched 1970 – became the first spacecraft to return data after landing on another planet. It transmitted signals after landing for 23 minutes.

Venera 9 – Soviet Union- launched 1975 –was the first spacecraft to send back images of the surface of another planet.

Pioneer Venus 1- NASA- launched 1978- used radar to map the surface of Venus and worked for 14 years before burning up in the atmosphere. 

Venera 13 - Soviet Union- launched 1981- sent back audio of the Venusian wind, which was the first audio from another planet. Venera 13 also took the first colour picture from the surface of Venus. Initially designed to work for about 32 minutes,

Magellan- NASA- launched 1989- an orbiter that imaged all of Venus’ surface using RADAR. Finding evidence of volcanism and lava channels, as well as tectonic movement.

Venus Express – ESA – launched 2005 –the first European mission to Venus and its aims were to study the clouds and atmosphere from orbit. It studied Venus for about 9 years.

Akatsuki- Japan- Launched 2010- aimed to study the weather patterns, confirm the presences of lightning, and look for any signs of active volcanoes. The mission initially failed to successfully orbit the planet in 2010, but in 2015 was successfully put in orbit. It is the only Venus mission that is currently operational.

An illustration of Mariner 2.
NASA
Model of Akatsuki.
江戸村のとくぞう CC by SA 4.0

Full image credits / references

(Banner image) 4% Illuminated Crescent Moon And Venus. Credit: Stephen Rahn (public domain)

(1) Venus surface taken using RADAR imagery by the spacecraft Magellan. Credit: NASA/PlanetUser CC BY-SA 4.0 (https://en.m.wikipedia.org/wiki/File:Venus_Rotation_Movie.gif)

(2) A diagram showing the phases of Venus as seen from Earth. Credit: NASA

(3) Volcanic domes also known as ‘pancake domes’. The cracks are formed from cooling lava. There is also an impact crater in the top right corner. Credit: NASA/JPL

(4a) Venus photographed by Mariner 10 as it performed a flyby on its way to Mercury. Credit: NASA/JPL-Caltech

(4b) The Solar System including the planets formed from a collapsing cloud of gas and dust called a nebula. Credit: NASA

(4c) A sequence of images composited together to show path of Venus across the Sun. Credit: SDO/NASA

(4d) Venus size to scale compared to the other terrestrial planets in our Solar System. Credit: NASA/JHUAPL/Carniegie Institution of Washington/Apollo 17 crew/ESA/MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA

(4e) Composite map of the complete radar image collection obtained by the Magellan mission. Credit: NASA/JPL

(4f) Venus' atmosphere interacting with the solar wind. Credit: C. Carreau/ESA

(5a) An illustration of Mariner 2. Credit: NASA

(5b) Model of Akatsuki. Credit: 江戸村のとくぞう CC by SA 4.0 (https://commons.wikimedia.org/wiki/File:Akatsuki-1.jpg)