Science Library - free educational site


Venus has an orbit, like Mercury, inside Earth's orbit. It is often called Earth's twin, but conditions on its surface are far from hospitable. It spins in the opposite direction to Earth and the other planets, with a day longer than its year!

    Vital statistics:
  • Mass: 4.87 x 1024 kg = 0.815 Earths
  • Diameter: 12104 km = 0.95 Earth's
  • Density: 5.24 tonnes/m3 = 0.950 Earth's density
  • Surface gravity: 8.9 m/s2 = 0.90g
  • Distance from Sun: 107.5 - 108.9 million km (108.2 Mkm semi-major axis) = 0.72 AU (Earth-Sun distances)
  • Period of orbit: 224.7 Earth days
  • Period of rotation: -243 Earth days (retrograde)
  • No. of moons: 0
  • Atmosphere: 92 bar/9200 kPa (90.8 times denser than Earth's atmosphere) 96.5% CO2, 3.5% nitrogen, and very small amounts of other gases, including SO2, argon, water vapour and others.
Venus seen from Mariner 10, 1973-4
Venus seen from Mariner 10, 1973-4

Venus has a thick cloud layer, making observations of the surface impossible. Orbiters have managed to collate a complete map of the surface using radar, revealing a rugged, mountainous surface, pockmarked with craters and rifts.

Earth and planets
Earth compared to the smaller planets and large moons

Missions to Venus

There have been 41 missions to Venus.


Venera 1 and 2 both failed, but Venera 3 (1966) managed to crash-land a probe on the surface of Venus, the first spacecraft to reach another planet's surface.

Venera 4, 1967, released a descent capsule, which entered the atmosphere to make measurements of temperature, pressure and density. It analysed the chemical composition of the atmosphere, revealing the high concentration of carbon dioxide (95%).

Venera 5 and Venera 6 had similar missions, and as for Venera 4 contact was lost with their descent capsules before reaching the surface, due to battery drain and being crushed by the pressure while still 18km above the surface.

Venera 7 (1970) did however manage to reach the surface, and continued to transmit data about temperatures for 23 minutes.

Venera 8 (1972) also managed to land a probe, lasting long enough to report that the clouds formed a high layer, 35 km above the surface, and to analyse the crust's chemical composition with a gamma ray spectrometer.

Surface of Venus
Surface of Venus, collage of images taken by Soviet Venera 9, 1975


Mariner 2

1962, USA. The first successful mission to Venus, and to any planet. Mariner discovered that the rotation of the planet is opposite to the other planets, and the surface temperature is 425 °C.



Read about sciences on
Radar image of Maat Mons Venus
Radar image of Magellan Crater, Venus
Venera 2, Russian probe to Venus, 1965-6
Venera 2, Russian probe to Venus, 1965-6
Venetian surface, composite radar image
Wheatley Crater, Venus, radar image
Wheatley Crater, Venus, radar image

Content © Renewable.Media. All rights reserved. Created : October 25, 2015 Last updated :January 17, 2016

Latest Item on Science Library:

The most recent article is:

Air Resistance and Terminal Velocity

View this item in the topic:


and many more articles in the subject:

Subject of the Week


Science resources on Games, puzzles, enigmas, internet resources, science fiction and fact, the weird and the wonderful things about the natural world. Have fun while learning Science with


Great Scientists

Johann(II) Bernoulli

1710 - 1790

Johann Bernoulli (II) was the son of Johan (I), and the younger brother of Daniel and Nicolaus, all noted mathematicians.

Johann Bernoulli (II), 1710 - 1790