Venus, Mars and Earth, three out of the four inner or ‘rocky’ planets of the Solar System, have a lot in common – a solid surface you could walk on, a comparable surface composition, an atmosphere and a weather system.

If you are looking for a twin sister to Earth, that would be Venus… or is it?

 Venus Earth
Mass 4.87 x 1024 kg 5.98 x 1024 kg
Radius 6052 km 6378 km
Density 5250 kg/m3 5520 kg/m3
Av. distance from Sun 108 million km 150 million km
Rotation period (day) 243 Earth days (retrograde) 23 hours 56 minutes
Orbit period (year) 224.7 Earth days 365.2 days
Surface temp. (mean) 465 °C 15 °C
Surface pressure 90 bar 1 bar (sea level)
Albedo (reflectivity) 0.76 0.37
Highest point on surface Maxwell Montes
(17 km)
Mount Everest
(8.8 km)
Atmosphere 96% CO2 , 3% N2 78% N2 , 21% O2, 1% Ar
Surface composition Basalt rock, altered materials Basalt, granite, altered materials
Orbit inclination 3.4° 0° by definition
Obliquity of axis 178° 23.5°
Surface gravity (equator) 8.9 m/s2 9.8 m/s2
Moons None 1 (The Moon)

3 thoughts on “Venus

    1. arnulfo Post author

      The atmosphere of Venus is made up almost completely of carbon dioxide. Nitrogen exists in small doses, as do clouds of sulfuric acid. The air of Venus is so dense that the small traces of nitrogen are four times the amount found on Earth, although nitrogen makes up more than three-fourths of the terrestrial atmosphere. This composition causes a runaway greenhouse effect that heats the planet even hotter than the surface of Mercury, although Venus lies farther from the sun. When the rocky core of Venus formed, it captured much of the gas gravitationally (

      For a comment on the Venus syndrome see


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