Space Facts

Planet Venus

No Goddess of Love, But One Hot Beauty

Venus cloud tops viewed by the NASA Hubble Space Telescope. This ultraviolet-light image was taken on January 24 1995, when Venus was at a distance of 70.6 million miles (113.6 million kilometers) from Earth. Image Credit: NASA/JPL

Venus is planet number two of the Solar system. Named for the Roman goddess of love, beauty and fertility (equivalent to the Greek goddess, Aphrodite). Why the association? The planet appears pure white and bright as both morning star and evening star.

The planet Venus was long considered to be a twin of Earth because it is only slightly smaller than our home planet and has a cloud cover. Some thought the planet to be an ocean planet with carbonic acid waves. Others considered it might contain rich jungles along with its oceans. But no more. Venus may be a beauty, but it is too hot to handle.

The thick atmosphere of planet Venus is better than 90% carbon dioxide which is an excellent greenhouse gas. The surface pressure is close to 92 Earth atmospheres (at Earth sea level). This makes Venus the best greenhouse in the Solar system. Because of this, planet Venus is even hotter than Mercury though it is nearly twice the distance of the first planet from the sun. How hot? Enough to melt lead — about 460 °C (860 °F).

The planet Venus is covered with clouds made of sulfuric acid, rather than the water-vapor clouds found on Earth. These clouds permanently shroud Venus' volcanic surface, which has been radar mapped by spacecraft and from Earth-based telescope. At ultraviolet wavelengths cloud patterns become distinctive. In particular, a horizontal "Y"-shaped cloud feature is visible near the equator. Similar features were seen from Mariner 10, Pioneer Venus, and Galileo spacecrafts. This global feature might indicate atmospheric waves, analogous to high and low pressure cells on Earth. Bright clouds toward Venus' poles appear to follow latitude lines. The polar regions are bright, possibly showing a haze of small particles overlying the main clouds. The dark regions show the location of enhanced sulfur dioxide near the cloud tops. From previous missions, astronomers know that such features travel east to west along with the Venus' prevailing winds, to make a complete circuit around the planet in four days.

Because Venus is closer to the Sun than Earth, the planet appears to go through phases, like the Moon. When Venus swings close to Earth the planet's disk appears to grow in size, but changes from a full disk to a crescent.

The planet Venus has a very thick atmosphere for a terrestrial world. It rotates once every 243 days, and orbits the sun once every 224.7 days. The slow rotation is reverse that of all other planets in the Solar system, or "retrograde."

Size comparison of terrestrial planets with the Moon (left to right): Mercury, Venus, Earth, Luna and Mars.		The first four planets of the Solar system are called "terrestrials" because of their rough similarity to Earth. The other type of planet is called "gas giant," because the bulk of each such planet is gaseous. The Solar System Facts table gives more comparisons between the planets.

Could Planet Venus Ever Sustain Life?

A number of factors work against Venus sustaining life. For one, it is so close to the sun. As with Mercury, this makes Venus too hot, of course. Because of the thick, greenhouse atmosphere, the temperature is constant day and night. If it weren't for the thickness of the atmosphere, the solid cloud cover would bring the Venusian temperature closer to that of Earth. If the atmosphere could be trimmed down and reduced of its greenhouse effects, we would still have to contend with the inordinately long Venusian days. Temperatures would still become dangerously hot during the day and dangerously cold at night, with Venus having a far more light-weight atmosphere while retaining its thick cloud cover.

As with Mercury, the planet Venus with a lighter atmosphere might be able to sustain life at the poles. The thick cloud cover, however, would mean that solar power cells would not work very efficiently.

<<Return to the Solar System page