7. Venus: The veiled planet

    • When visible, Venus is the brightest planet in the sky. It orbits the Sun inside Earthís orbit, appearing in the evening or morning hours and never in the middle of the night.

    • No human eye has ever gazed on the surface of Venus, which is forever hidden by a thick overcast of impenetrable clouds.

    • Venus has a day longer than its year. The planet rotates once every 243 Earth days, in the opposite, retrograde direction from other planets except Uranus, and it takes 224.7 Earth days for Venus to orbit once about the Sun.

    • Venera spacecraft have parachuted through the clouds of Venus, surviving long enough to measure the properties of its torrid surface and even photographing it.

    • The deadly efficient greenhouse effect of a thick, carbon dioxide atmosphere has scorched Venusís surface, raising its temperature to 735 kelvin, even hotter than Mercuryís average dayside temperature.

    • In size, density and composition, Venus is almost identical to the Earth, but radar signals and space probes have penetrated its clouds to reveal an unearthly surface without a trace of liquid water or life.

    • The pale yellow clouds of Venus are composed of concentrated sulfuric acid droplets.

    • The surface of Venus lies under a crushing atmosphere whose surface pressure is 92 times that on Earth.

    • It takes only 4 Earth days for the high-flying clouds to move once about Venus, from east to west, blown by fierce, rapid winds, but the slow winds near the surface rotate with the planet, once every Earth 243 days in the same backwards, retrograde direction.

    • The high, rapid winds on Venus spiral toward its poles, producing a huge, whirling polar vortex at both poles of the planet.

    • There is no detectable magnetic field on Venus, but its dense atmosphere deflects the solar wind.

    • The radar instrument aboard the Magellan spacecraft spent more than four years mapping out the surface of Venus in unprecedented detail, revealing rugged highlands, smooth plains, volcanoes, and sparse, pristine impact craters.

    • About 85 percent of the surface of Venus is covered by smooth, low-lying volcanic flows of lava, and much of the remaining 15 percent is high standing with towering volcanoes.

    • The entire surface of Venus was probably covered by rivers of outpouring lava roughly 750 million years ago, wiping out all previous craters and about 90 percent of the planetís history; volcanic activity has continued at a reduced level up to the present.

    • Tens of thousands of volcanoes now pepper the surface of Venus; some of the towering volcanoes could now be active.

    • High volcanic rises on Venus are kept up by active motions below.

    • Vertical motions associated with upwelling hot spots have buckled, crumpled, deformed, fractured and stretched the surface of Venus.

    • Venus exhibits every type of volcanic edifice known on Earth, and some, called arachnids and coronae, which have never been seen before.

    • The surface of Venus moves mostly up and down, rather than sideways.

    • Liquid water is nonexistent on Venus, and the lack of water could be why Venus does not have moving plates similar to those found on Earth.

Copyright 2010, Professor Kenneth R. Lang, Tufts University