7. Venus: The veiled planet
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.
human eye has ever gazed on the surface of Venus, which is forever hidden by a
thick overcast of impenetrable clouds.
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
- 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
- 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.
pale yellow clouds of Venus are composed of concentrated sulfuric acid
surface of Venus lies under a crushing atmosphere whose surface pressure is 92
times that on Earth.
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,
high, rapid winds on Venus spiral toward its poles, producing a huge, whirling
polar vortex at both poles of the planet.
is no detectable magnetic field on Venus, but its dense atmosphere deflects 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.
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
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
- High volcanic rises on Venus are
kept up by active motions below.
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.
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