The Astronomical Planet
At first glance, if Earth had a twin,
it would be Venus. The two planets are similar in size,
mass, composition, and distance from the Sun. But
there the similarities end. Venus has no ocean. Venus is
covered by thick, rapidly spinning clouds. These
clouds trap surface heat, creating a scorched
greenhouse-like world with temperatures hot enough to melt
The pressure on Venus is so
intense that standing on the surface would feel like the
pressure felt 900 meters deep in Earth's oceans. Venus' cloud
cover also reflects sunlight in addition to trapping heat.
Because Venus reflects so much sunlight, it is usually the
brightest planet in the sky.
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Planetary Statistics of Venus:
Venus: Second Planet from the Sun
Distance from the
Sun: 67.2 million miles
224.68 Earth days to make one complete revolution around the
243 Earth days to make one complete revolution on its axis.
Mean; 726 K (453 C, 847 F)
Chronology of Venus
Recent results from the Magellan spacecraft suggest
that Venus' crust is stronger and thicker than had previously
The atmosphere consists
mainly of carbon dioxide droplets of sulfuric acid, and
virtually no water vapor. Additionally, the thick
atmosphere allows the Sun's heat in but does not allow it to
escape. This results in surface temperatures over 450 °C. This
is hotter than the surface of the planet Mercury, which is
closest to the Sun. The high density of the atmosphere results
in a surface pressure 90 times that of Earth, which is why
probes that have landed on Venus have only survived several
hours before being crushed by the incredible pressure. In the
upper layers, the clouds move faster than hurricane- force
winds on Earth.
Venus sluggishly rotates on
its axis once every 243 Earth days, while it orbits the Sun
every 225 days - its day is longer than its year! Besides that,
Venus rotates retrograde, or
"backwards," spinning in the opposite direction of its orbit
around the Sun. From its surface, the Sun would seem to rise
in the west and set in the east.
Earth and Venus are similar
in density and chemical compositions, and both have relatively
young surfaces, with Venus appearing to have been completely
resurfaced 300 to 500 million years ago.
About 20 percent lowland
plains, 70 percent rolling uplands, and 10 percent highlands,
cover the surface of Venus. Volcanism, impacts, and deformation
of the crust have shaped the surface. No direct evidence of
currently active volcanoes has been found, although large
variations of sulfur dioxide in the atmosphere lead some
scientists to suspect that volcanoes may be active.
More than 1,000 volcanoes or volcanic centers larger than 20
km in diameter dot the surface of Venus. There may be close to
a million volcanic centers that are over 1 km in diameter. Much
of the surface is covered by vast lava flows. In the north, an
elevated region named Ishtar Terra is a lava-filled basin
larger than the continental United States. Near the equator,
the Aphrodite Terra highlands, more than half the size of
Africa, extend for almost 10,000 km. Volcanic flows have also
produced long, sinuous channels extending for hundreds of
Although Venus has no
rainfall, oceans, or strong winds to erode surface
features, some weathering and erosion does occur. The surface
is brushed by gentle winds, no stronger than a few kilometers
per hour or strong enough to move grains of sand.
Radar images of the surface
show wind streaks and sand dunes. In addition, the corrosive
atmosphere probably chemically alters rocks.
Impact cratering is also
affected by the dense atmosphere. Craters smaller than 1.5 to 2
km across do not exist on Venus, largely because small meteors
burn up in Venus’ dense atmosphere before they can reach the
Venus' interior is probably very similar to that of Earth,
containing an iron core about 3,000 km in radius and a molten
rocky mantle covering the majority of the planet.
Venus has no satellites and
no intrinsic magnetic field, but the solar wind rushing by
Venus creates a pseudo-field around the planet.
Information Courtesy of NASA
Jet Propulsion Laboratory at
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