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to: General Information, Earth's---
uh, Twin, Observations of Venus, Observations
by spacecraft and probes
GENERAL INFORMATION:
Venus is the second planet from the
sun. This planet is called the "twin" planet of Earth because
they are so similar in size. It's diameter is about 7,520 miles (12,100
kilometer), compared to the 7,926 mile (12,756 km) diameter of Earth, not that
much smaller than Earth. Venus was named after the Roman goddess of love
(the Greeks called her Aphrodite). Venus orbits in a nearly circular
orbit around the sun. The distance from the sun varies from 67.7 million
miles (108.9 million km) to about 66.8 million miles (107.5 million km).
The average distance is about 67.2 million miles (108.2 million km) from
the sun.
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Venus' clouds are
pretty thick and move very fast. This is an ultraviolet picture of
Venus' cloud cover. |
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EARTH'S--- UH, TWIN:
Venus has always been thought of to
be Earth's "twin." This was before spacecrafts were sent to
study Venus up close. Speculations on Venus' conditions were just guesses
because of the heavy cloud cover of Venus. The speculations ranged from
Venus being covered with oceans of carbonated water, to swamplands. Then
the international scientific teams came along with expensive
instruments, measuring the ultraviolet and radio waves from Venus. Radar
was then used to determine the rotation of Venus. It was then found that
Venus was not the "twin" that it was thought to be. Despite
the swift moving clouds of Venus that go about 250 miles-per-hour, the
planet rotates once every 243 days. Conditions on Venus are very
different; it seems pretty hellish; the opposite of Earth. The surface
temperature is about 864 degrees Fahrenheit (462 degrees Celcius). The
clouds are made of sulfuric acid and the air is mainly composed of
carbon dioxide, some nitrogen, and water vapor. The atmospheric pressure
is 90 times greater than on Earth, at an estimated 1,323 pounds per
square inch (9,122 kilopascals).
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OBSERVATIONS OF
VENUS
Venus comes the closest to the
Earth at only 25.7 million miles (41.4 million km) away from Earth. Due
to the short distance, Venus can be seen on Earth in the night or early
morning sky, depending on the time of the year. When visible, Venus is
the brightest astronomical body in the sky. Sometimes it is the first
planet or star seen in the western evening sky. Other times, it is the
last planet or star seen in the eastern sky in the morning. Venus can
also be seen in broad daylight when it is near its brightest point.
Ancient Greek astronomers called the Venus that appeared in the morning
Phosphorus, and the one that appeared at night, Hesperus. Later, they
found out they were the same planet. Galileo discovered Venus also had
phases like the moon. Phases are caused by the varying ability of the
observers on Earth to see the side of Venus that illuminated by the sun.
Depending on the varying line of sight from the Earth to Venus,
sometimes you can see all of Venus, half a circle, crescent, a sliver or
none of Venus.
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OBSERVATIONS BY
SPACECRAFT AND PROBES
Since the early astronomers,
international scientific teams and unmanned spacecraft have undertaken
the study of Venus with expensive instruments. The first spacecraft to
study Venus up close was the U.S. Mariner 2. It flew by the planet on
Dec. 14, 1962 after traveling for 3 1/2 months and measured various
conditions on and near Venus. Later, two unmanned Soviet spacecrafts,
Venera 2 and Venera 3 did similar exploration, a flyby and a not so
similar crash-into (Venera 3). Then came a series of spacecraft from
both the Soviet Union and the U.S.A.. The Soviet Venera 4 capsule was
parachuted down into the atmosphere of Venus on Oct. 18, 1967. The next
day the U.S. Mariner 5 passed within 2,480 miles of Venus. A few years
later, the Venera 7 landed on Venus on Dec. 15, 1970, and the Venera 9
and Venera 10, also followed and landed on Venus. The U.S., in December
1978 sent the crafts Pioneer Venus 1 to orbit the planet and Pioneer
Venus 2, which entered Venus atmosphere. More Soviet Venera crafts, the
11 and 12 also landed on Venus in December 1978, and the 13 and 14 in
March. In 1990, many years later the U.S. spacecraft, the Magellan,
began orbiting Venus on Aug. 10. Magellan was equipped with modern
instruments that provided radar images detailed enough to make maps.
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