Solar System Planets

The earth is only one small planet in an extremely large system of planets,
satellites, asteroids, meteors and comets that revolve around the sun. This
system is referred to as the solar system. A planet is defined as a "celestial
body that revolves around a central star and does not shine by its own light
" (Grolier,1992). The only planetary system known to our civilization is
our solar system. It is made up of nine planets that differ greatly size and
physical characteristics. The nine major planets in our solar system are

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. There
are also many other minor planets which are also in our solar system, but they
are unimportant compared to the nine major planets. Following are descriptions
of the differences that each of the nine planets have. The first planet to be
discussed is Mercury. Mercury is the planet that is closest to the sun at an
average distance of about 58 million km, or about 36 million miles. It takes

58.7 days for Mercury to rotate. The planet rotates one and one half times
during each revolution. Mercury has a density and composition close to that of

Earth and, like Earth has a magnetic field. This magnetic field is produced from
the planet’s outer core, which is said to be liquid iron. This liquid iron
generates a magnetic field with its movement. The atmosphere is extremely thin
and contains sodium and potassium. The photographs that have been taken of

Mercury\'s surface show the planet having craters and steep cliffs. The
temperatures on Mercury reach amazingly high levels of about 430° C, which is
about 810° F on the side facing the sun and about -180° C, or about 290° F on
the side facing away from the sun. It is speculated that these high
temperatures, resulting from the planet’s proximity to the sun made it
impossible for the gases present to become part of the planetary formation or
for Mercury to have any type of atmosphere. Venus is the second closest planet
to the sun and is said to most closely resemble Earth in size, density, and
distance from the sun. Venus is known as the sister planet to the Earth. One
differences is that Venus is shrouded in thick clouds that completely hide the
surface of the planet. The surface temperature is also much warmer than that of

Earth. Venus completes one revolution around the sun in 224.7 days. This makes
the a day on Venus equal to 117 earth days. It is thought that this slow
rotation may be the reason why Venus has no magnetic field. The atmosphere of

Venus made up of 98% carbon dioxide and 2% Nitrogen. This atmosphere also has
the presence of helium, neon, and argon. The surface of Venus is quite a bit
like that of the Earth. Cloud particles on Venus are mostly concentrated
sulfuric acid. Water and water vapor are very uncommon on Venus. Many scientists
hold the opinion that Venus, being close to the sun, was subjected to a kind of
extreme greenhouse effect. This effect caused any oceans to evaporate into the
atmosphere. Another viewpoint that is held is that Venus had very little water
to begin with. The surface has volcanoes and smooth plains. Much of the volcanic
activity on Venus takes the form of Basaltic eruptions that inundate large
areas, much as the mare volcanism flooded the impacted basins on the near side
of the moon. Because of the distances of the orbits of Venus and Earth from the
sun, Venus can never be seen for than three hours before sunrise or three hours
after sunset. When Venus is viewed through a telescope, it shows phases like the
moon. Venus rotates very slowly on its axis, in a direction that is opposite to
that of Earth. Cloud particles on Venus are mostly concentrated sulfuric acid.

Water and water vapor are very uncommon on Venus. Many scientists hold the
opinion that Venus, being close to the sun, was subjected to a kind of extreme
greenhouse effect. This effect caused any oceans to evaporate into the
atmosphere. Another viewpoint that is held is that Venus had very little water
to begin with. Higher-level winds circle the entire planet at 360 km/hr., or 225
mph. However, even with these high velocity winds, near the planet’s surface
more than half of Venus\'s tremendously dense atmosphere is practically still.

From the surface up to 10 km, or 6 mi. altitude, wind speeds are only about 3 to

18 km/hr, or about 2 to 11 mph.