"A planet is a celestial body that revolves around a .
central star and does not shine by its own light " (Grolier, .
1992). The only planetary system that is known to man is our .
solar system. It is made up of nine planets which range in size .
and make-up. 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. In this paper I will discuss the planets and how .
they are each unique. .
Mercury which is the planet that is closest to the sun is .
the first planet I will discuss. Mercury is the smallest of the .
inner planets. It is speculated that the heat from the sun made .
it impossible for the gases present to become part of the .
planetary formation. The surface of Mercury is extremely hot. .
It is approximately 470 degrees celsius on the surface and is .
thought to be even hotter at the two " hot spots." These " hot .
spots " are on opposite ends of the equator. It is the heat of .
the surface that makes it impossible for Mercury to have any type .
of atmosphere. .
Mercury orbits the sun once every 88 days and has a true .
rotation period of 58.6 days. " It is the closest planet to the .
sun and therefore orbits faster than any other planet " .
(Thompson/Turk, 542, 1993). It is said that Mercury rotates .
three times for every two trips around the sun, so that during .
Planets 3 .
every alternate perihelon passage the same face points directly .
at the sun. " Geologically, the most remarkable features of .
Mercury are compressional cliffs or faults, just the sort of .
wrinkles that might form in the crust if the interior of the .
planet shrank slightly " (Morrison, 74, 1993). It is speculated .
that it was the solidification of Mercury's metallic core that .
caused this global shrinkage. Mercury is also " . . . enriched .
in metal or depleted of rock " (Morrison, 74, 1993).