The nine planets which make up the Solar System fall into two groups. The first group, consisting of Mercury, Venus, Earth, and Mars, are terrestrial planets. All are made up of mostly iron rock. The second group, Jupiter, Saturn, Uranus, and Neptune are the Jovian, or gas planets. These giant planets all have fascinating moons. Pluto, the planet with the largest orbit, is made up of solid ice. The ninth planet has become the center of much debate. The argument is whether or not to include Pluto as a major planet, or to disregard it as just another comet-like object found beyond Neptune in the so-called Kuiper Belt.
Sun
sun..4.7 billion years old..average size star..reaches solar maximum 2001.top
Mercury
Mercury is the innermost planet and had been one of the least understood. Mercury is 0.4 AU from the Sun. It has only 5.5% the mass of the Earth. It is very difficult to get a really good view of the small planet because of its close distance to the Sun. Even the best photographs taken from Earth show Mercury as only a fuzzy ball. Surface temperatures, after a long day in the Sun, reach 800 degrees. At night, with no atmosphere to retain heat, the surface cools to below-300 degrees.top
Venus
Venus orbits the Sun at a distance of 0.7 A. U. Heavy cloud coverage makes viewing the surface impossible. These thick clouds are primarily made up of sulfuric acid. Probably the most curious of all the characteristics of Venus is the rotation of the planet. It rotates in the direction opposite from other planets called retrograde rotation. It is unsure as to why Venus rotates "the wrong way." One theory is that Venus was struck by a large clump of what is now the planet at an angle which caused it to rotate backwards. Studies have neither confirmed nor denied such a theory. top
Our Mother Earth
Who could forget the most perfect of all the planets in the Solar System? And perhaps any planet in the entire universe. Earth is constantly undergoing changes; volcanic activity, earthquakes, and nearly unpredictable whether patterns. The deep blue oceans which cover most of the planet have yet to be completely explored.top
Mars
Mars has always been the planet of most interest to scientists and astronomers for hundreds of years. The speculation as to whether or not life exists on Mars dates back to 1877 when Italian astronomer Giovanni Schiaperelli reported that he had seen canali, or channels, on the surface of the red planet. Of course, now we know these findings of his are false. But, the announcement that life had been found on a meteorite in 1996 had only intensified out interest of Mars. Currently there are several missions dedicated to finding life on Mars, or other clues to help explain the forming of our Solar System.top
Red Eye in the Sky
The largest planet, Jupiter, dominates the Sun's planetary system. Jupiter is 5 A. U. from the Sun and revolves around it once every 12 years. The Great Red Spot (lower right) is a storm which has been active for over 350 years. Through a telescope, bands of clouds across the surface are visible. The four Galleon satellites (Io, Ganymede, Europa, and Callisto) can be seen nearly edge on.top The Ringed Planet
At about 9.5 A. U., Saturn is the second largest planet next to Jupiter. Much is yet to be learned about Saturn. Cassini Spacecraft will make its approach to Saturn in the year 2004 and will tour its moons for four years. The project, launched in 1997, is focused on bringing back new detailed information on the mysterious planet. A prope named Huygens will be dropped into Titan's atmosphere to further enhance our knowledge of the largest moon in out Solar System. top Uranus
Uranus is very similar to Jupiter and Saturn in many ways. It has no solid surface and is composed of mostly hydrogen and helium. Uranus revolves around the Sun every 84 years, at an average distance of more than 19 A. U. Uranus rotates on an axis nearly perpendicular to other planetary axes. Its rotation is considered retrograde because its axis is tilted more then 90 degrees. Earth based observations, only five moons had been discovered. Voyager 2's flyby of the planet in 1986 discovered another 10 moons.top Neptune
Neptune is roughly the same size of Uranus and are nearly identical except for cloud coverage and a slight variation in color. Neptune is at a distance of 30 A. U. and takes 165 years to orbit the Sun. Like Jupiter, Neptune also has tremendous storms and a surface feature called the Great Dark Spot.top
Pluto, the Ninth Planet.
Pluto is the outer most planet in the Solar System. Pluto was discovered in 1905 by American astronomer Percival Lowell, who assumed the position of an object beyond Neptune as a result of a "wiggle" in the planet's motion. Members of his observatory thoroughly searched the sky for Planet X for 25 years until 1930 when Clyde William Tombaugh found Pluto near the predicted position. Pluto revolves around the Sun once in about 248 years at a distance of about 3.5 billion miles! Unfortunately, only large telescopes can view Pluto. Pluto has one moon, Charon, which orbits at a distance of 13,000 miles.
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Mercury
Pluto, the Ninth Planet.