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Sun Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto Outer Space

Space News Quick Access Menu History of Space Your Feedback Link to Us NASA Webpage Suggested Websites Universe Today - Space news from around the Internet, updated every weekday. Weight on other planets - Calculate your weight on different planets. Last updated on January 17th, 2001 Unveiling the Solar System. (Smithsonian Planets, Thomas R. Watters, page 14) Throughout history people have been fascinated by the planets - by what they are , how they move across the sky, and how these other worlds relate to Earth. Our concept of the solar system has changed dramatically over the centuries, although new views often were not welcomed. Now that the age of planetary exploration has begun, we have seen and learned things our ancestors never imaged. But while our knowledge have increased tremendously, our sense of wonder about the planets has not diminished. Read more about History of Space Discovery... The Planets (Smithsonian Planets, Thomas R. Watters, page 30) The nine planets orbits the sun on almost the same plane. Seen from Earth, they appear to move across the sky through a rather narrow zone, the so-called zodiac. Observed from a position far about the Earth's pole, all the planets appear to orbit the Sun in the counterclock wise direction. All the planets except Venus appear to rotate or spin in the same counterclockwise direction. Because of their histories and locations, the inner planets - Mercury, Venus, Earth, and Mars - differ from the outer gas giants, often called the "Jovian planets,"after Jupiter. The inner planets are smaller, denser, and rockier. What atmospheres they have due to internal activity and are not related to the masses of hydrogen and helium that originally enveloped them. They are also warmer and rotate more slowly than the outer Jovian plantes. Jupiter, Saturn, Uranis, and Neptune are much less dense than the inner planets. The bulk of their masses consists of hedrogen and helium , with some methane and ammonia. These rapidly rotating planets are cold and icy with deep atmospheres and ice rich moons. Pluto seems to be misfit. The farthest out, it is small and ice rich, with little atmosphere, and spins slowly. It probably has a unique history that accounts for its differences from other outer planets. The Sun (Smithsonian Planets, Thomas R. Watters, page 32) The Sun was worshiped as a god by early cultures. Structures were built in its honor and rituals performed to secure its favors. Such practicies and beliefs faded over the centuries as astronomers gained knowledge about the sphere whose nuclear furnance cradled and continues to support life on Earth. Not until the twintieth century, however were the Sun's complex nature and many of it's fascinating features revealed. The Inner Planets (Smithsonian Planets, Thomas R. Watters, page 32) Mercury, Venus, Earth, and Mars - the four planets closest to the Sun - share a common history in the solar system. Unlike the outer gaseous planets, these terrestrial planets were formed from dense rocky materials. Yet despite many basic similarities, the are sharply different worlds. From the intensely crattered surface of Mercury to the highlands of Venus to the giant volcanoes of Mars, each offer clues to story of our own Earth and its place int ehe scheme of planetary evolution.

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