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7planets, many dwarf planets, comets, natural satellites and asteroids. The Sun alone covers more than 99 percent of this system. Carol says, %u201cHow huge it is.%u201d%u201cYou are right,%u2019 said Mrs. Diana. %u201cIn its inner orbit, we have Mercury, Venus, Earth and Mars, and we call them inner planets. There are also four big planets in the outer solar system. They are Jupiter, Saturn, Uranus, and Neptune, and we call them the outer planets. Earth, Venus, and Mars have good atmospheres, but Mercury%u2019s is very thin. The outermost two planets, Uranus and Neptune, are really cold, and we call them ice giants.%u201d