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There are nine planets in our solar system, each circling around the sun. Each year, we learn more and more about their composition and origins.

MERCURY is the planet closest to the sun. It is very hot and dry and takes the shortest amount of time of any of the planets to circle around the sun. Mercury is gray and covered with craters bigger than the state of Texas. The length of a day on Mercury is 58.65 Earth days.

VENUS is located closer to Earth than any other planet. It is also almost the same size at Earth and is wrapped in a layer of sulfur clouds. The clouds trap the sun’s heat on the surface of Venus and make conditions very hot.

EARTH is the only planet in our solar system that supports animals, plants and human life. The Earth orbits the Sun every 365 days and it has one moon. It’s atmosphere is made of oxygen.

MARS is covered in red sand. Mars has two moons called Phobos and Deimos. Mars has huge volcanos. Possibly, volcanoes of such magnitude were able to form on Mars because the hot volcanic regions in the mantle under the surface that lasted for hundreds of millions of years.

JUPITER is made almost entirely of gases. It is covered by a layer of clouds that is miles deep and made of chemicals. Thin rings of ice and dust circle around Jupiter. It is the largest of the planets in our solar system. The Galileo spacecraft is now studying this giant planet up close and we are learning new and fascinating things about it every day.

SATURN is famous for the rings that surround it made of ice, rock and dirt. Saturn is also made of gases and is surrounded by more than 17 moons. To many, Saturn is the most interesting of all the planets. It has the most pronounced rings of any planet. The length of a year on Saturn is 29.6 Earth years.

URANUS is a gas planet also circled by rings. It is the only planet that is tipped totally on it’s side. It contains an atmosphere made up almost entirely of hydrogen. The greenish color of the planet’s atmosphere is due to methane and high-altitude photochemical smog.

NEPTUNE is one of last planets in our solar system and is made of gases. It is surrounded by chunky rings. It takes 165 years for Neptune to circle the Sun. Neptune shares many of the same characteristics as the other gaseous planets, even it’s three faint rings. The only spacecraft to visit Neptune has been Voyager 2.

PLUTO is the last planet in our solar system. After the most recent Hubble Telescope photographs of Pluto were reviewed, scientists now know that the diameter of the planet is 1440 miles and that a day on Pluto takes about 6.89 Earth days. A bright highlight on photographs of Pluto suggest it has a smooth and reflective surface.

New PLANETS are being discovered all the time. More than 30 planets have been found in orbit of stars outside the solar system in the last few years. Recently, astronomers searching for planets orbiting distant stars have found the smallest planets yet outside our solar system. This is an important step toward being able to detect planets the size of Earth that would have a good chance of supporting life.