A Tour through the Solar System

The Inner Planets Include Mercury, Venus, Earth, and Mars Include Mercury, Venus, Earth, and Mars Also known as terrestrial planets (terra means earth in Latin) Also known as terrestrial planets (terra means earth in Latin) All terrestrial planets are small, dense, and have rocky surfaces. All terrestrial planets are small, dense, and have rocky surfaces.

Mercury Named for the Roman messenger god (Greek - Hermes) Smallest terrestrial planet (diameter is 4,879 km) Smallest terrestrial planet (diameter is 4,879 km) Surface is covered by plains and craters Surface is covered by plains and craters Has no atmosphere and no moons Has no atmosphere and no moons Has the greatest temperature range of any of the planets: Day: 430°C Night: - 170°C Has the greatest temperature range of any of the planets: Day: 430°C Night: - 170°C

Venus Named for the Roman goddess of love and beauty (Greek - Aphrodite) Close to the size of earth (Diameter is 12,104 km) Close to the size of earth (Diameter is 12,104 km) Surface is very volcanic and has many plains covered in flowing lava Surface is very volcanic and has many plains covered in flowing lava Atmosphere is so thick it is considered one giant cloud. The air pressure is 90 times earth’s. Air is mostly carbon dioxide. Atmosphere traps in enough heat to melt lead (460°C), making it the hottest planet). Atmosphere is so thick it is considered one giant cloud. The air pressure is 90 times earth’s. Air is mostly carbon dioxide. Atmosphere traps in enough heat to melt lead (460°C), making it the hottest planet). No moons No moons Venus takes longer to rotate on its axis than it does to revolve around the sun. This makes its day longer than its year. Venus takes longer to rotate on its axis than it does to revolve around the sun. This makes its day longer than its year.

Earth Only Planet Name Not Derived from Mythology Diameter is 12,756 km Diameter is 12,756 km Only planet that has liquid water on the surface. The surface is solid rock with many volcanoes Only planet that has liquid water on the surface. The surface is solid rock with many volcanoes Only atmosphere rich in oxygen (20%) Most of the rest of the atmosphere is nitrogen Only atmosphere rich in oxygen (20%) Most of the rest of the atmosphere is nitrogen Has 1 moon commonly called moon, but also referred to as Luna (Roman goddess of the moon) Has 1 moon commonly called moon, but also referred to as Luna (Roman goddess of the moon) Is in the exact position in the solar system needed to support life. Any closer to the sun and it would be to hot; farther, too cold Is in the exact position in the solar system needed to support life. Any closer to the sun and it would be to hot; farther, too cold

Mars Named for the Roman god of war (Greek – Ares) Diameter – 6,794 km Diameter – 6,794 km Surface is red because of rich amounts of iron in the rocks. There are icecaps at the poles. Many volcanoes dot the surface but none are active. Surface is red because of rich amounts of iron in the rocks. There are icecaps at the poles. Many volcanoes dot the surface but none are active. Atmosphere is 95% carbon dioxide. Atmosphere is 95% carbon dioxide. 2 moons (Phobos and Diemos) 2 moons (Phobos and Diemos) Mars has a tilted axis and has seasons. Mars has a tilted axis and has seasons. Its largest volcano, Olympus Mons is the size of Missouri and is 3 times taller than Mt. Everest. Its largest volcano, Olympus Mons is the size of Missouri and is 3 times taller than Mt. Everest.

The Outer Planets Include Jupiter, Saturn, Uranus, and Neptune Include Jupiter, Saturn, Uranus, and Neptune Also known as the gas giants. Also known as the gas giants. Don’t have solid surfaces. Don’t have solid surfaces. Have a set of discs of small particles of ice and rock called rings Have a set of discs of small particles of ice and rock called rings

Jupiter Named for the Roman king of the gods (Greek – Zeus) Largest planet (Diameter – 143,000 km) Largest planet (Diameter – 143,000 km) Surface is gaseous. Surface is gaseous. Atmosphere made up of mostly hydrogen and helium. The Great Red Spot (GRS) is a storm twice as large as Earth. Storms on Jupiter never end. GRS first observed in the mid-1600’s. Atmosphere made up of mostly hydrogen and helium. The Great Red Spot (GRS) is a storm twice as large as Earth. Storms on Jupiter never end. GRS first observed in the mid-1600’s. Rings are barely noticeable. Rings are barely noticeable. 63 known moons; Io, Europa, Ganymede, and Callisto are the largest and were discovered by Galileo 63 known moons; Io, Europa, Ganymede, and Callisto are the largest and were discovered by Galileo Its mass is 2.5 times that of all the rest of the planets. Its mass is 2.5 times that of all the rest of the planets.

CallistoGanymede Io Europa

Saturn Named for the Roman god of agriculture (Zeus’ father) (Greek – Cronus/Kronos) 2 nd largest (Diameter – 120,500 km) 2 nd largest (Diameter – 120,500 km) Gaseous surface Gaseous surface Atmosphere is primarily hydrogen and helium. Also has clouds and storms Atmosphere is primarily hydrogen and helium. Also has clouds and storms Rings are 250,000 km in diameter, but only 1 km thick. Rings are 250,000 km in diameter, but only 1 km thick. 34 known moons, Titan is the largest 34 known moons, Titan is the largest Saturn’s density is less than water. Saturn’s density is less than water.

Uranus Named for the Greek god of the heavens (Chronus’ father, husband of Gaia) Diameter – 51,100 km Diameter – 51,100 km Gaseous surface Gaseous surface Traces of methane in the atmosphere give it the blue-green color Traces of methane in the atmosphere give it the blue-green color Rings go from north to south Rings go from north to south At least 25 moons, names come from writings of Shakespeare and Alexander Pope At least 25 moons, names come from writings of Shakespeare and Alexander Pope Uranus’ axis is tilted 90°. This causes a “north/south” rotation instead of the normal “east/west” rotation. Uranus’ axis is tilted 90°. This causes a “north/south” rotation instead of the normal “east/west” rotation.

Neptune Named for Roman god of the sea (Greek – Poseidon) Diameter – 49,500 km Diameter – 49,500 km Gaseous surface Gaseous surface Blue gases fill the atmosphere. White and dark-colored clouds dot the sky. Blue gases fill the atmosphere. White and dark-colored clouds dot the sky. Rings are barely noticeable. Rings are barely noticeable. 13 moons, largest is named Triton. 13 moons, largest is named Triton. Neptune had a huge storm called the Great Dark spot, but it didn’t last. Neptune had a huge storm called the Great Dark spot, but it didn’t last. The planet is actually sinking, causing the core to heat up, which results in clouds. The planet is actually sinking, causing the core to heat up, which results in clouds.

Why Pluto Isn’t a Planet It doesn’t meet the third part of the definition of a planet: It doesn’t meet the third part of the definition of a planet: 1. Must orbit around the sun 2. Must have a nearly round shape 3. Must have cleared the area around it so that no competing celestial bodies are around (Charon is a competing body that wasn’t cleared)

Pluto Named for the Roman god of the underworld (Greek – Hades) Diameter – 2,400 km, smaller than the moon, Io, Europa, Ganymede, Callisto, Titan, and Triton Diameter – 2,400 km, smaller than the moon, Io, Europa, Ganymede, Callisto, Titan, and Triton Rocky surface Rocky surface No atmosphere No atmosphere 1 moon – Charon (Greek figure who ferried people to the underworld) 1 moon – Charon (Greek figure who ferried people to the underworld) Orbit lasts 248 earth years. Orbit lasts 248 earth years. At times during the orbit Pluto is actually closer to the sun than Neptune. At times during the orbit Pluto is actually closer to the sun than Neptune. As of August 24, 2006 Pluto is considered a “dwarf planet.” As of August 24, 2006 Pluto is considered a “dwarf planet.”

Other Dwarf Planets Eris – largest dwarf planet, has 1 moon (Dysnomia) Eris – largest dwarf planet, has 1 moon (Dysnomia) Located in the Kuiper Belt (Out past Pluto) Located in the Kuiper Belt (Out past Pluto) Ceres – smallest dwarf planet Ceres – smallest dwarf planet Located in the asteroid belt (between Mars and Jupiter) Located in the asteroid belt (between Mars and Jupiter)

Other Dwarf Planets MakeMake was named a dwarf planet in June of MakeMake was named a dwarf planet in June of It’s the 3 rd largest dwarf planet. It’s the 3 rd largest dwarf planet. It is located in the Kuiper Belt, where Eris is located. It is located in the Kuiper Belt, where Eris is located. Haumea Haumea It’s the 4 th largest dwarf planet. It’s the 4 th largest dwarf planet. 2 moons – Hi’iaka and Namaka 2 moons – Hi’iaka and Namaka Located in the Kuiper Belt Located in the Kuiper Belt