1. The Outer Planets and Their Moons

2. Essential Questions 1. 1. What characteristics do the outer planets have in common? 2. 2. What characteristics distinguish each of the outer planets? 3. 3. Should Pluto be reinstated as a planet?

3. The Gas Giants Jupiter Saturn Uranus Neptune

4. The Outer Planets Much larger and more massive than the inner planets Much larger and more massive than the inner planets Do not have solid surfaces Do not have solid surfaces All are composed mainly of hydrogen & helium All are composed mainly of hydrogen & helium More gravity than Earth due to their high mass More gravity than Earth due to their high mass Thick atmospheres with high atmospheric pressure Thick atmospheres with high atmospheric pressure A lot of the hydrogen & helium inside the planets is liquid because of enormous pressure A lot of the hydrogen & helium inside the planets is liquid because of enormous pressure Outer layers of the planets are cold because of their distance from the sun, but temperatures increase inside the planets Outer layers of the planets are cold because of their distance from the sun, but temperatures increase inside the planets All have many moons All have many moons All have rings composed of small particles of ice and rock All have rings composed of small particles of ice and rock

5. Like the sun, the gas giants are composed mainly of hydrogen and helium. Because they are so massive, the gas giants exert a much stronger gravitational force than the terrestrial planets. These planets have thick atmospheres because gravity keeps these gases from escaping into space. “Gas Giants”

6. All of the gas giants have many moons and are surrounded by a set of rings. A ring is a thin disc of small particles of ice and rock. MULTIPLE MOONS RINGS Multiple Moons and Rings

7. Jupiter

8. Named for the Roman king of all gods, because other than the Sun, it’s the largest object in our solar system.

9. Jupiter The largest planet with the most mass Mass is about 2 ½ times all other planets combined

10. Thick atmosphere of mainly hydrogen & helium, with some methane, ammonia, water, and sulfur compounds The Great Red Spot – a giant storm large enough to fit two Earth’s side by side. Hurricane-like winds blow hundreds of miles an hour it has lasted for 350 years The lack of terrain features prevents the storm from weakening. Jupiter’s Atmosphere

11. The cloud speeds on Jupiter vary with latitude, an effect called differential rotation. Near the poles, the rotation period of Jupiter’s atmosphere is five minutes longer than that at the equator. POLAR REGION ROTATION TIME 9 hours 55minutes EQUATORIAL REGION ROTATION TIME 9hours 50minutes Jupiter’s Atmosphere – Differential Rotation

12. Jupiter’s clouds move in east-west bands Reddish-colored belts alternate with white-colored zones.

13. Jupiter’s Atmosphere – Color Belts Astronomers believe that the belts and zones are created by a combination of the planet’s convection and its rapid differential rotation.

14. Jupiter’s Structure A dense core of rock and iron at the center The core is surrounded by a thick mantle of liquid hydrogen & helium Pressure at Jupiter’s core may be 30 million times greater than the pressure at Earth’s surface Extreme pressure is caused by its thick atmosphere

15. Gravitational compression causes Jupiter to radiate more heat than it absorbs from the sun. Heat is probably left over from the original collapse of the primordial nebula to form the Solar System internal heat source drives the complex weather patterns in its atmosphere, unlike the Earth where the primary heat source driving the weather is the Sun. Jupiter’s Internal Sources of Energy

16. Jupiter’s Moons Galileo discovered Jupiter’s largest four moons in 1610 (Galilean moons) Galileo discovered Jupiter’s largest four moons in 1610 (Galilean moons) Many more have been discovered as technology improved – latest count is 63 Many more have been discovered as technology improved – latest count is 63 The four largest are very different from each other The four largest are very different from each other

17. Jupiter’s Largest Moons – its surface is covered with large, active volcanoes. Sulfur gives it a yellow-orange color. Io – its surface is covered with large, active volcanoes. Sulfur gives it a yellow-orange color. – it has an icy crust an ocean of liquid water underneath the ice. NASA is planning an unmanned mission to look for conditions that would support life. Europa – it has an icy crust an ocean of liquid water underneath the ice. NASA is planning an unmanned mission to look for conditions that would support life. – the largest moon in the solar system is larger than Mercury or Pluto. Water was recently discovered beneath its icy surface. It actually has more water than Earth does! Ganymede – the largest moon in the solar system is larger than Mercury or Pluto. Water was recently discovered beneath its icy surface. It actually has more water than Earth does! Is life possible? – has an icy, highly-cratered surface. It’s the most cratered object in our solar sysem Callisto – has an icy, highly-cratered surface. It’s the most cratered object in our solar sysem

18. Saturn

19. Mass: 5.7 x 10 26 kg Volume: 8.3 x 10 14 km 3 Diameter:116,464 km Density: 0.687 g/cm 3 Escape velocity: 35.5 km/s Surface gravity: 10.44 m/s 2 Moons: 60 Orbit period: 10,759.22 days Avg. Dist. to Sun:1.4 x 10 9 km Avg. orbital velocity: 9.69 km/s Length of day: 10.66 hours Axial tilt: 26.73° Saturn Statistics Named for the Roman god of the harvest and agriculture

20. Saturn The second-largest planet The second-largest planet Has a thick atmosphere of hydrogen & helium Has a thick atmosphere of hydrogen & helium Atmosphere has thick clouds and storms – though not as spectacular as those on Jupiter Atmosphere has thick clouds and storms – though not as spectacular as those on Jupiter The least dense planet (less dense than water) The least dense planet (less dense than water) The Voyager probes provided lots of information about Saturn The Voyager probes provided lots of information about Saturn

21. Saturn’s Rings Saturn has the most spectacular rings of any planet Saturn has the most spectacular rings of any planet The rings are broad and thin – like a CD The rings are broad and thin – like a CD The rings are made of chunks of ice and rock, each traveling in its own orbit around Saturn The rings are made of chunks of ice and rock, each traveling in its own orbit around Saturn

22. Saturn’s Moons Saturn is currently known to have more than 60 moons Saturn is currently known to have more than 60 moons The largest is Titan The largest is Titan It has a very thick atmosphere (so thick that light can hardly pass through) It has a very thick atmosphere (so thick that light can hardly pass through) There are four other moons that are larger than 1,000 kilometers in diameter There are four other moons that are larger than 1,000 kilometers in diameter

23. Saturn’s Moons TITAN: Saturn’s largest moon Saturn’s largest moon Second largest moon in the solar system Second largest moon in the solar system Has a dense nitrogen atmosphere Has a dense nitrogen atmosphere Surface Pressure: 1.6 atm Surface Pressure: 1.6 atm Similar in conditions to early Earth Similar in conditions to early Earth

24. Titan’s Primordial Soup? Titan is a complex moon that is more similar to a terrestrial planet than a typical outer planet moon. Titan's orbit carries it in and out of Saturn's magnetosphere Methane in the atmosphere reacts with sunlight to produce a hydrocarbon smog Titan's hidden surface may have exotic features: mountains sculpted by hydrocarbon rain, rivers, lakes and "waterfalls" of flammable liquids Water and ammonia magma may occasionally erupt, spreading across the surface, creating exotic landscapes

25. Two views of Titan From Far Away Very Close Up with special Lens

26. Saturn’s Moons MIMAS: Has an impact crater that is 1/3 the diameter of the satellite Has an impact crater that is 1/3 the diameter of the satellite Biggest impact Mimas could have taken and still survived Biggest impact Mimas could have taken and still survived “That’s no moon”. – Obi-Wan Kenobi (But it is!)

27. Saturn’s Moons PHOEBE: Discovered in 1898 First retrograde satellite known in the solar system Most likely a captured satellite Saturn’s outermost moon

28. Saturn’s Moons Iapetus: Along its orbit, it picks up dark dust from Phoebe Like our moon, the same side faces Saturn at all times (synchronous rotation) Because of the dust, it’s leading face is dimmer than its trailing face

29. Saturn’s Moons Hyperion: Only satellite in the solar system that is not in synchronous orbit Not spherical Probably a remnant of a larger moon that was destroyed

30. Saturn’s Moons Enceladus: 500 km in diameter 500 km in diameter Covered with water ice Covered with water ice Heavily cratered in the northern hemisphere Heavily cratered in the northern hemisphere Geologically active Geologically active Ice geysers supplied material for the E-Ring Ice geysers supplied material for the E-Ring

31. Uranus

32. Discoverer:Sir William Hershel (1781) Spacecraft Encounter(s):Voyager 2 (1986) Mean distance from Sun: 19.19 AU (2.871 billion km/1.784 billion mi) Length of year:84.01 Earth years Rotation period:17.24 hours Mean orbital velocity:6.81 km/s (4.2 m/s) Inclination of axis:97.92° Diameter:51,118 km Number of Observed Satellites: >20 Diameter:4.0 x Earth's Mean Distance from Sun:19.2 x Earth's Mass:14.5 x Earth's Density:0.22 x Earth's Uranus Facts The picture on the right uses false colors and contrast enhancement to bring out subtle details in the polar region of Uranus.

33. Uranus Uranus is named for the Greek god of the sky Uranus is named for the Greek god of the sky It is about four times the diameter of Earth, but much smaller than Jupiter and Saturn It is about four times the diameter of Earth, but much smaller than Jupiter and Saturn It is twice as far from the sun as Saturn, so it is much colder It is twice as far from the sun as Saturn, so it is much colder Has a unique blue-green color because of methane gas in its atmosphere Has a unique blue-green color because of methane gas in its atmosphere Its rings are thin, flat, and much darker than Saturn’s Its rings are thin, flat, and much darker than Saturn’s Discovered in 1781 by Willam Herschel in England, and is the first planet that was discovered after ancient times. Discovered in 1781 by Willam Herschel in England, and is the first planet that was discovered after ancient times.

34. Uranus In the 1980s (200 years after being discovered) Voyager 2 arrived at Uranus and sent back close-up pictures In the 1980s (200 years after being discovered) Voyager 2 arrived at Uranus and sent back close-up pictures It has few clouds, but astronomers calculated it rotated in about 17 hours It has few clouds, but astronomers calculated it rotated in about 17 hours Uranus is tilted on its side Uranus is tilted on its side It rotated top to bottom instead of side to side like other planets (and its rings and moons rotate around its tilted axis) It rotated top to bottom instead of side to side like other planets (and its rings and moons rotate around its tilted axis) Scientists think it was hit by an object billions of years ago that knocked it on its side Scientists think it was hit by an object billions of years ago that knocked it on its side

35. Uranus’s Moons Uranus has at least 27 moons Uranus has at least 27 moons Voyager 2 discovered the five largest moons have icy, cratered surfaces and lava flows Voyager 2 discovered the five largest moons have icy, cratered surfaces and lava flows

36. Neptune

37. Neptune Facts About 4 times diameter of Earth- a bit smaller than Uranus About 4 times diameter of Earth- a bit smaller than Uranus 4.5 billion km (2.8 billion miles) from Sun 4.5 billion km (2.8 billion miles) from Sun Period of revolution is 165 years Period of revolution is 165 years Rotation period is 18 hours Rotation period is 18 hours One large satellite (2700 km), seven smaller ones One large satellite (2700 km), seven smaller ones Four narrow rings Four narrow rings Named after the Roman god of the sea Named after the Roman god of the sea

38. Very cold, -225° C (-373° F) Gravitational compression produces more internal heat than it absorbs from the sun. The blue-green color of the planet is due to the presence of methane in the atmosphere. The atmosphere consists mostly of hydrogen, helium and methane. rings completely circle the planet, but the thickness of each ring varies along its length. Neptune

39. a great storm in the southern hemisphere called the “Great Dark Spot" is about half the size of Jupiter's Great Red Spot Spot is about the same diameter as the Earth at least one other smaller storm spot has been detected. Neptune has the fastest planetary winds in the Solar System, reaching as fast as 2,000 km (over 1,200 miles) per hour. Neptune’s Great Dark Spot

40. Neptune Neptune is similar in size and color to Uranus It is a blue color because of methane in its atmosphere Because it is so far from the sun, it is very cold It has clouds and storms in its atmosphere Scientists think the clouds and storms are happening because the planet is slowly shrinking, causing the interior to heat up

41. Discovering Neptune Neptune was discovered by mathematics astronomers noticed Uranus’s orbit wasn’t the exact path it should be and predicted an unseen planet was disturbing Uranus’s orbit By 1846 scientists had calculated the orbit of the unseen planet – soon after, Neptune was identified

42. Flying by Neptune In 1989 Voyager 2 flew by Neptune and photographed the Great Dark Spot (a storm about the size of Earth) In 1989 Voyager 2 flew by Neptune and photographed the Great Dark Spot (a storm about the size of Earth) Storms come and go on Neptune which tells us it has an active atmosphere Storms come and go on Neptune which tells us it has an active atmosphere

43. Neptune’s Moons Neptune has at least 13 moons The largest is Triton It has a thin atmosphere Its south pole is covered in nitrogen ice

44. Dwarf Planets Dwarf planets are round and orbits the sun, like a planet, but it has not cleared out the neighborhood around its orbit Dwarf planet classification was created in 2006 when an object larger than Pluto and farther from the sun was discovered At that time Pluto was reclassified as a dwarf planet and there are two others

45. Pluto Pluto is a dwarf planet It is much smaller and denser than the outer planets and has a solid surface Pluto is smaller than our Moon Pluto is so far from the sun that it takes 240 Earth years to revolve around the sun once This means that, since its discovery, Pluto hasn’t made a full revolution yet! Its orbit is very elliptical and it crosses inside Neptune’s orbit for part of its revolution Moons Pluto has five moons. The largest is Charon and is more than half as big as Pluto

46. Essential Questions - Answered 1.What characteristics do the gas giants have in common? No solid surface Thick atmosphere made mostly of hydrogen & helium A set of rings Very Large & massive Rotates quickly, revolves slowly

47. 2.What characteristics distinguish each of the outer planets? Jupiter – largest & most massive planet, Great Red Spot, most moons (63+) Saturn – second largest planets, best rings, least dense planet Uranus – blue-green color, rotates on its side Neptune – blue color, lots of storms Pluto – solid, rocky surface; no longer a planet