1. Chapter 30, Section 4 30.4 Satellites of Other Planets

2. Introduction Until the 1600s, astronomers thought that Earth was the only planet with a moon. Until the 1600s, astronomers thought that Earth was the only planet with a moon. In 1610, Galileo discovered moons orbiting Jupiter. In 1610, Galileo discovered moons orbiting Jupiter. All planets in our solar system have moons, except Mercury and Venus. All planets in our solar system have moons, except Mercury and Venus. Jupiter, Saturn, Neptune, and Uranus have rings. Jupiter, Saturn, Neptune, and Uranus have rings.

3. Questions Which planets have moons? Which planets have moons? Earth, Mars, Jupiter, Saturn, Uranus, Neptune Earth, Mars, Jupiter, Saturn, Uranus, Neptune Which planets have rings? Which planets have rings? Jupiter, Saturn, Neptune, and Uranus Jupiter, Saturn, Neptune, and Uranus

4. Moons of Mars - Phobos Phobos orbits Mars in 7 hours 40 minutes Phobos orbits Mars in 7 hours 40 minutes 27km at widest, 19km at shortest point. 27km at widest, 19km at shortest point. Many craters, one is 8km across. Many craters, one is 8km across. Not spherical. Not spherical.

5. Moons of Mars - Deimos Deimos orbits Mars in about 30 hours Deimos orbits Mars in about 30 hours 15km at widest, 11km at shortest point 15km at widest, 11km at shortest point Many craters Many craters What does a large number of craters suggest about the age of Phobos and Deimos? What does a large number of craters suggest about the age of Phobos and Deimos?

6. Question Name the two moons of Mars? Name the two moons of Mars? Phobos and Deimos Phobos and Deimos

7. Ring and Moons of Jupiter Galilean moon any one of the four largest satellites of Jupiter—Io, Europa, Ganymede, and Callisto - that were discovered by Galileo in 1610 Galilean moon any one of the four largest satellites of Jupiter—Io, Europa, Ganymede, and Callisto - that were discovered by Galileo in 1610 In addition to the four large moons discovered by Galileo, scientists have observed dozens of smaller moons around Jupiter. In addition to the four large moons discovered by Galileo, scientists have observed dozens of smaller moons around Jupiter. Of Jupiter’s four Galilean moons, three are larger than Earth’s moon. Of Jupiter’s four Galilean moons, three are larger than Earth’s moon. Jupiter has a single, thin ring made of microscopic particles that may have been given off by Io. Jupiter has a single, thin ring made of microscopic particles that may have been given off by Io.

8. Rings and Moons of Saturn Saturn has over 30 moons, but only five moons are fairly large. Saturn has over 30 moons, but only five moons are fairly large. Saturn’s largest moon is Titan, which has a diameter of over 5,000 km. Saturn’s largest moon is Titan, which has a diameter of over 5,000 km. Saturn’s set of rings was discovered over 300 years ago. Each of the rings circling Saturn is divided into hundreds of small ringlets, which are then composed of billions of pieces of rock and ice. Saturn’s set of rings was discovered over 300 years ago. Each of the rings circling Saturn is divided into hundreds of small ringlets, which are then composed of billions of pieces of rock and ice.

9. Question What are the names of the four moons of Jupiter discovered by Galileo? What are the names of the four moons of Jupiter discovered by Galileo? Io, Europa, Ganymede, and Callisto Io, Europa, Ganymede, and Callisto How many are bigger than earth? How many are bigger than earth? Three Three What is the name of Saturn’s largest moon? What is the name of Saturn’s largest moon? Titan Titan

10. Satellites of Uranus Uranus’s four largest moons, Oberon, Titania, Umbriel, and Ariel, were known by the mid-1800’s. Uranus’s four largest moons, Oberon, Titania, Umbriel, and Ariel, were known by the mid-1800’s. A fifth moon, Miranda, was discovered in 1948. Scientists now know that Uranus has over two dozen moons. A fifth moon, Miranda, was discovered in 1948. Scientists now know that Uranus has over two dozen moons. Uranus also has a dozen thin rings. Uranus also has a dozen thin rings.

11. Satellites of Neptune Neptune has at least eight moons. One of these moons, Triton, revolves around Neptune in a retrograde orbit. Neptune has at least eight moons. One of these moons, Triton, revolves around Neptune in a retrograde orbit. Neptune’s relatively small number of rings are clumpy rather than thin and uniform. Neptune’s relatively small number of rings are clumpy rather than thin and uniform.

12. Satellites of Pluto The relationship between Pluto and its moon Charon is unusual because Charon is almost half the size of Pluto itself. The relationship between Pluto and its moon Charon is unusual because Charon is almost half the size of Pluto itself. Because Pluto and Charon are similar in size, some scientists consider them to be a double- planet system. Because Pluto and Charon are similar in size, some scientists consider them to be a double- planet system. Charon completes one orbit around Pluto in 6.4 days, the same length of time as a day on Pluto. Because of these equal lengths, Charon stays in the same place in Pluto’s sky. Charon completes one orbit around Pluto in 6.4 days, the same length of time as a day on Pluto. Because of these equal lengths, Charon stays in the same place in Pluto’s sky.

13. Questions What are the names of Uranus’s four largest moons? What are the names of Uranus’s four largest moons? Uranus’s four largest moons are Oberon, Titania, Umbriel, and Ariel Uranus’s four largest moons are Oberon, Titania, Umbriel, and Ariel How many moons does Neptune have? How many moons does Neptune have? At least 8 At least 8 What is interesting between Pluto and Charon? What is interesting between Pluto and Charon? Because Pluto and Charon are similar in size, some scientists consider them to be a double-planet system. Because Pluto and Charon are similar in size, some scientists consider them to be a double-planet system.