1 A) 10, 300 B) 30, 100 C) 300, 10 D) 100, 30 2 A) Carbon dioxide and water vapor. B) Hydrogen, hydrogen-rich compounds, and helium. C) Methane and ozone. D) Nitrogen and oxygen. 3 A) It may become a star in about a billion years. B) It has a solid core of ice about 1000 km under the visible surface. C) It is the least dense of the Giant Planets. D) It is more massive than all other planets combined. 4 A) A region of gas on Jupiter's surface that contains a great deal of iron. B) A huge, spinning vortex larger than the Earth in Jupiter's atmosphere. C) A place on Jupiter's surface where Comet Shoemaker-Levy landed in 1992. D) It's another name for Jupiter. 5 A) These planets have no solid surfaces for them to land on. B) Their clouds are so hot that any spacecraft getting near it would burn up. C) Their gravitational attraction is so weak that they would float off. D) Astronauts will land on the Giant Planets -- the idea is perfectly reasonable. 6 A) Radioactive decay of elements in Io's core heat up the rock to molten temperatures. B) Io is very close to the Sun. C) Io was formed later than the other Galilean satellites, so it hasn't finished cooling yet. D) Io gets flexed between the changing gravitational pulls of Jupiter and Europa, heating it by friction. 7 A) Io B) Europa C) Ganymede D) Callisto. 8 A) Chunks composed of water, ice, and carbon compounds. B) A huge sheet of ice. C) Helium droplets. D) Saturn does not have rings. 9 A) The mass a planet must exceed to have satellites B) The greatest distance from a planet that its satellites can orbit without falling into the Sun. C) The distance at which a moon held together by gravity may be broken apart by the planet's gravitational attraction. D) The distance astronomers can see into a planet's clouds. 10 A) Jupiter B) Saturn C) Uranus D) Neptune 11 A) Hydrogen appears blue when it reflects sunlight. B) They reflect blue light from their moons. C) Methane in their atmospheres absorb red light and reflect blue light. D) The planets are very hot, so their blackbody spectra peak at blue wavelengths. 12 A) Hydrogen and helium. B) Hydrogen and methane. C) Water and carbon dioxide. D) Ice and rock. 13 A) Jupiter B) Saturn C) Uranus. D) Neptune 14 A) Hydrogen and helium. B) ice and rock. C) Rock and iron. D) Hydrogen and methane 15 A) They were able to use a modified form of Kepler's third law of planetary motion to calculate Pluto's mass. B) They determined that Charon's orbital plane, and thus Pluto's rotation axis, are tilted steeply. C) Eclipses of Pluto by Charon allowed them to calculate both Pluto's and Charon's diameters. D) All of the above.
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