Chapter 6

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Jupiter and the other jovian planets are sometimes called "gas giants." In what sense is this term misleading?
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What is the most likely method in which Jupiter generates its internal heat?by contracting, changing gravitational potential energy into thermal energyHow do the size and mass of Jupiter's core compare to the size and mass of Earth?Jupiter's core is about the same size but is 10 times more massive.How do the jovian planet interiors differ from one another?All have cores of about the same mass, but differ in the amount of surrounding hydrogen and helium.Why does Jupiter have several distinct cloud layers?Different layers represent clouds made of gases that condense at different temperatures.Why do Uranus and Neptune appear blue?The methane gas in their atmospheres absorbs all colors except blue.Which of the following is a general characteristic of the four jovian planets in our solar system?They are lower in average density than are the terrestrial planets.Which lists the jovian planets in order of increasing distance from the Sun?Jupiter, Saturn, Uranus, NeptuneSome jovian planets give off more energy than they receive because ofongoing contraction or differentiation.Hydrogen exists as a gas, liquid, and solid within Jupiter.TrueJupiter's Great Red Spot is a low-pressure storm, like a hurricane on Earth.FalseWhich of the following best explains why many jovian moons have been more geologically active than the Moon or Mercury?Jovian moons are made mostly of ice that can melt or deform at lower temperatures than can the rock and metal that make up the Moon and Mercury.Why do astronomers believe that Triton is a captured moon?Triton orbits Neptune in a direction opposite that of Neptune's rotation.Which statement about Io is true?It is the most volcanically active body in our solar system.Which moon has a thick atmosphere made mostly of nitrogen?TitanThe Huygens probe took numerous pictures as it descended to Titan's surface in 2005. What did the pictures show?features of erosion, including what appeared to be dry river valleys and lakebedsWhat is the primary reason an icy moon is likely to be more geologically active than a rocky moon of the same size?Ice has a lower melting point than rock.What mechanism is most responsible for generating the internal heat of Io that drives its volcanic activity?tidal heatingWhat is the most abundant gas in Titan's atmosphere?nitrogenThe large Jovian satellites have sizes comparable to Mercury. Why do they have an icy composition compared to Mercury's rocky composition?They formed beyond the frost line, where ices were more abundant than metals and rock.What is unusual about Triton?It orbits its planet backward.Saturn's many moons affect its rings throughorbital resonancesOnly one of the moons of the jovian planets has an atmosphere thicker than Earth's atmosphere.TrueThe Huygens landing showed that the surface of Titan is made of mostly rock.FalseTitan's surface may contain lakes of liquid methane.TrueGanymede is larger than Mercury, but it is not classified as a planet because it orbits Jupiter as opposed to the sun.TrueSuppose you could float in space just a few meters above Saturn's rings. What would you see as you looked down on the rings?countless icy particles, ranging in size from dust grains to large bouldersWhich of the following best describes the composition of the particles forming Saturn's rings?water iceWhat is the Cassini division in Saturn's rings?a large gap, visible from Earth, produced by an orbital resonance with the moon MimasWhich of the jovian planets have rings?all of the aboveSaturn's ringare continually supplied by impacts with small moons.If we could put all the asteroids together, their total mass would be ________.much less than the mass of any terrestrial planetWhy didn't a planet form where the asteroid belt is now located?Gravitational tugs from Jupiter prevented material from collecting together to form a planet.What do asteroids and comets have in common?Most are unchanged since their formation in the solar nebula.A rocky leftover planetesimal orbiting the Sun isan asteroid.An icy leftover planetesimal orbiting the Sun isa comet.Why do asteroids and comets differ in composition?Asteroids formed inside the frost line, while comets formed outside.The asteroid belt is located _________.between the orbits of Mars and JupiterHow do asteroids differ from comets?Asteroids are made mostly of rocky and/or metallic material. Comets are made mostly of icy material.What causes the "gaps" observed in the asteroid belt between Mars and Jupiter?Jupiter's gravity causes orbital resonances that nudge asteroids out of these areas.The greatest number of asteroids are foundbetween 2 and 3 AU from the sun.Which of the following statements about asteroids, Kuiper belt objects, and Oort cloud objects is true?Objects in the asteroid belt and Kuiper belt orbit the Sun in nearly the same plane as the planets, but objects in the Oort cloud do not.About how often does a 1-kilometer object strike the Earth?every million yearsA spacecraft traveling through the asteroid belt has a high risk of being destroyed through a collision.FalseWhich of the following objects are probably not located in the same general region of the solar system in which they originally formed?Oort cloud cometsWhere did comets that are now in the Oort cloud originally form?near the jovian planetsWhere did comets that are now in the Kuiper belt originally form?in the same region where they are found todayAccording to the nebular theory, how did the Kuiper belt form?It is made of planetesimals that formed beyond Neptune's orbit and never accreted to form a planet.According to the nebular theory, how did the Oort cloud form?It is made of planetesimals formed in the outer solar system that were flung into distant orbits by encounters with the jovian planets.Which are thought to have formed farthest from the Sun?Kuiper belt cometsSuppose that large jovian planets had never formed in our solar system. Which of the following would most likely be true?Neither the asteroid belt nor Oort cloud would exist.Which of the following is not a piece of evidence supporting the idea that an impact caused the mass extinction that occurred 65 million years ago?Fossilized dinosaur bones contain fragments of rock from the impact.If the hypothesis tracing the extinction of the dinosaurs to an impact is correct, the dinosaurs died off largely because ________.of global climate effects initiated by dust and smoke that entered the atmosphere after the impactWhich of the following statements best describes the general pattern of composition among the four jovian planets?Uranus and Neptune contain relatively more rock and hydrogen compounds than Jupiter and Saturn.Look at the average densities of the jovian planets given in Figure 1. Can you identify a trend in jovian planet densities with mass or distance from the Sun?There is no clear trend in the densities with mass or distance.Which of the following statements best explains why the densities of Uranus and Neptune are higher than that of Saturn, even though Saturn is much more massive?They have a higher proportion of hydrogen compounds and rock.Which of the following best explains why Jupiter's density is higher than Saturn's?Jupiter is more massive than Saturn.Based on the leading scientific theory of solar system formation, which of the following statements best explains why Uranus and Neptune have a significantly different composition than Jupiter and Saturn?Jupiter and Saturn captured more gas from the solar nebula than Uranus and Neptune.Based on what you learn about jovian moons by watching the videos or reading your textbook, what types of evidence for recent or ongoing geological activity have been observed on one or more jovian moons?ice crystals being sprayed out into space river valleys feeding into surface lakes of very cold liquids surfaces with very few impact craters active volcanoesMatch the moons listed to the left with the characteristics described in the sentences to the right.Europa: This moon of Jupiter has an icy surface with very few impact craters, suggesting that craters have been covered by upwelling water. Enceladus: Orbits Saturn and has been observed to be spraying fountains of ice crystals into space. Io: The most volcanically active world in the solar system. Triton: This moon of Neptune orbits "backward" compared to Neptune's rotation. Ganymede: The largest moon in the solar system, this moon has some regions that are heavily cratered other regions that have very few craters. Titan: The only moon in the solar system with a thick atmosphere, it also has lakes of liquid methane and ethane.In light of what we know about geological activity on the terrestrial worlds, why might it seem surprising to find geological activity on jovian moons?because they are relatively small in sizeWhich of the following can contribute to explaining why jovian moons are sometimes much more geologically active than terrestrial worlds of similar (or smaller) size?tidal heating ice-rich compositionWhat is the relevance of tidal heating to the possibility of life on jovian moons?Tidal heating can lead to subsurface zones of liquid water.Io experiences tidal heating primarily because __________.its elliptical orbit causes the tidal force to vary as Io orbits Jupiter.As you saw in Part A, Io's elliptical orbit is necessary to its tidal heating. This elliptical orbit, in turn, is a result of the orbital resonance among Io, Europa, and Ganymede. This orbital resonance causes Io to have a more elliptical orbit than it would otherwise, because __________.Io, Europa and Ganymede periodically return to the same orbital positions, creating the same gravitational tugsWe cannot see tidal forces or tidal heating; rather, we predict that they must occur based on the orbital characteristics of the moons. What observational evidence confirms that tidal heating is important on Io?active volcanoes on IoOrbital resonance also gives Europa an elliptical orbit, so it experiences tidal heating, too. However, Europa experiences less tidal heating than Io, because Europa __________ than farther from JupiterWe now know of many Jupiter-size planets around other stars. Suppose that future observations show that one of these planets has two orbiting moons. What additional information, if any, would we need to decide whether these moons experience tidal heating?We need to know their orbital periods.The following images show Earth and the four jovian planets of our solar system. Rank these planets from left to right based on their distance from the Sun, from closest to farthest. (Not to scale.)Closets Earth Jupiter Saturn Uranis NeptuneThe following images show Earth and the four jovian planets of our solar system. Rank these planets from left to right based on their size (average equatorial radius), from smallest to largest. (Not to scale.)Smallest radius Earth Neptune Uranus Saturn JupiterThe following images show Earth and the four jovian planets of our solar system. Rank these planets from left to right based on their mass, from lowest to highest. (Not to scale.)Lowest mass Earth Uranus Neptune Saturn jupiterSort each of the planetary properties below based on whether they apply to some, all, or none of the four jovian planets in our solar system.Jupiter and saturn only -interior is mostly liquid or metallic hydrogen -composed mostly of hydrogen and helium Uranus and Neptune only -blue color because of methane -composed mostly hydrogen compounds all four jovian planets -approximately 10 Earth-mass core -orbited by rings of ice and rock -magnetic field stronger than Earth's np jovian planets -solid surface under a thick atmosphereMatch the words in the left-hand column to the appropriate blank in the sentences in the right-hand column. Use each word only once.1. The largest moon in the solar system is Ganymede. 2. The jovian moon with the most geologically active surface is Io. 3. Strong evidence both from surface features and magnetic field data support the existence of a subsurface ocean on Europa. 4. Tidal heatingis responsible for the tremendous volcanic activity on Io. 5. Callistois the most distant of Jupiter's four Galilean moons. 6. The fact that Europa orbits Jupiter twice for every one orbit of Ganymede is an example of a(n) orbital resonance.Listed following are several objects in the solar system. Rank these objects from left to right based on their distance from the Sun, from closest to farthest.Closets -a typical asteroidin the asteroid belt Background Image Background Image -a typical Kuiper belt object Background Image Background Image -a typical Oort cloud objectListed following are several objects in the solar system. Rank these objects from left to right based on their orbital period around the Sun from shortest to longest.Shortes -a typical asteroidin the asteroid belt Background Image Background Image -a typical Kuiper belt object Background Image Background Image -a typical Oort cloud objectListed following are several objects in the solar system. Rank these objects from left to right based on the distance from the Sun at which they are presumed to have formed, from nearest to farthest.nearest to sun -a typical asteroidin the asteroid belt Background Image Background Image -a typical Oort cloud object Background Image Background Image -a typical Kuiper belt objectWhere do scientists find the key evidence linking the extinction of the dinosaurs to the impact of an asteroid or comet?in sediments separating rocks from the time when dinosaurs existed from those deposited after dinosaurs were no longer foundComplete the following sentences that describe evidence found in the K-T boundary layer.1. The presence of shocked quartz suggests an impact because these mineral grains form only under high-pressure conditions. 2. The presence of soot suggests that there were world-wide forest fires at the time this layer formed. 3. The unusually high abundance of iridium in this layer suggests that this material came from the impact of an asteroid (or comet). 4. The presence of solidfied rock "droplets" is thought to indicate that rock splashed upward by an impact was molten as it fell back down from the sky.Why does the abundance of iridium suggest that the iridium came from an impact?Iridium is rare on Earth's surface but common in meteorites that have impacted the Earth.Put the following events into the correct order in which they are thought to have occurred according to the impact hypotethesis.First event 1. impact 2. debris and tsunami devastate North America 3. soot released by global forest fires (ignited by rain of molten rock) 4. long global winter 5. extinction of large fraction of all speciesAssuming the impact hypothesis is correct, in what way(s) was the impact important to our existence on Earth today?It seems unlike that we would have evolved by now without the extinctions caused by the impact.According to this graph, the minimum size of an object that could cause a mass extinction is a little less than _____.10 kmAccording to the graph, an object 10 kilometers across hits Earth __________.about once every 100 million yearsWhat is the probability that an object 100 meters in diameter will hit Earth during the coming year?about 1 in 1000Based on this graph, which statement below most accurately describes the impacts we should expect on Earth during the coming year?Earth will be hit by at least one object a few meters in diameter, along with many smaller objects.The impact of a 100-meter object will not cause "widespread" devastation, but it could still kill millions of people if it struck a major city. In Part C, you found that the probability of such an impact in any single year is only 1 in 1000. Suppose we learn that it has already been 1200 years since the last such impact. What would that tell us?Nothing; we would still presume that the chance of such an impact during the next year is 1 in 1000.