Astronomy 101 Exam 4

2. The bright spherical part of a comet observed when it is close to the Sun is the

coma

Just as the surface area-to-volume ratio depends on size, so can other properties. To see how, suppose that your size suddenly doubled-that is, your height, width, and depth all doubled. (For example, if you were 5 feet tall before, you now are 10 feet tall.) By what factor has your weight increased? (Hint: Weight depends on the volume of your body.) -1 -2 -4 -8

-8

-about the same size (radius) as Jupiter *Notice that the curve turns back downward at masses just a couple times that of Jupiter, and the radius of a 10 Jupiter-mass object is about the same as the radius of Jupiter*

According to this graph, a planet with 10 times the mass of Jupiter would be: -about 100 times as large as Jupiter in size (radius) -about ten times as large as Jupiter in size (radius) -about 60% as large as Jupiter in size (radius) -about the same size (radius) as Jupiter

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.)

Closest: Earth Jupiter Saturn Uranus Neptune :Farthest

1. The largest moon in the solar system is

Ganymede

-the Kuiper belt *As shown, the Kuiper belt lies in the region just beyond Neptune's orbit.*

Each white dot in this figure represents the location of a small body in our solar system. The donut shaped ring of white dots just beyond Neptune's orbit represents the part of our solar system that we call: -the Kuiper belt -the solar nebula -the asteroid belt -the Oort cloud

-the asteroid belt *As shown, the asteroid belt lies between the orbits of Mars and Jupiter.*

Each white dot in this figure represents the location of a small body in our solar system. The donut shaped ring of white dots represents the region of our solar system that we call: -the Kuiper belt -the asteroid belt -the Sun's rings -the Oort cloud

3. Strong evidence both from surface features and magnetic field data support the existence of a subsurface ocean on

Europa

In Part A, you found that Earth emits only infrared light. This infrared light can be absorbed by greenhouse gases, such as carbon dioxide and water vapor, in the atmosphere. In fact, all the terrestrial planets emit infrared light from their surfaces. The following images show the four terrestrial planets in our solar system. Rank these planets from left to right based on the total amount of infrared-absorbing greenhouse gases in their atmospheres, from greatest to least.

Greatest Greenhouse Abundance: Venus Earth Mars Mercury :Least Greenhouse Gas Abundance *Venus has a thick atmosphere of carbon dioxide. Earth has greenhouse gases primarily in the form of water vapor, carbon dioxide, and methane. Mars has an atmosphere made mostly of carbon dioxide, but its atmosphere is so thin that it contains less total greenhouse gas than Earth's atmosphere. Mercury has essentially no atmosphere at all.*

HOMEWORK 11

HOMEWORK 11

2. The jovian moon with the most geologically active surface is

Io

6. The ____________________ extends from about beyond the orbit of Neptune to about twice the distance of Neptune from the Sun.

Kuiper belt

The following images show the four terrestrial planets in our solar system. Rank these planets from left to right based on the total amount of gas in their atmospheres, from most to least. (Not to scale.)

Most: Venus Earth Mars Mercury :Least *Note that this ranking is the same as the pressure ranking from Part A. This should not be surprising, because more atmospheric gas generally means more pressure (though the strength of gravity at a planet's surface also plays a role in determining the pressure).*

Each ring particle in the densest part of Saturn's rings collides with another about every 5 hours. If a ring particle survived for the age of the solar system, how many collisions would it undergo?

N = 8×10^12 collisions

1. About a trillion comets are thought to be located far, far beyond Pluto in the

Oort cloud

Listed 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.

Shortest: -A typical asteroid in the asteroid belt -A Trojan asteroid -A typical Kuiper belt object -A typical Oort Cloud Object :Longest *Be sure to notice that these objects obey Kepler's laws, so the more distant objects have longer orbital periods.*

-an impact crater *It is Meteor Crater in Arizona.*

The geological feature in this photo is _________. -a dried up lake basin -a volcano -an impact crater -the unusual cloud formation in the background

Why is the sky blue (on Earth)? -because the Sun emits mostly blue light -because molecules scatter red light more effectively than blue light. -No one knows—this is one of the great mysteries of science. -because molecules scatter blue light more effectively than red light -because deep space is blue in color

because molecules scatter blue light more effectively than red light

A few hundred tons of comet dust gets added to Earth daily from the millions of meteors that enter our atmosphere. Is this mass accumulation significant for Earth as a planet?

insignificant

5. Particles ejected from a comet can cause a(n) ________________________ on Earth.

meteor shower

6. The fact that Europa orbits Jupiter twice for every one orbit of Ganymede is an example of a(n) ___________________.

orbital resonance

3. A comet's _________________ stretches directly away from the Sun.

plasma tail

2. Earth's ________________ absorbs most of the ultraviolet light arriving here from the Sun.

stratosphere

3. Most of the X-rays coming from the Sun are absorbed in the

thermosphere

5. The extremely deep ocean Marianas Trench is a result of

-subduction

What was the Shoemaker-Levy 9 impact? -the impact thought to have wiped out the dinosaurs -the ninth impact witnessed by astronomers in modern times -the 1994 impact of a chain of comet fragments into Jupiter -the impact that created the Moon's largest crater

-the 1994 impact of a chain of comet fragments into Jupiter *This impact was studied by astronomers around the world and taught us a lot about how impacts occur.*

Overall, Jupiter's composition is most like that of _________. -the Sun -a comet -Earth -an asteroid

-the Sun

When a comet passes near the Sun, part of it takes on the appearance of a large, bright ball from which the tail extends. This part is called _________. -the nucleus -the plasma tail -the Oort core -the coma

-the coma

When a comet passes near the Sun, part of it takes on the appearance of a large, bright ball from which the tail extends. This part is called _____. -the plasma tail -the Oort core -the coma -the nucleus

-the coma *The coma is essentially a large atmosphere of gas and dust released by the comet.*

Just as the surface area-to-volume ratio depends on size, so can other properties. To see how, suppose that your size suddenly doubled-that is, your height, width, and depth all doubled. (For example, if you were 5 feet tall before, you now are 10 feet tall.) The pressure on your weight-bearing joints depends on how much weight is supported by the surface area of each joint. How has this pressure changed? -1 -2 -4 -8

-2

Just as the surface area-to-volume ratio depends on size, so can other properties. To see how, suppose that your size suddenly doubled-that is, your height, width, and depth all doubled. (For example, if you were 5 feet tall before, you now are 10 feet tall.) How much more material will be required for your clothes? (Hint: Clothes cover the surface area of your body.) -1 -2 -4 -8

-4

Which direction do a comet's dust and plasma tails point? -generally away from the Sun -perpendicular to the ecliptic plane -always almost due north -straight behind the comet in its orbit

-generally away from the Sun *They are pushed away from the Sun by radiation and the solar wind*

You have found that Planet Z should have active tectonics and volcanism and an atmosphere produced by volcanic outgassing. What single factor explains why the planet should have these characteristics? Planet Z: -has a slow rotation rate. -has a large size for a terrestrial planet. -closely orbits its star. -lacks axis tilt.

-has a large size for a terrestrial planet. *Large size means more internal heat. This internal heat drives active tectonics and volcanism, which is the source of outgassing.*

The 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: Earth Neptune Uranus Saturn Jupiter :Largest

-1 *The smooth, dark regions are the lunar maria.*

Which feature in this photo of the full moon is one of the lunar maria? -1 -2 -3 -4

Listed following are some distinguishing characteristics of comets, meteors, and asteroids. Match these to the appropriate category of objects.

*Comets*: -Visible in the sky as a fuzzy patch of light that rises and sets with the stars -Most are located either in Kuiper belt of Oort cloud -Form a coma when near the sun *Meteors:* -Dust particles entering Earth's atmosphere at high speed -Visible in the sky as a bright streak of light for only a few seconds *Asteroids:* -Typically orbit the sun at approximately 3 AU -Compositions similar to that of the terrestrial planets

Sort 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 of hydrogen compounds *All four jovian planets:* -Orbited by rings of ice and rock -Magnetic field stronger than Earth's -Strong atmospheric winds and storms -Approximately 10 Earth-mass core *No jovian planets:* -Solid surface under a thick atmosphere *The jovian planets share many characteristics in common such as approximate core size, severe weather, rings and numerous moons, and strong magnetic fields. Jupiter and Saturn have similar compositions of hydrogen and helium, while Uranus and Neptune are composed primarily of hydrogen compounds. Unlike the terrestrial planets, the jovian planets do not have solid surfaces.*

Which of the following shows the four jovian planets correctly scaled in size?

*Notice that Jupiter and Saturn (aside from the rings) are similar in size, even though Jupiter is more than three times as massive. Uranus and Neptune are much smaller, but similar to each other in both size and mass.*

What of the following sketches shows the dwarf planets Pluto and Eris correctly scaled in comparison to Earth?

*Notice that Pluto and Eris are much smaller than Earth in size; in mass, they are less than about 1% as large as Earth.*

Which of the following photos shows the planet Neptune?

*Notice the deep blue color and the storm called the Great Dark Spot.*

Which photo shows an object that looks most like a typical asteroid?

*The give-away is the non-spherical shape. This is the asteroid Ida, which happens to have a small moon (to the right).*

The following figures show four positions (1-4) of a comet during its orbit of the Sun. Also shown is the orbit of the Earth around the Sun. Rank the positions of the comet from left to right based on the size of its tail, from shortest to longest. (Not to scale; tails not shown.)

*The length of the tail depends primarily on the distance of the comet from the Sun. It is longer when the comet is closer to the Sun and shorter (or nonexistent) when the comet is farther from the Sun.*

A comet grows tails (plasma tail and dust tail) when it comes close to the Sun. Which of the following diagrams shows a comet's tails correctly oriented as they appear along its orbit?

*The tails point away from the Sun because they are pushed back by radiation and the solar wind.*

Pluto looks much like one of the following objects. Which one?

*This is Neptune's moon Triton, which probably was once a Kuiper belt object orbiting the Sun much like Pluto and Eris.*

These four photos show features of Earth that change with time, some fast and some slow. Which one of these features is being shaped primarily by the process we call tectonics?

*This photo shows the Himalayas, built by plate tectonics.*

The major processes that heat the interiors of the terrestrial worlds are: -(1) Volcanism; (2) tectonics; (3) erosion. -(1) Heat deposited as the planets were built from planetesimals; (2) heat deposited as the planets underwent differentiation; (3) heat released by radioactive decay. -(1) Heat of accretion; (2) heat from convection; (3) heat from thermal radiation. -(1) Heat deposited as the planets were built from planetesimals; (2) heat of accretion; (3) heat that came from the gravitational potential energy of incoming planetesimals.

-(1) Heat deposited as the planets were built from planetesimals; (2) heat deposited as the planets underwent differentiation; (3) heat released by radioactive decay. *The first two were important only in Earth's early history; radioactive decay continues to be important today, though at a lower level than in the past*

The major processes that heat the interiors of the terrestrial worlds are __________. -(1) heat deposited as the planets were built from planetesimals; (2) heat of accretion; (3) heat that came from the gravitational potential energy of incoming planetesimals -(1) heat deposited as the planets were built from planetesimals; (2) heat deposited as the planets underwent differentiation; (3) heat released by radioactive decay -(1) heat of accretion; (2) heat from convection; (3) heat from thermal radiation -(1) volcanism; (2) tectonics; (3) erosion

-(1) heat deposited as the planets were built from planetesimals; (2) heat deposited as the planets underwent differentiation; (3) heat released by radioactive decay

The total number of comets orbiting the Sun is estimated to be about ______. -100,000 -1 trillion -1,000 -1 million

-1 trillion *This number is estimated by counting the number of comets that we see in the inner solar system and then calculating how many must exist in the Oort cloud in order to account for those that we see.*

A few hundred tons of comet dust gets added to Earth daily from the millions of meteors that enter our atmosphere. Estimate the time it would take for Earth to get 0.1% heavier at this rate. -10^10 years -10^14 years -10^18 years -10^20 years

-10^14 years

The minimum size of an object that could cause a mass extinction is a little less than _____. -10m -100m -1km -10km -10 km

-10km *Looking straight down from the edges of the bracket labeled "mass extinction," you can tell that the smallest size object that falls into this bracket is just a little less than 10 kilometers.*

Just as the surface area-to-volume ratio depends on size, so can other properties. To see how, suppose that your size suddenly doubled-that is, your height, width, and depth all doubled. (For example, if you were 5 feet tall before, you now are 10 feet tall.) By what factor has your waist size increased? -1 -2 -4 -8

-2

Which of the following most likely explains why Venus does not have a global magnetic field like Earth? -Its rotation is too slow. -It does not have a metallic core. -It has too thick of an atmosphere. -Unlike Earth, Venus does not have a liquid outer core.

-Its rotation is too slow. *Rotation is required for a magnetic field.*

Make a prediction: If the rise in carbon dioxide concentration continues at its current pace, the concentration in the year 2037 will be about _____ parts per million. -330 -390 -430 -510

-430 *Note that this concentration is more than 40% higher than the maximum of about 300 parts per million that the carbon dioxide concentration reached naturally during the prior 400,000 years. In fact, the situation could be even worse: Careful study of the graph shows an acceleration of the rate of increase in recent years, which would lead the carbon dioxide concentration to be even higher than 430 parts per million by 2037.*

What are the basic requirements for a terrestrial world to have a global magnetic field? -A metal core, a rocky mantle, and sufficiently rapid rotation. -A core layer of molten, convecting material and sufficiently rapid rotation. -A core that has a molten layer and a mantle that has convection. -A metal core and rapid rotation.

-A core layer of molten, convecting material and sufficiently rapid rotation. *Earth has all three, which is why it has a global magnetic field.*

In the context of plate tectonics, what is a subduction zone? -A place where two continental plates are colliding. -A place where two plates are slipping sideways against one another. -A place where two plates are pulling apart. -A place where a seafloor plate is sliding under a continental plate.

-A place where a seafloor plate is sliding under a continental plate. *This process returns seafloor crust to the mantle.*

What is Eris? -The largest known asteroid. -A moon of Pluto. -An icy object that orbits in the Kuiper belt and is larger than Pluto -An extrasolar planet ejected by another solar system and captured by ours.

-An icy object that orbits in the Kuiper belt and is larger than Pluto *It is the largest known member of the Kuiper belt (as of 2007) and is officially classified as the largest known dwarf planet in our solar system.*

In general, which things below are affected by a magnetic field? -Charged particles or magnetized materials (such as iron). -Rocks of all types. -Gases and liquids. -Iron-bearing minerals only.

-Charged particles or magnetized materials (such as iron). *Magnetic fields do not affect most other materials or electrically neutral particles.*

Which statement is NOT thought to be true of all comets in our solar system? -Comets always have tails. -All comets orbit the Sun. -All comets are icy in composition. -All comets are leftover planetesimals that originally condensed beyond the frost line in the solar nebula.

-Comets always have tails.

Which statement is not thought to be true of all comets in our solar system? -Comets always have tails. -All comets orbit the Sun. -All comets are icy in composition. -All comets are leftover planetesimals that originally condensed beyond the frost line in the solar nebula.

-Comets always have tails. *Only the rare comets that enter the inner solar system have tails, and only when they are close to the Sun*

Why is Earth's continental crust lower in density than seafloor crust? -Continental crust comes from Earth's inner core while seafloor crust comes from the outer core. -Continental crust comes from volcanoes while seafloor crust comes from geysers. -Continental crust is made as the lowest-density seafloor crust melts and erupts to the surface near subduction zones. -Continental crust is made from a low-density volcanic rock called basalt.

-Continental crust is made as the lowest-density seafloor crust melts and erupts to the surface near subduction zones. *The higher density materials from the seafloor crust subduct downward and eventually are recycled back to the seafloor.*

From center to surface, which of the following correctly lists the interior layers of a terrestrial world? -Core, crust, lithosphere. -mantle, core, crust. -Core, mantle, crust. -mantle, crust, core.

-Core, mantle, crust. *These are the layers defined by density; by rock strength, we speak instead of the lithosphere, the stiff layer of rigid rock that encompasses the crust and the top of the mantle.*

Which of the following best describes the geological histories of the Moon and Mercury? -Impact cratering shaped these worlds early in their histories. Then, during the past few million years, they were reshaped by episodes of volcanism and tectonics. -All four geological processes were important in their early histories, but only impact cratering still reshapes their surfaces today. -Impact cratering is the only major geological process that has affected their surfaces. -Early in their histories, they suffered many impacts and experienced some volcanism and tectonics, but they now have little geological activity at all.

-Early in their histories, they suffered many impacts and experienced some volcanism and tectonics, but they now have little geological activity at all. *That pretty much summarizes the geological histories of the Moon and Mercury*

Which statement below most accurately describes the impacts we should expect on Earth during the coming year? -Earth will be hit by one object about 100 meters in diameter and several objects of about 10 meters in diameter. -Earth will be hit by at least one object a few meters in diameter, along with many smaller objects. -Earth will be hit by one object that is a few meters in diameter, but no larger or smaller objects. -Only objects smaller than 1 meter across will hit Earth.

-Earth will be hit by at least one object a few meters in diameter, along with many smaller objects. *A typical time of 1 year between impacts corresponds to impactor sizes between about 1 and 10 meters. The typical time is less for smaller objects. Therefore, on average, we'd expect that Earth will be hit by one object a few meters across and many smaller objects in the next year.*

Which moon is considered likely to have a deep, subsurface ocean of liquid water? -Europa -Triton -Io -Miranda

-Europa

Which of the following places is the result of volcanoes erupting over a hot spot in the mantle? -the Himalayas -California -the Appalachians -Hawaii

-Hawaii *The chain of islands has formed as the Pacific plate has moved over this hot spot.*

Which internal heat source still generates heat within the terrestrial worlds today? -Heat of accretion. -Heat from differentiation -Heat from convection. -Heat from radioactive decay.

-Heat from radioactive decay. *Radioactive decay generated even more heat in the past, since there are fewer radioactive materials left as time goes by.*

What is the leading hypothesis for Venus's lack of water? -Venus formed closer to the Sun and accreted very little water. -Its water is locked away in the crust. -Its water molecules were broken apart, and hydrogen was lost to space.

-Its water molecules were broken apart, and hydrogen was lost to space.

Which statement about asteroids is not true? -Many but not all orbit the Sun in the asteroid belt. -Some are more like loosely bound piles of rubble than solid chunks of rock. -Most asteroids are not spherical in shape. -If we could put all the asteroids together, they would make an object about the size of Earth.

-If we could put all the asteroids together, they would make an object about the size of Earth. *The total mass of the asteroids is much less than the mass of a terrestrial planet.*

Why is Io more volcanically active than our moon? -Io is much larger. -Io has a higher concentration of radioactive elements. -Io has a different internal heat source.

-Io has a different internal heat source.

From 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 __________. -Europa and Ganymede always pull on Io from the same direction as Jupiter pulls on Io -all three moons orbit with the same period, staying aligned at all times -Io periodically passes Europa and Ganymede in the same orbital position -Europa and Ganymede are unusually large moons

-Io periodically passes Europa and Ganymede in the same orbital position *The repeated passes at the same orbital position mean that Io experiences repeated gravitational tugs at the same place in each orbit, and these tugs make its orbit more elliptical than it would be otherwise.*

Io experiences tidal heating primarily because __________. -Io has an unusually elongated shape that makes it look more like an egg than a sphere -Io is made of relatively soft materials that deform quite easily -Io is located very close to Jupiter -Io's elliptical orbit causes the tidal force on Io to vary as it orbits Jupiter

-Io's elliptical orbit causes the tidal force on Io to vary as it orbits Jupiter *The strength of the tidal force depends on Io's distance from Jupiter, so the tidal force varies as Io moves around its elliptical orbit. The tidal bulge even changes direction slightly, because the orbital speed varies. These tidal effects essentially stretch and compress Io's interior, and this tidal friction is the source of the tidal heating.*

What happens to the energy that the ground absorbs in the form of visible sunlight? -It is returned upward in the form of infrared light. -It is returned upward in the form of visible light. -It makes the ground continually get hotter and hotter.

-It is returned upward in the form of infrared light. *Remember that objects emit thermal radiation characteristic of their temperatures. Earth's surface has a temperature for which its thermal radiation peaks in the infrared. In other words, Earth absorbs energy from space in the form of visible light, and returns this energy to space in the form of infrared light.*

Which statement about Io is true? -It is thought to have a deep, subsurface ocean of liquid water. -It is the most volcanically active body in our solar system. -It is the only moon in the solar system with a thick atmosphere. -It is the largest moon in the solar system.

-It is the most volcanically active body in our solar system.

Why does the Moon have a layer of "powdery soil" on its surface? -It is made by the same processes that make powdery sand on Earth. -It exists because the Moon accreted from powdery material after a giant impact blasted the Earth. -Recent, large impacts shattered lunar rock to make this soil. -It is the result of countless tiny impacts by small particles striking the Moon.

-It is the result of countless tiny impacts by small particles striking the Moon. *On Earth, these particles burn up in the atmosphere (creating what we see as meteors).*

What is unusual about Triton? -It orbits its planet backward. -It does not keep the same face toward its planet. -It is the only moon with its own rings.

-It orbits its planet backward.

On a cloudless day, what happens to most of the visible light headed toward Earth? -It is reflected by Earth's atmosphere. -It is absorbed and reemitted by gases in Earth's atmosphere. -It is completely reflected by Earth's surface. -It reaches Earth's surface, where some is reflected and some is absorbed.

-It reaches Earth's surface, where some is reflected and some is absorbed. *Most visible light passes through our atmosphere, and this light heats the surface as it is absorbed.*

What is the importance of the carbon dioxide (CO2) cycle? -It makes the growth of continents possible. -It regulates the carbon dioxide concentration of our atmosphere, keeping temperatures moderate. -It will prevent us from suffering any consequences from global warming. -It allows for an ultraviolet-absorbing stratosphere.

-It regulates the carbon dioxide concentration of our atmosphere, keeping temperatures moderate.

What is the importance of the carbon dioxide (CO2) cycle? -It makes the growth of continents possible. -It will prevent us from suffering any consequences from global warming. -It regulates the carbon dioxide concentration of our atmosphere, keeping temperatures moderate. -It allows for an ultraviolet-absorbing stratosphere.

-It regulates the carbon dioxide concentration of our atmosphere, keeping temperatures moderate.

You discover an impact crater that is 10 kilometers across. Which of the following can you conclude? -It was created by the impact of an object about 1 kilometer across. -It was created within the past 10 million years. -It was created by the impact of an object about 10 kilometers across. -It was created within the past 1 billion years.

-It was created by the impact of an object about 1 kilometer across. *Impact craters are typically 10 times as wide as the objects that create them*

Which describes our understanding of flowing water on Mars? -It was never important. -It was important once, but no longer. -It is a major process on the Martian surface today.

-It was important once, but no longer.

What would happen if a 1-kilometer object struck Earth? -It would break up in the atmosphere without causing widespread damage. -It would cause widespread devastation and climate change. -It would cause a mass extinction.

-It would cause widespread devastation and climate change.

Why is Jupiter denser than Saturn? -It has a larger proportion of rock and metal. -It has a higher proportion of hydrogen. -Its higher mass and gravity compress its interior.

-Its higher mass and gravity compress its interior.

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 and higher density than Jupiter and Saturn? -Jupiter and Saturn captured more gas from the solar nebula than Uranus and Neptune. -The lower temperatures at the locations of Uranus and Neptune allowed more material to condense into solid form into solid form. -The lower masses of Uranus and Neptune allowed more of their hydrogen and helium gas to escape into space. -Jupiter and Saturn formed closer to the Sun, where there was more hydrogen and helium gas and less hydrogen compounds and rock.

-Jupiter and Saturn captured more gas from the solar nebula than Uranus and Neptune. *Accretion is thought to have occurred more rapidly in the denser regions of the solar nebula that were closer to the Sun. Therefore, although all four jovian planets captured hydrogen and helium gas from the solar nebula around similar-mass planetesimals (made of hydrogen compounds and rock), Jupiter and Saturn had more time to capture this gas. As a result, Jupiter and Saturn accreted so much hydrogen and helium gas that these ingredients ended up dominating their composition. In contrast, Uranus and Neptune were left with compositions dominated by hydrogen compounds and rock, which also led to their higher densities.*

Which of the following statements best describes the general pattern of composition among the four jovian planets? -Jupiter and Saturn have compositions that are fairly different from the compositions of Uranus and Neptune. -All four planets have essentially the same composition. -Jupiter is made mostly of hydrogen and helium, while the other three jovian planets are made mostly of hydrogen compounds. -Jupiter is made mostly of hydrogen, Saturn is made mostly of helium, Uranus is made mostly of hydrogen compounds, and Neptune is made mostly of rock.

-Jupiter and Saturn have compositions that are fairly different from the compositions of Uranus and Neptune. *Jupiter and Saturn are made mostly of hydrogen and helium, while Uranus and Neptune are primarily made of hydrogen compounds such as water (H2O), methane (CH4), and ammonia (NH3).*

Which of the following best explains why Jupiter's density is higher than Saturn's? -Jupiter is closer to the Sun than Saturn. -Jupiter is more massive than Saturn. -Jupiter has a higher proportion of hydrogen compounds and rock than Saturn. -Jupiter has a stronger magnetic field than Saturn.

-Jupiter is more massive than Saturn. *Because Jupiter and Saturn have nearly identical composition, Jupiter's higher density indicates that its interior is more compressed than Saturn's. This greater compression is due to gravity, which is stronger for Jupiter because of its greater mass.*

Which lists the jovian planets in order of increasing distance from the Sun? -Jupiter, Saturn, Uranus, Pluto -Saturn, Jupiter, Uranus, Neptune -Jupiter, Saturn, Uranus, Neptune

-Jupiter, Saturn, Uranus, Neptune

Which are thought to have formed farthest from the Sun? -asteroids -Kuiper belt comets -Oort cloud comets

-Kuiper belt comets

The asteroid belt lies between the orbits of -Earth and Mars. -Mars and Jupiter. -Jupiter and Saturn.

-Mars and Jupiter

Recent evidence suggests that Mars once had a global magnetic field. Assuming this is true, which of the following could explain why Mars today lacks a global magnetic field like that of Earth? -Mars's interior has cooled so much that its molten core layer no longer undergoes convection. -The Martian core is made of rock, while Earth's core is made of metal. -Mars is too far from the Sun to have a global magnetic field. -Mars rotates much slower than the Earth.

-Mars's interior has cooled so much that its molten core layer no longer undergoes convection. *Convection of the molten core is required for a global magnetic field.*

Why does Neptune appear blue and Jupiter red? -Neptune is hotter, which gives bluer thermal emission. -Methane in Neptune's atmosphere absorbs red light. -Neptune's air molecules scatter blue light, much as Earth's atmosphere does.

-Methane in Neptune's atmosphere absorbs red light.

Although the data show only a correlation between the carbon dioxide concentration and the global average temperature, there are other reasons to think that a rise in the carbon dioxide concentration actually causes a rise in the global average temperature. All of the following statements are true. Which statements lend support to the idea that carbon dioxide is a cause of planetary warming? Check all that apply. -Models of the greenhouse effect successfully predict the temperatures of Venus and Mars from their atmospheric carbon dioxide amounts. -We understand the physical mechanism of the greenhouse effect, through which carbon dioxide can increase a planet's temperature. -Isotope ratios in atmospheric carbon dioxide show that much of the carbon dioxide in Earth's atmosphere today comes from the burning of fossil fuels. -Models of Earth's climate that include recent increases in the carbon dioxide concentration match observed temperature increases better than those that do not include it.

-Models of the greenhouse effect successfully predict the temperatures of Venus and Mars from their atmospheric carbon dioxide amounts. -We understand the physical mechanism of the greenhouse effect, through which carbon dioxide can increase a planet's temperature. -Models of Earth's climate that include recent increases in the carbon dioxide concentration match observed temperature increases better than those that do not include it. *Together, the success of the models and our clear understanding of the mechanism of the greenhouse effect leave little room for doubt that carbon dioxide is indeed a cause of higher temperatures on a planet.*

Which of the following statements about the moons of the jovian planets is NOT true? -Some of the moons are big enough that we'd call them planets (or dwarf planets) if they orbited the Sun. -Many of the moons are made largely of ices. -Most of the moons are large enough to be spherical in shape, but a few have the more potato-like shapes of asteroids. -One of the moons has a thick atmosphere.

-Most of the moons are large enough to be spherical in shape, but a few have the more potato-like shapes of asteroids. *Most of the moons are small, and small moons generally are NOT spherical*

Did a large terrestrial planet ever form in the region of the asteroid belt? -No, because there was never enough mass there. -No, because Jupiter prevented one from accreting. -Yes, but it was shattered by a giant impact.

-No, because Jupiter prevented one from accreting

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. -They are less massive then any of the terrestrial planets. -They have solid surfaces. -They have very little hydrogen, helium, and hydrogen compounds.

-They are lower in average density than are the terrestrial planets.

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. -We are overdue for the impact of a 100-meter object, so we should expect the impact of an even larger object during the next few years. -There must be something wrong with the graph, because if the 1 in 1000 probability were correct, then there would have been an impact some time during the past 1000 years. Since there wasn't, the actual probability must be lower than 1 in 1000. -We are clearly due for such an impact, so the actual probability for the coming year must be much higher than 1 in 1000.

-Nothing; we would still presume that the chance of such an impact during the next year is 1 in 1000. *The fact that it has been more than 1000 years since the last impact does not alter the overall probability in any given year. The probability remains the same 1 in 1000 for the coming year.*

Which of the following statements is not true? -Objects in the Oort cloud contain large proportions of ice. -Objects in the asteroid belt are made mostly of rock and metal. -Objects in the Kuiper belt are made mostly of rock and metal. -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.

-Objects in the Kuiper belt are made mostly of rock and metal. *Kuiper belt objects contain large amounts of ice; in fact, many comets that enter the inner solar system come from the Kuiper belt.*

Which of the following statements about asteroids, Kuiper belt objects, and Oort cloud objects is true? -Objects in the asteroid belt are made mostly of ice. -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. -Objects in the Oort cloud are made mostly of rock and metal. -Objects in the Kuiper belt are made mostly of rock and metal.

-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.

Which of the following Mars surface features provides dramatic evidence that volcanism has played a role in shaping the surface of Mars? -the polar caps -the southern highlands -Valles Marineris -Olympus Mons

-Olympus Mons *Olympus Mons is a very large shield volcano. You can also see numerous other volcanoes on Mars, including three large ones on the Tharsis bulge.*

Which have the most elliptical and tilted orbits? -asteroids -Kuiper belt comets -Oort cloud comets

-Oort cloud comets

What do we conclude if a planet has few impact craters of any size? -The planet was never bombarded by asteroids or comets. -Its atmosphere stopped impactors of all sizes. -Other geological processes have wiped out craters.

-Other geological processes have wiped out craters.

Which of the following statements correctly describes the motion of the particles in Saturn's rings? -Particles in all the rings hover motionlessly high above Saturn. -Particles in the inner rings orbit Saturn at a faster speed than particles in the outer rings. -Particles in the inner rings orbit Saturn at a slower speed than particles in the outer rings. -All the particles in the rings orbit Saturn with the same orbital period.

-Particles in the inner rings orbit Saturn at a faster speed than particles in the outer rings. *In accord with Kepler's third law, particles closer to Saturn orbit at a faster speed than more distant particles.*

How does seafloor crust differ from continental crust? -Seafloor crust is thicker, younger, and lower in density. -Seafloor crust is thicker, older, and higher in density. -Seafloor crust is thinner, younger, and higher in density. -Seafloor crust is thinner, older, and lower in density.

-Seafloor crust is thinner, younger, and higher in density. *This is because seafloor crust is continually recycled: It erupts along ocean ridges and then moves across the seafloor until it returns to the mantle through subduction.*

Why are there fewer large impact craters on the Earth's seafloor than on the continents? -The oceans slow large impactors and prevent them from making craters. -Seafloor crust is younger than continental crust, so it has had less time in which to suffer impacts. -Erosion erases impact craters must faster on the ocean bottom than on land. -Most impacts occur on the land.

-Seafloor crust is younger than continental crust, so it has had less time in which to suffer impacts. *Seafloor crust is continually recycled, so that the seafloor is nearly everywhere younger than about 200 million years. Therefore evidence of any earlier impacts has been erased as the seafloor crust was recycled.*

The choices below describe four hypothetical planets. Which one would you expect to have the most features of erosion? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.) -Size: twice as big as Earth. Distance from Sun: same as Mercury. Rotation rate: once every 6 months. -Size: same as Venus. Distance from Sun: same as Mars. Rotation rate: once every 25 hours. -Size: same as the Moon. Distance from Sun: same as Mars. Rotation rate: once every 10 days. -Size: same as Mars. Distance from Sun: same as Earth. Rotation rate: once every 18 hours.

-Size: same as Venus. Distance from Sun: same as Mars. Rotation rate: once every 25 hours. *This planet is large enough to have had outgassing make an atmosphere, and rotates fast enough to drive winds.*

The choices below describe four hypothetical planets. Which one's surface would you expect to be most crowded with impact craters? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.) -Size: same as Mars. Distance from Sun: same as Earth. Rotation rate: once every 18 hours. -Size: same as Venus. Distance from Sun: same as Mars. Rotation rate: once every 25 hours. -Size: twice as big as Earth. Distance from Sun: same as Mercury. Rotation rate: once every 6 months. -Size: same as the Moon. Distance from Sun: same as Mars. Rotation rate: once every 10 days.

-Size: same as the Moon. Distance from Sun: same as Mars. Rotation rate: once every 10 days. *The smallest size means the least geological activity to have erased past impact craters, so lots of craters would still be present.*

How do typical wind speeds in Jupiter's atmosphere compare to typical wind speeds on Earth? -They are slightly slower than average winds on Earth. -They are about the same as average winds on Earth. -They are much faster than hurricane winds on Earth. -They are slightly faster than average winds on Earth.

-They are much faster than hurricane winds on Earth.

The choices below describe four hypothetical planets. Which one would you expect to have the hottest interior? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.) -Size: same as Mars. Distance from Sun: same as Earth. Rotation rate: once every 18 hours. -Size: same as Venus. Distance from Sun: same as Mars. Rotation rate: once every 25 hours. -Size: same as the Moon. Distance from Sun: same as Mars. Rotation rate: once every 10 days. -Size: twice as big as Earth. Distance from Sun: same as Mercury. Rotation rate: once every 6 months.

-Size: twice as big as Earth. Distance from Sun: same as Mercury. Rotation rate: once every 6 months. *Largest size means the highest interior temperature.*

Assuming that features you see on Mars are similar to features found on Earth, what would a casual inspection of the interactive photo of Mars lead you to suspect about water on Mars? -Abundant surface water is found in large, brownish pools inside craters. -There are numerous small streams flowing with water. -Surface water only exists as frozen ice. -No surface water currently exists in any form.

-Surface water only exists as frozen ice. *There is nothing on the brownish surface to suggest liquid water, and close-up photos confirm that there is no liquid water on Mars today. However, the prominent polar caps look much like Earth's polar caps, and would therefore make you suspect that they are made of water ice. In fact, they contain both frozen carbon dioxide and frozen water*

Based on the evidence that atmospheric carbon dioxide is a cause of planetary warming, what aspect of the graphs should most concern us? -Earth's past temperature rises and falls naturally. -Earth's past carbon dioxide concentration rises and falls naturally. -The carbon dioxide concentration today is significantly higher than at any time in the past 400,000 years and is rapidly rising.

-The carbon dioxide concentration today is significantly higher than at any time in the past 400,000 years and is rapidly rising. *Therefore, if past trends continue, we would expect Earth's temperature to rise substantially as a result of this increase in the carbon dioxide concentration.*

On a day with complete cloud cover, what happens to the visible light headed toward Earth? -The clouds reflect much of it back to space, though some still reaches the surface. -It is absorbed by the clouds, which causes the clouds to heat up. -It reaches the surface just as it does on a cloudless day.

-The clouds reflect much of it back to space, though some still reaches the surface. *Clouds have a cooling effect because they reflect visible light. However, they do not reflect all of it; if they did, cloudy days would be dark as night.*

Which of the following is NOT an example of tectonics? -The formation of a cliff when the lithosphere shrinks. -The stretching of the crust by underlying mantle convection. -The gradual disappearance of a crater rim as a result of wind and rain. -The slow movement of Earth's lithospheric plates.

-The gradual disappearance of a crater rim as a result of wind and rain. *This is an example of erosion, not tectonics.*

Many scientists suspect that Venus has a stronger and thicker lithosphere than Earth. If this is true, which of the following could explain it? -The apparent lack of plate tectonics on Venus. -The high surface temperature that has "baked out" all the liquid water from Venus's crust and mantle. -The slow rotation of Venus. -The smaller size of Venus, which has allowed it to lose much more internal heat than Earth.

-The high surface temperature that has "baked out" all the liquid water from Venus's crust and mantle. *Without water, the rock would be stronger and the lithosphere could become thicker.*

What is Charon? -A captured moon of Neptune -The largest of Pluto's three known moons -The largest known Kuiper belt comet -The largest known asteroid

-The largest of Pluto's three known moons *It is much larger than the other two moons of Pluto, and is thought to have formed in a giant impact with Pluto (much as our own Moon is thought to have formed in a giant impact with Earth).*

Which of the following is not generally true of all the terrestrial world lithospheres? -The thickness of the lithosphere depends on interior temperature, with cooler interiors leading to thicker lithospheres. -The lithosphere extends from somewhere in the mantle all the way to the surface. -The lithosphere is broken into a set of large plates that float upon the softer rock below. -Rock in the lithosphere is stronger than rock beneath it.

-The lithosphere is broken into a set of large plates that float upon the softer rock below. *This is true of Earth, but not of the other terrestrial lithospheres*

Most of the Moon's surface is densely covered with craters, but we find relatively few craters within the lunar maria. What can we conclude? -Erosion affects the maria more than it affects other regions of the Moon. -The maria formed after the heavy bombardment ended. -The maria formed within the past 1 billion years. -The regions of the maria were hit by fewer impacts than the densely cratered regions.

-The maria formed after the heavy bombardment ended. *They contain few craters because they formed after most impacts had occurred*

Notice that the peaks and troughs on the temperature graph occur at the about the same times as peaks and troughs on the carbon dioxide graph. What can we infer from this fact alone? -Higher global average temperatures cause higher carbon dioxide concentrations. -There is a correlation between the carbon dioxide concentration and the global average temperature. -Higher carbon dioxide concentrations cause higher global average temperatures. -The carbon dioxide concentration is inversely related to the global average temperature.

-There is a correlation between the carbon dioxide concentration and the global average temperature. *A correlation means that two things go up and down together. In this case, there is a correlation between the temperature and the carbon dioxide concentration because both were generally high at the same times in the past and low at the same times in the past. *

Look at the densities of the jovian planets given in Figure 1. Which of the following statements best describes the pattern of jovian planet densities? -The more massive the planet, the lower the density. -Jupiter is the densest, and the densities of the other planets decrease in order of distance from the Sun. -The more massive the planet, the higher the density. -There is no clear trend in the densities. -Jupiter is the densest, and the densities of the other planets increase in order of distance from the Sun.

-There is no clear trend in the densities. *There is no obvious trend in the densities of the jovian planets. For example, Jupiter is the nearest and most massive of the four planets, but it is the second-lowest in density. The lack of a clear trend tells us that we need to look deeper at the nature of these planets in order to understand their densities.*

According to scientists, the naturally occurring greenhouse effect makes Earth about 31∘C warmer than it would be if there were no greenhouse gases in our atmosphere. How do scientists "know" what Earth's temperature would be without greenhouse gases? -They estimate it by averaging guesses made by many individual scientists. -Ancient fossils allow them to infer Earth's temperature at a time before our atmosphere contained greenhouse gases. -They calculate this temperature from Earth's reflectivity and distance from the Sun. -They assume that this temperature would be about the same as the temperature of Mars, which has much less of an atmosphere than Earth.

-They calculate this temperature from Earth's reflectivity and distance from the Sun. *Aside from the greenhouse effect, the only factors that affect a planet's average temperature are its reflectivity and distance from the Sun. Since both distance and reflectivity have been measured, the expected temperature can be calculated easily and precisely. (Note that this assumes that the Sun's total emission of energy remains steady; measurements and theory both indicate that it varies very little over time scales less than a few million years.)*

Which of the following statements best explains why the densities of Uranus and Neptune are higher than those of Jupiter and Saturn? -They have a higher proportion of hydrogen compounds and rock. -They are at greater distances from the Sun. -Their interiors are more compressed due to stronger gravity. -They have higher masses. -They have stronger magnetic fields.

-They have a higher proportion of hydrogen compounds and rock. *At similar temperature and pressure, hydrogen compounds and rock are much higher in density than hydrogen and helium. The internal conditions in the jovian planets are similar enough so that composition has a major effect on average density. Uranus and Neptune are higher in density than Jupiter and Saturn because they are made primarily of higher-density hydrogen compounds and rock.*

Which of the following best describes the nature and origin of the atmospheres of the Moon and Mercury? -They have very thin atmospheres produced by outgassing but still have the layers of a troposphere, thermosphere, and exosphere. -They have thin exospheres only, with gas coming from impacts of subatomic particles and photons. -They have thin tropospheres only, with gas coming from evaporation and sublimation. -They have only small amounts of gas, all of which is left over from outgassing long ago.

-They have thin exospheres only, with gas coming from impacts of subatomic particles and photons.

Which moon has a thick atmosphere made mostly of nitrogen? -Triton -Ganymede -Titan -Europa

-Titan

Which moon shows evidence of rainfall and erosion by some liquid substance? -Europa -Titan -Ganymede

-Titan

If Earth had as much carbon dioxide in its atmosphere as Venus, our planet would be too hot for liquid water to exist on the surface.

-True

Which terrestrial world has the most atmosphere? -Venus -Earth -Mars

-Venus

Which planet(s) have an atmosphere that consists mostly of carbon dioxide? -Venus and Mars -Venus, Earth, and Mars -Mars only -Venus only

-Venus and Mars

All of the following statements are true. Which one provides strong observational support for the claim that greenhouse gases make a planet warmer than it would be otherwise? -Earth is the only planet with an ozone layer in its atmosphere. -Earth has a higher average temperature than Mars. -Venus has a higher average temperature than Mercury. -Mercury is much hotter than the Moon.

-Venus has a higher average temperature than Mercury. *The fact that Venus is hotter than Mercury despite being nearly twice as far from the Sun tells us that its thick carbon dioxide atmosphere must warm it significantly—just as we expect from the theory of the greenhouse effect.*

All the following statements about Venus are true. Which one offers evidence of a global repaving about a billion years ago? -Venus has many circular features, called coronae, which appear to be tectonic in origin. -Venus has relatively few impact craters and these craters are distributed fairly evenly over the entire planet. -Venus's largest features are three elevated regions that look somewhat like continents. -Venus appears to lack any water that could lubricate the flow of rock in its crust and mantle.

-Venus has relatively few impact craters and these craters are distributed fairly evenly over the entire planet. *This suggests that older impact craters were covered over everywhere on the planet.*

Which of the following correctly lists the terrestrial worlds in order from the thickest atmosphere to the thinnest atmosphere? (Note: Mercury and the Moon are considered together in this question.) -Earth, Venus, Mars, Moon/Mercury -Venus, Mars, Moon/Mercury, Earth -Mars, Venus, Earth, Moon/Mercury -Venus, Earth, Mars, Moon/Mercury

-Venus, Earth, Mars, Moon/Mercury

Which of the following is an example of convection? -Gas bubbling upward through a liquid. -Warm air expanding and rising while cooler air contracts and fall. -Rocks sinking in water. -Different kinds of material separating by density, like oil and water.

-Warm air expanding and rising while cooler air contracts and fall. *Convection is any type of heat-driven circulation like this.*

We 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. -We need to know whether either moon is volcanically active. -We need to know whether the planet also has a third moon. -No other information is needed: With two moons, there is sure to be tidal heating. -No other information is needed: With two moons, there is no chance of any tidal heating

-We need to know their orbital periods. *We expect tidal heating to be possible only if there is an orbital resonance that helps maintain an elliptical orbit. An orbital resonance occurs when one moon's orbital period is a simple fraction of the other's, such as 1/2 or 1/3 or 1/4. Therefore, by measuring their orbital periods, we can determine if there is a resonance. Having an orbital resonance doesn't automatically mean that there is tidal heating, but it makes it a good possibility.*

In Part A, you found that Planet Z should not have polar ice caps or liquid water. What single change to Planet Z's characteristics would allow it to have these things? -a larger axis tilt -a larger size -a greater distance from its star -a smaller size

-a greater distance from its star *The planet is too hot for liquid water or ice, so moving it farther from its star would allow it to cool down. If it cooled enough—but not too much—it could have surface liquid water and ice caps.*

Based solely on an understanding of the greenhouse effect (as displayed in the figure), which one of the following statements is true? -Humans are causing global warming. -We do not yet understand the greenhouse effect well enough to make predictions about how it affects our planet. -Global warming poses a grave threat to our future. -We should expect an increase in the greenhouse gas concentration to lead to global warming.

-We should expect an increase in the greenhouse gas concentration to lead to global warming. *The evidence discussed in this tutorial makes it clear that greenhouse gases make a planet's surface warmer than it would otherwise be, so we should expect a rise in the greenhouse gas concentration to make Earth warmer. It is possible that there can be mitigating factors through feedbacks, but the basic link between greenhouse gas concentration and global warming is very strong.*

What do we mean when we say that the terrestrial worlds underwent differentiation? -They lost interior heat to outer space. -Their surfaces show a variety of different geological features resulting from different geological processes. -The five terrestrial worlds all started similarly but ended up looking quite different. -When their interiors were molten, denser materials sank toward their centers and lighter materials rose toward their surfaces.

-When their interiors were molten, denser materials sank toward their centers and lighter materials rose toward their surfaces.

What do we mean when we say that the terrestrial worlds underwent differentiation? -Their surfaces show a variety of different geological features resulting from different geological processes. -They lost interior heat to outer space. -The five terrestrial worlds all started similarly but ended up looking quite different. -When their interiors were molten, denser materials sank toward their centers and lighter materials rose toward their surfaces.

-When their interiors were molten, denser materials sank toward their centers and lighter materials rose toward their surfaces. *Differentiation therefore occurred very early in each planet's history, before it cooled enough for much of its interior to solidify.*

Can an asteroid be pure metal? -No, all asteroids contain rock. -Yes, it must have formed where only metal could condense in the solar nebula. -Yes, it must have been the core of a shattered asteroid.

-Yes, it must have been the core of a shattered asteroid.

What does Pluto most resemble? -a terrestrial planet -a jovian planet -a comet

-a comet

What are the basic requirements for a terrestrial world to have a global magnetic field? -a core layer of molten, convecting material and sufficiently rapid rotation -a metal core and rapid rotation -a metal core, a rocky mantle, and sufficiently rapid rotation -a core that has a molten layer and a mantle that has convection

-a core layer of molten, convecting material and sufficiently rapid rotation

In Part A, you found that Planet Z should not have strong winds and violent storms. What single change to Planet Z's characteristics would cause it to have strong winds and violent storms? -a greater distance from its star -a faster rotation rate -a smaller size -a larger axis tilt

-a faster rotation rate *The basic requirements for strong winds and violent storms are an atmosphere and relatively rapid rotation. An atmosphere is necessary to have wind of any type, while rotation is necessary to create the forces (in particular, the Coriolis force) that tend to drive winds on a planet's surface. Storms will be even stronger if there is also evaporation of surface water.*

On average, how fast do the plates move on the Earth? -a few kilometers per year -a few centimeters per year -a few millimeters per century -about 1 mile per hour

-a few centimeters per year *This sounds slow, but over tens of millions of years it completely rearranges the map of Earth's continents.*

Which of the following is the most basic definition of a greenhouse gas? -a gas that keeps warm air from rising, and therefore warms the surface -a gas that absorbs infrared light -a gas that reflects a lot of sunlight -a gas that makes a planet much hotter than it would be otherwise, even in small amounts

-a gas that absorbs infrared light

Based on its surface features, the most important event on Venus in the past billion years or so was _______. -the onset of mantle convection, which caused Venus's lithosphere to split into plates like those on Earth -the impact of an unusually large asteroid that left a deep scar on one side of the planet -a global "repaving" that erased essentially all the surface features that had existed earlier -the eruption of a giant volcano that formed one of Venus's "continents"

-a global "repaving" that erased essentially all the surface features that had existed earlier

Based on its surface features, the most important event on Venus in the past billion years or so was _______. -the onset of mantle convection, which caused Venus's lithosphere to split into plates like those on Earth -the eruption of a giant volcano that formed one of Venus's "continents" -a global "repaving" that erased essentially all the surface features that had existed earlier. -the impact of an unusually large asteroid that left a deep scar on one side of the planet

-a global "repaving" that erased essentially all the surface features that had existed earlier. *Crater counts suggest this occurred about 750 million years ago.*

Suppose we use a baseball to represent Earth. On this scale, the other terrestrial worlds (Mercury, Venus, the Moon, and Mars) would range in size approximately from that of ______. -a golf ball to a beach ball -a golf ball to a baseball -a dust speck to a golf ball -a dust speck to a basketball

-a golf ball to a baseball

Suppose we use a baseball to represent Earth. On this scale, the other terrestrial worlds (Mercury, Venus, the Moon, and Mars) would range in size approximately from that of ______. -a dust speck to a basketball -a dust speck to a golf ball -a golf ball to a baseball -a golf ball to a beach ball

-a golf ball to a baseball *A golf ball is about right for the Moon (1/4 Earth's diameter) and the baseball would work for Venus, since it is nearly the same size as Earth.*

How big an object causes a typical shooting star? -a grain of sand or a small pebble -a boulder -an object the size of a car

-a grain of sand or a small pebble

Which direction do a comet's dust and plasma tails point? -generally away from the Sun -straight behind the comet in its orbit -always almost due north -perpendicular to the ecliptic plane

-generally away from the Sun

What do we mean by a runaway greenhouse effect? -a greenhouse effect that heats a planet so much that its surface rock melts -a greenhouse effect that starts on a planet but later disappears as gases are lost to space -a process that heats a planet like a greenhouse effect, but that involves a completely different mechanism of heating that doesn't actually involve greenhouse gases -a greenhouse effect that keeps getting stronger until all of a planet's greenhouse gases are in its atmosphere

-a greenhouse effect that keeps getting stronger until all of a planet's greenhouse gases are in its atmosphere

What do we mean by a runaway greenhouse effect? -a process that heats a planet like a greenhouse effect, but that involves a completely different mechanism of heating that doesn't actually involve greenhouse gases -a greenhouse effect that keeps getting stronger until all of a planet's greenhouse gases are in its atmosphere -a greenhouse effect that starts on a planet but later disappears as gases are lost to space -a greenhouse effect that heats a planet so much that its surface rock melts

-a greenhouse effect that keeps getting stronger until all of a planet's greenhouse gases are in its atmosphere

Olympus Mons is ______. -a huge shield volcano on Mars -a large lava plain on the Moon -a great canyon on Mars -a huge stratovolcano on Venus

-a huge shield volcano on Mars *It is the largest mountain in the solar system.*

The reason that small planets tend to lose interior heat faster than larger planets is essentially the same as the reason that ________. -gas bubbles form and rise upward in boiling water -a large baked potato takes longer to cool than a small baked potato -thunderstorms tend to form on hot summer days -Earth contains more metal than the Moon

-a large baked potato takes longer to cool than a small baked potato *A smaller object has proportionally more surface area through which to lose its interior heat.*

According to current evidence, Pluto is best explained as ______. -an escaped moon of Jupiter or Saturn -a terrestrial planet that is surprisingly far from the Sun -a large member of the Kuiper belt -a very small jovian planet

-a large member of the Kuiper belt

According to current evidence, Pluto is best explained as ______. -a large member of the Kuiper belt -an escaped moon of Jupiter or Saturn -a very small jovian planet -a terrestrial planet that is surprisingly far from the Sun

-a large member of the Kuiper belt *And it is not even the largest known member, as an object discovered in 2005 is larger.*

In Part A, you found that Planet Z should not have seasons. What single change to Planet Z's characteristics would cause it to have seasons? -a greater distance from its star -a faster rotation rate -a larger axis tilt -a smaller size

-a larger axis tilt *Seasons are caused primarily by axis tilt, so a planet without axis tilt is not expected to have seasons (unless it has a highly elliptical orbit)*

A terrestrial world's lithosphere is ________. -a layer of hot, molten rock encompassing the core and part of the mantle -a layer of relatively strong, rigid rock, encompassing the crust and part of the mantle -a thin layer of rock that lies between the mantle and crust -the interior region in which the planet's magnetic field is generated

-a layer of relatively strong, rigid rock, encompassing the crust and part of the mantle

A terrestrial world's lithosphere is ________. -a thin layer of rock that lies between the mantle and crust -a layer of hot, molten rock encompassing the core and part of the mantle -a layer of relatively strong, rigid rock, encompassing the crust and part of the mantle -the interior region in which the planet's magnetic field is generated

-a layer of relatively strong, rigid rock, encompassing the crust and part of the mantle *The depth of the lithosphere varies among the different worlds, with larger worlds (like Venus and Earth) having thinner lithospheres.*

A rock found on Earth that crashed down from space is called ______. -an impact -a meteor -an asteroid -a meteorite

-a meteorite

A rock found on Earth that crashed down from space is called _________. -a meteorite -an impact -a meteor -an asteroid

-a meteorite

What do we mean by a primitive meteorite? -a meteorite that was discovered by primitive people -a meteorite that fell to Earth at least 4 billion years ago -a type of meteorite that is usually made mostly of high-density metals -a meteorite that is essentially unchanged since it first condensed and accreted in the solar nebula some 4.6 billion years ago

-a meteorite that is essentially unchanged since it first condensed and accreted in the solar nebula some 4.6 billion years ago *It's called primitive because the word means "first."*

In the context of plate tectonics, what is a subduction zone? -a place where two continental plates are colliding -a place where a seafloor plate is sliding under a continental plate -a place where two plates are slipping sideways against one another -a place where two plates are pulling apart

-a place where a seafloor plate is sliding under a continental plate

In general, what kind of planet would you expect to have the thickest lithosphere? -a large planet -a small planet -a planet far from the Sun

-a small planet

On the graphs shown, you can identify an ice age by looking for __________. -a trough (bottom of a dip) on the temperature graph -a place on the temperature graph where the temperature curve falls steeply -a peak on the temperature graph -a trough (bottom of a dip) on the carbon dioxide graph

-a trough (bottom of a dip) on the temperature graph *The graph shows that one ice age ended only about 10,000 years ago, and there have been numerous other ice ages during the past 400,000 years.*

What is the probability that an object 100 meters in diameter will hit Earth during the coming year? -about 1 in 2 -about 1 in 10 -about 1 in 1000 -about 1 in 100 million -zero

-about 1 in 1000 *The graph shows the typical, or average, time between impacts for objects of various sizes. This can be converted to a probability as follows: Suppose that a particular size object hits Earth about once every 10 years on average. Then the probability of such an impact in any single year is 1 in 10. Similarly, suppose that a particular size object hits Earth about once every 500 years on average. Then the probability of such an impact in any single year is 1 in 500. You can use this idea to answer Part D by finding the average time between impacts for 100-meter objects and converting this to a probability.*

An object 10 kilometers across hits Earth __________. -about once every 1 million years -about once every 100 million years -about once every 1 billion years -just once in Earth's history

-about once every 100 million years *The point on the red line that is directly above 10 kilometers on the horizontal axis corresponds to just under 100 million years on the vertical axis, indicating that such impacts occur a little less than once every 100 million years on average.*

Greenhouse gases in the atmosphere, such as carbon dioxide and water vapor, make Earth warmer than it would be otherwise because these gases __________. -reflect visible light coming from the Sun -form clouds that emit thermal radiation -absorb visible light coming from the Sun -absorb infrared light emitted by the surface

-absorb infrared light emitted by the surface *Although the absorbed infrared light is quickly reemitted, it is reemitted in a random direction. As a result, greenhouse gases tend to slow the escape of infrared light from Earth to space, so that there is more heat (which means more energy) in the atmosphere than there would be if the infrared light escaped directly to space.*

Based on Planet Z's size, orbital distance, and rotation rate, which of the following properties is it likely to have? Check all that apply. -seasons -erosion due to liquid water -polar ice caps -active volcanoes -active tectonics -strong winds and violent storms -a surface crowded with impact craters -an atmosphere produced by outgassing

-active volcanoes -active tectonic -an atmosphere produced by outgassing

We 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? -Io's unusual, egg-like shape -active volcanoes on Io -the orbital resonance between Io, Europa, and Ganymede -Io's surprisingly elliptical orbit

-active volcanoes on Io *Io is barely larger than our Moon, and the Moon long ago cooled enough so that it no longer has volcanic activity. Without some ongoing source of internal heating, Io would be similarly inactive. Therefore, the fact that Io is the most volcanically active world in the solar system tells us that it must have an ongoing internal heat source, which we identify as tidal heating.*

Saturn's rings -have looked basically the same since they formed along with Saturn. -were created long ago when tidal forces tore apart a large moon. -are continually supplied by impacts between small moons.

-are continually supplied by impacts between small moons.

Saturn's rings: -have looked basically the same since they formed along with Saturn. -were created long ago when tidal forces tore apart a large moon. -are continually supplied with new particles by impacts with small moons.

-are continually supplied with new particles by impacts with small moons.

Among discovered meteorites, we have found some with all the following origins EXCEPT _________. -being a fragment from the surface of the Moon -being a fragment of a shattered asteroid -being a fragment from the surface of Mars -being a fragment from Comet Halley

-being a fragment from Comet Halley

Among discovered meteorites, we have found some with all the following origins except _________. -being a fragment from the surface of Mars -being a fragment from Comet Halley -being a fragment from the surface of the Moon -being a fragment of a shattered asteroid

-being a fragment from Comet Halley *No such fragments are known and they are unlikely to exist, since comet fragments should be ice that would burn up as they passed through our atmosphere.*

The asteroid belt is located ______. -beyond the orbit of Neptune -between the orbits of Earth and Mars -between the orbits of Mars and Jupiter -between the orbits of Jupiter and Saturn

-between the orbits of Mars and Jupiter

The asteroid belt is located _________. -between the orbits of Earth and Mars -between the orbits of Mars and Jupiter -beyond the orbit of Neptune -between the orbits of Jupiter and Saturn

-between the orbits of Mars and Jupiter

In which direction do hurricanes in the Southern Hemisphere rotate? -clockwise -counterclockwise -either direction

-clockwise

4. Australia is composed of relatively old and thick

-continental crust

Which of the following best describes the internal layering of Jupiter, from the center outward? -solid rock core; layer of solid metallic hydrogen; layer of pure liquid hydrogen; cloud layer -liquid core of hydrogen compounds; liquid hydrogen layer; metallic hydrogen layer; gaseous hydrogen layer; cloud layer -core of rock, metal, and hydrogen compounds; thick layer of metallic hydrogen; layer of liquid hydrogen; layer of gaseous hydrogen; cloud layer -core of rock and metal; mantle of lower density rock; upper layer of gaseous hydrogen; cloud layer

-core of rock, metal, and hydrogen compounds; thick layer of metallic hydrogen; layer of liquid hydrogen; layer of gaseous hydrogen; cloud layer

From center to surface, which of the following correctly lists the interior layers of a terrestrial world? -mantle, crust, core -mantle, core, crust -core, crust, lithosphere -core, mantle, crust

-core, mantle, crust

Suppose you could float in space just a few meters above Saturn's rings. What would you see as you looked down on the rings? -Nothing—up close, the rings would be so completely invisible that you'd have no way to know they are there. They can be seen only from a distance. -dozens of large "moonlets" made of metal and rock, each a few kilometers across -a solid, shiny surface, looking much like a piece of a DVD but a lot bigger -countless icy particles, ranging in size from dust grains to large boulders

-countless icy particles, ranging in size from dust grains to large boulders

About how often does a 1-kilometer object strike Earth? -every year -every million years -every billion years

-every million years

7. The earthquakes that occur in Southern California generally occur above a

-fault

A comet entering the inner solar system from afar will __________. -form a tail and some time later form a coma. -form a coma and some time later form a tail -always form a tail, but only sometimes form a coma

-form a coma and some time later form a tail *The coma consists of dust and gas released from the comet as it is heated by the Sun. Only later, as the solar wind affects the comet, does material from the coma extend out to form a tail.*

Halley's comet is named after the English scientist Edmund Halley (1656--1742) because ______. -he was the first person to see it when it passed near Earth in 1682. -it was in honor of his financial support. -he was the most famous astronomer alive in England during its appearance in 1758. -he calculated its orbit and predicted the year in which it would next be seen.

-he calculated its orbit and predicted the year in which it would next be seen. *Yes, but he did not live to see the return of the comet himself.*

2. Old Faithful Geyser at Yellowstone National Park in the United States acquires its energy from a

-hot spot

The main ingredients of most satellites of the jovian planets are -rock and metal. -hydrogen compound ices. -hydrogen and helium.

-hydrogen compound ices.

When you zoom in on the section labeled "Southern Highlands," which geologic processes are most clearly evident? -volcanism and erosion -impact cratering and erosion -impact cratering and volcanism -tectonics and erosion -volcanism and tectonics

-impact cratering and erosion *The most obvious features of the southern highlands are the many impact craters, but a close examination shows that many of them have been "smoothed out," indicating erosion that has occurred over time.*

The processes responsible for virtually all surface geology are _________. -impact cratering, volcanisms, tectonics, and erosion -eruptions, lava flows, and outgassing -accretion, differentiation, and radioactive decay -convection, conduction, and radiation

-impact cratering, volcanisms, tectonics, and erosion *Virtually all surface features trace to one or more of these four processes.*

Earth's temperature remains fairly steady, which means that Earth must return the same amount of energy to space that it receives from the Sun. In what forms does Earth return most of this energy to space? Check all that apply. -infrared light emitted by the surface and atmosphere -visible light emitted by the surface and atmosphere -ultraviolet light reflected by the surface -visible light reflected by clouds -visible light reflected by the surface

-infrared light emitted by the surface and atmosphere -visible light reflected by clouds -visible light reflected by the surface *The total amount of energy returned to space in these three forms of radiation equals the amount of energy that reaches Earth in the form of sunlight.*

The orbital resonance also gives Europa an elliptical orbit, so it also experiences tidal heating. However, Europa experiences less tidal heating than Io, because Europa __________ than Io. -is much smaller -is farther from Jupiter -is more perfectly spherical in shape -contains much more ice

-is farther from Jupiter *It is Jupiter's gravity that exerts the primary tidal force on the Galilean moons, and both this force and the difference in this force across a moon (the source of tidal heating) weaken with distance from Jupiter. Io is closest to Jupiter and therefore experiences the most tidal heating; Europa is next, and Ganymede experiences even less tidal heating. (Callisto is not expected to have any tidal heating, since it does not participate in the orbital resonance that makes the other moons' orbits more elliptical.)*

The greenhouse effect raises Earth's surface temperature (from what it would be otherwise) because the infrared light radiated by Earth's surface __________. -travels directly out to space -becomes permanently trapped by greenhouse gases -is temporarily absorbed by greenhouse gases and then reemitted in random directions

-is temporarily absorbed by greenhouse gases and then reemitted in random directions *This absorption and reemission means that the infrared light follows a much longer path through the atmosphere until it reaches space than it would without greenhouse gases. In essence, the greenhouse gases keep more infrared light in the atmosphere at any one time, thereby raising the temperature from what it would be otherwise.*

Based on all we know about the terrestrial worlds, what single factor appears to play the most important role in a terrestrial planet's geological destiny? -whether or not it has liquid water -its size -its composition -its distance from the Sun

-its size *Size determines how long the planet can retain internal heat, which drives geological activity.*

Which of the following is the underlying reason why Venus has so little wind erosion? -its thick atmosphere -its slow rotation -it's relatively close distance to the Sun -its small size

-its slow rotation *Without rotation, it lacks significant wind and therefore lacks wind erosion*

What's the fundamental reason that Mars, unlike the Earth, has become virtually geologically dead? -its farther distance than Earth to the Sun -its large size compared to the Earth -its rapid rotation compared to the Earth -its slow rotation compared to the Earth -its closer distance than Earth to the Sun -its small size compared to Earth

-its small size compared to Earth *Small size leads to less volcanic outgassing and greater atmospheric loss.*

Saturn's rings look bright because __________. -light from the Sun reflects off the material in the rings -the material in the rings is hot and creates its own light -light from Saturn reflects off the material in the rings

-light from the Sun reflects off the material in the rings *Saturn's rings look bright because icy particles in the rings reflect (scatter) sunlight.*

What kind of gas is most affected by thermal escape? -greenhouse gases -light gases -all gases equally

-light gases

What is the name of the outer rigid layer of a planet? -crust -mantle -lithosphere

-lithosphere

Where is most of the CO2 that has outgassed from Earth's volcanoes? -in the atmosphere -escaped into space -locked up in rocks

-locked up in rocks

Saturn's rings are composed of __________. -gas from the early solar system -a series of solid concentric circles -lots of individual particles of ice and rock -parts of Saturn's upper atmosphere being vented into space

-lots of individual particles of ice and rock *Although Saturn's rings appear solid when viewed from Earth, they are actually made of countless icy particles ranging in size from dust grains to small boulders.*

Which two factors are most important to the existence of plate tectonics on Earth? -the existence of life and oxygen in the atmosphere -oxygen in the atmosphere and mantle convection -mantle convection and a thin lithosphere -Earth's liquid outer core and solid inner core

-mantle convection and a thin lithosphere *Mantle convection helps move the plates, and the plates probably exist because the lithosphere was thin enough to break into these plates.*

The cores of the terrestrial worlds are made mostly of metal because ______. -the terrestrial worlds as a whole are made mostly of metal -metals sunk to the centers a long time ago when the interiors were molten throughout -over billions of years, convection gradually brought dense metals downward to the core -the core contained lots of radioactive elements that decayed into metals

-metals sunk to the centers a long time ago when the interiors were molten throughout *This sinking was part of the process called differentiation.*

What atmospheric constituent is responsible for the blue color of Uranus and Neptune? -methane -ammonia -hydrogen -water

-methane

What atmospheric constituent is responsible for the blue color of Uranus and Neptune? -water -ammonia -hydrogen -methane

-methane

Suppose we had a device that allowed us to see Earth's interior. If we looked at a typical region of the mantle, what would we see happening? -dense metals falling downward while low-density rock rises upward -not much - on human time scales, the mantle looks like solid rock -a rapid, up and down churning of the material in the mantle -hot molten rock rising upward throughout the mantle and cool, solid rock falling downward

-not much - on human time scales, the mantle looks like solid rock *The mantle is solid. Mantle convection is the slow flow of this solid rock, but it occurs too slowly to notice on human time scales. (The cycling time for rock from the bottom to the top of the mantle is about 100 million years.)*

If the hypothesis tracing the extinction of the dinosaurs to an impact is correct, the dinosaurs died off largely because ______. -the impact caused massive earthquakes worldwide -of global climate effects initiated by dust and smoke that entered the atmosphere after the impact -of injuries suffered from direct hits of pieces of the asteroid or comet -radiation from iridium in the asteroid caused the dinosaurs to die of cancer

-of global climate effects initiated by dust and smoke that entered the atmosphere after the impact

A comet's plasma tail always points directly away from the Sun because __________. -of pressure exerted by the fast-moving charged particles in the solar wind -centrifugal forces throw the tail outward as the comet travels around the Sun -the comet's nucleus overheats on the Sun-facing side, forcing energetic jets of gas to shoot out from the dark side -the tail is left behind as the comet moves through its orbit

-of pressure exerted by the fast-moving charged particles in the solar wind *The plasma tail is always directed away from the Sun because it is pushed outward by the solar wind*

Some jovian planets give off more energy than they receive because of -fusion in their cores. -tidal heating. -ongoing contraction or differentiation.

-ongoing contraction or differentiation.

Jupiter nudges the asteroids through the influence of -tidal forces. -orbital resonances. -magnetic fields.

-orbital resonances.

Saturn's many moons affect its rings through -tidal forces. -orbital resonances. -magnetic field interactions.

-orbital resonances.

A typical meteor is created by a particle about the size of a _________. -baseball -pea -basketball -car

-pea

A typical meteor is created by a particle about the size of a _________. -basketball -pea -baseball -car

-pea *We do not see the particle itself, but rather the flash of light it generates as it enters (and burns up in) the atmosphere at high speed.*

What causes the release of oxygen into Earth's atmosphere? -outgassing -evaporation/sublimation -photosynthesis

-photosynthesis

What are the two geological features that appear to set Earth apart from all the other terrestrial worlds? -mantle convection and a thick atmosphere -significant volcanism and tectonics -plate tectonics and widespread erosion -shield volcanoes and plate tectonics

-plate tectonics and widespread erosion *Neither of these features appear to exist on any other terrestrial world in our solar system.*

What is the longest-lasting internal heat source responsible for geological activity? -accretion -radioactive decay -sunlight

-radioactive decay

Which of the following best describes the lunar maria? -densely cratered regions on the Moon -mountainous regions on the Moon -relatively smooth, flat plains on the Moon -frozen oceans of liquid water on the Moon

-relatively smooth, flat plains on the Moon

Which of the following best describes the lunar maria? -relatively smooth, flat plains on the Moon -densely cratered regions on the Moon -frozen oceans of liquid water on the Moon -mountainous regions on the Moon

-relatively smooth, flat plains on the Moon *These plains are the dark, circular regions visible on the face of the Moon.*

6. ____________________ found in the Atlantic Ocean between North America and Europe is composed of dense and relatively young rock.

-seafloor crust

1. The slowly increasing distance between South America and Africa is due to

-seafloor spreading

3. Layered __________________ exposed by erosion can be seen when looking at the Grand Canyon in the United States.

-sedimentary rock

Which of a planet's fundamental properties has the greatest effect on its level of volcanic and tectonic activity? -size -distance from the Sun -rotation rate

-size

According to Figure 12.25, the odds of a 100-meter asteroid hitting Earth over the course of one year is approximately __________. -somewhat less than 1 in 100 -That information cannot be inferred from the figure, which only reports typical time between impacts. -about 1 in 1,000,000 -somewhat less than 1 in 1000

-somewhat less than 1 in 1000

During the time that a comet passes through the inner solar system, the comet can appear quite bright because __________. -heat from the Sun causes the comet's nucleus to glow -increasing friction causes the comet's nucleus to glow -sunlight reflects off the comet's tail and coma -sunlight reflects off the comet's nucleus

-sunlight reflects off the comet's tail and coma *Comets are too cool to emit their own visible light, so they shine by reflecting sunlight. The coma and tail can become quite large, and therefore reflect a lot of sunlight.*

What do we mean by a mass extinction? -the extinction of a large fraction of the world's plant and animal species in a relatively short period of time -the extinction of large animals, such as dinosaurs -the extinction of any species of plant or animal that has mass -an extinction caused by the impact of an asteroid or comet

-the extinction of a large fraction of the world's plant and animal species in a relatively short period of time *Several mass extinctions have been detected in the fossil record, including the one that wiped out the dinosaurs*

Based on everything we have learned about Venus and Mars, what is the most surprising aspect of Earth's climate history? -the fact that Earth had enough water to form oceans -the fact that Earth apparently got a lot of atmospheric gas from outgassing by volcanoes -the fact that Earth's climate can be affected by changes in its axis tilt -the fact that the temperature of our planet has remained relatively steady throughout our planet's history

-the fact that the temperature of our planet has remained relatively steady throughout our planet's history

Which of the following is NOT an example of tectonics? -the slow movement of Earth's lithospheric plates -the stretching of the crust by underlying mantle convection -the gradual disappearance of a crater rim as a result of wind and rain -the formation of a cliff when the lithosphere shrinks

-the gradual disappearance of a crater rim as a result of wind and rain

Which of the following does NOT provide evidence that Mars once had abundant liquid water on its surface? -the presence of canali, discovered in the late 1800s by Giovanni Schiaparelli and mapped by Percival Lowell -the presence of features that look like dried-up riverbeds -the presence of very old craters that appear to have been eroded by rain -the presence of "blueberries" made of the mineral hematite

-the presence of canali, discovered in the late 1800s by Giovanni Schiaparelli and mapped by Percival Lowell

Which of the following does NOT provide evidence that Mars once had abundant liquid water on its surface? -the presence of features that look like dried up river beds -the presence of canali, discovered in the late 1800s by Giovanni Schiaparelli and mapped by Percival Lowell. -the presence of "blueberries" made of the mineral hematite -the presence of very old craters that appear to have been eroded by rain

-the presence of canals, discovered in the late 1800s by Giovanni Schiaparelli and mapped by Percival Lowell. *These don't really exist.*

What observational evidence supports the idea that Mercury once shrank by some 20 kilometers in radius? -the presence of many impact craters -the presence of many long, tall cliffs -Mercury's unusually high density -the characteristics of the Caloris Basi

-the presence of many long, tall cliffs *These cliffs formed as the crust shrank and buckled.*

In the context of planetary geology, what do we mean by outgassing? -another name for a volcanic eruption -the evaporation of water that adds water vapor (a gas) to an atmosphere -the loss of atmospheric gas to outer space -the release by volcanism of gases that had been trapped in a planetary interior

-the release by volcanism of gases that had been trapped in a planetary interior *Outgassing therefore released all the gases from Earth's interior that ultimately became our atmosphere or condensed to form the oceans.*

The greenhouse effect occurs in the -troposphere. -stratosphere. -lithosphere.

-troposphere.

How many of the five terrestrial worlds are considered "geologically dead"? -none -two -four

-two

What kind of light warms the stratosphere? -infrared -visible -ultraviolet

-ultraviolet

The average temperature over the past 1000 years has been about 15∘C. From the graphs, you can conclude that Earth's average temperature during the past 400,000 years has __________. -varied between about −10∘C and +4∘C -stayed remarkable steady, never varying by more than about 2∘C -varied between about 7∘C and 19∘C -never been as high as it is today

-varied between about 7∘C and 19∘C *The zero level on the graph represents the 15∘C average temperature over the past millennium, so the peaks near +4 on the graph represent a temperature of about 15∘C+4∘C=19∘C and the troughs near −8 represent 15∘C−8∘C=7∘C.*

The energy that warms Earth's surface comes primarily in the form of __________. -infrared light from the Sun -heat from Earth's interior -ultraviolet light from the Sun -visible light from the Sun -heat from the Sun

-visible light from the Sun

Which of the following is NOT an expected consequence of global warming? -an increase in the number and intensity of hurricanes -melting of polar ice and glaciers -warming up of the entire Earth by the same amount -an increase in the severity of winter blizzards

-warming up of the entire Earth by the same amount

Which of the following is a strong greenhouse gas? -nitrogen -water vapor -oxygen

-water vapor

Suppose that Earth's atmosphere had no greenhouse gases. Then Earth's average surface temperature would be _______. -slightly warmer, but still well below the boiling point of water -slightly cooler, but still above freezing -well below the freezing point of water -about the same as it is now

-well below the freezing point of water

About how long would it take for a footprint to be erased? (Hints: Use the Moon's surface area to determine the impact rate per square centimeter, and estimate the size of a footprint.) -≈100days -≈10years -≈1,000years -≈1,000,000years

-≈1,000,000years

5. __________________ is the most distant of Jupiter's four Galilean moons.

Callisto

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.

Closest: -A typical asteroid in the asteroid belt -A Trojan asteroid -A typical Kuiper belt object -A typical Oort Cloud Object *The asteroid belt is located between Mars and Jupiter. The Trojan asteroids share Jupiter's orbit of the Sun. The Kuiper belt is a region beginning just beyond the orbit of Neptune. The Oort cloud is located far beyond the orbits of the planets.* :Farthest

Shown below are the four terrestrial planets of our solar system. Assume that all the planets started out equally hot inside. Rank the planets based on their expected cooling rates, from fastest cooling to slowest cooling.

Fastest Cooling: Mercury Mars Venus Earth :Slowest Cooling *Smaller planets cool faster than larger planets for the same reason that smaller hot potatoes cool faster than larger hot potatoes: An object's total heat content depends on its volume, while its rate of heat loss depends on its surface area. Smaller objects have greater ratios of surface area to volume (the surface area-to-volume ratio) and therefore cool faster. Note that the differing cooling rates explain why the smallest planet, Mercury, has lost most of its interior heat by now, while the largest terrestrial planets — Venus and Earth — still are quite hot inside.*

The following images show four types (wavelengths) of light. Rank these from left to right based on the amount of each that is emitted (as thermal radiation) by Earth's surface, from greatest to least. If you think that two (or more) types should be ranked as equal, drag one on top of the other(s) to show this equality.

Greatest: Infrared All the same: X-ray, Ultraviolet, Visible *Earth emits thermal radiation characteristic of its surface temperature, which means it is almost entirely infrared (extending, in principle, down into the radio). For Earth, the surface temperature is too low to emit any visible, ultraviolet, or X-ray light, so those are all ranked equally. (Note: Technically, thermal emission extends over all wavelengths, so even at low temperatures there might be an occasional photon of visible or higher-energy radiation. However, this emission is negligible for Earth, which is why we rank them all equal to zero.)*

The following images show the four terrestrial planets in our solar system. Rank these planets from left to right based on the atmospheric pressure at the surface, from highest to lowest. (Not to scale.)

Highest pressure: Venus Earth Mars Mercury :Lowest pressure *Note that the pressure differences are quite extreme. Mercury has essentially no atmosphere and no pressure. Earth's atmospheric pressure is more than 100 times that of Mars, and Venus's atmospheric pressure is about 90 times that of Earth.*

Listed following are some of the distinguishing geological characteristics of the moons orbiting Jupiter. Match each characteristic to the appropriate moon.

Io: -Source of ionized gas in he donut-shaped charged particle belt around Jupiter -Hot glowing lava visible in some photos -Volcanoes currently erupting Europa: -Surface features provide evidence of a subsurface liquid ocean -Ice covered surface with few impact craters Ganymede: -Heavily cratered terrain adjacent to much younger terrain -Largest moon in the solar system *Remember that these differences are consequences of the different levels of tidal heating these moons experience. Io is very hot because it is the nearest of the three to Jupiter and has the most tidal heating; Europa is intermediate, and Ganymede has the least tidal heating of the three moons.*

The following images show the four terrestrial planets in our solar system. Rank the planets from left to right based on the amount by which the greenhouse effect increases their surface temperatures, compared to what their temperatures would be without the greenhouse effect, from largest to smallest increase.

Largest Increase: Venus Earth Mars Mercury :Smallest Increase *A stronger greenhouse effect means a greater temperature increase, which is why the rankings here are the same as the rankings for Parts B and C. The differences are quite extreme: Mercury has no greenhouse effect, so its temperature is determined solely by its distance from the Sun and its reflectivity. The greenhouse effect raises the temperature of Mars by about 6°C from what it would be otherwise; it raises Earth's temperature by about 31°C (which means our planet would be frozen over without the greenhouse effect); and it raises Venus's temperature by about 510°C, explaining the extremely high temperature of Venus.*

Shown following are three terrestrial planets of our solar system. Rank the planets based on the amount of time the surface of the planet has had a moderate to high level of volcanic/tectonic activity, from longest to shortest.

Longest time: Earth Mars Mercury :Shortest time *Earth still has a great deal of tectonic activity today, Mars has much less ongoing tectonic activity, and Mercury probably has very little or no ongoing tectonic activity. Note that we can trace these facts directly back to the cooling rates from Part A: Tectonic activity requires interior heat, so planets that cool faster lose their tectonic activity in a shorter time.*

The 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 Jupiter :Highest Mass

Listed 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: -A typical asteroid from the asteroid belt -A typical Oort cloud object -A typical Kuiper belt object *Although Oort cloud comets are now located far beyond the Kuiper belt, they are thought to have formed in the region of the jovian planets. They were then "kicked out" to their current orbits by gravitational encounters with the jovian planets.*

The following images show the four terrestrial planets in our solar system. Rank the planets from left to right based on the strength of the greenhouse effect occurring at their surfaces, from strongest to weakest.

Strongest: Venus Earth Mars Mercury :Weakest *The greenhouse effect is caused by greenhouse gases in the atmosphere, so more greenhouse gas means a stronger greenhouse effect. That is why the rankings here are the same as the rankings for Part B.*

-Valles Marineris *Notice that it is a large canyon stretching almost halfway around Mars.*

The arrow in this photo is pointing at a feature known as: -Olympus Mons -Hellas Basin -Ishtar Terra -Valles Marineris

-2 *This is the mid-Atlantic ridge, where mantle material emerges to the ocean floor and spreads out as new seafloor crust.*

This diagram represents the conveyor-like action of plate tectonics on Earth. Which numbered position represents a place where new seafloor crust is being made? -1 -4 -2 -3

-The most important factor in a planet's geological history is its size. *Notice that size is the key factor in volcanism and tectonics. Impacts (show at the top) affect all worlds equally. The only geological process not shown is erosion, but we know that erosion depends on having an atmosphere, which in turn depends on having outgassing from volcanism (and tectonics).*

This figure summarizes the geological histories of the terrestrial worlds. Based on this figure, what can you conclude? -The most important factor in a planet's geological history is its size. -Earth is the only planet in the inner solar system capable of harboring life. -The most important factor in a planet's geological history is its distance from the Sun. -We can trace almost all the key properties of a planet's geology back to the number of impacts it suffered during the heavy bombardment.

-about once every 50 million years *These are rare events, but they have had a profound effect on Earth's biological history.*

This graph shows the frequency of impacts on Earth by objects of various sizes. According to this graph, objects large enough to cause a mass extinction hit Earth ________. -about once every 1,000 years -about once in Earth's history -about once every 50 million years -about once every 500 million years

-every day *But nearly all of these objects burn up in the atmosphere and therefore do not hit the ground.*

This graph shows the frequency of impacts on Earth by objects of various sizes. According to this graph, objects smaller than about 1 meter in diameter hit Earth ________. -every day -about once every 1 million years -about once a year -never

-There are few if any asteroids at the indicated orbital period of about 4 years. *The gap means few asteroids, and notice this is at an orbital period of 4 years.*

This graph shows the number of asteroids with different orbital periods. Notice the gap indicated by the black arrow. What does this graph tell us about this gap? -There are exactly 495 asteroids with an orbital period of 4 years. -There are few if any asteroids at the indicated orbital period of about 4 years. -There are more asteroids concentrated at the orbital period indicated by the arrow than at any other orbital period. -Asteroids with an orbital period of about 4 years are all located very close together - so close that collisions occur frequently.

-The yellow color is arbitrary, since this image was created with radar data rather than visible light. *We use radar to study the surface of Venus because we cannot otherwise see through Venus's thick clouds.*

This image shows two tall volcanoes on Venus. Why is it yellow? -The camera used to take this photograph had a yellow filter on it. -Lava from volcanoes on Venus is yellow rather than the red of lava on Earth. -Venus is yellow all over, apparently due to some sort of sulfurous dust that coats its surface. -The yellow color is arbitrary, since this image was created with radar data rather than visible light.

-About a size that you could hold in your arms. *Most of the ring particles are about this size, though there is lots of variation.*

This painting shows an artist's conception of what it would look like to be within Saturn's system of rings. Notice the many whitish "balls" visible in this painting. Based on what you have learned about rings, about how large are each of these "balls," on average? -They are microscopic clusters of about 10 to 20 atoms each. -About the size of Earth's Moon. -About the size of a large asteroid. -About a size that you could hold in your arms.

-It would have looked virtually the same. *A comet does not move noticeably through our sky in a matter of minutes. In fact, the comet will still be in nearly the same place relative to the stars for many days, because it is quite far away and therefore moves slowly through our sky.*

This photo shows comet Hale Bopp over Mono Lake in California. Suppose you had taken another photograph from the same spot 10 minutes after this photo was taken. How would the scene have appeared at that time? -We'd still see the same stars, but the comet would have moved far enough so that we'd be able to see only its tails and not its coma above the horizon. -We'd still see the same stars, but the comet would be out of sight, having passed below the horizon. -We would see lots of steam coming from the point where the comet crashed into the lake. -It would have looked virtually the same.

-It is quite small in size compared to moons that are spherical. *If it were larger, it would be spherical.*

This photo shows one of Saturn's moons. Based on its shape, what can you conclude? -It is a gap moon within Saturn's rings. -It is made entirely of water ice. -It is a captured asteroid. -It is quite small in size compared to moons that are spherical.

-Mars, because we see dried up riverbeds *Notice the pattern that looks like branches, which is actually lots of small channels feeding into a larger river.*

This photo was taken from orbit around some planet. What planet is it, and how do you know? -Mercury, because we see gigantic cliffs -Venus, because of its yellowish color. -the Moon, because it has craters. -Mars, because we see dried up riverbeds

-Liquid water still flows occasionally at or near the surface. *The gullies are presumably formed by flowing water, and they must be recent or they would have been erased by winds. (Photos taken a few years apart also show new gullies, providing further evidence of their recent origin.)*

This photograph shows gullies on the wall of a crater on Mars (much like the gully photo shown in your textbook). What does this photo seem to be telling us about Mars? -Mars still has active volcanoes. -There must not be any wind on Mars, or these features would have been erased. -Liquid water still flows occasionally at or near the surface. -It still rains on Mars at least once every few million years.

Listed following are characteristics of the atmospheres of Venus, Earth, and Mars. Match each atmospheric characteristic to the appropriate planet.

Venus: -Sulfuric acid clouds -Almost no surface winds -Runaway Greenhouse effect Earth: -Ultraviolet-absorbing stratosphere -Atmosphere composed primarily of nitrogen Mars: -Extremely low density atmosphere -global dust storms *Be sure to recognize that Venus has very little surface wind because of its slow rotation rate. Venus suffered a runaway greenhouse effect because of its distance from the Sun; If Earth were placed at the same distance, our planet would suffer the same fate. Earth has an ultraviolet-absorbing stratosphere because of the oxygen in the atmosphere, which at high altitudes forms molecules of ultraviolet-absorbing ozone.*

Listed below are geographic features of the terrestrial worlds. In each case, identify the geological process: impact cratering, volcanism, erosion, or tectonics (where tectonics is any large-scale processes affecting the structure of the planetary crust), most responsible for the feature described. Match the geographic feature to the appropriate geologic process.

Volcanism: -Mars's Olympus Mons -Big Island of Hawaii -Smooth surfaces of the lunar maria Impact cratering: -Old surface features of the lunar highlands Erosion: -Earth's Grand Canyon Tectonics: -Current location of Earth's continents -Mercury's many long, tall cliffs -Mars's Valles Marineris *Remember that the four processes are interrelated, so although one may be most important to a particular feature, others often also play a role. For example, some erosion has occurred on the volcanic island of Hawaii, there are impact craters on the slopes of Olympus Mons, and volcanism and tectonics almost always go hand-in-hand.*

-volcanoes on Jupiter's moon Io *Tidal heating makes Io the most volcanically active place in the solar system.*

What are all the black spots on this object? -impact craters on Uranus's moon Miranda -volcanoes on Jupiter's moon Io -giant cliffs on the planet Mercury -methane lakes on Saturn's moon Titan -wind streaks on Neptune's moon Triton

-Jupiter's magnetic field *The magnetic field is stronger where the lines are closer together and weaker where they are farther apart.*

What are all the blue lines around Jupiter supposed to represent in this picture? -blue light reflected from methane clouds -Jupiter's magnetic field -the orbits of some of Jupiter's many moons. -the solar wind

-the Great Red Spot *The Great Red Spot is a very large storm, wide enough to swallow two or three Earths.*

What is the name of the feature indicated by the arrow in this photo? -the Cassini Division -the Great Red Spot -the Great Dark spot -the Io torus

-They represent boundaries between the plates that make up Earth's lithosphere. *And the white arrows indicate directions of plate movement.*

What is the significance of the yellow lines on this map of Earth? -The yellow lines are lined everywhere by chains of volcanoes. -They represent borders between continents. -The yellow lines represent the locations of deep trenches. -They represent boundaries between the plates that make up Earth's lithosphere.

-Jupiter's moon Europa *Notice the long cracks in the icy surface.*

What is this object? -Neptune's moon Nereid -Uranus's moon Miranda -Saturn's moon Titan -Jupiter's moon Callisto -Jupiter's moon Europa

-Saturn's moon Titan *Notice the fuzzy atmosphere that is clearly visible.*

What is this object? -Neptune's moon Triton -Jupiter's moon Europa -Jupiter's moon Callisto -Uranus's moon Miranda -Saturn's moon Titan

What important change in the Sun over the past four billion years is thought to be very important to understanding the climates of Venus, Earth, and Mars? -a gradual reduction in the amount of ultraviolet and X-ray radiation coming from the Sun -a gradual brightening with time -a gradual weakening of the solar wind with time -a gradual dimming with time

a gradual brightening with time

4. Gas particles in Earth's atmosphere most easily escape from the

exosphere

1. Most of the charged particles from the Sun are deflected around Earth by the

magnetosphere

4. A comet's _________________ is the frozen portion of a comet.

nucleus

4. _________________ is responsible for the tremendous volcanic activity on Io.

tidal heating

5. The densest layer of the atmospheres of Venus, Earth, and Mars is the

troposphere