Deck 14: Uranus, Neptune, Pluto, and the Kuiper Belt: Remote Worlds

Question 1

How was Uranus discovered?

A)by a careful search in the 1930s by an astronomer who was convinced it must be there
B)by accident, by an astronomer conducting a sky survey
C)by an astronomer studying old photographs of the sky, several years after they were taken
D)by careful application of Newton's laws to the motion of other planets

Answer 1

B

Question 2

Which of the following objects was discovered by accident by an astronomer who was surveying the sky with his telescope to look for comets but had no idea that he would discover something larger?

A)Uranus
B)Neptune
C)Saturn
D)Pluto

Answer 2

A

Question 3

If Uranus has an orbital period of about 84 years, how far does it appear to move across our sky in 1 year?

A)0.23°
B)a very small angle because Uranus is a very long way away from Earth
C)43°
D)4.3°

Answer 3

D

Question 4

Using the best telescopes under the best observing conditions, the smallest angle in the sky that can be resolved from Earth's surface is approximately 0.1 arcsec. (You may wish to review the small-angle formula in Box 1-1 of Universe, 11th ed.) Consequently, the smallest feature that can be resolved at the distance of Uranus is about:

A)1/400 of the diameter of Uranus.
B)1/4 of the diameter of Uranus.
C)4 times the diameter of Uranus.
D)1/40 of the diameter of Uranus.

Question 5

The distance between the orbits of Uranus and Neptune is roughly the same as the distance between:

A)the orbits of Jupiter and Saturn.
B)the orbits of Earth and Uranus.
C)Jupiter and the Sun.
D)Saturn and the Sun.

Question 6

Neptune was discovered by:

A)the careful application of Newton's laws to the motion of other planets.
B)an astronomer who was conducting a sky survey.
C)a more precise theoretical prediction.
D)a careful search by an astronomer in the 1930s who was convinced that one extra planet must be out there.

Question 7

Neptune was discovered:

A)totally by accident.
B)because of deviations observed in the predicted orbit of Uranus.
C)when it collided with a bright comet.
D)by the Hubble Space Telescope (HST).

Question 8

The orbital data that were used by Le Verrier and by Adams to compute the expected position of Neptune were taken when:

A)Neptune exhibited retrograde motion as viewed from Uranus.
B)Uranus was at opposition and Neptune was in conjunction.
C)Uranus was in conjunction and Neptune was at opposition.
D)Earth was at maximum distance from Uranus but minimum distance from Neptune.

Question 9

We believe Galileo may have unknowingly observed Neptune in January 1613, because at that time it was:

A)at opposition.
B)almost lined up with Jupiter as viewed from Earth.
C)almost lined up with the Sun as viewed from Earth.
D)at superior conjunction.

Question 10

When Couch Adams, the English student, and Le Verrier, the French astronomer, independently predicted the existence of Neptune on the basis of measured deviation of Uranus's motion by gravitational interaction, what factor ultimately led to Neptune's discovery by Galle at Berlin Observatory rather than by Challis at Cambridge, England, even though Challis was told of the prediction much earlier than Galle?

A)better eyesight
B)Galle used photography, while Challis had to rely on eye observation.
C)better star charts
D)better telescope

Question 11

How did the discovery of Neptune differ from the discoveries of Uranus and Pluto?

A)Neptune's presence was first predicted using Newton's gravitational law to interpret deviations in the motion of another planet, whereas Uranus and Pluto were discovered during sky searches.
B)Neptune was discovered by accident by an amateur astronomer, whereas Uranus and Pluto were both found by professional astronomers doing specific searches for a new planet.
C)Neptune was found during a survey of the sky, whereas Uranus and Pluto were found after being predicted on the basis of their gravitational influence on the motions of neighboring planets, Saturn and Neptune, respectively.
D)Neptune was discovered by photographic surveys of the sky, whereas Uranus and Pluto were found by visual searches.

Question 12

Which object was discovered as a result of the detailed prediction of its position using Newton's gravitational theory to explain deviations in the motions of known planets?

A)Pluto
B)Neptune
C)Mercury
D)Saturn

Question 13

The object whose discovery was prefaced by accurate prediction using the measured deviations of known planets from regular orbits and the application of Newton's laws of mechanics, is:

A)Uranus.
B)Neptune.
C)Pluto.
D)Mercury.

Question 14

The shape and alignment of the orbit of Neptune is:

A)almost circular (eccentricity = 0.009), larger than the orbit of Uranus, and close to the ecliptic plane.
B)almost circular (eccentricity = 0.009), smaller than the orbit of Uranus, and close to the ecliptic plane.
C)almost circular (eccentricity = 0.009), but steeply inclined to the ecliptic plane (17°).
D)very elliptical, such that its orbit occasionally carries it beyond Pluto's circular orbit, but in the ecliptic plane.

Question 15

The smallest angle in the sky that can be resolved from Earth's surface, using the best telescopes under the best observing conditions, is approximately 0.1 arcsec. (You may wish to review the small-angle formula in Box 1-1 of Universe, 11th ed.) The smallest feature that can be resolved at the distance of Neptune is therefore approximately:

A)1/2 of the diameter of Neptune.
B)1/200 of the diameter of Neptune.
C)20 times the diameter of Neptune.
D)1/20 of the diameter of Neptune.

Question 16

Uranus is just visible as a naked eye object when seeing conditions are very good and when it is at:

A)superior conjunction.
B)inferior conjunction.
C)opposition.
D)greatest elongation.

Question 17

During its flyby of Uranus, Voyager 2 spent many days imaging the planet, but it was able to photograph only the southern hemisphere of Uranus. Why was this?

A)Uranus's rotation period was such that it kept the same face, the southern hemisphere, facing Voyager 2 for the whole encounter.
B)Because of Uranus's extreme axis tilt and the planet's position in its orbit, the northern hemisphere was pointed away from the Sun during the Voyager 2 passage and was therefore in darkness for the whole time.
C)The very long rotation period of Uranus meant that Voyager 2 was not able to observe the planet for more than part of a rotation.
D)Voyager 2 passed by the side of the planet that contained the southern hemisphere, and Uranus's extreme axis tilt meant that planet rotation would never bring the other hemisphere into view.

Question 18

Which planet has its spin axis tilted 98° from the perpendicular to its orbital plane?

A)Mercury
B)Neptune
C)Venus
D)Uranus

Question 19

The tilt of Uranus's axis was first deduced from observed orbital motions of its moons. For the deduction of this tilt to be correct, it was necessary to assume that the moons:

A)moved in the ecliptic plane, or at least in the plane of the orbit of Uranus.
B)passed over both north and south poles of the planet, thereby indicating the planet's spin axis.
C)were not affected by the gravitational field of the Sun, which would force their orbits to deviate from the planet's equatorial plane.
D)were orbiting in the equatorial plane of Uranus.

Question 20

The expected seasonal changes on Uranus because of its orbital and spin-axis alignments, compared to those on Earth, will be:

A)the same, because the tilt of the spin axis is the same as that of Earth.
B)much less, because its orbit is circular.
C)absent, because the spin axis is perpendicular to the orbital plane.
D)very much exaggerated, because the spin axis is almost in the orbital plane.

Question 21

If the orbital period of Uranus is 84 years, its axis tilt is 98°, and its rotational period is about 17 hours, how often will the Sun be at the zenith at the north pole?

A)never, because of the extreme tilt of the spin axis to the ecliptic plane
B)once every 42 years
C)once every 17 hours
D)once every 84 years

Question 22

If the south pole of Uranus (orbital period = 84 years) was pointing as close as it ever points toward the Sun in 1986, when would the Sun next be over the equator of this planet?

A)2070
B)never, because of the large tilt of Uranus's axis to the perpendicular to its orbital plane
C)2028
D)2007

Question 23

Which major planets rotate about their axes in a retrograde direction, opposite to their orbital directions?

A)Mercury and Neptune
B)Venus and Neptune
C)Venus and Uranus
D)Mercury and Uranus

Question 24

The blue-green appearance of Uranus is caused by:

A)the atmosphere of methane gas, which preferentially absorbs the red parts of the solar spectrum.
B)the reflection of blue light by the ice crystals on the planet's surface and in its atmosphere.
C)the color of the surface of the planet.
D)scattering of light from the dust in the thick atmosphere.

Question 25

The atmosphere of Uranus appears to be similar to those of Jupiter and Saturn except that it shows far less structure and patterns than they. Why is this?

A)Dust storms continually hide the features and patterns in the Uranus atmosphere.
B)Substances that make up the clouds and patterns on Jupiter and Saturn, such as NH₃ and H₂O, have frozen and fallen out of Uranus's colder atmosphere.
C)The glow of atomic auroral emissions from the polar regions of Uranus, caused by the magnetosphere, outshines the dim reflected light from the Sun, particularly because methane absorbs most the sunlight.
D)A very high and featureless haze layer hides the clouds and patterns expected to occur on Uranus.

Question 26

One reason Uranus's atmosphere appears almost featureless is that many substances freeze out at its cold temperature. One substance that does NOT freeze out is:

A)ammonia.
B)ammonium hydrosulfide.
C)methane.
D)water.

Question 27

If methane were absent from Uranus's atmosphere, what color would the atmosphere appear?

A)the same blue-green color it appears now because methane is colorless
B)more yellow (like Saturn) because methane absorbs longer wavelengths
C)a deeper blue (like Neptune) because methane absorbs longer wavelengths
D)a deeper blue (like Neptune) because methane absorbs shorter wavelengths

Question 28

In the sunlit southern hemisphere of Uranus, the observed variation of temperature with latitude is:

A)unknown, because Uranus is too far away for us to measure temperatures at different latitudes.
B)much cooler at the equator than at the south pole because the south pole is tilted almost directly toward the Sun.
C)much cooler at the south pole than at the equator because the Sun is always close to (or below) the horizon, as seen from the pole of any planet.
D)almost nonexistent between the equator and the south pole, implying an efficient equator-to-pole circulation pattern.

Question 29

The pattern of winds observed on Uranus by Voyager 2 is:

A)in bands parallel to the equator, as on Jupiter and Saturn.
B)unknown, because Uranus is too featureless for us to detect wind patterns.
C)primarily in bands perpendicular to the equator, with winds alternating between north-south and south-north directions.
D)dominated by individual cyclones and anticyclones linked by an overall west-to-east flow, similar to the pattern in the mid-latitudes on Earth.

Question 30

The interior rotational period of a jovian planet is determined by:

A)measuring the precession of the spin axis of the planet, which is related directly to the planet's interior.
B)observing the effects of gravitational field variations on the orbital periods of the planet's moons.
C)observing cloudtops, because the clouds rotate with the overall planet on all the jovian planets.
D)observing radio emission variations that are associated with the magnetic field, the origin of which is deep in the planet's interior.

Question 31

How has the rotational period of the interior of Uranus been determined?

A)by using measurements of Uranus's magnetic field taken by Voyager 2 during its flyby
B)by photographing Uranus's surface through occasional holes in the clouds
C)from measurements taken by the lander vehicle from Voyager 2 that penetrated to Uranus's surface through the clouds
D)by measuring the speeds of clouds moving around the planet

Question 32

Why do scientists use magnetic field measurements and observations of radio emission to determine the rotation rates of the interiors of the outer planets such as Uranus?

A)The radio emission comes primarily from the moons, and their motion is governed to some extent by the magnetic field generated in the planet's interior.
B)The magnetic field originates deep inside the planet and radio emission originates in the magnetosphere, the structure and motion of which is linked to this internal magnetic field.
C)Radio energy is produced when cosmic rays pass through magnetic fields in the deep interiors of the planets and variations in this output reflect internal motions.
D)Magnetic field changes produce radio emission in the deep interiors of the planets.

Question 33

If you could "stand" on the equator of Uranus, what would the Sun's apparent motion look like? Three of the following statements are correct; which is INCORRECT?

A)When the northern hemisphere experiences spring, the Sun would rise in the east and set in the west, one full day lasting about 17 hours.
B)When the northern hemisphere experiences summer, the Sun would rise and set very close to the north polar direction.
C)When the northern hemisphere experiences autumn, the Sun would rise in the east and set in the west, one full day lasting about 17 hours.
D)When the northern hemisphere experiences winter, the Sun would not be visible.

Question 34

The tilts of the equators of Uranus and Neptune to their respective orbital planes are:

A)almost zero for both planets.
B)very similar-each about 45°.
C)very similar-at a large angle, near 90°.
D)very different.

Question 35

Which planet is characterized by a blue-green appearance, with dark storms and white, high-altitude methane clouds?

A)Saturn
B)Jupiter
C)Neptune
D)Uranus

Question 36

What does Neptune look like from space?

A)blue-green with white, high-altitude clouds and dark storms
B)perpetually covered with yellowish, sulfur-rich clouds
C)blue-green and featureless
D)reddish belts and light zones parallel to the equator

Question 37

The Great Dark Spot on Neptune, photographed by Voyager 2 during its flyby of the planet, was a:

A)cyclonic system with clockwise winds, opposite to those in Jupiter's Great Red Spot.
B)cyclonic system with counterclockwise winds, the same direction as those in Jupiter's Great Red Spot.
C)volcanic caldera.
D)region of upwelling gas in Neptune's atmosphere, above a hot-spot on its surface.

Question 38

Which of the following statements describes correctly how the atmosphere of Neptune differs from that of Uranus?

A)Neptune's atmosphere is almost featureless, whereas the atmosphere of Uranus shows wispy clouds and whirlpool-like vortices.
B)Methane clouds form in Neptune's atmosphere, but not in that of Uranus, because of Neptune's much greater distance from the Sun.
C)All parts of Neptune's visible atmosphere rotate at the same speed, whereas different parts of the atmosphere of Uranus rotate differently.
D)Neptune's atmosphere shows considerable vertical convective motion in addition to east-west circulation, whereas Uranus's atmosphere has very little up-and-down motion.

Question 39

Each of the following statements comparing Neptune with Jupiter and Saturn is true EXCEPT ONE. Which one is NOT true?

A)Like Jupiter and Saturn, Neptune has a number of whirlpool-like vortices in its atmosphere.
B)Unlike Jupiter and Saturn, Neptune has a distinct bluish-green color.
C)Like Jupiter and Saturn, Neptune gives off more heat than it receives from the Sun.
D)Like Jupiter and Saturn, Neptune's atmosphere is divided into many prominent, differently colored belts and zones of alternating eastward and westward circulation.

Question 40

How do the global wind patterns compare on Uranus and Neptune?

A)On Neptune the winds flow parallel to the equator, but because of Uranus's extreme tilt, its winds flow generally from pole to pole.
B)Both planets have very similar wind patterns with flow westward along the equator but eastward north and south of the equator.
C)Uranus has winds flowing westward along the equator and eastward north and south of the equator. The winds on Neptune are exactly opposite of this pattern.
D)Both planets have wind patterns similar to Jupiter. Winds flow in bands parallel to the equator, with many direction reversals as latitude changes.

Question 41

Neptune is about 1.5 times as far from the Sun as is Uranus. The average atmospheric temperature on Uranus is about 55 K. What is the approximate average atmospheric temperature on Neptune?

A)80 K
B)55 K
C)40 K
D)10 K

Question 42

We have determined that the temperatures in the high atmospheres of Uranus and Neptune are, on the average, about the same. How do we explain this?

A)They are both about the same distance from the Sun.
B)The chemical composition is completely different on the two planets, and the chemicals in the atmosphere of Neptune retain solar heat better than those in the atmosphere of Uranus.
C)The greenhouse effect is stronger on Neptune than on Uranus.
D)Neptune is still contracting and giving out energy by the Kelvin-Helmholtz contraction, but Uranus is not.

Question 43

Which of the giant jovian planets has an internal energy source that is so weak that it is masked by the energy received from the Sun so that, from evidence of excess infrared emission, it appears not to be generating energy internally?

A)Jupiter
B)Saturn
C)Uranus
D)Neptune

Question 44

The most likely reason why Neptune shows significant cloud-forms and associated activity in its atmosphere, compared to the quiet atmosphere of Uranus, is that:

A)Neptune does not have the deep, high-altitude layer of haze that blankets Uranus.
B)Neptune is rotating much faster, thereby stirring the atmosphere into rotating storms like hurricanes on Earth.
C)Neptune is closer to the Sun at the present time and receives more energy to cause more convection and turbulence.
D)Neptune has a significant source of internal heat that causes convection and turbulence.

Question 45

Uranus lacks an internal source of heat. One consequence of this is that:

A)Uranus lacks dynamic atmospheric activity.
B)it is much colder than Neptune, even though it is closer to the Sun.
C)the atmosphere is very thin because most of the atmospheric materials lie frozen on the surface.
D)frozen material on the surface results in a much higher albedo than, say, Neptune.

Question 46

If Uranus and Neptune had the same abundance of the elements as Jupiter and Saturn, they would have:

A)the same densities as Jupiter and Saturn even though they have smaller masses.
B)smaller densities than Jupiter and Saturn because density is proportional to mass, implying that smaller masses always have smaller densities.
C)larger densities than Jupiter and Saturn because density is inversely proportional to volume, implying that smaller volumes always have larger densities.
D)smaller densities than Jupiter and Saturn because their smaller masses would produce less gravity, and the materials would be compressed less.

Question 47

How do the densities of Jupiter, Saturn, Uranus, and Neptune compare?

A)Jupiter and Saturn, being more massive, have larger densities than Uranus and Neptune.
B)Jupiter has the largest density. The other three have approximately equal densities, although all less than Jupiter.
C)Saturn's ring system contains much of the less dense material that used to be part of the planet. Thus the remainder of Saturn is most dense, with the others all about the same density, although less dense than Saturn.
D)Uranus and Neptune are more dense than Jupiter or Saturn.

Question 48

What is believed to be the basic structure of the interior of Uranus?

A)rocky core; thick layer of water and ammonia; thin gaseous atmosphere
B)iron core; thick layer of rock; thin, gaseous atmosphere
C)rocky core; thick layer of water and ammonia; thick layer of liquid hydrogen and liquid helium; thin, gaseous atmosphere
D)rocky core; thick layer of liquid hydrogen and liquid helium; thin, gaseous atmosphere

Question 49

The mantles of Uranus and Neptune are believed to contain each of the following EXCEPT:

A)liquid molecular hydrogen.
B)liquid metallic hydrogen.
C)liquid helium.
D)liquid methane.

Question 50

Uranus and Neptune appear to be smaller versions of Jupiter and Saturn, but they differ significantly from these planets, in that:

A)they show much more structure and activity on their "surfaces."
B)their masses are larger than those of Jupiter and Saturn, even though they are smaller planets.
C)their average densities are greater; hence their internal structure and constituents must be different.
D)their rotation periods are much shorter, a few hours compared to Jupiter and Saturn's periods of a few days.

Question 51

The presently favored theory of the origin of Uranus and Neptune is that they:

A)condensed directly out of the gases of the solar nebula at their present orbital radii.
B)condensed directly out of the gases of the solar nebula, but in the inner part of the solar system.
C)formed from planetesimals at their present orbital radii.
D)formed from planetesimals, but much further out in the solar system.

Question 52

The idea that Uranus and Neptune formed at their present orbital radii by the accretion of planetesimals has some serious difficulties. One of these is that:

A)these planets contain abnormally large amounts of hydrogen and helium, suggesting they were formed further out in the solar system.
B)we do not expect planetesimals to exist that far out in the early solar system.
C)evidence from other stars suggests that solar nebulae do not last long enough to form a massive planet at that distance by the accretion of planetesimals.
D)planetesimals at this distance would be expected to have far more iron than we have postulated for the composition of Uranus and Neptune.

Question 53

If Uranus and Neptune had formed at their present distances from the Sun, we might expect that their properties would be quite different from what they are now. Which one of the following would NOT be a good description of Uranus and Neptune in this case?

A)They would contain a larger percentage of hydrogen and helium.
B)They would be smaller than their present sizes.
C)Their densities would be larger than their present values.
D)Their compositions would include liquid metallic hydrogen.

Question 54

In what way do Uranus and Neptune differ from Jupiter and Saturn?

A)Uranus and Neptune do not have observable magnetic fields.
B)Uranus and Neptune apparently do not have rocky cores.
C)The atmospheric winds of Uranus and Neptune are not parallel to the equator.
D)Hydrogen and helium make up a smaller fraction of the total mass of Uranus and Neptune.

Question 55

In addition to being highly inclined to the rotation axes, the magnetic axes of Uranus and Neptune differ from that of Earth in what way?

A)The magnetic axes are oriented north-south, along the direction of the geographic axes, whereas Earth's is oriented south-north, opposite to the direction of its geographic axis.
B)The magnetic axes are oriented south-north, along the direction of the geographic axes, whereas Earth's is oriented north-south, opposite to the direction of its geographic axis.
C)Although inclined at different angles from their rotation axes, the magnetic axes of both planets are almost perpendicular to the ecliptic.
D)The magnetic fields do not seem to be centered close to the middles of the planets.

Question 56

The magnetic fields of Uranus and Neptune are generated by:

A)the flow of atmospheric (gaseous) methane that has been ionized by solar UV.
B)the flow of electrically conducting molten iron in the core.
C)the bulk flow of liquid metallic hydrogen.
D)electrical currents in water, rendered electrically conducting by ionized molecules such as ammonia.

Question 57

The source of the magnetic fields in Uranus and Neptune is probably:

A)the flow of ionized solar wind particles around the planets in their magnetospheres.
B)the flow of impure water in deep layers of these planets.
C)the flow of liquid metallic hydrogen in the planets's interiors.
D)permanently magnetized solid iron cores.

Question 58

The north pole of a bar magnet would be attracted to which pole of Uranus?

A)the magnetic pole above the ecliptic
B)the magnetic pole below the ecliptic
C)the spin axis pole above the ecliptic
D)the spin axis pole below the ecliptic

Question 59

In which of the following planets was a ring system first discovered by the occultation or blocking of light from a distant star, as the planet and rings moved in front of it?

A)Saturn
B)Uranus
C)Mercury
D)Jupiter

Question 60

How were the rings of Uranus first discovered?

A)by the Ulysses spacecraft, when observing from above the Sun's north pole
B)by the Hubble Space Telescope, observing in infrared light
C)by Voyager 2, during its pass through the Uranian system
D)from an airborne telescope, when each ring momentarily blocked off light from a background star

Question 61

By 2006, 13 rings had been discovered around Uranus. Each of the following methods had discovered some of them, EXCEPT ONE. Which method did NOT yield discovery of some of Uranus's rings?

A)observations from Earth of the occultation of a star by the ring system
B)direct observation by astronauts from space
C)observation by the robotic Voyager 2 flyby mission
D)observations from Earth's orbit by the Hubble Space Telescope

Question 62

The rings of Uranus are much more difficult to observe than the rings of Saturn. Each of the following statements is true EXCEPT ONE. Which is the exception?

A)Uranus is much farther away from the Sun than is Saturn.
B)The rings of Uranus are much narrower.
C)The ring particles of Uranus are made of ices and are thus transparent.
D)Radiation darkening has greatly reduced the albedo of Uranus's ring particles.

Question 63

The particles in the rings of Uranus and Neptune are very dark. This is thought to be because they are composed partly of:

A)iron.
B)ice particles coated with dark dust, probably carbon.
C)methane ice, damaged by impact by electrons from the magnetosphere: radiation darkening.
D)very dark rock.

Question 64

What mechanism appears to have made the surfaces of many moons and the particles in the ring material of the outer planets very dark?

A)collection of large amounts of fine dust, perhaps carbon dust or soot, from interplanetary space
B)long-term bombardment by electrons and ions in the magnetosphere: radiation darkening
C)burning and charring of the surfaces by successive passages through the planet's atmosphere, similar to the formation of dark fusion crusts on meteorites that have hit Earth
D)chemical changes that are caused by long-term exposure to solar ultraviolet radiation

Question 65

How were the rings of Neptune first discovered?

A)direct photography from Earth
B)direct photography by a flyby mission
C)occultation of a star as the rings moved in front of it
D)ultraviolet emissions picked up by the Hubble Space Telescope

Question 66

In which of the following characteristics is Uranus significantly different from the rest of the jovian planets?

A)It has an atmosphere composed primarily of hydrogen and helium.
B)It has a planet-wide magnetic field.
C)It does not have an internal source of heat.
D)It has a system of rings.

Question 67

The moons of Uranus orbit the planet in:

A)a plane inclined a few degrees to the ecliptic, like the jovian moons.
B)the plane of the ecliptic.
C)polar orbits (orbits over both poles).
D)the same plane as the rings.

Question 68

The densities of the five largest moons of Uranus-about 1500 kg/m³ compared with the value of 3340 kg/m³ for Earth's Moon and 1000 kg/m³ for water ice-suggest a composition of:

A)primarily hydrogen and helium, with a slushy core of ice-forming compounds, such as water, methane, and ammonia.
B)50% rock and 50% ice-forming compounds, such as water, methane, and ammonia.
C)50% rock and 50% pure water ice.
D)almost entirely water ice, with small amounts of other ice-forming compounds, such as methane and ammonia.

Question 69

Small bodies are expected to have little internal heating and thus to be geologically dead, with heavily cratered surfaces. Surprisingly, only two of the five moderate-sized moons fit this description. They are:

A)Ariel and Titania.
B)Miranda and Ariel.
C)Umbriel and Oberon.
D)Miranda and Oberon.

Question 70

Miranda, a satellite of Uranus:

A)shows a rough surface, indicating that it has either been shattered by one or more large impacts or has undergone partial chemical differentiation.
B)is almost completely smooth and featureless.
C)is smooth, with networks of cracks that were apparently created during the formation of its icy crust.
D)has an ancient surface covered with impact craters like the highland areas of our Moon.

Question 71

Which one of the following statements correctly describes Miranda, one of the satellites of Uranus?

A)icy surface with chaotically varied terrain
B)rocky surface with lava lakes and several active volcanoes
C)smooth and very dark (1% reflectivity), showing only a network of fine cracks
D)icy, frost-covered surface with vents of rising gas visible in the northern hemisphere

Question 72

Miranda, a satellite of Uranus:

A)is almost spherical and has a very smooth uncratered surface, suggesting that it consists almost completely of ice.
B)appears to have undergone a period of partial chemical differentiation during internal tidal heating.
C)shows an ancient surface covered with impact craters.
D)shows active geysers and resurfacing due to water flows.

Question 73

Which planetary satellite shows strong evidence of having undergone partial chemical differentiation as a result of tidal heating some time in its past?

A)Io
B)Callisto
C)Triton
D)Miranda

Question 74

We often think of the solar system as an unchanging mechanical system. But only one of the following features has remained unchanged over the past few decades. Which one?

A)the brightness of Neptune's rings
B)the Great Dark Spot on Neptune
C)the orbits of Uranus's small inner satellites
D)the unusual topography of Miranda, one of the larger satellites of Uranus

Question 75

Which property of Triton, a moon of Neptune, makes it significantly different from all other major moons in the solar system?

A)Its orbit is at right angles to the equator of its mother planet.
B)It has an extremely dark, smooth surface and consequently was not discovered until very recently.
C)It orbits in a direction opposite to most other moons and opposite to the normal direction of planetary rotation and revolution.
D)It has an atmosphere of nitrogen and oxygen, with H₂O clouds.

Question 76

Which planet has among its satellites one large moon, which orbits in a retrograde direction, and one moderate-sized moon with a highly elliptical orbit?

A)Uranus
B)Saturn
C)Neptune
D)Jupiter

Question 77

Which of the following does NOT describe Triton, the strange moon of Neptune?

A)size almost as big as Earth's Moon
B)orbit inclined at 23° to Neptune's equator
C)retrograde orbital motion
D)rocky, cratered surface

Question 78

The plumes that were seen to rise from the surface of Triton, Neptune's largest satellite, are believed to be:

A)sulfur dioxide from geysers heated by tidal stresses.
B)volcanic ash from eruptions similar to, but much smaller than, an Earth-bound eruption.
C)water, methane, and ammonia ice crystals above volcanic vents.
D)dark material projected upward by nitrogen gas released by sunlight warming the surface or by undersurface heating.

Question 79

How was an atmosphere detected on Triton?

A)Material ejected from geyserlike plumes was seen to form streaks against the surface, indicating high-altitude winds.
B)Clouds of nitrogen crystals were seen to move at speeds different from the rotational speed of the surface.
C)Infrared radiation was seen to be Doppler shifted off moving cloud layers.
D)Dust layers were seen to blow onto and off portions of the surface, much like the situation on Mars.

Question 80

The orbit of Triton is inclined about 23° to the equatorial plane of Neptune. By contrast, all of the other large moons in the solar system are in nearly equatorial orbits around their planets. What can you surmise about Triton from this?

A)Triton's orbital inclination has existed since the beginning of the solar system.
B)A large orbital inclination is a relatively recent development for Triton-perhaps only a few hundred million years old.
C)Neptune's own axial tilt toward its equatorial plane must have been 23° more when it was formed than it is now.
D)Triton was probably formed in an equatorial orbit, but it is now in the process of transitioning to a polar orbit.