Chapter 10: Vagabonds of the Solar System

Section: Introduction

1. Some of the definitions of the different types of objects in the solar system overlap. Which one of these pairs does NOT overlap? That is, if an object can be described by one of the labels, it cannot be described by the other.

A) dwarf planet and asteroid

B) dwarf planet and Kuiper belt object

C) satellite and Kuiper belt object

D) meteoroid and planet

2. Which one of these is a small solar system body?

A) Rhea, a moon of Saturn

B) Pluto

C) Ceres (an asteroid)

D) Mathilde (an asteroid)

Section: 10-1

3. Which of these objects was discovered during the twentieth century?

A) Pluto

B) Uranus

C) Neptune

D) Ceres

4. Pluto was discovered in

A) 1930.

B) 1846.

C) 1609.

D) 1781.

5. How was the dwarf planet Pluto discovered?

A) by prediction using Newton’s laws to account for the deviations from uniform orbits of Uranus and Neptune

B) by the infrared cameras on the IRAS spacecraft

C) by Voyager spacecraft cameras, which were used between planetary encounters to survey the planetary system

D) by searching photographs of the sky for an object that moved against the background of distant stars

6. Pluto is believed to have

A) no atmosphere at all.

B) a thick atmosphere of carbon dioxide.

C) a thin atmosphere of water vapor.

D) a thin atmosphere containing some nitrogen, methane, and carbon monoxide.

7. Pluto is NOT believed to have an unusually large

A) number of craters.

B) satellite (relative to its own size).

C) orbital eccentricity.

D) orbital inclination.

8. Which of these objects was farthest from the Sun in 1990?

A) Pluto

B) Charon

C) Neptune

D) Uranus

9. Which planet or dwarf planet in the solar system has the moon with the largest diameter compared with the diameter of the planet or dwarf planet itself?

A) Earth

B) Saturn

C) Neptune

D) Pluto

10. Which of these solar system objects has the greatest orbital inclination (orbit at the greatest angle to that of Earth’s orbit around the Sun)?

A) Mercury

B) Mars

C) Jupiter

D) Pluto

11. Which of these solar system objects has the greatest orbital eccentricity and therefore the MOST elliptical orbit?

A) Mercury

B) Mars

C) Earth

D) Pluto

12. What is the largest moon of the dwarf planet Pluto called?

A) Chiron

B) Callisto

C) Charon

D) Triton

13. How often would an observer standing on Pluto’s surface see the satellite Charon rise above the horizon each day?

A) once each 6-hour day as Pluto rotates on its axis

B) twice each 6-hour day because Charon is in a retrograde orbit

C) once every 2 days because Charon orbits in the same direction Pluto rotates but more slowly

D) never—Charon is a synchronous satellite with an orbital period exactly equal to Pluto’s rotation period

14. Earth’s Moon subtends an angle of about 0.5° when viewed from Earth. Charon is about 1200 km in diameter and about 18,490 km away from the surface of Pluto. How large an angle does it subtend when viewed from Pluto?

A) about the same size angle as Earth’s Moon

B) about 7 times larger an angle than Earth’s Moon

C) about 11 times larger an angle than Earth’s Moon

D) over 100 times larger an angle than Earth’s Moon

15. What technique allowed scientists to determine accurately, for the first time, the relative sizes of Pluto and Charon?

A) imaging by the Voyager spacecraft in 1989

B) direct photography using adaptive-optics telescopes on Earth in 1995

C) occultation of this planet by Earth’s Moon during the 1980s

D) eclipses of the planet’s surface by its moon, Charon, during 1985–1990, viewed from Earth

16. What is unique about the Pluto–Charon system, compared with all other planets and dwarf planets in the solar system?

A) Both Pluto and Charon are volcanically active, with lava flows and vents of sulfur dioxide gas.

B) Charon is an icy moon, but it is in orbit around a giant planet made mostly of liquid hydrogen.

C) Pluto has only one satellite.

D) Both Pluto and Charon are in synchronous rotation, so each object maintains the same face toward the other object at all times.

17. Pluto’s mass was poorly known before 1978. What happened in that year to change this?

A) The Hubble Space Telescope was launched.

B) The new Keck telescopes became operational.

C) Charon was discovered.

D) The return echo of a radar pulse, sent many years before, returned to Earth allowing a Doppler shift measurement of its rotation rate.

18. The Pluto–Charon system moves in which way in its mutual motion?

A) Charon orbits Pluto with exactly Pluto’s rotation period.

B) Charon orbits Pluto once while Pluto rotates twice.

C) There is no relationship between rotation period of Pluto and orbital period of Charon.

D) Charon orbits Pluto twice while Pluto rotates once.

19. Compared to the planets in the solar system, the dwarf planet Pluto is

A) similar to the Jovian planets in composition, although it is much smaller in size.

B) similar to the terrestrial planets in composition, although it is much smaller in size.

C) similar to the terrestrial planets in composition, although it is much larger in size.

D) a real oddity, denser than the Jovian planets but lighter than the terrestrial planets.

20. The dwarf planet Pluto appears to be composed of

A) rock and iron.

B) a mixture of rock and ice.

C) gases such as methane and ammonia, possibly with a small, liquid core.

D) the very lightest elements, hydrogen and helium.

21. The first satellite discovered in orbit about Pluto was Charon. What is unusual about this moon?

A) Charon is the only moon in the solar system known to have an atmosphere.

B) Charon is much warmer than it should be, given its position in the solar system.

C) Compared with planet-satellite systems in the rest of the solar system, Charon is very large and very close to Pluto.

D) Charon is geologically active.

Section: 10-2

22. Haumea is all of these EXCEPT

A) a trans-Neptunian object.

B) a dwarf planet.

C) a Kuiper belt object.

D) an asteroid.

23. What is unusual about the surface of Haumea’s moons?

A) It is solid rock.

B) It appears to be a mixture of rock and ice.

C) It is almost pure water ice.

D) It is almost perfectly round.

24. Which solar system object was found on January 1, 1801, located between the orbits of Mars and Jupiter?

A) asteroid Ceres

B) Comet Halley

C) Kuiper belt object 1993 SC

D) asteroid Gaspra

25. Who was the first person to discover an asteroid?

A) German astronomer Johann Bode

B) English astronomer Sir William Herschel

C) German mathematician Karl Friedrich Gauss

D) Italian astronomer Guiseppe Piazzi

26. On New Year’s Day, 1801, Giuseppe Piazzi discovered the asteroid Ceres. His search was inspired by an event that had occurred only about 20 years before. What event?

A) first astronomical use of the telescope by Galileo

B) invention of the first practical reflecting telescope by Newton

C) discovery of Uranus by Herschel

D) discovery of Pluto by Tombaugh

27. What is the largest known asteroid in the solar system?

A) Phobos

B) Gaspra

C) Ceres

D) Pallas

28. The size of the largest asteroid, Ceres, compared with the largest mare or impact basin on the Moon, which covers about one-quarter of the Moon’s face, is

A) not comparable because all asteroids are very small objects (1 km diameter), whereas most maria are large (100–1000 km diameter).

B) much smaller, only about 1/3 the size.

C) very similar, about 1000 km across.

D) much larger, by a factor of more than 2.

29. What is the diameter of Ceres, the largest asteroid in the solar system, compared with the diameter of Earth, which is about 12,800 km?

A) smaller than 1/100 Earth’s diameter

B) slightly less than 1/10 Earth’s diameter

C) about 1/4 Earth’s diameter

D) about 1/2 Earth’s diameter

30. What is a trans-Neptunian object?

A) a solar system object that may impact Neptune in the next billion years

B) a moon of Neptune

C) a solar system object that orbits the Sun with a semimajor axis larger than Neptune’s

D) an exoplanet roughly the same mass as Neptune

31. Which of these is LARGER than Pluto?

A) Eris

B) Ceres

C) Haumea

D) Earth’s Moon

32. Haumea is classified as a dwarf planet even though its shape resembles a watermelon. Why is it so distorted?

A) It has a massive, nearby moon.

B) Its two hemispheres have very different densities.

C) It has recently undergone a collision.

D) It rotates rapidly.

33. Which of these is LEAST similar in size to Pluto?

A) Ceres

B) Mercury

C) Makemake

D) Eris

34. Unlike the other dwarf planets in the Kuiper belt, Makemake has no moons. Is this important?

A) No. Having or not having a moon does not affect what astronomers can learn about a solar system body.

B) Yes. It indicates that Makemake is older than the others.

C) Yes. It indicates that Makemake is younger than the others.

D) Yes. It means that it is harder to determine the mass of Makemake.

Section: 10-3

35. According to the Dawn flyby of asteroid Vesta, which of these is NOT a characteristic of Vesta?

A) It shows chemical differentiation.

B) It is orbited by its own satellite.

C) Its hemispheres show different amounts of cratering.

D) It possesses at least one very tall mountain.

36. When compared with the diameter of Earth’s Moon, the diameters of the biggest asteroids are

A) very much smaller (less than 1/10).

B) about the same size.

C) very much larger, by a factor of at least 5.

D) between 1/10 and 1/3 as large.

37. If all the material in the asteroid belt were to be combined to produce a planet, how big would it be?

A) about 1500 km in diameter, less than half the diameter of the Moon

B) only a few kilometers in diameter, similar to an average mountain on Earth

C) about the size of Earth, with a diameter of about 13,000 km

D) about the size of Mercury, with a diameter of about 5000 km

38. A few of the largest asteroids appear to be spherical. How does this occur?

A) The visible outer atmospheres of these large asteroids are spherical even though the underlying surfaces are irregular.

B) The largest asteroids solidified from spherical gas clouds in their early history and retained this shape.

C) Repeated collisions with other asteroids have worn the largest asteroids down to spheres.

D) Self-gravity was sufficient to pull the largest asteroids into a spherical shape during their early history.

39. The asteroid belt exists between the orbits of the planets

A) Earth and Mars.

B) Jupiter and Saturn.

C) Venus and Earth.

D) Mars and Jupiter.

40. Most of the asteroids of the solar system move around the Sun between the orbits of which planets?

A) Earth and Mars

B) Jupiter and Saturn

C) Venus and Earth

D) Mars and Jupiter

41. Which of these statements about asteroids is NOT true?

A) Only a minority of all asteroids are in the asteroid belt.

B) Some asteroids have orbits that carry them inside Earth’s orbit.

C) Some asteroids occupy the same orbit as Jupiter.

D) The total mass of all asteroids is much smaller than the mass of Earth.

42. The number of asteroids with diameters greater than 100 km is

A) just over 1000.

B) 3.

C) about 30.

D) about 290.

43. The total number of asteroids orbiting the Sun in the main belt is estimated to be

A) several thousand.

B) hundreds of billions.

C) more than ten million.

D) a few hundred.

44. How would a typical asteroid appear on a time exposure photograph of the sky as it orbited the Sun if the camera were tracking the background stars?

A) The asteroid would look like a star, a small extra dot not shown on star charts of this area of the sky.

B) The asteroid would look like a small, diffuse patch against the sharp images of stars because of the dust and gas surrounding it.

C) The asteroid would produce a flash of light as it crossed the field of view of the camera.

D) The asteroid would produce a short trail as it moved slowly against the background stars.

45. The number of known asteroids rose sharply in the 1890s. What caused this?

A) The technique of astrophotography was introduced.

B) The first very large telescopes were built.

C) Better theoretical predictions of where to look for asteroids became available.

D) A series of collisions involving large objects between the orbits of Mars and Jupiter resulted in many more asteroids being formed.

46. By 1891 only about 300 asteroids had been discovered. After 1891 hundreds more were discovered quickly. What caused this increased discovery rate for asteroids?

A) invention of the telescope

B) invention of photography

C) advent of astrophotography

D) heightened interest in the solar system fueled by Percival Lowell and the Martian canals controversy

47. The average sidereal period for an asteroid moving around the Sun in the asteroid belt, according to Kepler’s law, is

A) 46.8 years.

B) 2.8 years.

C) 4.68 years.

D) 1.99 years.

48. If an asteroid was moving in a circular orbit around the Sun with an orbital period of 1/5 that of Jupiter, what would be the radius of its orbit? The semimajor axis of Jupiter’s orbit is 5.2 au.

A) 1.78 au

B) 15.2 au

C) 1.04 au

D) 3.65 au

49. The asteroid belt is believed by most astronomers to be composed of

A) rocky debris left over from the formation of the solar system.

B) former moons of Jupiter.

C) rather dirty ice balls similar to the nuclei of comets.

D) the remnants of a gaseous planet disrupted by a massive impact.

50. Computer simulations of the formation of the solar system show that the material in the vicinity of the asteroid belt is NOT in the form of one large planet because

A) most of the material originally in the asteroid belt crashed into Mars, creating the heavily cratered terrain seen there.

B) a violent collision destroyed two protoplanets, the debris from which became the asteroid belt.

C) this region is where the gravitational field of the Sun is exactly balanced by that of Jupiter.

D) Jupiter’s gravitational pull prevented them from coalescing into a planet.

51. Why does no major planet orbit the Sun at the location of the asteroid belt?

A) One such object did form there but was destroyed by a collision with an early comet; the asteroid belt is the debris from the collision.

B) Jupiter’s gravitational pull stirred up the planetesimals, preventing them from coalescing into a single large object.

C) In the early solar nebula, the temperature that close to the Sun was too high for rock or iron to condense into solid form.

D) Three Earth-sized planets did form there, but they destroyed each other by mutual collisions; the asteroid belt is the debris from these collisions.

Section: 10-4

52. The Kirkwood gaps are in the

A) asteroid belt at places where there are very few asteroids.

B) rings of Saturn, where there is less material than at other radii.

C) spectrum of hydrogen gas, where light has been absorbed by molecules first identified by Kirkwood.

D) equatorial region of the Sun, where no sunspots are found.

53. The Kirkwood gaps are caused by

A) large asteroids moving in circular orbits within the asteroid belt, which sweep out and collect smaller objects in their path.

B) large asteroids whose orbits carry them periodically through the asteroid belt, where they sweep out a path and leave it devoid of asteroids.

C) the gravitational pull of Jupiter, which nudges asteroids into new orbits.

D) large asteroids on the outer fringe of the asteroid belt, which gravitationally affect the paths of smaller objects within the belt.

54. Jupiter’s orbital period is approximately 12 years. Based on this number, astronomers would be MOST likely to find an asteroid belt asteroid with a period of how many years?

A) 4

B) 6

C) 7.3

D) 24

55. What effect does Jupiter have on asteroids in the asteroid belt at the present day?

A) Jupiter has no effect whatever on such small objects because they are a long way away from Jupiter, and Jupiter’s gravitational influence varies as the inverse square of distance, by Newton’s law.

B) Jupiter perturbs only the orbits of asteroids whose orbital periods are a simple fraction (e.g., 1/2, 1/3, 2/3, 2/7) of its orbital period.

C) Jupiter disturbs only the orbits of asteroids whose orbital distances (or semimajor axes) are a simple fraction (e.g., 1/2, 1/3, 2/3, 2/7) of the radius of Jupiter’s orbit.

D) Jupiter disturbs the orbits of all the asteroids in the belt, slowing them down and causing them to spiral slowly in toward the Sun.

56. What is the relationship between the Kirkwood gaps in the asteroid belt and the Cassini division in the rings of Saturn?

A) Both the Kirkwood gaps and the Cassini division are caused by large objects passing through swarms of smaller objects, sweeping out gaps in the swarms.

B) Both the Kirkwood gaps and the Cassini division were discovered by observers from the same group; Kirkwood and Cassini both worked at the same observatory.

C) Both the Kirkwood gaps and the Cassini division are caused by disruptions of the orbits of small objects by larger planets or moons. In both cases, the orbital distance of small objects in the gaps is related by simple fractions to the orbital distance to the disturbing object.

D) Both the Kirkwood gaps and the Cassini division are caused by disruptions of the orbits of small objects by larger planets or moons. In both cases, the periods of the small objects are simple fractions of those of the larger disturbing object.

57. One of the Kirkwood gaps in the asteroid belt is described as “3/7 of Jupiter’s orbital period.” What does this mean?

A) This location corresponds to the radius where an asteroid would complete 3 solar orbits in the same time Jupiter completes 7 solar orbits.

B) This location corresponds to the radius where an asteroid would complete 7 solar orbits in the same time Jupiter completes 3 solar orbits.

C) This location corresponds to a radius that is 3/7 of the orbital radius of Jupiter.

D) The asteroids are apparently the remnants of material that never formed into a larger body. If that body had orbited at this location it would have had 3/7 of Jupiter’s mass.

58. The asteroid belt has a gap where few objects are found because of repeated gravitational disturbances from Jupiter. At what distance from the Sun will this gap be found if objects in the gap have a period one-third that of Jupiter? (Hint: Jupiter’s orbital period is about 12 years.)

A) 8 au

B) 3.5 au

C) 2.5 au

D) 1.4 au

59. Jupiter’s orbital period is approximately 12 years. If it were exactly 12 years, which of these periods would NOT produce an effective resonance with Jupiter?

A) 3.0 years

B) 6.0 years

C) 5.1 years

D) 8.0 years

60. What is the typical distance between asteroids in the asteroid belt?

A) 6000 km

B) 1.2 au

C) 25 km

D) 1 million km

61. What is the average distance between asteroids?

A) about 3 times the length of a football field

B) about twice the diameter of Earth

C) about half the distance between Earth and the Moon

D) many times the distance between Earth and the Moon

62. How are space probes to the outer planets such as Jupiter protected from being obliterated by collisions with asteroids in the asteroid belt?

A) They aren’t. Only one out of every four spacecraft is lost to collisions with asteroids, so it is less expensive to take this risk.

B) The spacecraft are equipped with cameras to detect asteroids so that they can be directed safely around them.

C) The spacecraft are sent in an inclined orbit that arcs above or below the asteroid belt, and then they cross the ecliptic again near Jupiter.

D) They aren’t. Asteroids are so far apart that the spacecraft just sail through.

63. What is a Hirayama family of asteroids?

A) group of asteroids that have nearly identical orbits

B) either of two groups of asteroids that orbit at Jupiter’s distance from the Sun

C) group of asteroids that have identical spectra and therefore identical compositions

D) group of asteroids that have orbits that cross Earth’s orbit but remain outside Venus’s orbit

64. What is unusual about the asteroid Karin?

A) Karin is the Apollo asteroid that comes closest to Earth.

B) Karin was the first of the Trojan asteroids to be discovered.

C) Karin sits at the stable Lagrange point in Earth’s orbit.

D) Karin is the largest asteroid in a cluster of asteroids that all orbit the Sun together.

65. Which of these is NOT a reason to believe asteroids have collisions with each other?

A) Astronomers have observed satellites of asteroids that appear to have been captured after collisions.

B) Almost all of the asteroids orbit the Sun in the same direction.

C) There are several families of asteroids with very similar orbits.

D) Astronomers have observed asteroids that appear to be two lobes connected by a narrow collar, as though two asteroids had collided and stuck together.

66. Why is the star Zeta Leporis, in Lepus the Hare, an object of particular interest?

A) Zeta Leporis is still in the nebular stage; it is only a few hundred million years old.

B) Zeta Leporis appears to have an Earthlike planet.

C) Zeta Leporis is believed to have passed near the Sun early in the history of the solar system, causing gravitational disruptions that affect the orbits of the asteroids.

D) Zeta Leporis appears to have an asteroid belt of its own.

67. Which of these is NOT true of asteroids in the solar system?

A) The masses of all the known asteroids in the asteroid belt, added together, would produce a body too small to be classified as a planet.

B) All known asteroids orbit between Mars and Jupiter.

C) Despite the vast average separations between asteroids, they can sometimes collide.

D) Almost all asteroids have orbits that lie near the plane of the ecliptic.

Section: 10-5

68. Often, an asteroid viewed from Earth appears to change its brightness periodically because the

A) albedo is significantly different on one side than the other.

B) leading side is very dark and the trailing side is very bright like Iapetus, a satellite of Saturn.

C) asteroid is elongated, so it may present a larger or a smaller cross section to Earth as it rotates.

D) asteroid is simply passing through the shadow of another asteroid.

69. In the orbits of which of the planets do Lagrange points occur?

A) all planets

B) Jupiter; only Jupiter is massive enough to produce a Lagrange point.

C) Jupiter and the planets beyond it; a Lagrange point must be a certain distance from its planet, and only the orbits of Jupiter and the planets beyond it are large enough to accommodate a Lagrange point.

D) only the planets with moons

70. Which of these characteristics has NOT been observed in an asteroid?

A) regolith

B) craters

C) satellites

D) plate tectonics

71. Asteroids that orbit the Sun in the stable Lagrange points in Jupiter’s orbit are known as

A) adenoids.

B) Apollo asteroids.

C) Trojans.

D) Jupitoids.

72. How could astronomers detect a large asteroid if it were heading straight for Earth?

A) The asteroid would appear as a slowly brightening starlike object where no star was previously charted, with a redshifted solar spectrum of reflected light.

B) The asteroid would appear as a short trail against the background stars on a sky-tracked long-exposure photograph, and its spectrum would show no Doppler shift.

C) The asteroid would appear as a slowly brightening point of light where no star had previously been charted, and the spectrum of sunlight reflected from it would be blueshifted by the Doppler effect.

D) The asteroid would appear as a slowly brightening and growing diffuse sphere of light where no star was charted because of light scattered from the dust and gas surrounding it, and it would show a blueshifted spectrum.

73. Where do the Trojan asteroids orbit the Sun?

A) in nearly circular orbits at the same orbital distance as Jupiter

B) in nearly circular orbits at the same orbital distance as Earth

C) in the asteroid belt

D) in elliptical orbits that cross the orbit of Earth

74. What kind of orbit is traced by the Trojan asteroids as they move around the Sun?

A) elliptical orbits that carry them from outside Neptune’s orbit to inside the orbit of Jupiter

B) long, elliptical orbits that cross the orbit of Earth

C) circular orbits at Jupiter’s orbital distance, at angles of ±60° away from the planet

D) circular orbits at about 2.8 au from the Sun, within the asteroid belt

75. What is the orbital sidereal period of a Trojan asteroid?

A) The Trojan asteroids have different orbital periods, depending on their masses.

B) 5.9 years, the same as most asteroids in the asteroid belt

C) 11.86 years, the same as Jupiter

D) 1.88 years, the same as Mars

76. If an asteroid were found to be orbiting in a circular path around the Sun at the same distance as Jupiter (5.2 au), what would be its orbital period compared with that of Jupiter, which is 11.86 years?

A) about 10 times as long as Jupiter’s period, or 118.6 years, because the Sun’s gravitational force is much smaller on such a small object

B) about 1/10 of Jupiter’s period because it is a much smaller object

C) same as Jupiter’s period, 11.86 years

D) exactly 1/2 of Jupiter’s period, or 5.93 years, because it would be in a synchronous orbit with Jupiter

77. The two stable Lagrange points in the Jupiter–Sun planetary system are

A) positions in space at Jupiter’s orbital distance from the Sun where the combined gravitational forces from the Sun and Jupiter produce an equilibrium point at which asteroids can become trapped.

B) points at high latitudes on Jupiter where auroras (called Lagrange auroras on Jupiter) occur most frequently.

C) areas in the asteroid belt where gravitational interaction of Jupiter with asteroids disturbs their orbits and causes a Kirkwood gap.

D) an area between the Sun and Jupiter where the gravitational forces on an object from these massive bodies are equal and opposite.

78. What is the magnitude of the net force on a Trojan asteroid?

A) zero

B) the same as the net force on Jupiter

C) slightly less than the net force on Jupiter if it is 60 degrees ahead of Jupiter in its orbit, and slightly more if it is 60 degrees behind

D) enough to give it the same acceleration as Jupiter

79. One significant feature of the Lagrange points produced by the Sun and Jupiter is that

A) they are regions of reduced gravitational force in the asteroid belt from which asteroids can escape, producing the gaps within the belt.

B) gravitational forces combine to trap asteroids at these points.

C) gravitational forces combine to enhance the overall force on particles passing through them, accelerating them out of the solar system.

D) they are points of maximum gravitational force near Jupiter, where the major moons Io and Europa are held.

80. Asteroids whose orbits carry them across Earth’s orbit are known as

A) Kirkwood asteroids.

B) Amor asteroids.

C) Trojan asteroids.

D) Apollo asteroids.

81. Asteroids whose elliptical orbits have perihelia inside the orbit of Mars but outside the orbit of Earth are called ­­­­­­­_____ asteroids.

A) Apollo

B) Trojan

C) Hirayama family

D) Amor

82. What is the difference between an Apollo asteroid and an Amor asteroid?

A) Apollo asteroids cross the orbit of Earth, whereas Amor asteroids cross the orbit of Mars but not Earth’s orbit.

B) Apollo asteroids orbit entirely inside Earth’s orbit and therefore do not cross it, whereas Amor asteroids cross Earth’s orbit and therefore might hit Earth.

C) Apollo asteroids pass near terrestrial planets, whereas Amor asteroids remain in the same orbit as Jupiter.

D) Apollo asteroids approach the orbit of Mercury, whereas Amor asteroids pass only within the orbit of Earth.

83. A useful technique for estimating the shapes of many asteroids has been

A) measurement by many closely spaced observers of occultations of stars by asteroids.

B) direct photography of the asteroid’s shape from Earth.

C) photography from spacecraft, such as Galileo.

D) measurement of brightness variations caused by asteroid rotation.

84. What is unusual about the asteroid Mathilde, which was studied and photographed by the NEAR spacecraft? See Figure 10-23a in the text.

A) Mathilde is not much denser than water.

B) Almost no craters are visible anywhere on Mathilde’s surface.

C) Mathilde’s surface is very bright, possibly a result of fresh material thrown out by impacts.

D) Mathilde has a much higher mass for its volume than any other known asteroid.

85. Refer to Figures 10-17, 10-23a, and 10-24 in the text. The surfaces of Ida, Mathilde, and Eros, asteroids photographed by the Galileo and NEAR Shoemaker spacecraft are

A) densely covered with ancient large and small overlapping craters, similar to the surface of the highland areas of the Moon.

B) irregular, somewhat rounded, and moderately cratered.

C) covered with ice that is crisscrossed with cracks and systems of parallel grooves.

D) covered with young, sharp, jagged protrusions, due to fragmentation by collision with other asteroids, and few craters.

86. Which two spacecraft have taken detailed photographs of the surface of an asteroid?

A) NEAR Shoemaker and Cassini

B) Hyabusa and NEAR Shoemaker

C) Magellan and Cassini

D) Voyager 1 and Galileo

87. Which is the only spacecraft known to have landed on the surface of an asteroid?

A) Cassini

B) Viking

C) NEAR Shoemaker

D) the Soviet Venera 8 spacecraft

88. As of 2019, which of these has NOT been accomplished by planetary scientists studying asteroids?

A) close flyby of an asteroid

B) soft landing on an asteroid

C) placing a spacecraft in a permanent orbit around an asteroid

D) returning a spacecraft to Earth with a sample of dust from an asteroid

Section: 10-6

89. What was the purpose of the Stardust space probe?

A) to plunge into the nucleus of a comet, throwing dust and icy grains out from under the comet’s surface into space, where they can be seen and analyzed from Earth

B) to analyze dust samples from other stars and transmit the results back to Earth

C) to fly through the tail of a comet and transmit images back to Earth

D) to collect samples of comet material and bring them back to Earth

90. Which of these was NOT found by the Stardust probe during its visit to Comet Wild 2?

A) craters

B) gas jets

C) possible fossilized life-forms like those found in the Mars meteorites

D) amino acids

91. The major difference between the orbital paths of comets that is seen in the inner solar system and those of the asteroids in the asteroid belt is that

A) comet orbits are mostly circular and in the ecliptic plane, whereas the asteroids have elliptical orbits inclined at random to the ecliptic plane.

B) asteroids orbit the Sun continuously, whereas all comets approach the Sun’s vicinity only once before leaving the solar system.

C) comets never approach nearer the Sun than approximately Jupiter’s orbit, whereas some asteroids approach very near to the Sun.

D) cometary orbits are highly elliptical and can have large inclinations relative to the ecliptic plane compared with the circular orbits of asteroids in the ecliptic plane.

92. The MOST likely origin of the “dirty snowballs” that become comets when they are deflected into orbits that bring them closer to the Sun is the

A) icy surfaces of the moons of Jupiter and Saturn.

B) dust and gas clouds in the Milky Way Galaxy.

C) asteroid belt because most asteroids are actually comet nuclei.

D) Kuiper belt and Oort cloud surrounding the solar system.

93. To what does the term “plutino” refer?

A) satellite, or moon, of Pluto

B) icy object orbiting the Sun in the region of Pluto

C) object in the Oort cloud similar in size to Pluto but orbiting much farther from the Sun

D) object in the Kuiper belt of comet nuclei beyond the orbit of Pluto

94. The period of Comet Halley is approximately 76 years. Its perihelion position is 0.6 au from the Sun, so its aphelion distance from the Sun is approximately

A) 1.2 au.

B) 17 au.

C) 35 au.

D) 75 au.

95. The Kuiper belt is

A) another name for the asteroid belt.

B) a doughnut-shaped distribution of distant comets around the Sun, extending out about 500 au.

C) a spherical distribution of distant comets around the Sun, extending out about 50,000 au.

D) a random distribution of short-period comets extending from inside the orbit of Jupiter to approximately the orbit of Neptune.

96. The Oort cloud is

A) a random distribution of short-period comets extending from inside the orbit of Jupiter to approximately the orbit of Neptune.

B) another name for the asteroid belt.

C) a flat or doughnut-shaped distribution of distant comets around the Sun, extending out about 500 au.

D) a spherical distribution of distant comets around the Sun, extending out about 50,000 au.

97. What is the approximate orbital period of a comet nucleus that orbits the Sun on the outer fringes of the Oort cloud?

A) 10 million years

B) 10,000 years

C) 100,000 years

D) 1000 years

98. Each one of these is an attribute of Comet Halley. Which is NOT typical of an object originating in the Kuiper belt?

A) It has a period of about 76 years.

B) Its orbit is inclined only slightly (18 degrees) from the ecliptic.

C) Its orbit is retrograde.

D) Its aphelion is at about 35 au.

99. Visible comets originating in the Oort cloud do NOT have orbits that are

A) circular.

B) highly elliptical.

C) parabolic.

D) slightly hyperbolic.

100. The Oort cloud of comets surrounding the solar system at a distance of about 50,000 au is believed to be

A) material flung outward by the gravity of the newly formed giant planets early in the history of the solar system.

B) an interstellar cloud through which the Sun and planets happen to be passing but is not otherwise connected to the solar system.

C) debris left behind at that distance by the collapse of the interstellar cloud that formed the Sun and planets.

D) material captured from interstellar space by the Sun’s gravity.

101. Most comet nuclei are believed to be

A) carbonaceous chondrite meteorites—carbon material—ignited by sunlight and resulting in long smoke trails.

B) pieces of dusty ice left over from the formation of the solar system.

C) pieces of dirty ice ejected from the surface of the icy satellites of the outer planets by asteroid impacts.

D) pieces of rock or iron chipped from asteroids by impacts.

102. The nucleus of Comet Halley, as seen on close-up photographs taken by the Giotto spacecraft, is

A) roughly spherical, moderately cratered, and covered with dark dust.

B) roughly spherical, light-colored, icy, and covered with many cracks and grooves.

C) potato-shaped and darker than coal.

D) oblong, with a bright ice surface.

103. The measured diameter of the core of Comet Halley is closest to

A) 10 km.

B) 10⁶ km.

C) 10⁷ km.

D) 100 m.

104. Compared with the coma, or the visible fuzzy ball, of a comet 10⁶ km in diameter, the diameter of the nucleus of a typical comet is

A) about 1/100, or 10,000 km.

B) about the size of the largest asteroid, 1/1000, or 1000 km.

C) extremely small, 1/10⁸, or 10 m.

D) very small, about 1/10⁵, or 10 km.

105. The nucleus of a typical comet is

A) irregular in shape, with a bright and very reflective, icy surface.

B) spherical, with a very smooth, dark surface.

C) irregular in shape, with a very dark and cratered surface.

D) spherical, smooth, and very light-colored, being composed mostly of ice.

106. The nucleus of Comet Tempel 1 has been described as a “rubble pile,” a loose accumulation of material held together by gravity. It is similar to

A) Charon, the satellite of Pluto.

B) Miranda, the satellite of Uranus.

C) the dwarf planet Ceres.

D) Vesta, a large asteroid.

107. Which of these was NOT observed in the jets escaping from the nucleus of Comet Hartley 2?

A) water ice

B) magnetic fields

C) small, rocky pebbles

D) carbon dioxide gas

108. Why do astronomers believe that Earth’s water could NOT have come from comets similar to Comet Churyumov-Gerasimenko?

A) Comets do not come close enough to Earth’s orbit.

B) There is not nearly enough water stored in the comet population to provide Earth’s water.

C) That comet’s water has a very different isotope ratio than Earth’s water.

D) Comets were not formed until after Earth already had most of its water.

109. A comet is observed to have an orbit that is highly inclined relative to the orbits of the solar system planets. It MOST likely originated from

A) the Oort cloud.

B) the Kuiper belt

C) another star.

D) the breakup of a body passing too close to a giant planet.

110. The ecliptic is the plane defining Earth’s orbit around the Sun. The orbits of most other objects in the solar system generally lie fairly close to the ecliptic. Which of these objects often have orbits that do NOT generally lie close to the ecliptic?

A) Trojan asteroids

B) asteroid belt asteroids

C) comets

D) Kuiper belt objects

111. The size of the coma or gas cloud surrounding the comet nucleus as it reaches its closest point to the Sun can be as large as about

A) 10⁵ km.

B) 10 km.

C) 10⁷ km.

D) 10⁶ km.

112. How large does the coma, or gas cloud surrounding a comet nucleus, become when it reaches its closest point to the Sun?

A) only 10 km, but it glows brightly in sunlight

B) about 10⁶ km, as big as the Sun

C) about 10⁸ km, close to the size of Mercury’s orbit

D) about 10⁷ km, close to 1/10 of Mercury’s orbit

113. The huge hydrogen cloud that surrounds the nucleus of a comet, discovered by its UV emission, has a typical diameter of about

A) 1/2 au.

B) 2  10⁷ km.

C) 2 au.

D) 10⁶ km.

114. What is Sedna?

A) largest object discovered beyond the orbit of Pluto

B) bright comet to which scientists hope to send a rendezvous mission

C) largest object in the asteroid belt

D) largest of the Trojan asteroids

115. The aphelia (farthest distances from the Sun) of the orbits of periodic comets are

A) all located far beyond the orbit of Pluto.

B) mostly confined to the region between Mars and Jupiter, although some comets have orbits that reach beyond the orbit of Pluto.

C) always closer to the Sun than the orbit of Pluto.

D) located anywhere from inside the orbit of Pluto to as far as 100,000 au from the Sun.

116. The orbits of periodic comets

A) are confined to distances closer to the Sun than the orbit of Pluto and are mostly in the ecliptic plane.

B) can extend far beyond the orbit of Pluto and are primarily in the ecliptic plane.

C) are confined to distances closer to the Sun than the orbit of Pluto and are oriented randomly in the solar system.

D) can extend far out beyond the orbit of Pluto and can be oriented in any direction in the solar system.

117. The orbits of comets are

A) primarily in the plane of the ecliptic and can extend far out beyond the orbit of Pluto.

B) randomly oriented in the solar system and confined to distances closer to the Sun than approximately the orbit of Pluto.

C) primarily in the plane of the ecliptic and confined to distances closer to the Sun than approximately the orbit of Pluto.

D) randomly oriented in the solar system and can extend far beyond the orbit of Pluto.

Section: 10-7

118. In a single photograph of a comet and its tail, the only direction that one can determine with certainty is the direction

A) in which the comet is moving, from the trailing tail.

B) toward Jupiter because the gravity of this giant planet pulls the tail material toward it.

C) toward the Sun, indicated by the tail direction because gas and dust in the tail are attracted toward the Sun by its gravity.

D) away from the Sun because the tail is pushed in this direction by the solar wind.

119. Comet tails always point away from the Sun. This observation led Ludwig Biermann to predict the existence of the

A) hydrogen envelope around the comet nucleus.

B) solar wind.

C) solar corona.

D) solar magnetic field.

120. Comet tails are the result of

A) sublimation and evaporation of ices from the comet core.

B) sunlight glinting on the central icy comet core.

C) interplanetary dust collected by the comet as it moves in its orbit.

D) interplanetary material streaming into the comet because of its gravity.

121. A comet’s tail always

A) points toward the nearest planet, attracted by the planet’s gravity field as the comet passes by the planet.

B) trails behind the comet in its orbit and so points away from the Sun only while the comet is approaching the Sun.

C) points away from the Sun, regardless of the motion of the comet.

D) points toward the Sun because the tail is caused by jets of gases evaporated from the comet’s nucleus on the side heated by the Sun.

122. The gas and ion tail of a comet

A) are always blown away from the comet in the anti-Sun direction by the solar wind.

B) always lie in the ecliptic plane because a comet is a part of the solar system.

C) lie between the comet and the Sun because of gravitational attraction.

D) always trail along the orbital path, being left behind by the comet.

123. The ionized gas tail of a comet is always aligned along the

A) comet-Sun line.

B) line between the comet and the nearest planet to it in its orbital motion.

C) comet’s direction of motion.

D) celestial equator.

124. A comet’s tail always points from the comet head

A) toward the nearest planet because of gravitational attraction for the tail material.

B) toward the Sun because of gravitational attraction.

C) away from the Sun.

D) in a direction along its orbital path, always behind the comet.

125. The particular feature of a comet that points away from the Sun and can vary significantly over the course of a few days is its

A) hydrogen envelope.

B) ion or gas tail.

C) coma, or gas cloud.

D) dust tail.

126. What mechanism controls the direction in which a comet’s ion tail is aligned in space?

A) gravitational attraction of the tail material toward the giant planet Jupiter

B) flow of solar wind past the comet’s head

C) tail’s direction of motion because the tail simply trails behind the comet in its orbit

D) gravitational attraction of the tail material toward the Sun

127. The dust tail of a comet has which group of characteristics?

A) spherical, very large, and of low brightness, centered on the comet nucleus, showing up only on UV photographs

B) curved, wide, and without structure, but thin and transparent to starlight

C) long, straight, structured, and pointed directly away from the Sun

D) narrow and straight and pointed directly at the Sun at all times

128. Dust grains released by the melting and sublimation of ice in a comet nucleus

A) drift away from the Sun along magnetic field lines, outlining the structure of the field.

B) become a straight, highly structured, and very variable tail blown away from the comet by the solar wind.

C) become a cloud around the nucleus, the coma, scattering sunlight very efficiently at blue wavelengths.

D) become a uniform, curved tail moving away from the comet under radiation pressure from sunlight.

129. What causes the dust tail of a comet to separate from the nucleus?

A) radiation pressure

B) gravity

C) magnetic repulsion

D) collisions with the solar wind

130. How does the dust tail of a comet compare with its gas tail?

A) Dust tails often appear blue and gas tails white.

B) Dust tails are straight, whereas gas tails are curved.

C) Dust tails are more massive than gas tails.

D) Dust tails point toward the Sun, whereas gas tails point away.

131. What was the purpose of the Genesis spacecraft?

A) to land on an asteroid

B) to move alongside a bright comet nucleus

C) to collect some of the solar wind and return to Earth

D) to collect several small asteroids and return to Earth

Section: 10-8

132. The Deep Impact mission sent an impactor crashing into Comet Tempel 1. What happened?

A) The impactor disappeared into the rubble and regolith covering the comet’s nucleus without leaving a trace.

B) The impactor incinerated in the comet’s coma and never reached the nucleus.

C) The comet was shattered into many small fragments.

D) The collision caused a huge cloud of debris, but 90% of it was pulled back to the surface by the nucleus’ gravity.

133. What did planetary scientists learn from the Deep Impact mission to Comet Tempel 1 in 2005?

A) A comet of this size can be completely shattered by a rather minor impact.

B) Comet nuclei are highly radioactive.

C) The dust thrown up by the impact showed evidence of organic molecules.

D) The mission success or failure to collect samples will not be known until the spacecraft returns to Earth.

134. The collision of the Deep Impact probe with the nucleus of Comet Tempel 1 in 2005 revealed the nucleus as a “rubble pile,” held together by

A) cohesive forces much stronger than those holding rocks together on Earth.

B) frozen ices.

C) gravitation.

D) a fusion crust.

Section: 10-9

135. How far will Comet Halley be from the Sun when it reaches its farthest point from the Sun, or aphelion, if its sidereal period is 76 years? (Note: This calculation needs Kepler’s law and a little care. Assume that the comet’s perihelion distance from the Sun is negligible.)

A) about 18 au, between the orbits of Saturn and Uranus

B) about 1324 au, well beyond the orbit of Pluto

C) about 9 au, between the orbits of Jupiter and Saturn

D) about 36 au, between the orbits of Neptune and Pluto

136. Which of these events will NOT significantly change the orbit of a comet?

A) The comet has a collision with another body in the Kuiper belt.

B) The comet passes close to a major planet.

C) The comet is influenced by a number of smaller bodies (planets, asteroids, etc.), which it passes while in the inner solar system.

D) As it nears the Sun, the blast of the material streaming away to form its tails can change its direction.

137. What defines a comet as a long-period comet?

A) The comet makes only one pass near the Sun and then leaves the solar system forever.

B) The comet falls in from the Oort cloud rather than from the Kuiper belt.

C) The comet has a period longer than 1000 years.

D) The comet has a period longer than 200 years.

138. The longest period for a comet that can be considered a Jupiter family comet is 20 years. If the perihelion of such a comet’s orbit is very close to the Sun, where is aphelion? (The semimajor axes of the orbits of Jupiter, Saturn, Uranus, and Neptune are about 5, 9.5, 19, and 30 au, respectively.)

A) between the orbits of Jupiter and Saturn

B) between the orbits of Saturn and Uranus

C) between the orbits of Uranus and Neptune

D) in the Kuiper belt

139. A typical comet in an elliptical orbit around the Sun will lose what fraction of its mass by melting each time it passes close to the Sun (i.e., at each perihelion passage)?

A) 1/1000

B) very small fraction, less than 1/10,000

C) 1/10

D) 1/100

140. The number of times a typical comet can pass close to the Sun (i.e., the number of orbits the comet can complete) before it is completely vaporized or destroyed is about

A) 1 million.

B) 1000.

C) 1.

D) 100.

141. Suppose a comet is observed to have a surface of pure ice with very little dust and rock on its surface. What can be said about this comet?

A) The comet originated in the Kuiper belt rather than the Oort cloud.

B) The comet is probably making its first passage near the Sun.

C) The comet is very old, having made many trips around the Sun.

D) The comet is part of the family of Kreutz comets.

142. A few thousand comets with perihelia very close to the Sun have been observed. These originate from

A) the breakup of a single comet, so these comets all have very nearly the same orbit.

B) gravitational disturbances of the Oort cloud by a nearby star.

C) gravitational disturbances of the Kuiper belt by Jupiter.

D) gravitational disturbances of the Kuiper belt caused by resonances between Neptune and Kuiper belt objects.

143. A Kreutz comet is unusual because it

A) has a small orbital inclination relative to the ecliptic.

B) has a gas tail that bends away from the Sun-comet line.

C) has a perihelion within about 0.01 au of the Sun.

D) has been captured by a giant planet.

Section: 10-10

144. A shooting star is a

A) violently erupting star ejecting matter rapidly away from it into interstellar space.

B) near-neighbor star moving rapidly across Earth’s field of view.

C) large asteroid disintegrating near the Sun.

D) small piece of rocky or metallic debris burning up and glowing as it enters Earth’s atmosphere.

145. When a piece of space debris enters Earth’s atmosphere it makes a bright streak. Which of these is NOT a name for this flash of light?

A) shooting star

B) fireball

C) bolide

D) meteoroid

146. The luminous trails of small dust particles that are completely vaporized in Earth’s atmosphere result from

A) auroral flashes.

B) meteorites.

C) meteors.

D) meteoroids.

147. A chunk of rock and metal 10 km in diameter orbiting the Sun would be called a(n)

A) asteroid.

B) comet.

C) moon.

D) meteoroid.

148. A small particle of rock (with a diameter smaller than 10 m) orbiting the Sun would be called a

A) meteor.

B) micrometer.

C) meteorite.

D) meteoroid.

149. “Meteoroid” is the term used to describe a solid particle, smaller than 10 meters or so in diameter, that

A) is drifting around in space.

B) has fallen to Earth from space.

C) burns up as it falls through Earth’s atmosphere.

D) originated on the Moon but was knocked onto Earth by a massive impact.

150. The Meteor (Barringer) Crater is located in

A) Australia.

B) the Yucatán Peninsula, Mexico.

C) Quebec, Canada.

D) Arizona, United States.

151. The estimated impact energy of the object that produced the Meteor Crater in Arizona, in terms of explosive power (tons of TNT equivalent, a somewhat dubious and frightening scale!), is

A) greater than 1000 megatons.

B) about 1 megaton.

C) about 20 megatons, similar to the most powerful hydrogen bombs.

D) similar to the first nuclear weapons—less than 10 kilotons.

152. The cause of the meteor showers seen at regular times each year on Earth is MOST likely

A) Earth running into material within the spiral arm structure of the Milky Way.

B) unstable weather conditions on Earth.

C) Earth moving through the remnant dust and rock fragments of an old comet that are orbiting the Sun in the comet’s old orbit.

D) sunspot activity and the resultant geomagnetic disturbances.

153. What causes a meteor shower?

A) If Earth happens to be near a comet when it breaks up, a meteor shower as debris enters Earth’s atmosphere will be observed.

B) Earth passes through the orbit of a comet. If the comet happens to be nearby, the normal ejecta from the nucleus will cause a meteor shower.

C) Earth passes through the tail of a comet.

D) Earth passes through the orbit of a former comet. The debris strewn through this orbit enters Earth’s atmosphere and causes meteor showers.

154. Most meteor showers occur when Earth moves through the

A) orbit of a comet (or of a former comet).

B) Kuiper belt.

C) asteroid belt.

D) Oort comet cloud.

155. A meteor shower occurs when

A) the head of a comet hits Earth’s atmosphere.

B) a meteor disintegrates in Earth’s atmosphere.

C) Earth passes through the asteroid belt.

D) Earth passes through a swarm of dust particles in space.

156. A meteor shower results from

A) material ejected by a massive impact on the Moon; Earth’s gravity attracts it toward Earth.

B) material reentering Earth’s atmosphere after being ejected into space by violent volcanic eruptions on Earth.

C) Earth passing through debris of an old comet.

D) a small piece of rock fragmenting as it passes through Earth’s atmosphere.

157. A meteor shower, or the appearance of many more “shooting stars” at a particular time in the year from a specific sky direction, is related to which astronomical phenomenon?

A) passage of Earth through the remnants of an old comet

B) passage of Earth through intense streams of solar wind

C) Earth’s passage through part of the asteroid belt

D) Earth’s passage through different parts of the spiral arms of the Galaxy

158. Why do the meteors that are seen in the sky in a particular meteor shower appear to come from one specific direction in the sky?

A) The meteors only appear to come from a specific direction because of Earth’s orbital motion.

B) The meteors appear this way because the direction is that of the orbit of the comet that disintegrated to produce the shower.

C) This direction is always along the ecliptic plane because meteor showers occur when Earth catches up with a collection of particles moving in its orbit.

D) This direction is the one along which objects pass on being attracted to the Sun from outer space by the Sun’s gravity.

159. Which of these was NOT a result of the 1908 Tunguska Event?

A) a huge dust cloud

B) a loud explosion

C) a huge shock wave

D) a large crater

160. When investigators reached the site of the 1908 Tunguska event, which of these did they NOT find?

A) a large crater

B) a lack of obvious meteorites

C) a large area of burned and downed trees

D) reports of witnesses hearing and feeling a significant shock wave

161. Recent calculations show that the Tunguska explosion in Siberia in 1908 was probably caused by a

A) large stony meteorite about 1 m across striking the ground at a high speed.

B) small nuclear explosion.

C) small comet nucleus about 1 km across suddenly vaporizing in the atmosphere.

D) small stony asteroid about 80 m across exploding well above the ground.

162. In 2013 a large meteoroid did considerable damage to the city of Chelyabinsk, Russia. Most of the damage was caused by

A) fires started by hot meteorites raining down on the city.

B) breaking glass caused by the sonic boom and shock wave accompanying the meteoroid’s rapid passage through the atmosphere.

C) meteorites striking objects on the ground.

D) contamination from hydrocarbons carried by the meteoroid.

Section: 10-11

163. A piece of rock from outer space that reaches Earth’s surface after surviving a fiery passage through Earth’s atmosphere is known as a(n)

A) meteoroid.

B) asteroid.

C) meteor.

D) meteorite.

164. In order of abundance, from most abundant to least abundant, the occurrence of meteorite impacts (“falls”) is believed to be

A) stony, iron, stony iron.

B) stony iron, iron, stony.

C) iron, stony iron, stony.

D) stony, stony iron, iron.

165. How do scientists determine the fraction of all meteorite impacts that are stony meteorites?

A) by traveling immediately to the sites of impacts

B) by counting accumulated debris in Antarctica

C) by taking spectra of nearby asteroids

D) by inventorying museum collections

166. The estimated total infall of meteoritic and extraterrestrial material from space per day on Earth is

A) about 30 tons.

B) less than 1 ton.

C) about 1 million tons.

D) about 300 tons.

167. Interplanetary material

A) falls on Earth at the rate of several hundred tons per day, mostly as micrometeoroids.

B) occasionally hits Earth in the form of fairly large objects that form craters, but there is no continuous stream of incoming matter.

C) hits Earth at specific times of the year in the form of small particles that produce meteor showers, but interplanetary material does not fall on Earth at other times.

D) falls on Earth only very rarely in the form of single large objects, but these individual impacts can devastate parts of Earth and threaten life.

168. Which are the MOST common types of meteoroids in space?

A) stony irons

B) stones

C) irons

D) carbonaceous chondrites

169. The MOST common meteorites to hit Earth are

A) carbonaceous chondrites.

B) iron meteorites.

C) stony iron meteorites.

D) stony meteorites.

170. Stony meteorites

A) are very much like ordinary silicate rocks.

B) contain large quantities of carbon and water and even hydrocarbons and amino acids.

C) have solid iron cores surrounded by rocky silicate shells.

D) are made of solid iron and small quantities of nickel and cobalt.

171. What fraction of the material arriving on Earth from outer space is in the form of iron meteorites?

A) 50 percent

B) a few percent

C) 95 percent

D) 10 to 20 percent

172. What fraction of the material arriving on Earth from outer space is in the form of stony meteorites?

A) a few percent

B) 10 to 20 percent

C) 50 percent

D) 95 percent

173. For which of these descriptions would one identify a rock as a fallen meteorite?

A) basalt rock full of hollow spaces, shiny and dark colored, with fine details on its surface

B) rock containing large, transparent crystals of common salt embedded in sandstone

C) layered rock consisting mainly of limestone

D) irregular and very heavy solid iron rock with a distinctive crystal structure throughout its interior

174. The Widmanstätten pattern found in many iron meteorites consists of

A) a myriad of small iron crystals formed when the rock cooled quickly in the vacuum of space.

B) small holes created by the heating and partial melting of the meteorite as it entered Earth’s atmosphere.

C) fracture lines created by the original impact that knocked the meteoroid off the parent asteroid.

D) large crystals formed as the iron cooled slowly over many millions of years.

175. The Widmanstätten pattern of crystals found in many iron meteorites is evidence that the meteorites

A) cooled slowly over many millions of years.

B) cooled quickly, in only a few years at most.

C) have suffered highly energetic collisions with asteroids or other meteorites.

D) have been subject to periodic heating by close approaches to the Sun.

176. Widmanstätten patterns are a test for which kind of meteorite?

A) stones

B) stony irons

C) irons

D) carbonaceous chondrites

177. Most meteorites show evidence of having melted or of being fragments of asteroids that were once differentiated by heat. Carbonaceous chondrites, however, are believed to have never melted. Which one of these is NOT a reason to believe carbonaceous chondrites have never melted?

A) Carbonaceous chondrites contain complex carbon compounds that would have been broken down into simpler compounds by high heat.

B) The minerals in carbonaceous chondrites contain as much as 20% water. The water would have been driven out if the minerals had been heated.

C) Amino acids that are occasionally found in carbonaceous chondrites would have been destroyed by melting.

D) Carbonaceous chondrites do not show fusion crusts after passage through Earth’s atmosphere.

178. Which of these have scientists NOT discovered in carbonaceous chondrite meteorites?

A) small glass-rich beads called chondrules

B) minerals that contain water

C) amino acids

D) interior rock that has obviously been melted and resolidified

179. Stony iron meteorites are believed to

A) have been ejected by volcanoes on Mars.

B) originate from differentiated asteroids (in which iron sank to the center).

C) be pieces of primordial solar system material, unaltered since the solar system formed.

D) originate from undifferentiated asteroids (same composition throughout).

180. The existence of distinct and separate types of meteorites, stony, stony iron, and iron, is probably a result of

A) differentiation of material in molten asteroid interiors, with the iron sinking to the core, followed by fragmentation and separation of the iron core and rocky shell.

B) preferential accretion of iron particles to other iron particles because of their magnetic properties, leaving stony particles to accrete separately.

C) different amounts of heating and “erosion” of the outer layers of meteorites as they pass through Earth’s atmosphere; the irons lose their outer rocky shells.

D) their formation in different parts of the early solar nebula, with stones condensing closer to the Sun and irons condensing farther away from the Sun.

181. What is the origin of iron meteorites?

A) Because they are iron, they must have been produced within the nearby supernova that exploded 4.6 billion years ago and caused the collapse that resulted in Earth’s solar nebula.

B) Because iron has a high condensation temperature, these must have been formed in orbits very close to the Sun. They were probably drawn outward by the pull of the Jovian planets when they were in the inner solar system (Nice model).

C) Iron is formed in various chemical reactions, but only at very low temperatures. So, these meteoroids must have been formed in the outer solar system and drifted toward the Sun along with the Jovian planets.

D) They came from the core of an asteroid that had differentiated due to the heat of radioactive materials within it.

182. Which meteorites are believed to be samples of primordial solar nebula material?

A) carbonaceous chondrites

B) stony irons

C) meteorites showing Widmanstätten patterns when etched with acid

D) irons

183. Which of these biochemical materials have been found and identified in carbonaceous chondrites that have hit Earth?

A) living viruses

B) amino acids, or proteins

C) lichens and mosses

D) fossilized single-cell organisms

184. Which of these characteristics of carbonaceous chondrites is unusual compared with other meteorites?

A) Carbonaceous chondrites never show Widmanstätten patterns.

B) Carbonaceous chondrites contain water—a sure sign that they have never melted.

C) Carbonaceous chondrites show a fusion crust—a sure sign of short-lived, rapid heating.

D) Carbonaceous chondrites contain rocky material—a sure sign that they come from a differentiated asteroid.

185. Why are carbonaceous chondrites thought to be original material that formed in the early solar nebula?

A) Carbonaceous chondrites show a Widmanstätten pattern, which indicates slow condensation from gaseous material.

B) The minerals of a carbonaceous chondrite contain up to 20% water, which would have evaporated away if the chondrite had been strongly heated.

C) Carbonaceous chondrites consist mostly of carbon, which was the dominant substance condensing in the outer solar nebula.

D) Carbonaceous chondrites consist almost entirely of ice, which would have sublimed away by now if this were not the first time the chondrite was passing close to the Sun.

186. A stony meteorite would NOT show evidence of which these properties?

A) carbonaceous chondrites

B) fusion crust

C) former deposits of a short-lived radioactive isotope of aluminum

D) Widmanstätten pattern

Section: 10-12

187. What has been discovered in some meteorites that suggests that the formation of the Sun and solar system might have been triggered by a supernova explosion?

A) decay products of short-lived radioactive elements, which only could have been produced in intense nuclear reactions

B) super-pure iron, produced only in nuclear reactions

C) fusion crusts around most meteorites, indicating that they were heated intensely at some time in their history

D) amino acids, which can be produced only in very specific conditions

188. A meteorite that recently fell to Earth was found to contain evidence of the existence earlier in its history of a short-lived radioactive isotope of aluminum, ²⁶Al, which can be produced only under extremely energetic conditions and in nuclear reactions. What conclusion can be drawn from this observation?

A) An energetic nuclear event, a supernova, occurred near the formation site of the Sun, and it produced the ²⁶Al at about the time the meteorite was formed.

B) The meteorite became so hot on its descent through Earth’s atmosphere that it became radioactive, and the ²⁶Al was formed at that time.

C) The meteorite had probably passed through radioactive clouds in space and collected the ²⁶Al before hitting Earth.

D) Radioactivity occurs spontaneously in normal matter, so this finding is not surprising.

189. The Allende meteorite contained an abundance of ²⁶Mg, an isotope of magnesium. ²⁶Mg is the stable product of the decay of radioactive ²⁶Al. What is the significance?

A) Magnesium has a high melting point, so the asteroid of which Allende was originally a part must have formed in the inner part of the solar system.

B) The decay of ²⁶Al would have produced enough radioactivity to cause the melting and differentiation of the Allende meteoroid.

C) The ²⁶Al from which the ²⁶Mg formed was probably produced in a nearby supernova explosion about the time the solar system was formed.

D) This discovery suggests that heavy elements such as magnesium were more abundant in the early Kuiper belt than originally thought.

Section: 10-13

190. What metal is crucial to identifying meteorite impacts in the geologic record?

A) iron

B) nickel

C) cobalt

D) iridium

191. What astronomical event is thought to have led to the mass extinction of the dinosaurs 65 million years ago?

A) extraordinary solar eruption or flare

B) very large volcanic eruption on Earth

C) supernova that exploded relatively close to the solar system

D) asteroid impact on Earth

192. On the basis of the recent interpretation of geological evidence, the impact of a 10-km-diameter asteroid on the surface of Earth would be very likely to

A) disrupt the global ecology and cause the extinction of a large percentage of all species living on Earth.

B) create significant damage near the impact site but have relatively little lasting worldwide effect.

C) shatter Earth into fragments.

D) completely destroy life on Earth.

193. An impact that took place at about the time of the extinction of the dinosaurs (and may in fact have caused their extinction) is believed to have created

A) Meteor Crater in Arizona.

B) Manicouagan Crater in Quebec.

C) Hudson Bay in northern Canada.

D) Chicxulub Crater in the Yucatán Peninsula.

194. The Chicxulub Crater, believed by many scientists to have been created by the impact that caused the extinction of the dinosaurs, is

A) an eroded, water-filled depression in the Canadian Shield area of northern Quebec.

B) hidden under the Yucatán Peninsula and adjacent Caribbean Sea.

C) a prominent landmark in northern Arizona.

D) a large, round valley with a central peak high in the Andes Mountains.

195. What is the likely connection between the metal iridium and the demise of Earth’s dinosaur population?

A) Iridium, which is found in abundance on Earth’s surface, is poisonous to reptiles.

B) Iridium is found beneath Earth’s crust. Meteor impacts during the dinosaur age probably exposed and uncovered enough of it to poison the dinosaurs.

C) Iridium is found in meteorites but is rare on Earth. The existence of a worldwide layer of it suggests a large meteor impact during the dinosaur age. The impact probably raised enough dust to block out sunlight and kill the dinosaurs.

D) Iridium is highly radioactive. Its presence in a geologic layer dating to the dinosaur age suggests that natural radioactivity reached dangerous levels at that time, and the dinosaurs died from overexposure.

196. Rocks laid down at around the time of the Permian/Triassic mass extinction 250 million years ago contain a surprising amount of fullerenes (football-shaped carbon molecules). What evidence is there that the fullerenes came from outer space?

A) The isotope ratio of carbon¹³ to carbon¹² is too great for the fullerenes to have originated on Earth.

B) The fullerenes show evidence of having been irradiated by the solar wind for millions of years.

C) Gases trapped inside the fullerenes could have come only from stars.

D) The rocks in which the fullerenes are found contain decay products of short-lived radioactive aluminum isotopes that are believed to be produced only in supernovae (explosions of stars).

197. At the end of the Permian era 250 million years ago, 80% of all species living on land and 90% of all species living in the oceans disappeared. Which of these is among the MOST plausible explanations for this massive extinction?

A) global warming from volcanic gases released during the breakup of the Gondwanaland supercontinent

B) nearby supernova (the explosion and total destruction of a star)

C) devastating impact by an asteroid

D) “snowball Earth” episode in which global cooling caused Earth’s ocean surfaces to freeze and glaciers to cover the continents

198. Fullerenes (“buckeyballs”) are spherical molecules composed exclusively of carbon atoms. What is their connection with meteoric impacts?

A) Fullerenes are not produced naturally on Earth, so any fullerenes found here must have been carried here from space.

B) Fullerenes are not produced naturally on Earth, but they can be created in the tremendous heat and compression of a large meteoric impact.

C) Fullerenes with gas molecules trapped inside could only have been produced in supernova explosions.

D) Fullerenes with gas molecules trapped inside could only have been produced in the tremendous heat and compression of a large meteoric impact.