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CHAPTER 25—METEORITES, ASTEROIDS, AND COMETS
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
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1. A bit of matter that enters Earth's atmosphere and survives to reach the ground is called
a. a meteor.
b. a meteoroid.
c. a meteorite.
d. a minor planet.
e. an asteroid.
2. The Widmanstätten patterns found in some meteorites show that the material
a. cooled very slowly.
b. cooled very rapidly.
c. was never heated to the point of being molten.
d. was molten just before it entered Earth's atmosphere.
e. is composed primarily of organic compounds.
3. A chondrite is a meteor that has
a. never been heated.
b. been heated, but never very hot.
c. been heated to a high temperature.
d. been melted.
e. entered Earth's atmosphere but will be destroyed before reaching the ground.
4. A meteor shower is produced when
a. a large number of sporadic meteors are observed.
b. the Earth passes through the asteroid belt.
c. massive particles are carried outward from the sun by the solar wind and enter Earth's
atmosphere.
d. the Earth passes through the orbital path of a comet.
e. meteors cause condensation in the upper atmosphere that leads to early morning rains.
5. Most of the asteroids orbit the sun in a belt between the orbits of
a. Venus and Earth.
b. Earth and Mars.
c. Jupiter and Saturn.
d. Mercury and Venus.
e. Mars and Jupiter.
6. Which of the following could not be caused by the gravitational influence of the planets?
a. Trojan asteroids.
b. Kirkwood's gap.
c. Hirayama families.
d. All of the above were caused by gravitational influence of the planets.
e. None of the these were caused by gravitational influence of the planets.
7. An asteroid could produce an iron core and a silicate mantle if it
a. differentiated.
b. outgassed.
c. condensed.
d. accreted.
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e. sublimed.
The gas tail of a comet always
a. trails behind the head along the orbital path.
b. extends ahead of the head along the orbital path.
c. points toward the sun.
d. points away from the sun.
e. points perpendicular to the orbital path
The short-period comets do not have randomly oriented orbits because
a. they are affected by the sun's gravity.
b. they are affected by the solar wind.
c. their orbits are altered by encounters with the planets.
d. their orbits are altered by the drag of their tails in the solar wind.
e. they all were originally objects ejected from the asteroid belt.
One theory suggests that the bodies in the Oort cloud formed
a. near the present orbits of the terrestrial planets.
b. near the present orbits of the Jovian planets.
c. at high temperatures
d. from silicate materials.
e. in outside of the original solar nebula.
The density of Comet Halley was found to be about 0.2 g/cm3. This implies that Comet Halley
a. is composed of about 50% rock and 50% frozen water and methane.
b. is loosely packed ices with a small amount of rocky material.
c. formed in the inner solar system and was ejected by Jupiter to the Kuiper belt.
d. is really an S-type asteroid.
e. was once a moon of Neptune and was ripped away by a large impact.
The diagram below is a plot of an object's albedo versus its ultraviolet minus visual color (U - V color). In this
diagram, which of the asteroids would be most reflective?
a. Object A
b. Object B
c. Object C
d. Object D
e. Object E
____ 13. What evidence exists that some of the asteroids were geologically active?
a. A few of the larger asteroids show small volcanic mountains.
b. The moons of Mars, which are thought to be captured asteroids, show evidence of
flooding by lava.
c. The meteorites that are breccias could only have formed in a molten mantle.
d. Spectroscopically, Vesta appears to have regions of small lava flows.
e. Io is very geologically active with sulfur volcanoes.
____ 14. The _______________ is a disk-shaped cloud of icy bodies believed to extend from about 40 AU out to 100
AU. It is believed that short period comets originate from this region.
a. Oort cloud
b. Widmanstätten cloud
c. Apollo-Amor
d. Kirkwood region
e. Kuiper belt.
____ 15. Sungrazers are
a. asteroids located inside the orbit of Mercury.
b. meteorites that have a composition very similar to that of the sun.
c. asteroids removed from Kirkwood's gap by the influences of the sun and Jupiter.
d. comets that get very close to the sun.
e. cattle that only feed when the sky is clear.
____ 16. The diagram below shows the relative size of Earth's moon and the asteroid 10 Hygiea. Based on this
diagram, what is the diameter of 10 Hygiea?
a. 460 km
b. 46 km
c. 4600 m
d. 46 m
e. 4600 km
____ 17. Currently the most accepted explanation of the Tunguska Event is the explosion of
a. a German U-2 rocket.
b. an iron meteor just above the surface of the earth.
c. a stony asteroid just above the surface of the earth.
d. a mini black hole in the earth's atmosphere.
e. an alien space craft as it crashed to earth.
____ 18. The type I, or gas, tail of a comet
a. is smooth and featureless with a spectrum identical to that of the sun.
b. is present even when the comet is located in the region of the Kuiper belt.
c. is unaffected by the magnetic field of the sun.
d. always points toward the sun.
e. is streaked and shows emission lines of ionized atoms.
____ 19. The diagram below is a plot of an asteroid's albedo versus it ultraviolet minus visual color (U - V color). In
this diagram, which of the asteroids is most likely an S-type asteroid?
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a. Object 1
b. Object 2
c. Object 3
d. Object 4
e. Object 5
The Allende meteorite is important because
a. it is the largest iron meteorite ever found.
b. its composition suggests that it is very old and unchanged from when it formed.
c. it is the object that produced the Tunguska event.
d. it contains the most well defined Widmanstätten patterns ever found.
e. it is the only meteorite to ever strike and kill a person.
Uranium, thorium, and the radioactive isotope of potassium cannot supply the heat to melt small
planetesimals, but yet are sufficient to melt the interior of Earth. This is because these elements
a. decay slowly and the heat generated must be trapped by a thick crust if it is to melt the
interior.
b. were not present in the solar nebula at the location where the asteroids formed.
c. are only found in the outer layers of asteroids and not in the core.
d. are very volatile and evaporated from the asteroids before they could decay.
e. are only found on rocks that formed on the earth and in no other celestial objects.
The iron meteorites
a. represent the largest number of falls.
b. are only found in the Antarctic.
c. are composed of carbonaceous chondrites.
d. are responsible for most of the meteor craters on the surface of the moon.
e. appear to have formed from the interiors of molten objects of planetesimal size.
Comet Hayakutake 1995 B2 was observed on the night of March 25, 1996, with a tail that extended 20°. At
this time the comet was 0.10 AU from Earth. What is the minimum length of the tail in AU?
a. 0.1 AU
b. 0.005 AU
c. 1.1. AU
d. 20 AU
e. 0.03 AU
An asteroid has an orbital period around the sun of 5.2 years. How far from the sun is this asteroid?
a. 5.2 AU
b. 10.4 AU
c. 27.0 AU
d. 3.0 AU
e. 2.3 AU
____ 25. If 200,000 asteroids that were each 0.5 km in radius combined to form a single object, what would the radius
of the new object be?
a. 224 km
b. 29 km
c. 100,000 km
d. 0.224 km
e. 1000 km
True/False
Indicate whether the sentence or statement is true or false.
____ 26. Meteorites seem to come from both the asteroid belt and the comets.
____ 27. The meteors in meteor showers are believed to be the debris left behind in comet orbits.
____ 28. Carbonaceous chondrites have been heated to high temperature at least once since they formed.
____ 29. Achondrites are rich in volatiles.
____ 30. Jupiter was probably influential in preventing the formation of a planet at the present location of the asteroid
belt.
____ 31. Some asteroids show evidence of surface activity such as lava flows.
____ 32. The tail of a comet always points toward the sun.
____ 33. The dirty snowball theory suggests that the head of a comet is composed of ices.
____ 34. Sungrazers are comets that come very close to the surface of the sun.
____ 35. The existence of the Oort cloud cannot be confirmed observationally from Earth because the objects are too
small.
CHAPTER 25
Answer Section
MULTIPLE CHOICE
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ANS: C
ANS: A
ANS: B
ANS: D
ANS: E
ANS: C
ANS: A
ANS: D
ANS: C
ANS: B
ANS: B
ANS: C
ANS: D
ANS: E
ANS: D
ANS: A
ANS: C
ANS: E
ANS: C
ANS: B
ANS: A
ANS: E
ANS: E
Note to the Instructor: This question requires the use of mathematics and is similar to the problems found at
the end of the chapter.
24. ANS: D
Note to the Instructor: This question requires the use of mathematics and is similar to the problems found at
the end of the chapter.
25. ANS: B
Note to the Instructor: This question requires the use of mathematics and is similar to the problems found at
the end of the chapter.
TRUE/FALSE
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ANS:
ANS:
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F
F
T
T
F
33. ANS: T
34. ANS: T
35. ANS: T