Name: __________________________  Date: _____________

1.	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.	

2.	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, significantly smaller than the Moon	
B)	Only a few kilometers in diameter, similar to an average mountain on the Earth	
C)	About the size of the Earth, with a diameter of about 13,000 km.	
D)	About the size of Mercury, with a diameter of about 5000 km.	

3.	The number of asteroids with diameters greater than 100 km is	
A)	just over 1000.	
B)	3.	
C)	about 30.	
D)	about 230.	

4.	The total number of asteroids orbiting the Sun among the planets is estimated to be	
A)	several thousand.	
B)	hundreds of billions.	
C)	more than a million.	
D)	a few hundred.	

5.	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)	It would look like any other star, a small extra dot not shown on star charts of this area of the sky.	
B)	It would look like a small, diffuse patch against the sharp images of stars because of the dust and gas surrounding it.	
C)	It would produce a flash of light as it crossed the field of view of the camera.	
D)	It would produce a short trail as it moved slowly against the background stars.	

6.	Where do the Trojan asteroids orbit the Sun?	
A)	In circular orbits at the same orbital distance as Jupiter	
B)	In circular orbits at the same orbital distance as the Earth	
C)	Within the asteroid belt, so-named because they are large	
D)	In elliptical orbits that cross the orbit of the Earth	

7.	What is the difference between an Apollo asteroid and an Amor asteroid?	
A)	Apollo asteroids cross the orbit of the Earth, whereas Amor asteroids cross the orbit of Mars but not the Earth's orbit.	
B)	Apollo asteroids orbit entirely inside the Earth's orbit and therefore do not cross it, whereas Amor asteroids cross the Earth's orbit and therefore might hit the 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 the Earth.	

8.	The Kuiper belt is	
A)	another name for the asteroid belt.	
B)	a flat or donut-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.	

9.	Most comet nuclei are believed to be	
A)	carbonaceous chondrite meteorites, carbon material, ignited by sunlight and trailing 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.	

10.	Comet tails are the result of	
A)	melting 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.	

11.	A comet's tail	
A)	always points toward the nearest planet, being attracted by its gravity field as the comet passes by it.	
B)	always trails behind the comet in its orbit, and so points away from the Sun only while the comet is approaching the Sun.	
C)	always points away from the Sun, regardless of the motion of the comet.	
D)	points toward the Sun because it is caused by jets of gases evaporated from the comet's nucleus on the side heated by the Sun.	

12.	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.	

13.	A meteoroid is the name used to describe a solid particle that	
A)	is drifting around in space.	
B)	has fallen to the Earth from space.	
C)	burns up as it falls through the Earth's atmosphere.	
D)	originated on the Moon but was knocked onto the Earth by a massive impact.	

14.	A meteor shower results from	
A)	material ejected by a massive impact on the Moon; the Earth's gravity attracts it toward the Earth.	
B)	material re-entering the Earth's atmosphere after being ejected into space by violent volcanic eruptions on the Earth.	
C)	the Earth passing through debris of an old comet.	
D)	a small piece of rock fragmenting as it passes through the Earth's atmosphere.	

15.	Which are the most common types of meteoroids in space?	
A)	Stony-irons	
B)	Stones	
C)	Irons	
D)	Carbonaceous chondrites	

16.	The most common meteorites to hit the Earth are	
A)	the carbonaceous chondrites.	
B)	the iron meteorites.	
C)	the stony-iron meteorites.	
D)	the stony meteorites.	

17.	What fraction of the material arriving on the Earth from outer space is in the form of iron meteorites?	
A)	50%	
B)	A few %	
C)	95%	
D)	10 to 20%	

18.	What fraction of the material arriving on the Earth from outer space is in the form of stony meteorites?	
A)	A few %	
B)	10 to 20%	
C)	50%	
D)	95%	

19.	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).	

20.	Why are carbonaceous chondrites thought to be original material that formed in the early solar nebula?	
A)	They show a Widmanstätten pattern, which indicates slow condensation from gaseous material.	
B)	Their minerals contain up to 20% water, which would have evaporated away if the chondrite had been strongly heated.	
C)	They consist mostly of carbon, which was the dominant substance condensing in the outer solar nebula.	
D)	They 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.	

21.	What is the likely connection between the metal iridium and the demise of the Earth's dinosaur population?	
A)	Iridium, which is found in abundance on Earth's surface, is poisonous to reptiles.	
B)	Iridium is found beneath the 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 the Earth.  The existence of a world-wide layer of it suggests a large meteor impact during the dinosaur age.  This 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.	

Answer Key

1.	D	
2.	A	
3.	D	
4.	C	
5.	D	
6.	A	
7.	A	
8.	B	
9.	B	
10.	A	
11.	C	
12.	D	
13.	A	
14.	C	
15.	B	
16.	D	
17.	B	
18.	D	
19.	B	
20.	B	
21.	C