Name: 
 

Chapter 18 - A Family of Planets - Section III



Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
 

1. 

Which of the following statements about comets is TRUE?
a.
They originate from the cold, outer solar system.
b.
They are probably leftovers from the process of planet formation.
c.
They may help scientists piece together the history of the solar system.
d.
All of the above
 

2. 

What's the difference between the orbit of a planet and the orbit of a comet?
a.
A comet's orbit is highly elliptical and a planet's orbit is more circular.
b.
A planet's orbit is highly elliptical and a comet's orbit is more circular.
c.
A comet orbits clockwise around the sun and a planet orbits counterclockwise.
d.
A planet orbits clockwise around the sun and a comet orbits counterclockwise.
 

3. 

A comet's ion tail always extends
a.
towards the sun.
c.
towards the planet that its passing.
b.
away from the sun.
d.
away from the planet that its passing.
 

4. 

A comet’s ion tail consists of
a.
dust.
c.
light rays.
b.
electrically charged particles of gas.
d.
comet nuclei.
 

5. 

Stony, metallic, and stony-iron are the three major types of
a.
planets.
c.
moons.
b.
comets.
d.
meteorites.
 

6. 

Which is NOT true about impacts?
a.
They are very destructive.
b.
They can bring water to dry worlds.
c.
They only occurred as the solar system formed.
d.
They can help us do remote geology.
 

7. 

Which of the following celestial bodies is most likely to have many craters?
a.
a giant gaseous planet
b.
a white dwarf star
c.
a terrestrial planet with no atmosphere
d.
a terrestrial planet with a thick atmosphere
 

8. 

Objects smaller than ____ across usually burn up in Earth's atmosphere and do not pose a risk to Earth's surface.
a.
10 m
c.
100 km
b.
10 km
d.
1000 km
 

9. 

An impact large enough to cause a global catastrophe—such as the extinction of the dinosaur—is estimated to occur once every ____ years on average.
a.
1,000 to 2,000
c.
1 million to 2 million
b.
30,000 to 50,000
d.
30 million to 50 million
 



 
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