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Transcript
Objective
III.1.d – Describe the characteristics of comets, asteroids, and meteors.
Comets and asteroids orbit the Sun the way the Earth does. Scientists believe comets
and asteroids have changed very little since they were formed. Asteroids and comets
can tell us what the early Solar System was like.
NASA likes it when scientists use their imaginations to find creative ways to explore
the Solar System. NASA uses robotic spacecraft to be their eyes and unlock the
mysteries of comets and asteroids.
A comet nucleus comes in a smaller range
of sizes. Tempel 1 is about 3.5 miles
across.
s.
Comet Facts
 Reside mostly in Kuiper Belt beyond orbit of Neptune. Also found in Oort
Cloud in outer Solar System.
 Probably formed in the outer Solar System.
 Diameters range from about 6-25 miles.
 Contain a lot of ice, along with rock and dirt.
 Surface is unstable and changes as ice vaporizes off comet as it approaches the
Sun.
 Orbit can be disturbed to toss comet into elongated orbit, so we see it in the
inner Solar System.
 May have contributed large part of Earth’s water.
 Part of Solar System, leftovers from its formation.
Objective
III.1.d – Describe the characteristics of comets, asteroids, and meteors.

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Orbits the Sun.
Irregular shapes.
Not massive enough to be round like a planet.
May spin because of irregular shape.
Have crashed into Earth.
Asteroid Facts
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Most reside in Asteroid Belt between orbits of Mars and Jupiter.
Probably formed inside the orbit of Jupiter.
Diameters range from 100 yards to 600 miles.
Composed of rock and metals.
Surface is solid and stable, showing craters where other objects have crashed into
it.
Surface does not vaporize.
Orbit is stable and circular.
Have left craters on Earth, and may have caused mass extinctions, such as of the
dinosaurs.
Part of Solar System, leftovers from its formation.
Orbits the Sun.
Irregular shapes.
Not massive enough to be round like a planet.
May spin because of irregular shape.
What is a comet?
For centuries, astronomers were baffled by these strange and unpredictable visitors in
Earth’s sky. Now we know that comets are part of our Solar System. They are small
bodies made of dust, ice, and rocks left over after the Sun and planets formed.
Why do we study comets?
Scientists want to find out all about comets to help them understand better how the
Solar System began and evolved to what it is today.
NASA has sent several spacecraft to visit comets. Deep Space 1 flew by Comet
Borrelly. Stardust collected dust from Comet Wild (Vilt) 2 and returned the sample to
Objective
III.1.d – Describe the characteristics of comets, asteroids, and meteors.
Earth. Deep Impact sent a small impactor to collide with Comet Temple 1. EPOXI
took pictures of Comet Hartley 2 as jets of gas erupted from its surface. In 2011,
Stardust-NExT returned to Comet Tempel 1 to see how the surface had changed after
the comet completed one full orbit around the Sun.
Where do comets come from?
Most comets come from the Kuiper Belt, a
region beyond the orbit of Neptune. Comets
from this neighborhood usually take 200 years
or less to make one orbit around the Sun.
These are called short-period comets.
Comets also come from their other hangout,
the Oort Cloud. The Oort Cloud is a far-fardistance cloud of possibly a trillion comets that
surrounds the Solar System. One trip around
the Sun could take one of these comets 30
million years! They are called long-period
comets.
What do comets look like?
Space missions have shown us close-up
photos of the nucleus, or solid part, of a
comet. Of course, comets may not all look
the same. So far, Deep Space 1 had found
that Comet Borrelly has rugged terrain,
smooth rolling plains, deep fractures and is
covered with very, very dark material.
Deep Impact and Stardust-NExT showed
Comet Tempel 1 as very black on the
outside.
On the inside, comets seem to be mostly ice, some rocks and dust, and some gas.
Deep Impact crashed an impactor into Comet Tempel 1. It found a fragile and weak
surface. Inside it is spongy, with lots of holes. It has ice beneath its surface. Other
comets may be different.
Objective
III.1.d – Describe the characteristics of comets, asteroids, and meteors.
What makes comets look fuzzy and have tails?
When they are at home in the Oort Cloud or Kuiper Belt, comets are just dull, dark
chunks of ice, dust, and rock. In this state, they may not be much different from
asteroids. But as comets get closer to the Sun and begin to warm up, some of the
materials start to boil off. This material forms a cloud around the nucleus. The cloud
is called the coma and may be hundreds of thousands of miles across.
Comet tails appear as the comet
approaches the Sun and can grow to be
millions of miles long. The particles in
the solar wind push the small dust
particles in the coma into a long, curved
path. This tail is known as the dust tail.
Another tail, the ion tail, is made of
electrically charged molecules of gas. The
ion tail points directly away from the Sun.
What is an asteroid?
Ancient astronomers studied the night sky, mapping
everything they saw. Guiseppe Piazzi found the first
(and largest) asteroid in 1801 and named it “Ceres.”
Asteroids are small, rocky objects, left over from the
formation of our Solar System. They range from the
size of small rocks to the size of asteroid Ceres, which
is more than 600 miles across. Ceres is so large, it is a
dwarf planet, rather than an asteroid.
Objective
III.1.d – Describe the characteristics of comets, asteroids, and meteors.
Where do asteroids hang out?
Most asteroids orbit the Sun in nearly circular
orbits in the Asteroid Belt between Mars and
Jupiter. There are probably millions of asteroids
here. Even so, all of them put together don’t
contain as much material as Earth’s Moon.
What are asteroids made of?
Scientists have put asteroids into three different
categories.
 One type is very dark and probably
contains clay and silicate rock. Silicates
are the most common forms of rocks, minerals, and sand on Earth.
 Another type is made of silicate and metals.
 The third type is mostly metals.
Asteroids have irregular shapes and are often covered with craters from having been
hit by smaller objects over billions of years.
How do asteroids move?
Besides their orbital motion around the Sun, asteroids
also rotate or spin. Since they are irregularly shaped,
they may tumble like a badly thrown football.
Oblong-shaped Asteroid 2008 HU is about 39 feet
(13 yards) wide and about 79 feet (26 yards) long
(smaller than a tennis court). It rotates every 42.7
seconds (the length of its “day”). It is the fastest
known rotating natural object in the Solar System.
Why do we study asteroids?
Asteroids have not change much in billions of years. They can tell us a lot about what
the early Solar System was like.
NASA’s Dawn mission is studying the two most massive asteroids up close. It orbited
Vesta for 13 months and is on its way to orbit Ceres. Another asteroid mission,
Objective
III.1.d – Describe the characteristics of comets, asteroids, and meteors.
NEAR Shoemaker, orbited asteroid Eros for about one year and landed on its surface.
It sent back amazing images and many other data about the asteroids.
Studying asteroids closely will help scientists understand the conditions and processes
that went into making or Solar System what it is today.
Fun facts about comets and asteroids.
 Although comets may look bright in our night skies as their comas and tails reflect sunlight, the
nucleus of a comet is black as charcoal.
 Comets may have delivered a lot of water to early Earth, as well as the molecules needed to give
life its start.
 Although a comet nucleus is usually smaller than 25 miles across, the coma may be as big as
2,000,000 miles across!
 Asteroid Ceres is about the same size as Texas.
 Asteroid Vesta is about the same size as Arizona.
 Vesta and Ceres contain more than one-third of all the mass of the hundreds of thousands of
asteroids in the main Asteroid Belt.
 Vesta has a mountain thirteen miles high! That’s more than twice as high as Mt. Everest!
 Pieces of Vesta may be found on Earth! Scientists have studied a number of meteorites they
believe originated on Vesta. Vesta was bombarded by objects that blasted chunks of its surface
into space.
Objective
III.1.d – Describe the characteristics of comets, asteroids, and meteors.
Comets vs. Asteroids Worksheet
Do Not Write on This Sheet of Paper
Identify which fact describes an asteroid or a comet or both.
_____1. Composed of rock and metals.
A. Asteroid
_____2. Contain a lot of ice, along with rock and dirt.
B. Comet
_____3. Diameters range from 100 yards to 330 miles.
_____4. Diameters range from about 6-25 miles.
_____5. Have crashed into Earth.
_____6. Irregular shapes.
_____7. May have caused mass extinctions, such as of the dinosaurs.
_____8. Most reside in Asteroid Belt between orbits of Mars and
Jupiter.
_____9. Orbits the Sun.
_____10. Reside mostly in Kuiper Belt beyond orbit of Neptune.
Also found in Oort Cloud in outer Solar System.
_____11. Surface is solid and stable, showing craters where other
objects have crashed into it.
12. Scientists study comets to help them understand better…
a. better understand asteroids.
b. how the planets formed.
c. how the Solar System began.
d. what causes icy objects in the Solar System.
C. Both
Objective
III.1.d – Describe the characteristics of comets, asteroids, and meteors.
Match the space probe with the comet it studied.
_____13. Comet Borrelly
A. Deep Impact
_____14. Comet Hartley 2
B. Deep Space 1
_____15. Comet Tempel 1 (There are two answers to this
C. EPOXI
question.)
D. Stardust
_____16. Comet Wild 2
E. Stardust-NExT
17. From where do short-period comets come?
a. Kuiper Belt
b. Oort Cloud
18. From where to long-period comets come?
a. Kuiper Belt
b. Oort Cloud
19. What happens to comets as they approach the Sun?
a. They become larger.
b. They vaporize.
c. Nothing.
d. Some material boils off.
Match the part of the comet with its description.
____20. Coma
A. The actual comet itself.
____21. Nucleus B. The cloud that forms around the nucleus.
____22. Tail
C. Particles from the comet pushed off by the Solar Wind.
23. Giuseppe Piazzi discover the first…
a. asteroid.
b. comet
c. dwarf planet.
24. This asteroid was once the largest asteroid, but now it is a dwarf planet.
a. Ceres
b. Janus
c. Konko
d. Vesta
Objective
III.1.d – Describe the characteristics of comets, asteroids, and meteors.
25. The Asteroid Belt is found between which two planets?
a. Earth
b. Jupiter
c. Mars
d. Saturn
26. Of what are asteroids made? (There are two or more answers to this question.)
a. Clay and silicate rock.
b. Gas and rock.
c. Mostly metals.
d. Silicate metals.
27. Asteroids have not changed much in billions of years.
a. True
b. False
28. This mission has successful studied Vesta and is now heading towards Ceres.
a. Dawn
b. Juno
c. NEAR Shoemaker
d. Rosetta
29. This mission successful studied asteroid Eros...
a. Dawn
b. Juno
c. NEAR Shoemaker
d. Rosetta
Match the fun fact to what it is.
____30. Its coma may be as big as 2,000,000 miles across!
A. Asteroid
____31. Its nucleus is black as charcoal.
B. Comet
____32. Ceres is about the same size as Texas.
____33. Vesta is about the same size as Arizona.
____34. These may have delivered a lot of water to early Earth.
____35. Pieces of Vesta may be found on Earth!
____36. Vesta has a mountain thirteen miles high! That’s more than
twice as high as Mt. Everest!
Objective
III.1.d – Describe the characteristics of comets, asteroids, and meteors.
Comets vs. Asteroids Worksheet – Key
A 1. Composed of rock and metals.
B 2. Contain a lot of ice, along with rock and dirt.
A 3. Diameters range from 100 yards to 600 miles.
B 4. Diameters range from about 6-25 miles.
C 5. Have crashed into Earth.
C 6. Irregular shapes.
A 7. May have caused mass extinctions, such as of the dinosaurs.
A 8. Most reside in Asteroid Belt between orbits of Mars and Jupiter.
C 9. Orbits the Sun.
B 10. Reside mostly in Kuiper Belt beyond orbit of Neptune. Also found in Oort
Cloud in outer Solar System.
A 11. Surface is solid and stable, showing craters where other objects have crashed into
it.
12. Scientists study comets to help them understand better…
c. how the Solar System began.
B 13. Comet Borrelly
C 14. Comet Hartley 2
A, E 15. Comet Tempel 1
D 16. Comet Wild 2
Objective
III.1.d – Describe the characteristics of comets, asteroids, and meteors.
17. From where do short-period comets come?
a. Kuiper Belt
18. From where to long-period comets come?
a. Kuiper Belt
18. What happens to comets as they approach the Sun?
d. Some material boils off.
B 19. Coma
A 20. Nucleus
C 21. Tail
22. Giuseppe Piazzi discover the first…
a. asteroid
23. This asteroid was once the largest asteroid, but now it is a dwarf planet.
a. Ceres
24. The Asteroid Belt is found between which two planets?
b. Jupiter; c. Mars
25. Of what are asteroids made? (There are two or more answers to this question.)
a. Clay and silicate rock; c. Mostly metals; d. Silicate metals
26. Asteroids have not changed much in billions of years.
a. True (2 choices)
Objective
III.1.d – Describe the characteristics of comets, asteroids, and meteors.
27. This mission has successful studied Vesta and is now heading towards Ceres.
a. Dawn
28. This mission successful studied asteroid Eros..
c. NEAR Shoemaker
B 29. Its coma may be as big as 2,000,000 miles across!
B 30. Its nucleus is black as charcoal.
A 31. Ceres is about the same size as Texas.
A 32. Vesta is about the same size as Arizona.
B 33. These may have delivered a lot of water to early Earth.
A 34. Pieces of Vesta may be found on Earth!
A 35. Vesta has a mountain thirteen miles high! That’s more than twice as high as Mt.
Everest!
Comets vs. Asteroids Worksheet – Scoring Guide
Objective
III.1.d – Describe the characteristics of comets, asteroids, and meteors.
1. A (3 choices)
2. B (3 choices)
3. A (3 choices)
4. B (3 choices)
5. C (3 choices)
6. C (3 choices)
7. A (3 choices)
8. A (3 choices)
9. C (3 choices)
10. B (3 choices)
11. A (3 choices)
12. c
13. B (5 choices)
14. C (5 choices)
15. A, E (5 choices)
16. D (5 choices)
17. a (2 choices)
18. a (2 choices)
19. d
20. B (3 choices)
21. A (3 choices)
22. C (3 choices)
23. a (3 choices)
24. a
25. b, c
26 a, c, d
27. a (2 choices)
28. a
29. c
30. B
31. B
32. A
33. A
34. B
35. A
36. A
Scoring
Guide
36 – 4
34-35 – 3.5
29-33 – 3
25-28 – 2.5
20-24 – 2
13-19 – 1.5
7-12 – 1
1-6 – .5
0–0