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Exploring Comets
Consider This
Comets Have Had “Impact” Throughout History
Historical Facts
Comets appear suddenly and look different. Some fear them and others worship
them.
Some believed comets predicted coming events.
Comets were believed to foretell the death of kings, the fall of empires and the
coming of plagues.
Halley’s Comet appeared in 1066. This was during the Battle of Hastings. The
British believed Halley’s Comet’s appearance meant they would lose and King
Harold II would die. They did and he did.
In 1910, poisonous gases were found in Halley’s Comet. Earth passed through the
comet’s tail. Con men sold “comet insurance policies” and special medicines for
“Comet Fever”.
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Scientific
Comets striking Earth may have provided the water on Earth.
About 40,000 tons of dust particles from comets and asteroids fall to Earth
every year.
Comets have hit Earth in the past.
Comets are “leftovers” from the formation of the Solar System. They help to
understand better how the Solar System formed about 4.5 billion years ago.
A Comet’s Place in the Solar System
Our Solar System has four rocky inner planets and four giant gas outer planets. There
are also the "small bodies." Comets are an example of the “small bodies.” Comets are
“dirty snowballs.” They are made of ice, frozen ammonia, rocks, and dirt.
Comets seem to be found in two places. There are found in the Kuiper Belt. The Kuiper
Belt is made of icy objects of different sizes. It begins outside the orbit of Neptune.
It ends about 15,000,000,000 miles from the Sun.
Comets are also found in the Oort Cloud. It may contain a trillion icy comets. The Oort
Cloud is over 6,000,000,000,000 miles from Earth.
Comets are “leftovers” from the formation of the Solar System. Some comets crashed
into forming planets. This added water and rocks to the planet. Other comets orbited
the Sun.
The earliest people saw comets. They didn’t know what they were. Over time, they
noticed comets moved from night-to-night. Later, they were able to begin track the
comet’s orbit.
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Parts of a Comet
Spacecraft Sent to Comets
ISEE-3/ICE – 1978 (United States)
First probe to visit a comet.
Studied Comet Giacobini-Zinner.
Proved the "dirty-snowball" theory (comets are made of ice, dirt, and rocks).
Sakigake – 1985 (Japan)
Reached Comet Halley.
Approached with 7,000,000 miles.
Giotto – 1985 (European Space Agency)
Europe's first deep-space mission.
First close-up images of a comet nucleus (Comet Halley).
Discovered the size and shape of Halley's nucleus.
Discovered that the surface is very dark and that bright jets of gas and dust
spring out of its nucleus.
Closest approach to any comet – 120 miles (Comet Grigg-Skjellerup).
First spacecraft to encounter two comets,
Measured the size, composition, and velocity of dust particles and measured the
composition of those two comets.
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Deep Space One – 2001 (United States)
First mission to use an ion engine.
Explored Comet Borrelly.
Returned pictures and information about Comet Borrelly.
Stardust – 2004 (United States)
Sent to collect samples of Comet Wild (pronounced Vilt) 2.
First mission to return samples of a comet (Comet Wild 2) to Earth.
Successfully flew by Comet Tempel 1 in 2011.
Photographed comet seven years after Deep Impact probe crashed on Tempel 1’s
surface.
Deep Impact – 2005 (United States)
Flew by Comet Tempel 1.
Crashed probe on surface of Comet Tempel 1.
Helped to understand better what makes up a comet.
Later flew by Comet Hartley 2.
Returned photographs of the nucleus of Comet Hartley 2.
Rosetta – Launched 2004 (European Space Agency)
First probe launched to land on a comet (2014).
Comet Questions
What are comets?
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From where do comets come?
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List the parts of a comet.
a.
b.
c.
Draw a diagram of what a comet might look like.
Identify three missions to comets. List name, year, who launched probe, which comet
was visited, what was accomplished.
Mission: _________________________________________________
a. Year launched: ____________
b. Who launched probe: _________________________
c. Which comet(s) visited: ________________________________________
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d. What was accomplished: ________________________________________
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Mission: _________________________________________________
a. Year launched: ____________
b. Who launched probe: _________________________
c. Which comet(s) visited: ________________________________________
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d. What was accomplished: ________________________________________
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Mission: _________________________________________________
a. Year launched: ____________
b. Who launched probe: _________________________
c. Which comet(s) visited: ________________________________________
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d. What was accomplished: ________________________________________
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Ten Important Comet Facts
Created for Deep Impact Mission
Maura Rountree-Brown Educator/Student Enrichment
1. Comets are in orbit around the Sun as are our
planets.
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2. Comets are composed of ices, dust and rocky debris carried from the early formation
of the solar system about 4.5 billion years ago.
3. Comets are remnants from the cold, outer regions of the solar system. They are
generally thought to come from two areas - the Oort Cloud and the Kuiper Belt. Both of
these are areas where materials left over from the formation of our solar system have
condensed into icy objects. Both regions extend beyond the orbits of Neptune and Pluto
but are still part of our solar system and much closer to us than the closest star.
4. Comet orbits are elliptical. It brings them close to the sun and takes them far away.
5. Short period comets orbit the Sun every 20 years or less. Long period comets orbit
the Sun every 200 years or longer. Those comets with orbits in between are called
Halley-type comets.
6. Comets have three parts: the nucleus, the coma and the tails. The nucleus is the solid
center component made of ice, gas and rocky debris. The coma is the gas and dust
atmosphere around the nucleus, which results when heat from the Sun warms the
surface of the nucleus so that gas and dust spew forth in all directions and are driven
from the comet's surface. The tails are formed when energy from the Sun turns the
coma so that it flows around the nucleus and forms a fanned out tail behind it extending
millions of miles through space.
7. We see a comet's coma and tail because sunlight reflects off the dust (in the coma
and dust tail) and because the energy from the Sun excites some molecules so that they
glow and form a bluish tail called an ion tail and a yellow one made of neutral sodium
atoms.
8. Scientists have seen comets range in size from less than 1 km diameter to as much as
300 km, although the 300km (called Chiron) does not travel into the inner solar
system.
9. We know a comet could impact Earth and that it is important to understand the
nature of comets so we can design better methods to protect ourselves from them
should one be on a collision path with Earth.
10. A comet nucleus has a dark, sometimes mottled surface but we don't know if it has
an outer crust or if it is layered inside. We don't really know what comets are like
beneath their surface and that's why we need a mission like Deep Impact.
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Select and answer three comet facts. In the space below, explain the fact, why you
selected it, and how it helps us better understand comets. A sentence or two will not
adequately answer the question.
Fact One
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Fact Two
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Fact Three
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Comet Acrostic Poems
An acrostic poem is a poem in which the letters of a word are used to start each line.
Your assignment is to write two comet acrostic poems that explain the features of a
comet.
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C
O
M
E
T
S
C
O
M
E
T
S
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Comet on a Stick
(A NASA/Deep Impact Lesson)
Materials
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Small paper plate
Three 1 – 2 ft lengths of crepe paper
One 2” strip of tape
One non-bending drinking straw
An electric hairdryer/electrical power available
One marker pen
Procedures
1. Tear your plate so it has no even edges.
2. Evenly place the crepe paper strips on your plate. Tape them onto the plate.
3. Decide a “front” for your comet and represent it with the letter “H” for head. On the
opposite side, mark the letter “T” for tail of the comet.
4. Use a hairdryer to simulate a portion of the Sun’s solar wind as it meets the comet
5. Aim the hairdryer at the comet as it approaches and as it moves away.
Questions and Analysis
1. Explain what occurred when your model comet met the “solar wind.”
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Select and answer one of the following questions:
How does this model show the influence of the Sun on a comet?
How is this model unsuccessful at showing the proper influence of the Sun?
Describe problems with using a “comet on a stick” as a model for a comet.
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What Can Craters Tell Us About a Planet?
Materials
Flour
One of hot chocolate powder or cocoa
Container for flower
Garbage bags
Three rulers
Various sizes of balls (marbles, golf balls, etc.)
1.5 meters of string per team
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Scissors
Chair
Drop cloth or newspaper
Safety goggles for each team member
Overhead projector
Transparency sheet with images of
Barringer Crater and Mimas
Procedures
Follow these steps to make craters.
1. Make sure the string is 1.5 meters in length.
2. Measure the diameter of each of your impactors.
3. Take team positions, with the dropper standing on the chair and the material
specialist spotting the dropper.
4. Have the reporter check the height of the
string and make sure the setup is correct.
5. Drop the first impactor from the first
height.
6. Carefully remove the impactor and measure
the crater’s diameter.
7. Fill in the information in the chart on the
worksheet.
8. Repeat procedure for the next height.
9. Repeat procedure for the next impactor.
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Comet Cratering Worksheet
Your Mission
Your mission is to make craters and examine
them closely. What you learn about craters will
help you tell a story about the life of the planets
and moons in the images.
Roles
Decide which role each team member will assume:
Dropper: Drops impactors on the surface at the direction of the recorder.
Material Specialist: Is in charge of setting up materials and safety.
Measurer: Measures impactors and crater diameters.
Recorder: Writes down group answers and checks that calculations are done correctly.
Setup
1. Lay down the drop cloth or newspaper.
2. Place the tray in the middle and fill the tray 3 inches (about 8 centimeters) high with
flour.
3. Sprinkle a THIN layer of hot chocolate powder on top using a flour sifter.
4. Move a chair close to the tray.
5. Gather the impactors, string, and rulers.
Crater Making
1. Observe the setup of your testing field. What does the surface look like?
2. Put two rulers on either side of an impactor and use the third ruler to measure the
distance between them. This is the width or diameter of the impactor. Measure the
diameter of all three impactors.
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Ball 1 is ________ cm. Ball 2 is ________ cm. Ball 3 is ________ cm.
3. You will now make craters by following the directions on the Crater Making Procedure
Sheet.
Data Table
Ball 1 Diameter
_______ cm
Ball 2 Diameter
_______ cm
Ball 3 Diameter
_______ cm
Height
Crater Diameter
1st Try – 30 cm
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2nd Try – 1.5 meters
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1st Try – 30 cm
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2nd Try – 1.5 meters
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1st Try – 30 cm
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2nd Try – 1.5 meters
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4. Graph the results on a bar graph, following the example above.
5. How did the size of the impactor change the size of the crater?
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6. How did different heights change the size of the crater?
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7. Pick the best crater in your tray. Draw what it looks like.
8. Look at your best crater. Notice the mixture of flour and cocoa. What does this
mixture tell us about what craters do to the surfaces of planets?
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