PURPOSE: to define the basic properties and classifications of asteroids, meteorites, and comets

MATERIALS: calculator, meteorite sample, ruler, comet activity bucket, graph paper (1 sheet)

INSTRUCTIONS: print out these pages and complete the activities according to the instructions below

2.1. (2 pts) What is the difference between an asteroid and a meteoroid?

2.2. (1 pt) List the four classifications of asteroids.

2.3. (3 pts) An object is discovered and studied in detail. Answer the following questions:

a) The object is found to be about 475 km in diameter. Is this object more likely a meteroid or an asteroid?


b) Based on the fact that the object was located at 3.4 AU, what sub-class is it likely to be?


c) Examination of this object’s spectrum, however, indicate traces of the compound iron oxide (FeO) and the element magnesium (Mg). What sub-class is this object then?

2.4. (3 pts) The largest asteroid we have discovered, Ceres, is about D = 950 km in diameter. A lot of meteorites we
find on Earth are around 6 x 10^-4 km across. How much larger is Ceres than the average meteorite?

2.5. (3 pts) Let's suppose that Ceres is observed when it is about d = 2.64 x 10⁸ km from Earth. Use this along with
data from Table 1 in the lab text to calculate the total solar flux we can observe from the asteroid.

2.6. (1 pt) List the three major classifications of meteorites.

2.7. (3 pts) Suppose a meteor approaches Earth at a speed of v_APP = 10 km/s. Calculate its likely speed of impact if
it makes it to the surface without breaking up.

2.8. (2 pts) The major sub-classes for meteorites break down into stony, iron, or a combination thereof. Metal can be
melted more easily than rock can. Using Table 3 in the lab text, which sub-class is most common? In terms of “falls”
versus “finds”, give a reason why this is.

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**EXPERIMENT**
Now let's examine some meteorites.

Go to the following meteorite gallery website. It has links to pictures of many meteorites found on Earth. Look through
some pictures to get an idea of what typical meteorites look like.

2.9. (3 pts) Click on the picture for the iron octahedrite (medium) called Boxhole. Describe it in terms of the 8 indentifying characteristics for meteorites (exclude mass, density, and magnetism).

2.10. (3 pts) Click on the picture for the stony chondrite (amphoterite LL3-LL7) called Bison. Describe it in terms of the 8 indentifying characteristics for meteorites (exclude mass, density, and magnetism).

2.11. (3 pts) Click on the picture for the stony-iron mesosiderite called Esterville. Describe it in terms of the 8 indentifying characteristics for meteorites (exclude mass, density, and magnetism).

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**EXPERIMENT**
Now your TA will provide some meteorite/rock samples for you to look at.

Go to the experiment set-up table and select one to analyze. You must stay at the demo table under the supervision
of your TA for this experiment.

2.12. (11 pts) Using the scale, ruler, magnet, and magnifying glass provided fill in the table below :

2.13. (2 pts) Given your answers in Table 1 and what you have learned about meteorites, do you think your sample is
a terrestrial rock or a meteorite? Give at least two reasons why.

2.14. (2 pts) Volume (V) is length x width x height. Calculate the volume of your sample object in cm3.

2.15. (2 pts) Now, density (ρ) is mass / volume. Calculate the density of your sample in g/cm3.

2.16. (3 pts) Given your data table results and answers to questions #2.12 - #2.14, do you think your sample is a
terrestrial rock or a meteorite? Give two reasons why. If a meteorite is it most likely iron, stony, or stony-iron and why?

3.1. (6 pts) Draw a comet and label its four main components. Be sure to also indicate the direction of the Sun and the
comet’s direction of motion.

3.2. (1 pt) Short-period comets have __________ orbits and originate in the __________, while long-period comets
have __________ orbits and originate in the __________.

  a)   regular / Oort cloud; irregular / Kuiper belt

  b)   irregular / Kuiper belt ; outside the Solar System

  c)   regular / Kuiper belt; irregular / Oort cloud

  d)   irregular / Oort cloud; regular / Kuiper belt

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**EXPERIMENT**
Now you will work in groups to actually simulate a comet out of household materials including water, corn syrup,
ammonia, and dry ice (CO₂ ice).

Some of the ingredients in this experiment are harmful to you. Please follow all the rules and instructions your TA
gives you! Go get a bucket of supplies from the TA. Read these instructions carefully before you begin:

Step 1: Open the plastic trash bags and use them to line your bucket. Please double bag in case of tears.
Step 2: Place about ½ - 1 cups of water in the bucket.
Step 3: Add about ¼ - ½ cups dirt, 2 caps full of ammonia, and a dash of corn syrup … stir the mixture. (NOTE: Be
careful not to rip the plastic bags!!!)
Step 4: When the items are well-mixed, obtain chunk(s) of dry ice from the TA and place it in the bucket. (NOTE: DO
NOT TOUCH DRY ICE WITH BARE HANDS! … always wear gloves!!!)
Step 5: Stir the mixture until it is almost frozen.
Step 6: With one person loosely holding the plastic bag closed (DO NOT HOLD IT TIGHTLY CLOSED OR IT
MAY EXPLODE) and lifting it out of the bucket, another person should shape and mold the mixture as if you were
forming a snowball.
Step 7: If it is not taking shape, try adding more water, syrup, dirt, and/or ice to the mixture and shape again.
Step 8: When the mixture holds its shape, unwrap it from the plastic bag … now you have a comet!

3.3. (4 pts) Place your comet (with plastic bag underneath) on the desk. Observe it and describe the following physical characteristics - shape, color, smell, and texture, or other unique properties.

3.4. (2 pts) When finished with the comet, place it as close as possible to the supplied light source (representing the Sun)
and let it sit there for at least 10 minutes. Then observe the comet and describe what is happening to it.

3.5. (3 pts) Finally, take your comet outside. Find a large rock to represent a meteorite/asteroid. Now, drop both objects
on the sidewalk and describe what happened to both. Which has more internal strength? Why is this so?

3.6. (2 pts) List 2 ways in which comets and asteroids/meteorites are similar. List 2 ways they are different.

4.1.   Below is a table of some observed molecules in a comet. The data is loosely adapted from 1998 LPI v29 p1053 (PUMA). The elements are listed in order of increasing atomic number. Compare the elements found in the comet with
this graph of cosmic abundances.

4.2. (1 pt) Astronomers estimate that the typical approach speed for asteroids is v_APP ~ 20 km/s and for comets is v_APP
~ 30 - 60 km/s. Will the impact speed, then, be larger for an asteroid or a comet?

4.3. (2 pts) Look at this interplanetary objects graph.

a) The Earth's atmosphere protects us from most near earth objects (NEOs) smaller than half a football field (i.e., 0.05 km). About how many meteors this size are estimated to be the Solar System?


b) If an NEO has a diameter of 2 km or more, an impact with Earth can cause major casualties and damage as well as severe environmental damage on a global scale. How many asteroids of this size are estimated to be in our Solar System?

4.4.   Now look at this NEO graph. Two imfamous impacts are noted. The K/T event is the one thought to have caused
the extinction of dinosaurs about 6.5 x 10⁶ years ago. The Tunguska event occured in 1908 when a 50 m meteor exploded above the area leveling over 2000 miles² of forest. Also for reference, the atomic bomb has an equivalent yield of about
10⁴ tons of TNT.

a) (1 pt) Based on this graph, does the likelihood of an impact increase or decrease the larger the impact object?


b) (2 pts) Based on this graph, should we currently (within next 5 - 10 years) be worried about a moderate size (10 - 30 m) NEO impact? Why or why not?





c) (2 pts) Astronomers estimate that there are probably about 1000 NEOs in the Solar System that could cause global consequences on impact (i.e., those with diameters ≥ 10³ m). Based on the graph, calculate how many objects of this size per year we can expect to impact.

4.5. (3 pts) Give 3 reasons why studying asteroids, meteorites, and comets is vital to solar system astronomy.

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