University of Michigan - Department of Astronomy




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Comets worksheet

Before answering these questions, take a good look at the comet nucleus. You may want to refer to the text and images in the introduction when answering these questions.


  1. In what way is the description "dirty snowball" an appropriate description of a comet? In what way is it inappropriate?

  2. Describe the model comet nucleus: What is its shape? Is it smooth, jagged, bumpy...? Is it bright or dark? What about the gas coming off it: does it come from specific areas or all over; does it just drift away or form little streams? Compare it to a picture of a comet nucleus like the one in the introduction or in your text book. Other than it's size, how is your model comet similar and different from real comets?

  3. Break one of the comets apart and look inside. Compare it to the interior of the terrestrial planets. How is it similar and different?

  4. The material in the comet was simply mixed together and solidified. What does this tell you about the formation of comets compared to the planets and major moons? What extra steps does a planet go through?

  5. Compare the internal structure of Pluto to comets. How are they similar and different? Is Pluto more like a comet, a terrestrial planet, or ajovian planet? What does this tell you about Pluto's formation?

  6. The solar constant at Earth is 1400 W/m2 and at 50 AU is 0.56 W/m2. Give two reasons why comets are only discovered when they are close to the Sun.

  7. Measure the diameter of the model comet. What is the size of a real comet? Justify the size you choose. What is the scale factor of this model comet? Show your work.

  8. Determine the volume of water in your comet (approximately). What is the volume of water in a real comet (multiply the previous answer by your scale factor)?

  9. Given that there are 1.3x1018 m3 of water on Earth, how many comets would have to strike Earth to be the source of Earth's water?

Lat update: 4/20/12 by SAM

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