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Make a Comet Model and Eat It!

Created for the Deep Impact Mission, A NASA Discovery Mission

Comets have sometimes been described as dirty snowballs, snowy dirtballs or something in between. But what does that really mean? It means that these dirty snowballs are believed to be a cold mixture of frozen water, dry ice, and other sandy/rocky materials left over from the early formation of our solar system. In this activity, you are going to develop a comet model that you can eat. One instrument on the Deep Impact spacecraft is called a spectrometer. Spectrometers are able to do different jobs to collect different kinds of information. Pretend to be a spectrometer and use three of your senses individually to confirm what is in your ice cream. Most of the ingredients can be found at home or can be incorporated there after the activity.

Materials - Each baggie makes enough for two people to try.

  • One sandwich size re-closeable plastic bag (Good thick quality)
  • One Gallon size re-closeable plastic bag
  • Small cups for eating ice cream
  • Plastic spoons
  • Pairs of rubber kitchen gloves or have them use cloths or sweaters (comet gets cold!!)
  • Ice (enough to fill a gallon size bag 1/2 full per bag)
  • Whole milk (2% won't work)
  • Sugar
  • Vanilla extract
  • Evaporated milk
  • Salt
  • Can opener

"Comet Debris" - Chunky cookies in black or brown, crushed candies (like toffee or peppermint), gummy bears, coconut flakes and peanuts

  • Something to use to crush cookies and other additives
  • Food Gloves if food will be handled

HINT: One person should hold the bag while another pours ingredients into the bag. To cut the activity time, you can pre-mix the milk, evaporated milk, sugar and vanilla to the small bags and pre-measure the salt into the large bags. Squeeze the air out and seal the sandwich bags carefully each time they are opened to add ingredients. The recipe included for each sandwich bag makes enough ice cream for two people.

STEP #1:
Mix to the sandwich size bag
One-third cup evaporated milk (or cream)
Two-thirds cup whole milk
5 level spoonfuls of sugar
Less than 1/4 tsp of vanilla

Comet connection: The following ingredients to be added to the ice cream represent dust (Black/brown cookies in fine and large chunks), rocks (peanuts), carbon dioxide ice (dry ice) (coconut flakes). They can also add some ingredients to represent what we might find in a comet. Possibilities are: gummy bears (early organics for life?), peppermint, toffee or other ingredients you might choose. Remember to choose food that will not dissolve while the ice cream is setting. Now close the bags.

HINT: Squeeze any extra air out of the sandwich bag and close it. Be sure it cannot leak. [Turn it upside down to check]

Place the sandwich bag into the bottom of the gallon bag. Put in approximately 10 heaping spoonfuls of salt if you did not pre-load the salt earlier. You can pre-load salt into the bags at home.

Fill the gallon bag (containing sandwich bag) at least 1/3 full of ice.


  1. Close the larger bag tightly to remove as much air as possible. Check for leaks.
  2. Gently shake and roll the bag while keeping it in constant motion for approximately 6 - 10 minutes or until half the bag has turned to water.
    [SUGGESTION: Rubber gloves, mitts, cloth towels or other thick fabric may be needed to hold the bag because it will get extremely cold. Start with bare hands so people can feel the temperature change].
  3. Gently feel the sandwich bag through the icy mixture. When the milk/sugar mixture in the sandwich bag has hardened into soft ice cream, open the gallon bag and remove the sandwich bag containing the ice cream.

Briefly rinse the outside of the sandwich bag with fresh water before opening so that no salt flavor is transferred to the ice cream.

Split the ice cream comet by spooning some into the cups provided, one for each team member. Make one extra cup and put it aside. Don't eat this one!

Split the ice cream comet by spooning some into a cup for each person.

A spectrometer takes different kinds of data through different filters. Pretend that your eyes, nose and taste buds are scientific instruments taking data from your "comet". Even though you know what is in the ice cream, discuss which "data" each sense is telling you:

  • Look at the "comet" and see what you can observe visually.
  • Smell the ice cream and see if you find any additional information.
  • Taste the ice cream and record any final information about what is in it.

SUGGESTIONS FOR LARGER GROUPS: For 20 (10 groups of 2)

  • 3 - 4 cans - 12 fl oz each of evaporated milk
  • 1 gallon of whole milk (you'll have some left over)
  • 20 cookies
  • 1/4 lb of sugar
  • 1 bag of peanuts and 1 bag of coconut flakes
  • 1/4 bottle of vanilla or leave this ingredient out
  • 10 sandwich size re-closeable bags (but best to make a couple extra)
  • 10 gallon size re-closeable bags
  • 2 - 3 containers of table salt (you'll have some left over)

OPTION: If you want an option to the activity below for your concession booth or need to move faster with fewer materials, use pre-made ice cream and supply the added "debris" materials below for people to add. The ice cream can be loaded into a cup or baggie so that the added materials can be mixed in.


  • If the participants toss the bags back and forth or bang them against a surface while freezing the ice cream, they may break.
  • Bring dishtowels, cloths or other insulator for hands to guard against discomfort while they are turning their bags over and over.
  • Have a mop available for dripping water or do the activity outside.
  • Limit the amount of any material participants put into their ice cream to one plastic spoonful so supplies last.
  • Mark one of your serving cups with sugar and salt measurements to pre-load bags faster.
  • Materials need to be purchased fresh and kept in store-bought containers. Anything that is used to measure, hold or eat with/out of should never have been used for any chemical storage.
  • A mop and sponge is very helpful for desks or floor areas where measuring is done.
  • You may choose to pre-load cream bags and salt bags at home.
  • The ice needs to be either freshly bought or well frozen in storage. The container for transporting and storing the ice should be pre-cooled if possible or very efficient. If the ice has "warmed", it will be difficult to get the milk/cream to solidify.
  • Have napkins or wipes to clean hands and faces.
  • Provide a bucket or sink to dispose of used bags of salt water. Have a trashcan for the rest of your materials.

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