MAKE A COMET NUCLEUS
To make a comet nucleus we'll need these ingredients:
- Dry Ice (5 lbs) available from ice companies or ice cream parlors; CAUTION: Dry ice is -79 degrees C (-110 degrees F). Any more than brief exposure will cause "burns. Be careful when handling it.
- Water (around half a gallon) in pitcher;
- Ammonia (a few drops or sprays of window cleaner);
- Dirt (fine grained, one handful);
- Corn Starch, or Worcester Sauce (a couple of pinches or drops);
- Trash Bags (2);
- Large Bowl or Small Pot;
- Water Proof Gloves (the better insulated the warmer your hands will remain);
- Cloth Towel; Paper or Cloth Towels; Hammer;
- Mixing Spoon or Stick.
Line the bowl with a trash bag. Place the other trash bag on the floor. Pour about a pint of water into the bowl. Add the corn starch or Worcester sauce, ammonia, and some of the dirt; mix a bit.
Put on the gloves. Wrap the dry ice in a cloth towel; place it over the trash bag on the floor. Use the hammer to grind up the dry ice into a powder. Gradually pour the dry ice powder into the water, mixing as you pour. There will be lots of vapor formed. The dry ice, water and other ingredients should form a thickening slush. Keep stirring for a few seconds as it thickens.
Now, using the trash bag to lift the slush away from the sides of the bowl, use your gloved hands to pack the slush into a ball. Keep packing and forming until the ball solidifies as a big lump.
Peel back the trash bag. Scatter some more dirt over the lump. Pour some of the remaining water over the lump, turning it as you do so, so that a layer of water ice forms over the entire lump.
Observe the behavior of your miniature comet nucleus. It can be handled without gloves if the water ice coating is intact. If a spot feels sticky, pour water on the spot. It hisses and pops as carbon dioxide sublimes (goes from the solid state directly into a gas) and forces its way through weak spots in the water ice crust. On real nuclei this results in slight jetting forces that can cause the nucleus to spin, slightly alter its orbit, or split apart (or "calve").
Next month you will learn how to make IMPACT CRATERS !