A Gourmet Comet Recipe (From "The Cosmic Cookbook") 
Place in a large mixing bowl: 
    Several billion tons of water ice 
    Several billion tons of dry ice 
      (frozen carbon dioxide) 
    Several million tons of silicate sand 
    Several million tons of ammonia ice (frozen NH3)
    Several million tons of carbonaceous particles 
    A pinch of seasonings 
      (sodium, potassium, calcium, iron, copper, etc.) 
    Miniscule amount of organic material 

Combine all ingredients and stir well.  

Place in a freezer at a temperature of -200 C until solid.  

Yield: One 10 billion ton cometary nucleus.