• A sterile spacecraft environment is extremely important. To understand this importance and to test for the presence of alien life forms, try this experiment.


  • Dry beans (soaked in water overnight)
  • Four 250ml containers
  • Water
  • 3% Iodine
  • 70% Alcohol
  • Lysol


  • Place equal number of beans in each bottle
  • Cover the beans with water
  • Add 10 drops of the following to each bottle in turn:
    • Bottle A—Iodine
    • Bottle B—Alcohol
    • Bottle C—Lysol
    • Bottle D—Nothing
  • Stopper the bottles with cotton and allow them to stand in a warm place for two or three days.
  • Periodically examine the bottles for cloudiness and odor.


  • How does one account for any changes in color or odor in the bottles?
  • What difference might using sterile bottles have made in this experiment?
  • Would sterilization of the beans have made a difference?
  • What would happen if different temperatures had been used?
  • How many variables can you identify in this experiment?
  • How many did you account for or control?