from Come Fly With Me – Exploring Science through aviation and aerospace concepts.

SUBJECT: Science
GRADE: 7,8,9
TIME: Several short periods
TYPE OF ACTIVITY: Teacher Demo or Student Activity
CONCEPTS: Sterile Environment Decontamination
SKILLS: Control of Variables Hypothesizing

Objective: To understand the importance of a sterile environment in which to test for the presence of alien life forms.

Materials: Dry beans (soaked in water overnight); four 250ml containers; water; iodine 3%; alcohol 70%; Lysol.

Place beans in each bottle and cover them 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. Examine the bottles periodically 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?

Now have the students consider the problems involved with testing for life forms in samples of soil from another planet or in the moon rocks. How easy is it to introduce contamination from the testing materials? Consider what kinds of problems were encountered in sterilizing an entire space vehicle before it was allowed to land on another planet. Why might this be so vital? What methods might you envision could be used to sterilize a spacecraft?

Adapted from educational materials available from the NASA Teacher Resource Room, Kennedy Space Center

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