How do we determine if an apparently inert material contains living organisms?
By feeding them!
Try the expermient:
Step 1: Take three medium sized lab beakers. Put a 3 cm layer of sand in each, and add 200mls of water.
- In Beaker 1, add a small amount salt.
- In Beaker 2, add some sodium bicarbonate.
- In Beaker 3, add some yeast.
Step 2: Leave in a fridge overnight – Mars is a cold place!
Step 3: Add some food (Sugar solution – use warm water ) and stir.
Discuss with your class what they think will happen (Beaker 1 will not react, Beaker 2 will react but briefly, Beaker 3 will react continuously after less than one hour).
Guess which sample has living material in it.
You will have just simulated an experiment carried out on the surface of Mars by the Viking Landers in 1976!
The sample taken did react like Beaker 3. However, most scientists still think that the reaction was not due to life. One hypothesis is that ultraviolet radiation has built up a thin layer of a very strong oxidant that reacted with the added water to produce oxygen and hydrogen, and with the nutrients to produce carbon dioxide (CO2).