Stephen Wheeler, age 13, of Troutdale, ore., for his question:

How do peat bogs preserve human bodies intact?

Plants and animals are composed mostly of complex molecules of hydrogen and carbon. When the remains of once living things are left on or in the ground or in the water, they tend to rot and decay and finally become dust. Decay is a breaking down process of the m01ecui es constructed by living plants and animals. Most of the work is done by armies of microscopic bacteria.

Decay bacteria need oxygen to carry on their lives and work, and oxygen in various forms is the earth's most plentiful substance. But there are a few places where oxygen is scarce, so scarce that there is not enough of it to support decay bacteria. Stagnant swamps and bogs lack oxygen. Human bodies and the remains of plants and animals buried deep in a bog may be preserved intact, because there are no decay bacteria to break up the molecules from which they are made.