Jeffrey Baer, age 9, of Alameda, California, for his question:

Can there be life on Mars or Venus?

Scientists insist on proving that things are either true or false. To do this they need to know a lot of facts, more facts and still more facts. Some of the later facts often prove old ones to be false. Then a scientist. changes his mind. This happens all the time. For example, long ago many scientists thought that there was life on other planets. They thought that most likely there were plants and perhaps animals on Mars and Venus.

Later they learned more true facts about our solar system. Mars seemed to lack the water or oxygen that living things need. Venus proved to be seething hot and dusty. Many scientists gave up hope of finding life on these planets. Then a short while ago, researchers found that certain small creatures can live where water and oxygen are scarce. Others can live in seething dry heat. So now it's time to start hoping again. Perhaps, after all, we shall find strange little living things on Mars . But we cannot be certain until we go there and look. For the latest information on the search for life on Mars go to:Jet Propulsion web site listed on the Science for Kids menu.