SOLAR SYSTEM

Good Things From Space Travel

by Diane Boudreau

Human beings have been traveling to outer space for almost four decades. In that time, astronauts have orbited the Earth in spacecraft for weeks and in space stations for periods of more than a year. During all of those space flights, medical scientists were watching and studying the astronauts. They have learned several important things about the how time living in space affects the human body.

First, scientists now know that human cells grow differently in space than they do on Earth. Cells bind together and form tissues much more easily in zero gravity.

To learn more, scientists are using the Space Shuttle as a laboratory for growing cells that will be used to help sick or injured people. For example, they can grow corneal cells to transplant in people who are losing their sight, or islet cells to produce insulin for diabetics. Other researchers are studying how zero gravity affects the growth of cancer cells.

During experiments aboard the Space Shuttle, astronauts grow cell cultures in a special mixture of water and nutrients. The fluid must remain at a particular pH level for the cells to survive. The cell cultures require almost constant monitoring to keep the nutrient and pH levels right.

The term pH refers to the measure of a fluid's acidity or alkalinity. On a scale of 0 to 14, a pH of 7.0 indicates a neutral substance. A substance with a pH below 7.0 is considered acidic. Strong acids, such as those found in car batteries, have a pH of about 2. Citrus and other acidic fruits have a pH of about 4. Above 7.0 is considered alkaline. Weak alkalis such as soap have a pH of 9 to 10. Fertile soil has a pH of about 6.5 to a neutral 7.

Unfortunately, we can't afford to send a lot of biologists into space. In the past, astronauts have helped out, says Bruce Towe, an ASU professor of biomedical engineering.

"The problem is that astronauts simply don't have a lot of time to do these kinds of experiments. It's just not a good way to do science," he explains.

To solve this problem, Towe has developed a sensor that monitors and tweaks nutrient and pH levels automatically. Unlike sensors used on Earth, this new device is designed to withstand the forces of liftoff, work in zero gravity, and operate reliably over a long period of time without maintenance.