Profile of Mission Specialist Laurel Clark

Laurel Clark, 41, was a diving medical officer aboard submarines and then a flight surgeon before she became an astronaut in 1996.

She had been on board Columbia to help with science experiments.

"I think my family has a fairly practical and pragmatic view of this whole thing, and that's that the actual launching into space is much more dangerous than any of the other security concerns," said Clark, who lived in Racine, Wisconsin, and was married with an 8-year-old son.

She added: "There's a lot of different things that we do during life that could potentially harm us and I choose not to stop doing those things."