NASA observed a Day of Remembrance Thursday to honor those who gave their lives for the cause of exploration and discovery.

National Aeronautics and Space Administration Administrator Michael Griffin remembered NASA employees, the astronauts who died in Apollo 1 and on the Space Shuttles Challenger and Columbia.

"Today we pause to remember the loss of all of our employees, including our Apollo 1, Challenger and Columbia astronauts, and to honor their legacy," said Griffin. "Nearly 50 years into the space age, spaceflight remains the pinnacle of human challenge, an endeavor just barely possible with today's technology.

"We at NASA are privileged to be in the business of learning how to do it, to extend the frontier of the possible, and, ultimately, to make space travel routine. It is an enormously difficult enterprise. The losses we commemorate today are a strong and poignant reminder of the sternness of the challenge."

Copyright 2006 by United Press International