Astronauts aboard space shuttle Discovery and the international space station took a few moments Thursday to mark the deaths of U.S. astronauts and Russian cosmonauts.
"Even if the future is equally unimaginable to us, we can be sure that future generations will look upon our endeavors in space as we look upon those early expeditions across the seas," Discovery mission specialist Wendy Lawrence was quoted as saying by Houston Chronicle.
"To those generations, the need to explore space will be as self-evident as the need previous generations felt to explore the Earth and the seas."
The United States has lost three crews of astronauts during spaceflight preparations, launches and landings.
In January 1967, three Apollo 1 astronauts died in a launch pad fire during a countdown test. About 19 years later, and 73 seconds after liftoff, seven astronauts died aboard space shuttle Challenger. Then, 2 1/2 years ago, seven astronauts died when Columbia disintegrated during its descent.
The Russians have lost two crews. One cosmonaut, Vladimir Komarov, died when Soyuz 1 re-entered Earth's atmosphere out of control and crashed just three months after the Apollo 1 launch pad fire. Then, in June 1971, three cosmonauts died when the Soyuz 11 capsule decompressed during descent.
The service included comments in Japanese by one of Discovery's two spacewalkers, Soichi Noguchi, and in Russian by Sergei Krikalev, commander of the space station crew.