Wednesday marks 20 years since the Space Shuttle Columbia disaster killed seven astronauts.

The shuttle lifted off on January 16, 2003, from Kennedy Space Center with a crew of seven. Fatefully, it disintegrated over Texas as it reentered the atmosphere on February 1, killing every crew member.

The crew members on board were mission commander Rick Husband, shuttle pilot William McCool, payload commander Michael Anderson, mission specialists David Brown, Kalpana Chawla, and Laurel Clark, and payload specialist Ilan Ramon.

The tragedy resulted from a 1.7-pound piece of foam that broke off the shuttle’s external fuel tank a little more than one minute after liftoff. After colliding with the shuttle’s left wing, the scrap punctured a hole in the vessel’s thermal armor.

This proved disastrous 16 days later when the space shuttle was scheduled to land in Florida. Upon reentry, hot atmospheric gases entered through the punctured wing of the ship, breaking apart the space shuttle just 16 minutes before it was due to touch down.

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Before Columbia began its reentry, NASA managers had dismissed the extent of the damage to the shuttle’s left wing. That same kind of disregard led to the loss of the Space Shuttle Challenger during liftoff on January 28, 1986, which also killed all seven astronauts aboard.

NASA uses the last Thursday of every January as a day of remembrance for its fallen astronauts, which also includes the three astronauts who died in the Apollo 1 launch pad fire on January 27, 1967.

Last Thursday, space centers across the country lowered their flags to half-staff. Officials discussed the importance of spaceflight safety during the ceremonies.

At the Kennedy Space Center Visitor Complex, a crowd of over 100 people formed to remember all the astronauts killed in the line of duty. The Columbia and Challenger accidents account for more than half of the astronauts lost on duty, while plane crashes caused most of the rest.

Columbia’s final mission was its 28th. Its first mission launched on April 12, 1981, with the late John Young on board as commander with pilot Robert Crippen, the first of 160 astronauts in total who traveled on the ship.

During its 22 years of operation and 300 days in space, Columbia logged more than 125 million miles, which is equivalent to orbiting the Earth 4,808 times.

Making the Columbia disaster all the more tragic was that it was preventable, like NASA’s earlier tragedies, according to former shuttle commander Bob Cabana, who is now NASA’s associate administrator.

“When we look back, why do we have to keep repeating the same hard lessons?” Cabana told the Associated Press. “I don’t ever want to have to go through another Columbia.”