Though no one knew it when it happened, one of the worst days in American spaceflight history took place nine years ago this week.

On January 16, 2003, the Space Shuttle Columbia launched on her STS-107 mission, her payload a battery of space research experiments. During launch, a piece of foam fell from the shuttle's orange external tank and hit the leading edge of the orbiter's left wing. Columbia had been fatally damaged, and neither her crew nor flight controllers realized it.

The debris incident had been recorded, and the crew informed of it. But its seriousness was severely misunderstood until the morning of February 1, when Columbia left orbit for what would be the final time to return home.

Flight controllers began receiving unusual telemetry readings from the vehicle, with an off-nominal tire pressure reading being one of the first signs something was wrong. Contact was lost with the crew. Meanwhile, observers on the ground were surprised at the strange sight they witnessed. For some reason, instead of one bright streak flying above them, there were other glowing specks or multiple streaks. In Houston, telemetry from the vehicle was lost completely. As the scheduled time to landing ticked away toward zero, it became obvious that this was not just a communications problem -- Columbia and her crew were gone.

As NASA and the nation grieved Columbia's crew -- commander Rick Husband, pilot Willie McCool, mission specialists Michael Anderson, David Brown, Kalpana Chawla, Laurel Clark, and Israeli astronaut Ilan Ramon -- work began to recover the debris of the vehicle and to investigate exactly what had happened.

The foam debris strike during launch quickly became a leading suspect, but a dubious one. Columbia had been cleared to return despite the impact precisely because the foam should have been unable to cause serious damage to the reinforced leading edge of the wing, covered with tiles to protect it from the incredible heat of reentry.

And yet, the unlikely explanation fit. The tire pressure reading was indeed the first clue -- super-hot plasma had broken through the protective tile barrier and entered the inside of the wing. The tire reading was an indicator of the heat that had entered the wing. Columbia's left wing burned from the inside out. The vehicle became unstable and the aerodynamic pressures began tearing her apart. Finally, she lost control completely and was destroyed by the forces of reentry.

But consistency is not proof. The explanation that the foam strike had caused the damage that allowed the plasma into the wing made sense, but if such was impossible, the explanation, however logical, was wrong.

A key part of the evidence that provided the almost-literal smoking gun is on display at the U.S. Space & Rocket Center. Engineers analyzed again what the relative velocity of the foam and the wing would have been at the time of impact, and what the forces involved would have been. They took reinforced carbon carbon (RCC) tiles like those protecting Columbia's wing. And they fired foam at the tiles with momentum matching what occurred during the STS-107 launch. Visitors to the Space & Rocket Center will be able to see the hole the foam put through the tiles in the test.

It was a lesson learned at too too high a price, and a lesson NASA took very seriously as a result. Though the end of the space shuttle program had already been planned by the time Discovery returned the fleet to flight, every effort was made to fly the remaining missions as safely as possible; a mission that was accomplished successfully with the STS-135 flight in July 2011.

Today, NASA and industry partners are working together on the vehicles that will return America to space once more, and eventually carry astronauts into the solar system. But as they do, the legacy of Columbia lives on -- safety must never be taken for granted.

Contributing Author: David Hitt