"The footage," says space history curator Valerie Neal, "has become seared into our memory."

On January 28, 1986, the Space Shuttle Challenger launched from Florida's Kennedy Space Center. The mood leading up to the launch was full of promise. NASA was coming off of nine missions in 1985, and with 12 scheduled missions, 1986, says space history curator Valerie Neal of the National Air and Space Museum, "was supposed to be a banner year." Christa McAuliffe, sponsored by a NASA project, was about to be the first teacher in space, and classrooms of students across the country were tuned in for the television coverage. "This was to be a teachable moment. But that teachable moment," says Neal, which was to inspire future astronauts to come, "became much different."

A rubber O-ring seal in one of the Challenger's solid rocket boosters had failed during liftoff, causing hot gases to leak through a joint and flames to burn through the support attaching the booster to an external fuel tank. The booster crashed into the tank, liquid hydrogen and oxygen ignited and, just 73 seconds into flight, the shuttle tore apart. The crew compartment crashed into the ocean, killing all seven crew members.

Neal shared her memory of that day with me:

"At the time, I was living in Huntsville, Alabama, and I was a writer under contract to NASA. I was specifically working on the early shuttle missions in the 1980s, writing about them, what would be happening on the missions, especially what kind of scientific research would be done on the missions. I was also writing about the upcoming Hubble space telescope. So I had some familiarity with shuttle operations and with crew training. On that particular morning, I had just returned from a business trip, and I was in my office. My office mates called me into the conference room at launch time. We had a television in there, and it was our custom to gather to watch the launches. So we were standing around chatting during the countdown and had the usual exclamations of joy that the launch had happened on time and apparently perfectly. As we were lingering there in the conference room and watching as the camera followed the shuttle during its ascent, it quickly became evident that something had gone terribly awry. The exhaust plume didn't look like it was supposed to. Instead of being straight and confined, suddenly there was a big bulge in it, and then trails of vapor started falling from it, almost like they do in a fireworks display. We were all stunned into silence. Even the NASA announcer was stunned into silence. Nobody quite new what to make of it.

I decided I didn't want to stay in the room very long and see it over and over again and hear speculation and chit chat. I just felt like I needed to get outside and get a breath of fresh air. I think that it struck me that soberly because I had just recently sent in an application for the Journalist-in-Space competition, which was to be the next citizen flight after the Teacher in Space. At the time, part of what Christa McAuliffe represented was the fact that the shuttle was safe enough that ordinary citizens could now fly on it, that you didn't have to be a professional astronaut. I realized very keenly that it wasn't perfectly safe. I was a young mother at the time with a six-year-old. I knew that Christa McAuliffe and the men in the crew also had young children. It just struck me that there was a lot more to flying on the shuttle than I had quite realized. That added a whole new dimension to my thoughts about going into space. I knew that there would be plenty of news and analyses, and I could process that all later. But I just wanted this shell of silence around me that day to absorb the tragedy. As it happened, later that day when the mail came, I had a postcard from NASA saying that my application packet for Journalist in Space had been received. I knew then that that flight was not likely to happen any time soon, and, in fact, it never did."

That night, President Reagan, who was supposed to deliver his State of the Union, instead acted, says Neal, as "mourner-in-chief." In a televised address, he declared the tragedy a national loss. "We mourn seven heroes: Michael Smith, Dick Scobee, Judith Resnik, Ronald McNair, Ellison Onizuka, Gregory Jarvis and Christa McAuliffe," he said. And the president ended on an eloquent note, borrowing phrasing from poet John Gillespie Magee, Jr.'s "High Flight": "We will never forget them, not the last time we saw them this morning, as they prepared for their journey and waved goodbye, and 'slipped to the surly bonds of Earth...to touch the face of God.'"

Flowers, flags and other mementos started appearing in a spontaneous memorial at the National Air and Space Museum. "We have become a gathering place for that," says Neal, "to both celebrate or mourn events in space." On display in the museum's Moving Beyond Earth exhibition is a particularly poignant Challenger artifact—a commemorative plaque that NASA gave to each of the astronauts' families and the museum on the first anniversary of the disaster. On it, are the names and portraits of Challenger's crew members, a mission patch and a small United States flag that was recovered from debris on the ocean floor.