For the rest of time, three men will be linked by the Columbia (search) disaster, strangers thrown together by that awful Saturday morning in February.

The accident has altered the lives of three individuals forever: NASA's most visible persona during those dreadful first days; a scientist who would dig into the cause of the accident; and the grieving husband of one of the two women on the flight.

Ron Dittemore, the space shuttle program manager who took the most dramatic public fall, remains emotionally scarred one year later. He left NASA (search) and now holds a low-profile aerospace job in Utah.

The seven lost lives weigh heavily on him. After repeatedly delaying previous shuttle launches for all sorts of reasons, he wonders what prevented him and others from seeing the risk in the piece of foam that broke off and hit the shuttle wing. "Why didn't the hair stand up on your neck?" he asks himself.

Douglas Osheroff (search), the Nobel Prize-winning physicist who investigated the accident, still wonders if NASA can save itself.

He sensed from the start that the flyaway chunk of foam at liftoff likely doomed Columbia. But he forced himself to keep an open mind and followed the evidence, over six months, to that very conclusion.

Dr. Jon Clark, still numbed at times by the pain of losing his wife and the mother of his son, uncomfortably straddles two worlds.

Clark is an insider, working for NASA as a neurologist. But ever since Laurel Clark (search) and six other astronauts perished aboard Columbia, he feels more like an outsider as he pushes for cultural change within an agency that he sadly believes does not have what it takes to put humans on the moon or Mars.

The three men had no way of knowing that on Feb. 1, 2003, their lives would intersect.

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Moments after 9 a.m. EST, Columbia shattered in the sky over Texas while streaking through the atmosphere toward Cape Canaveral, just another 16 minutes on top of a journey that had spanned 16 days.

The families of the seven Columbia astronauts waited along the runway. The twin sonic booms that herald a shuttle's arrival never came. The sky was empty.

Clark, with his all his intimate knowledge about launches and landings, knew something was very wrong. He'd been listening to Mission Control's commentary on the loudspeakers and was disturbed by the call to Columbia about the tire-pressure alarms and the commander's truncated reply.

His brain went into high-speed analytical mode: The crew was probably going to have to bail out and his wife was in one of the worst spots, on the upper flight deck. By his count, she would be the fifth to jump.

What was happening, though, was unimaginable -- even to him.

Descending at nearly 20 times the speed of sound in a bucking spacecraft, the astronauts could not have bailed out, least of all from 200,000 feet.

They never stood a chance.

Within a minute or a little more, it was all over. The Columbia and its seven souls were gone, hurled all over Texas and Louisiana.

The families were rushed to astronaut quarters where they were told that while there was no confirmation of fatalities, the accident was believed to be unsurvivable.

The screams were bloodcurdling.

President Bush (search) later called the families to console them and then announced to the world that Columbia was lost and that all seven on board -- Rick Husband, William McCool, Kalpana Chawla, Laurel Clark, Michael Anderson, David Brown and Israel's first astronaut, Ilan Ramon -- were dead.

A shell-shocked Dittemore appeared before the TV cameras in midafternoon and urged journalists not to rush to judgment about the foam impact back during the Jan. 16 launch.

"There are a lot of things in this business that look like the smoking gun but turn out not even to be close," Dittemore said from Houston.

Four days later, he insisted the foam was not to blame. The very next day, once the accident investigators hit town, he acknowledged he was wrong to rule out anything so early.

NASA Administrator Sean O'Keefe (search) was outraged by Dittemore's swift dismissal of the foam.

It turned out that the suitcase-size section of foam insulation was the biggest piece ever to break off a shuttle fuel tank, and it slammed into the underside of Columbia's left wing edge at more than 500 mph, 81 seconds after liftoff.

Shuttles had been struck before by foam and other debris, to no great consequence. But while viewed as a problem, little was ever done to stop the foam from breaking off.

Jon Clark -- a doctor, not an engineer -- was puzzled during Columbia's flight when he saw a reference to the launch-day foam strike as he read the Mission Control log notes.

He decided not to make a fuss. It wasn't his area of expertise.

Mission managers, grown accustomed to uneventful landings and under the flight schedule gun, dismissed the concerns of low-level engineers and did not seek spy satellite pictures of the damaged wing.

NASA's top safety official, Bryan O'Connor, learned of the foam strike while Columbia was still in orbit. He was tipped off by a colleague with a friend in the Pentagon (search) that people there were surprised the space agency had not requested zoom-in pictures.

O'Connor, didn't have military clearance to deal with the issue, so he passed it off to shuttle managers in Houston where it languished.

One year later, O'Connor is filled with regret. He offered to quit after the accident, but O'Keefe urged him to stay and make the shuttle program safer.

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As Dittemore briefed the world on NASA's second shuttle accident in 17 years, Osheroff, the Stanford University physicist, was driving with his wife through the Santa Cruz Mountains in Northern California to their favorite dim sum restaurant.

Neither had listened to the news before leaving home, and Osheroff was puzzled when he turned on the car radio and heard a NASA news conference in progress. The radio announcer finally came on and summarized what had happened: The shuttle Columbia had broken up on re-entry and, perhaps not so coincidentally, a chunk of foam had fallen off the fuel tank during launch 16 days earlier and hit the left wing.

Osheroff cursed. He knew enough about the brittle graphite leading edge of the shuttle wing to know that the foam had likely created catastrophic damage. He had no way of knowing then that within a month he'd be called to join an investigation into the catastrophe.

As Dittemore grimly answered reporters' questions and Osheroff listened in disbelief across the country, Clark was on a NASA jet flying back to Houston from Cape Canaveral with the other astronaut families.

The newly widowed flight surgeon was playing the card game War with son Iain, then 8, in hopes of distracting the boy. Just as the plane passed over the Texas-Louisiana border, where most of the wreckage had fallen, the child froze and instead of looking at his cards, raised a hand and moved it back and forth.

"Iain, what are you doing?" Clark asked.

"I'm waving goodbye to Mommy," he said. "I felt her."

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Osheroff says he's been thinking a lot, since the investigation board's report came out in August, about how and why NASA's bizarre culture evolved -- not just in its approach to safety issues but its lack of curiosity. The only conclusion he can reach is, "This is what happens to an organization that simply doesn't have the money to do what it wants to do safely."

Dittemore, the former shuttle program manager, refuses to discuss NASA's culture or whether his departure was essential.

He is, however, one of the few to readily accept full responsibility for the tragedy.

"It doesn't get any easier as the time passes, because I still focus on seven families, and what did we miss to allow such a tragedy to occur," Dittemore says.

While progress is being made on the technical front for the grounded shuttles' return to flight, perhaps by fall, Clark says not enough is being done to fix NASA's crucial cultural issues.

It's important to be frank about the crew survivability issues, Clark says, especially since a new spaceship is on the horizon and lifesaving improvements could be made.

President Bush has laid out plans for a manned mission to the moon and Mars. In the mind of Scott Hubbard, the director of NASA's Ames Research Center (search) in California who served on the Columbia accident board, "It's the best legacy the crew could possibly have."

He had hoped for a new direction for the space agency. But he never imagined it would come so soon, within a year of the disaster.

NASA is going to need money, though, to ask all the necessary questions to pull it off, Osheroff says.

"It's like a kid in school who asks why is the sky blue and how do homing birds home?" he explains. If he doesn't get answers to his questions, maybe he is discouraged from asking them.

Osheroff's guess is that NASA will start asking questions. His own question, though, is whether NASA will keep it up.