Space shuttle Columbia disintegrated 39 miles over Texas on Saturday in a meteoric streak that rained smoking debris over hundreds of miles of countryside. All seven astronauts were lost, a tragedy that echoed the Challenger explosion almost exactly 17 years earlier.
The catastrophe occurred in the last 16 minutes of the 16-day mission as the spaceship glided in for a landing in Florida.
"The Columbia is lost," said President Bush, after he telephoned the families of the astronauts to console them.
"The same creator who names the stars also knows the names of the seven souls we mourn today," Bush said, his eyes glistening. "The crew of the shuttle Columbia did not return safely to Earth but we can pray they are safely home."
The cause of the tragedy was not immediately known. An independent commission was appointed to investigate. One potential focus: possible damage to Columbia's protective thermal tiles on the left wing from a flying piece of debris during liftoff. NASA said the first indication of trouble Saturday was the loss of temperature sensors in that wing's hydraulic system.
The spacecraft had just re-entered the atmosphere and had reached the point at which it was subjected to the highest temperatures.
Authorities said there was no indication of terrorism; at 207,135 feet, the shuttle was out of range of any surface-to-air missile, one senior government official said. Security was extraordinarily tight on this mission because Ilan Ramon, Israel's first astronaut, was among the crew members.
Television footage showed a bright light followed by white smoke plumes streaking diagonally across the brilliant, blue sky. Debris appeared to break off into separate balls of light as it continued downward.
"We saw it coming across the sky real bright and shiny and all in one piece. We thought it was the sun shining off an airplane," said Doug Ruby, who was driving with his father along a Texas highway, headed for a fishing trip. "Then it broke up in about six pieces — they were all balls of fire — before it went over the tree line."
Pieces of the spacecraft were found in several east Texas counties and in Louisiana. There was at least one report of human remains recovered — in Hemphill, Texas, near the Louisiana line, a hospital employee on his way to work reported finding what appeared to be a charred torso, thigh bone and skull on a rural road near what was believed to be other debris.
The Army's 1st Cavalry Division sent a helicopter search-and-rescue task force from Fort Hood, Texas. NASA also asked members of the public to help in its search for debris, but warned people not to touch the pieces because they might be contaminated with toxic propellants.
The shuttle flight was the 113th in the shuttle program's 22 years and the 28th flight for Columbia, NASA oldest shuttle.
The horrific end of shuttle mission STS-107 was a devastating blow to the nation's space program; the Challenger explosion led to a 2 1/2-year moratorium on launches, and Saturday's accident could bring construction of the international space station to a standstill.
The shuttle delivers components of the space station to be installed; it also carries crews to and from the station. The three astronauts now on board the station could return to Earth at a moment's notice via a Russian vehicle attached to the space station.
Six shuttle flights had been planned for 2003 — five of them to the space station. The next was scheduled for March 1.
The loss of seven explorers of space's dark reaches — shuttle commander Rick Husband, Michael Anderson, David Brown, Kalpana Chawla, Laurel Clark, William McCool and Ramon — brought a new round of grief to a nation still in mourning after the terrorist attacks of Sept. 11, 2001.
"We trust the prayers of the nation will be with them and with their families. A more courageous group of people you could not have hoped to know," said NASA Administrator Sean O'Keefe.
Columbia had been scheduled to land at Kennedy Space Center at 9:16 a.m.
Shuttle program manager Ron Dittemore said "there was no indication of any impending threats to the vehicle." Then there was a loss of data from temperature sensors on the left wing, followed by a loss of data from tire pressure indicators on the left main landing gear.
The final radio transmission between Mission Control and the shuttle, at 9 a.m., gave little indication of any trouble.
Mission Control radios: "Columbia, Houston, we see your tire pressure messages and we did not copy your last."
Columbia's commander, Rick Husband, calmly responds: "Roger, uh, buh ..."
For several seconds, the transmission goes silent.
Then, there is static.
Texas Sen. Kay Bailey Hutchison, in her Dallas neighborhood, said she heard a "boom, which I thought was the breaking of the sound barrier" — and it may have been just that, because the shuttle was traveling at 12,500 mph, 18 times the speed of sound.
"The barn started shaking and we ran out and started looking around," said Benjamin Laster of Kemp, Texas. "I saw a puff of vapor and smoke and saw big chunk of material fall."
On the edge of downtown Nacogdoches, 135 miles northeast of Houston, a National Guardsman stood watch over a steel rod with silver bolts that landed in the grass outside a yard. People streamed up to take photos of the debris.
Dentist Jeff Hancock said a metal bracket about a foot long had crashed through his office roof.
"It's all over Nacogdoches," said James Milford, owner of a barber shop in downtown. "There are several little pieces, some parts of machinery. ... There's been a lot of pieces about 3 feet wide."
In 42 years of U.S. human spaceflight, there had never been an accident during the descent to Earth or landing.
Two hours after the shuttle had been expected to land, the giant screen at the front of Mission Control showed a map of the southwest United States and what should have been Columbia's flight path. The American flag next to the center's countdown clock was lowered to half-staff.
O'Keefe met with the astronauts' families, who had been waiting at the landing site for the shuttle's return. Six of the seven astronauts were married, and five had children.
The shuttle is essentially a glider during the hour-long decent from orbit toward the landing strip. It is covered by about 20,000 thermal tiles to protect against temperatures as high as 3,000 degrees.
On Jan. 16, shortly after Columbia lifted off, a piece of insulating foam on its external fuel tank came off and was believed to have hit the left wing of the shuttle. Leroy Cain, the lead flight director in Mission Control, had assured reporters Friday that engineers had concluded that any damage to the wing was considered minor and posed no safety hazard.
"As we look at that now in hindsight, we can't discount that there might be a connection," Dittemore said Saturday. "But we have to caution that we can't rush to judgment, because a lot of things in this business that look like the smoking gun but turn out not to be close."
Columbia's crew had completed 80-plus scientific research experiments during their time in orbit. It was a relatively inexperienced crew; only three — Husband, Anderson and Chawla — had ever flown before.
The others were rookies, including Ramon, the 48-year-old Israeli Air Force colonel. A former fighter pilot who survived two wars, he carried into space a small pencil drawing titled "Moon Landscape" by Peter Ginz, a 14-year-old Jewish boy killed at Auschwitz.
"The state of Israel and its citizens are as one at this difficult time," Prime Minister Ariel Sharon's office said in a statement.
Just in the past week, NASA observed the anniversary of its only two other space tragedies, the Challenger explosion on Jan. 28, 1986, and the Apollo spacecraft fire that killed three on Jan. 27, 1967.
The Associated Press contributed to this report. For the very latest, stay with ABC News and KAKE, and watch for local reaction tonight on KAKE News at 6 and 10.