'Columbia is lost'

High over Texas and just short of home, space shuttle Columbia fell to pieces Saturday, raining debris over hundreds of miles of countryside. Seven astronauts perished -- a gut-wrenching loss for a country and world already staggered by tragedy.

The catastrophe occurred 39 miles above the Earth, in the last 16 minutes of the 16-day mission as the spaceship re-entered the atmosphere and glided in for a landing in Florida. In its horror and in its backdrop of a crystal blue sky, the day echoed one almost exactly 17 years before, when the Challenger exploded.

"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."

Tile question

The search for the cause began immediately. One focus: possible damage to Columbia's protective thermal tiles on the left wing from a flying piece of debris during liftoff on Jan. 16.

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 Ilan Ramon -- brought a new round of grief to a nation still in mourning after the terrorist attacks of Sept. 11, 2001.

And again, Americans were forced to confront the risks of space, along with the glories.

"The reality of what these people do has often escaped me," said Charlie Dillon, 52, of Denver. "But they are frontiersman, they're out there making my life better and creating endless possibilities for my children."

NASA appointed an independent commission to investigate. The agency said the first indication of trouble Saturday was the loss of temperature sensors in the left 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.

NASA officials said they suspected the wing was damaged on liftoff, but felt there was no reason for concern. They cautioned that it may have had nothing to do with the accident.

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 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 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."

Flight helmet found

Pieces of the spacecraft were found in several east Texas counties and in Louisiana. Among the items found: An astronaut's charred patch, and a flight helmet.

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 FAA issued a notice to airmen because the National Weather Service radar picked up a debris cloud about 95 miles long and 13 to 22 miles wide over Lake Charles, La.

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's oldest shuttle. It was built in 1981 at a cost of about $1 billion.

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.

"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.

Jeff Foreman, an engineer with a physics degree, told CBS News he was taking video and realized quickly something had gone awry.

"When multiple pieces started coming off, I thought that it was highly unusual, that it shouldn't be happening," he said. His suspicions were confirmed when he heard seven or eight sonic booms; during typical fly-bys he hears only two.

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.

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 hourlong 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 Fahrenheit.

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 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. "But we have to caution you and ourselves that we can't rush to judgment on it because there are a lot of things in this business that look like the smoking gun but turn out not even 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 disaster on Jan. 28, 1986 -- it was set aflame by a leak in the seals of one of its right booster rockets -- and the Apollo spacecraft fire that killed three on Jan. 27, 1967.