Space Center, Houston ? Under sapphire blue skies that once held Columbia and her crew, President Bush paid tribute Tuesday to the shuttle’s seven astronauts and rededicated the nation to space travel. “They go in peace for all mankind. And all mankind is in their debt,” he said.

The president joined at least 10,000 teary-eyed NASA workers, aging astronauts, political leaders and families of the fallen crew for a memorial service in a plaza outside Mission Control usually reserved for celebrations of space triumphs.

The shuttle broke up Saturday as it was returning to earth. In Bush’s words: “Their mission was almost complete, and we lost them so close to home.”

The president met with family members after the service, which ended with the ringing of a Navy bell — seven times, one for each of the deceased astronauts — and a “missing man” formation flyover: four T-38 NASA jets roared above the crowd, with one peeling away and soaring high and out of sight.

Bush bowed his head, and first lady Laura Bush wiped tears from her eyes as the United States Navy Band Sea Chanters led the crowd in song. At one point in the service, Bush pulled a handkerchief from his pocket and handed it to a weeping relative of a crew member.

The words to a hymn, “God of Our Fathers, Whose Almighty Hand,” were printed on the back of the service’s programs, allowing the NASA family to raise its voice in tribute to “shining worlds in splendor through the skies.”

Leading the crowd in prayer, Harold Robinson, a captain in the Navy’s Chaplain Corps, said the astronauts found true humility while viewing “our little planet from outer space.”

Fighting back tears, NASA Administrator Sean O’Keefe then declared, “Today, our grief is overwhelming.”

Earlier, aides said the president supported continuing the shuttle program, despite criticism by some.

The president spoke briefly about each astronaut as their smiling faces looked down from a picture of the crew placed on stage.

Iain Clark, leaning forward, son of shuttle astronaut Laurel Clark, sits with father Jonathan Clark, right, during a memorial service for the astronauts of the space shuttle Columbia at the Johnson Space Center in Houston. The seven astronauts died Saturday when the shuttle broke apart as it prepared to land in Florida. Jean Pierre Harrison, third from left, husband of astronaut Kalpana Chawla, is joined by Chawla's father Banarsilal, second from left, and sister Sunita, at Tuesday's service.

Chawla, a native of India, wanted to reach for the stars, Bush said, and “she went there and beyond.”

Of David Brown, Bush said, “He was first drawn to the stars as a little boy with a telescope in his back yard. He admired astronauts, but, as he said, ‘I thought they were movie stars. I thought I was kind of a normal kid.’ David grew up to be a physician, an aviator who could land on the deck of a carrier in the middle of the night, and a shuttle astronaut. His brother asked him several weeks ago what would happen if something went wrong on their mission. David replied, ‘This program will go on.”‘

Col. Ilan Ramon, 48, son of a Holocaust survivor and Israel’s first space traveler, spoke of the quiet of space and was quoted by Bush as saying, “I only hope that the quiet can one day spread to my country.”

Navy flight surgeon Laurel Clark, 41, liked to say, “Life continues in a lot of places.”

Air Force Col. Rick Husband, the shuttle commander, 45, loved the hymn “How Great Thou Art,” which includes the phrase: “I see the stars. I hear the mighty thunder. Thy power throughout the universe displayed.”

Columbia pilot William McCool, 41, was a former Eagle Scout and “fearless test pilot,” Bush said.

And, finally, payload commander Michael Anderson, 43, who Bush said told his pastor, “If this thing doesn’t come out right, don’t worry about me; I’m just going on higher.”