US: Led by President George W. Bush, thousands of grieving space workers and their families, friends, neighbours and political leaders paid a solemn farewell last night to the seven Columbia astronauts.
President Bush bowed his head in grief and first lady Laura Bush wiped away tears as the men and women who perished in the space shuttle disaster were memorialised at the home of Mission Control in Houston.
The shuttle broke up Saturday as it was returning to Earth.
The memorial service, held at NASA's Johnson Space Centre, opened with in invocation by a navy rabbi and the singing of the hymn, God of Our Fathers.
Mr Sean O'Keefe, NASA's administrator, said the bond between those who go into space and those on the ground "is incredibly strong. Today, our grief is overwhelming.
"We also have a tremendous duty to honour the legacy of these fallen heroes by finding out what caused the loss of the Columbia and its crew, to correct the problems we find and to make sure that this never happens again," Mr O'Keefe said.
The president and first lady were accompanied on Air Force One by Neil Armstrong, the first man on the moon.
Former senator and astronaut John Glenn and his wife, Annie, also were on the board.
"It's too bad we couldn't have pushed this day back forever," lamented Glenn, the first US astronaut to orbit the Earth.
NASA estimated the crowd at between 10,000 and 15,000. Mourners spilled beyond the square and crowded around a pond.
They stood among the trees and on the lawns - waiting to hear the presidential eulogy.
"He's the leader of our country, and his being here wasn't necessary, but it does show we are mourning," said Ms Rochelle Pritchard, a NASA contract worker who helps manufacture robotic flight control gear.
The memorial service had a personal dimension for Ms Pritchard, who said she attended a Texas university with shuttle Commander Rick Husband, who was among those who perished on Saturday.
"He was just the greatest guy - always smiling, always approachable," she said.
Ms Laura Lucier, an employee of the Canadian space agency who is based at Johnson Space Centre, said that the passion for space exploration drew workers here and gave the memorial service deeper meaning.
"There's nobody who works at NASA who isn't passionate about it," Ms Lucier said.
"When workers are lost, it means a lot more. You work here because you love it, not because it's a pay cheque."
The impact of the Columbia's loss was felt well outside the space centre's gates.
Flags flew at half-staff throughout the region. The sign at a fast-food restaurant just outside Johnson's gates read "Our prayers to our NASA family".