Representing the families of the Columbia seven, the widow of commander Rick Husband told the hushed audience that the accident was so unexpected and the shock so intense, "that even tears were not freely able to fall."
"They would come in the weeks, months and years to follow in waves and in buckets," said Evelyn Husband Thompson.
She assured everyone, though, that healing is possible and that blessings can arise from hardships. She attended the ceremony with her two children, her second husband and Sandra Anderson, widow of Columbia astronaut Michael Anderson.
"God bless the families of STS-107," said Thompson, referring to the mission designation for Columbia's last mission. "May our broken hearts continue to heal and may beauty continue to replace the ashes."
A pair of songs added to the emotion of the day. The young nephew of a NASA worker performed a song he wrote, "16 Minutes from Home," on the keyboard, along with a vocalist. And Grammy award-winning BeBe Winans, an R&B and gospel singer, performed "Ultimate Sacrifice," which he wrote for soldiers serving overseas in harm's way.
As it turns out, Anderson had taken a CD of Winans' music took into orbit with him. It was recovered in the debris that rained down on East Texas that fateful morning. Winans did not know that until it was mentioned at Friday's ceremony.
"I honor you today, I really do honor the families and those who have given the ultimate sacrifice," he added. Some in the crowd wiped away tears as he sang.
Also present were 44 students from Israel, the homeland of Columbia astronaut Ilan Ramon. He was Israel's first astronaut.
The teenagers were proud to note that they go to the same school as Ramon once did. They wore white sweat shirts with an emblem of their nation's first spaceman and the religious items he took into orbit.
"He represented Israel in the best way possible, so I think it's an honor for us to be here," said Eden Mordechai, 15.
The other Columbia crew members were co-pilot William McCool, Kalpana Chawla, Dr. Laurel Clark and Dr. David Brown.
NASA's human exploration chief, Bill Gerstenmaier, said no single person or event caused the Columbia disaster. Rather, "a series of technical and cultural missteps" were to blame, dating back to the first shuttle launch in 1981 when fuel-tank foam insulation started coming off and doing damage.
A chunk of foam punched a hole in Columbia's left wing during liftoff, leading to the catastrophic re-entry.
The astronaut who led the charge back to shuttle flight two years later, Eileen Collins, stressed that the 30-year shuttle program had its share of successes along the way and achieved its ultimate goal, building the International Space Station. The shuttles were retired in 2011.
"We still miss you," Collins said of the Columbia seven. "How can we ever thank you for your contributions to the great journey of human discovery."
The hourlong ceremony was held in front of the huge black granite monument bearing the names of all 24 astronauts who have died in the line of NASA duty. The three-man crew of Apollo 1 died in the Jan. 27, 1967, launch pad fire. The Challenger seven were killed Jan. 28, 1986, during liftoff. Husband and his crew honored them during their own flight, just four days before dying themselves.
On Friday, the names of each of the dead were read aloud. Afterward, mourners placed carnations and roses on the grating in front of the mirror-faced monument.
"I felt compelled to be here to memorialize those who were a big part of my life," said David Nieds, 39, a grocery store manager who got up early to drive from Fort Lauderdale with his mother and 16-year-old nephew.
He attended dozens of launches. Some people like sports, he explained, while he follows the space program.
Memorial services also were held at Arlington National Cemetery, where three of the Columbia crew are buried; in East Texas, where the shuttle wreckage fell; and in Israel.