Americans around the nation gathered in their houses of worship Sunday to mourn the seven astronauts killed when space shuttle Columbia disintegrated as it re-entered the atmosphere Saturday morning.

Ministers who had planned to address the prospect of war with Iraq, the economy and other topics dominating public discussion instead spoke of the sacrifice the astronauts made to further science.

"There have always been those people who had the courage and the faith to move through frontiers. They do that at great risk sometimes, and we are the beneficiaries of their great spirit and bravery," said the Rev. Victor Nixon, of Pulaski Heights United Methodist Church in Little Rock, Ark.

The names of Rick Husband, Michael Anderson, David Brown, Kalpana Chawla, Laurel Clark, William McCool and Ilan Ramon were recited during the customary prayers for departed loved ones at St. Bartholomew's Church in New York City.

A 9-year-old girl stood on her toes to light seven memorial candles on the altar of the First United Methodist Church of Titusville, Fla., where many Kennedy Space Center workers live.

The pastor, the Rev. David Waller, called the trail of smoke from the shattered spacecraft a "glistening tear across the face of the heavens."

"We will remember and respect with gratitude and honor the contributions of these seven astronauts," Waller said.

Members of Temple Israel of Greater Miami recited the Mourner's Kaddish, or traditional prayer for the dead, for Ramon and the six other crew members. The tragedy happened on the Sabbath, when Jews are prohibited from mourning, so many congregations held special services Sunday.

"It is like something has broken," said Karina Zilberman, who helped lead the Temple Israel service. "The purpose was for them to come back and share their experiences."

At the Roman Catholic Our Lady of the Angels Cathedral in downtown Los Angeles, seven candles burned beside the altar. Mass began with 70 seconds of silence and the church bells tolling seven times.

The loss of the Columbia crew brought a new round of grief to a nation still in mourning after the terrorist attacks of Sept. 11.

"The same creator who names the stars also knows the names of the seven souls we mourn today," President Bush said Saturday.

Israel mourned Ramon, its first astronaut, whose journey had infused a troubled nation with hope and pride.

Children hung his picture in schools, flags were lowered to half-staff and the Cabinet honored him as a national hero.

In India, grieving relatives and friends laid garlands of marigolds across a picture of Chawla on Sunday in accordance with Hindu tradition, remembering the first Indian-born woman in space.

The shuttle tore to pieces Saturday 39 miles above Texas, in the last 16 minutes of a 16-day mission, as the spaceship re-entered the atmosphere. It was almost exactly 17 years after the Challenger exploded.

The 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.

Television footage showed a bright light followed by white smoke plumes streaking diagonally across the brilliant sky.

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.

Meanwhile, NASA teams were resuming their somber search for debris from the space shuttle at daybreak Sunday.

An independent commission was appointed to investigate the cause of the tragedy.

Authorities said there was no indication of terrorism; at 207,135 feet, the shuttle was out of range of any surface-to-air missile, a senior government official said. Security was extraordinarily tight on the mission because Ramon was among the crew members.

The investigation focused immediately on possible damage to the protective thermal tiles on the left wing of the shuttle. A piece of insulating foam broke off from the external fuel tank during the Jan. 16 liftoff and may have knocked against the wing.

The Associated Press contributed to this report.