Videotapes of Columbia's launch on Jan. 16 show what appears to be a piece of foam insulation from the shuttle's external fuel tank falling off, hitting the shuttle's left wing and possibly damaging its delicate heat-resistant tiles that protect the ship during the 3,000-degree Fahrenheit temperatures experienced during atmospheric re-entry.
Extensive analysis by ground control teams during the 16-day flight, however, determined the impact was not a serious safety issue.
"It just doesn't make sense to us that a piece of debris would be the root cause for the loss of Columbia and its crew," shuttle program manager Ron Dittemore said Wednesday afternoon. "There's got be another reason," he added.
"We're trying to find the missing link. As you focus your attention on the debris," he said addressing the media, "we're focusing our attention on what we didn't see. We believe there is something else."
NASA is eager to retrieve wreckage from shuttle Columbia that landed west of Texas, where the ship was flying when all communications and radio links with ground control teams was cut off at 9 a.m. ET on Saturday. The shuttle was headed toward a landing strip in Florida after a scientifically productive 16-day research mission. The shuttle fell from the sky 16 minutes before its planned homecoming.
Earlier Wednesday, NASA's deputy associate administrator for spaceflight Michael Kostelnik told reporters that the astronauts knew the shuttle's left wing might have been damaged from the debris impact.
In an interview with the Orlando Sentinel, an unnamed participant at NASA's internal briefings said, "Maybe (managers) felt it was the only conclusion they could reach because otherwise, what could they do? Do you tell the crew their vehicle might break up?"
NASA has no ability to repair tile damage while the shuttle is in orbit and has no contingency plans for a spacewalk to the underside of the ship. Dittemore said spacewalking astronauts likely would cause even more damage to the delicate structures if they did.
Also, the shuttle had no power or equipment to change orbit and, for example, seek a safe haven aboard the International Space Station, he added.
Dittemore said it was NASA policy to "tell the crew everything."
Sen. George Allen, R-Va., said in a televised speech on Tuesday that the brother of Columbia astronaut David Brown disclosed receiving an e-mail from orbit that conveyed the crew's "concern" about the left wing, the Richmond (Va.) Times-Dispatch reported in Wednesday's paper. According to the report, the senator said Doug Brown, who lives in Virginia, told him his brother's e-mail said the crew had taken a photo of the left wing.
Kostelnik said from inside the crew cabin the astronauts would not have been in a position to see the underside of the wing and the crew's e-mails to family members and friends were private. He hastened to add, however, the NASA-appointed board investigating the disaster would welcome any communications from the crew families relevant to the ongoing probe.
In addition to searching for debris from the shuttle's failed landing attempt, NASA is studying ocean current data in the off-chance of picking up debris shed during launch that went undetected.
"It's a long-shot," conceded Dittemore. "I'm not very hopeful that we'll find anything."