April 4, 2007  -- Astronaut Laurel Clark wore her wedding ring on a chain around her neck while she orbited Earth in the space shuttle Columbia.

Four years later, the whereabouts of that ring, believed to be stolen, have puzzled law enforcement and embarrassed NASA.

Video shot on that Columbia mission shows Clark laughing as she works on experiments on the shuttle's middeck, the ring floating on the chain in zero gravity.

It was Clark's first mission, and her last. She died when Columbia broke up over Texas on Feb. 1, 2003, leaving behind her husband, Jonathan, and her son, Iain.

The shuttle crashed because foam had come off the external fuel tank during the launch. It punctured the leading edge of the left wing. During re-entry, superheated air penetrated the wing and spread through the orbiter, causing it to break up as it headed toward Florida to land at the Kennedy Space Center. Columbia disintegrated over Texas, at a height and speed that made it impossible for the crew to survive.

It took months for searchers to recover the shuttle's pieces, which were scattered across east Texas. The bodies of the seven crew members were recovered, but to protect the grieving families of the crew, little information was released.

Documents reviewed by ABC News as part of an investigation into Robert Cobb, NASA's inspector general, detail an effort to cover up the search for Clark's wedding ring.

The report states, "The remains of deceased astronaut Laurel Clark were recovered shortly after the Columbia accident, and a ring was allegedly present on, and then stolen from her recovered remains."

Law Enforcement Joins the Search

Texas Rangers were investigating the theft of the ring and wanted to release a public Crime Stoppers Report to the public to find the stolen ring.

Jonathan Clark wanted his wife's ring found, according to the report, but in a meeting with Cobb he was told that going public with news of a stolen wedding ring would not be good publicity for NASA.

"The whole NASA Columbia investigation was not going well. NASA wanted it finished, and for the outcome to reveal nothing that would make NASA look bad or would shake the public's trust in NASA," Cobb said, according to the documents.

Witnesses in the investigation suggest that Cobb, who as an inspector general was supposed to be an independent arm of NASA, was anything but neutral.

One NASA employee in the report quoted Cobb as saying, "Can you believe how embarrassing that would have looked for the agency if that [Crime Stoppers Report] went out?"

According to the documents just released, a Texas Ranger involved in the investigation informed the Office of the Inspector General that he believed someone at NASA wanted the investigation shut down because if it got out that the ring was stolen, questions would arise about the conduct of NASA's investigation into the Columbia accident.

Members of the House Science Committee are convinced hearings will be necessary to find out whether there was a cover-up at NASA.

In the meantime, Jonathan Clark just wants to know what happened to his wife's ring.