NASA is examining a theory that something struck or fell away from the shuttle Columbiaa day after its launch to cause last week's break-up of the craft.
Radar images from the military agency that tracks space objects show something moving slowly away from the orbiting Columbiaon January 17th.
It could be debris, a small meteor, a piece of the shuttle or simply ice formed by a routine shuttle wastewater dump, NASA officials said.
NASA engineers are examining data to see if the shuttle shook at the same time the object was spotted, indicating a possible impact, officials said.
The image was detected by the North American Aerospace Defense Command at Peterson Air Force Base, Colorado, which tracks orbiting satellites and space debris and routinely warns shuttles when they are on a collision course with space objects.
It is the latest possible clue NASA is evaluating in its investigation into the disintegration of the agency's oldest shuttle.
The spacecraft launched on January 16th on a 16-day science mission fell to earth in thousands of pieces after breaking up high over Texas just 16 minutes from landing at Kennedy Space Center in Florida on February 1st.
In the spacecraft's final moments, sensors showed rising heat on the its left side and a struggle by its computerised flight system to maintain control as drag increased on the left wing.