High-resolution images taken from a ground-based Air Force tracking camera in southwestern U.S. show serious structural damage to the inboard leading edge of Columbia’s left wing, as the crippled orbiter flew overhead about 60 sec. before the vehicle broke up over Texas killing the seven astronauts on board Feb. 1.

According to sources close to the investigation, the images, under analysis at the Johnson Space Center in Houston, show a jagged edge on the left inboard wing structure near where the wing begins to intersect the fuselage. They also show the orbiter’s right aft yaw thrusters firing, trying to correct the vehicle’s attitude that was being adversely affected by the left wing damage. Columbia’s fuselage and right wing appear normal. Unlike the damaged and jagged left wing section, the right wing appears smooth along its entire length. The imagery is consistent with telemetry.

It’s still not clear what caused it, though.

UPDATE: This story is interesting, as is this earlier story, on upper-atmosphere electrical phenomena known as blue jets, elves, and sprites. (Also interesting — these phenomena were reported by pilots for years but the reports were dismised before scientists realized that they were real.)