still don't understand. 16 minutes from home. we begin our field reporting with abc's ned potter. >> lift-off of space shuttle "columbia" -- >> reporter: "columbia" was on a science mission. seven astronauts, 16 days, 70 experiments. >> a more courageous group of people, you could not have hoped to know. >> reporter: this morning the crew finished packing up for re-entry, landing planned for 9:16 this morning eastern time on the runway at florida's kennedy space center. at 8:15 a.m. they fired their engines to begin their return from orbit. >> this is mission control houston. >> reporter: shuttle landings are normally quiet but at 8:53 a.m. mission control saw some odd temperature readings here, along the left wing. a few minutes later, there were more oddities, apparently having to do with the landing gear on the left side. at 8:59 a.m. the shuttle came over texas, still 39 miles high and moving at 12,000 miles an hour. mission control had its last contact with the crew.