Solar scientists have been preparing for years for a 4-minute window, during the total solar eclipse on 8 April, in which they will study the sun's corona. | New Scientist

NASA Astronaut Mark Kelly was classmates with Columbia astronauts Laurel Clark, David Brown and William McCool. Kelly has spent 54 days in space over four missions. Here, he describes the startling experience of a space shuttle launch. We piece together intimate footage and interviews with family members of the crew, key players at NASA, and journalists who were on the ground to uncover in forensic detail the events that ultimately led to Columbia’s final mission in 2003. Space Shuttle Columbia: