Summary: Wednesday marks 20 years since the space shuttle Columbia disintegrated on its way home. The tragedy not only killed all seven astronauts on board but also was the beginning of the end for the space shuttle program and changed how we explore space now. Science correspondent Miles O'Brien spoke with retired astronaut and Senator Mark Kelly about the Columbia disaster. PBS NewsHour is supported by - https://www.pbs.org/newshour/about/funders
