On July 20, 2003, the Space Shuttle Columbia broke apart during re-entry, killing all seven crew members. The crew had been on a 16-day mission to conduct scientific experiments in space. The disaster occurred when damage sustained during launch allowed heat to enter the shuttle upon re-entry. The tragedy led to a halt in shuttle flights and widespread investigations into NASAs safety practices. It also brought attention to the challenges of human spaceflight and the risks associated with space exploration.