Sally Kristen Ride was an American astronaut, physicist, and engineer. Born in Los Angeles, she joined NASA in 1978 and became the first American woman in space in 1983. Ride was the third woman in space overall, after USSR cosmonauts Valentina Tereshkova (1963) and Svetlana Savitskaya (1982). Ride remains the youngest American astronaut to have traveled to space, having done so at the age of 32. After flying twice on the Orbiter Challenger, she left NASA in 1987. She worked for two years at Stanford University's Center for International Security and Arms Control, then at the University of California, San Diego as a professor of physics, primarily researching nonlinear optics and Thomson scattering. She served on the committees that investigated the Challenger and Columbia space shuttle disasters, the only person to participate in both. Ride died of pancreatic cancer on July 23, 2012.