Apollo 13 was the seventh crewed mission in the Apollo space program and the third intended to land on the Moon. The craft was launched on April 11, 1970, from Kennedy Space Center, but the lunar landing was aborted after an oxygen tank in the service module (SM) exploded two days into the mission. The crew instead looped around the Moon, and returned safely to Earth on April 17, 1970, six days after launch. The mission was commanded by Jim Lovell with Jack Swigert as Command Module Pilot (CMP) and Fred Haise as Lunar Module Pilot (LMP). Swigert was a late replacement for the original CMP Ken Mattingly, who was grounded by the flight surgeon after exposure to German measles.