Neither Shepard nor Lovell expected there would be much difference between Apollo 13 and Apollo 14, but Apollo 13 went disastrously wrong. An oxygen tank explosion caused the Moon landing to be aborted and nearly resulted in the loss of the crew. It became a joke between Shepard and Lovell, who would offer to give Shepard back the mission each time they bumped into each other. The failure of Apollo 13 delayed Apollo 14 until 1971 so that modifications could be made to the spacecraft. The target of the Apollo 14 mission was switched to the Fra Mauro formation, the intended destination of Apollo 13.