50 years ago today: on April 13, 1970, Apollo 13 was aborted after an oxygen tank ruptured on the way to the moon. Later deemed a “successful failure” because of experience gained in rescuing the crew, Apollo 13 became a case study of managing change and working together. The “Mailbox,” pictured here, helped bring astronauts Jim Lovell, Fred Haise, and Jack Swigert back to Earth. Because the original explosion happened in the Service Module, the astronauts had to use the Lunar Module as a lifeboat in space. So flight controllers and engineers on the ground created this DIY hack to make the air more breathable. (If you’re curious: the Mailbox connected the Command Module’s lithium hydroxide canisters, used to purge carbon dioxide, to the Lunar Module, which was carrying a limited amount of lithium hydroxide.) And as luck would have it, the CM’s filters were square…and the LM’s filters were round. You do what you can with the tools you have. (Photo: NASA)