On this date, April 12, in 1961, Yuri Gagarin rocketed into space and history as the first human to orbit our planet. Yet more than 60 years later, his subsequent death remains something of a mystery.

Gagarin lifted off from Baikonur Cosmodrome in Kazakhstan, U.S.S.R., and reached an altitude of about 325 kilometres on a single orbit that lasted less than two hours before he landed — far off course but still in the Soviet Union — in front of a young girl and her grandmother. They were terrified.