42 days into their stay aboard the military space station Salyut 5, Soviet cosmonauts Boris Volynov and Vitaly Zholobov report unusual odors in the station’s air. On the 49th day of their stay, the two men bundle into their Soyuz 21 capsule to return home on only 10 hours’ notice, an unprecedented event. Details of the causes of the emergency return remain closely guarded to this day, including the possibility of toxic gas escaping into the station’s atmosphere and causing one or both cosmonauts to suffer rapidly deteriorating health. Neither of them fly in space again after their return.
