Kosmos 96, or 3MV-4 No.6, was a Soviet spacecraft intended to explore Venus. A 3MV-4 spacecraft launched as part of the Venera programme, Kosmos 96 was to have made a flyby of Venus. However, due to a launch failure, it did not depart low Earth orbit. Its re-entry into Earth's atmosphere is often speculated as the cause of the Kecksburg UFO incident. This was the third and last spacecraft prepared for a Venus encounter for the 1965 launch window. The 3MV-4 No.6 spacecraft was originally built for a mission to Mars with launch scheduled for late 1964. After it was not launched by the end of its launch window, the spacecraft was repurposed, along with two other spacecraft which were launched as Venera 2 and Venera 3, to explore Venus.

Wikipedia: https://en.wikipedia.org/wiki/Kosmos_96. Original timeline Wikipedia link: https://en.wikipedia.org/wiki/Cosmos_program. Related NASA reference: https://nssdc.gsfc.nasa.gov/planetary/chronology.html#1965. Description adapted from Wikipedia contributors (CC BY-SA 4.0; https://creativecommons.org/licenses/by-sa/4.0/).