Sputnik 29 was an attempted Mars flyby mission, presumably similar to the Mars 1 mission launched 8 days later. The spacecraft either broke apart as it was going into Earth orbit or had the upper stage explode in Earth orbit. In either case, the spacecraft broke into many pieces, some of which apparently remained in Earth orbit for a few days. (This occurred during the Cuban missile crisis and was picked up by U.S. military radar installations, who originally feared it might by the start of a Soviet nuclear attack.)