Soviet satellite Kosmos 954, with a nuclear reactor on board, burns up in Earth's atmosphere, scattering radioactive debris over Canada's Northwest Territories. Only 1% is recovered.

The Soviet Union, officially the Union of Soviet Socialist Republics (USSR), was a transcontinental country that spanned much of Eurasia from its formation in 1922 until its dissolution in 1991. It was the world's third-most populous country, the largest by area, and bordered twelve other…