The worst ever radiation spill from a derelict space vehicle came in January 1978 when the nuclear-powered Cosmos 954 satellite crashed over northwestern Canada. The Soviets claimed the craft completely burned up on re-entry, but a massive recovery effort by Canadian authorities recovered a dozen fragments, most of which were radioactive.
The Phobos-Ground also contains a tiny quantity of the radioactive metal Cobalt-57 in one of its instruments, but Roscosmos said it poses no threat of radioactive contamination.
The spacecraft also carries a small cylinder with a collection of microbes as part of an experiment by the Pasadena, California-based Planetary Society that designed to explore whether they can survive interplanetary travel. The cylinder is attached to a capsule that was supposed to deliver Phobos ground samples back to Earth.