Space debris. Paperweight made from part of an oxygen tank that fell to Earth as the US Skylab space station re-entered the Earth's atmosphere in July 1979. The tank and its insulation were recov- ered at Rawlinna, Australia on July 12. Skylab was launched in 1973 and three successive teams of astronauts spent a total of 171 days on board, conducting scientific experiments. Tens of thous- ands of man-made objects are in orbit around the Earth, remnants left by the many space missions carried out since the 1950s. These objects are a hazard to future space missions and, if they re- enter its atmosphere, to property on Earth.