Launched on 2 July 1985 by an Ariane-1 rocket, on 13 March 1986 the Giotto probe passed by the nucleus of Halley's comet at a distance of 600 km. The project was a success. It was the first time that such a precise image of a comet's nucleus had been obtained.
It confirmed the fact that comets are a mixture of rock and ice. This ice sublimes under the effect of solar radiation, projecting dust into space as illustrated below. Note that the dust spray seriously damaged the probe.
A view of Halley's comet taken by the Giotto probe.