This image of the nucleus of Halley's comet comes from the Giotto spacecraft.
Click on image for full size
Measurements from Halley's comet
Among the things we learned from a suite of spacecraft which visited Halley's comet in 1986 are
- what a comet nucleus looks like up close (no one had ever seen the nucleus before.)
- that the nucleus had craters and other surface features
- that evaporation occured only from specific jets, or cracks in the surface
- how big the coma is, compared to the actual nucleus (100,000 miles vs. 15 miles)
- that instead of being bright like a surface made of ice, the nucleus was "dark" as if the ice were covered with something
- how the magnetic field of the Sun responded to the presence of the comet coma
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