Core of Halleys Comet
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Core of Halley's Comet

October 15, 2009
This is slide 4 of 12 from the second Giotto slide set. The following caption is the one originally provided with the slide set.

For the first time images of a comet nucleus could be taken during the encounter with comet Halley. The nucleus was larger than expected (16 km x 7.5 km x 8 km) implying a lower albedo (- 0.04) than predicted. It was confirmed that the nucleus can be described as a 'dirty snowball' or even as an 'icy dirt ball'. The nucleus is probably very fluffy and might have a bulk density as low as 0.3g cm-3.

The discovery of gas and dust jets being emitted from the nucleus suggested that only about 10% of the surface was active. The structure clearly identified in the images, such as hills and depressions, were obviously related to variations in the surface topography. The insert explains in graphic form the different surface features of comet Halley, as observed in the actual image.

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