Is the nucleus of comet Halley a low density body?

An important finding of the Vega and Giotto missions to comet Halley was evidence that the cometary nucleus is a consolidated body^1-5. The shape, size and rotation of the nucleus were studied as well its albedo^1-3 and surface temperature^6-8. In determining the nature of the cometary nucleus, a value for the average density ρ would be informative. In this paper we estimate ρ to be 0.6 ^+0.9-0.4g cm^-3 compatible with the 'snow-ball' models of the nucleus, although a more compact ice structure could correspond to such a density value.