Title: Comet Halley: A carrier of interstellar dust chemical evolution
Abstract: Cometary material, as deduced from comet Halley results, bears a remarkable resemblance to the chemical and morphological structure of a primitive aggregate of interstellar dust. The principal clues are found in 1) the sizes of cometary dust, 2) the non volatile organics in cometary dust, 3) the surface albedo, 4) the physical and photochemical break-up of the dust molecules in the coma via the appearance, for example, of CN and very abundant C+ ions. 5) the high surface temperature but low internal temperature. 6) low comet density. 7) solar orientation of gas and dust jets. 8) low C/O ratio in coma. There are several reasons to expect no significant modification of the interior of comet Halley since it was formed 412 thousand million years ago. The proven presence of a major complex organic dust component along with the low comet density implied by the low albedo - and large size - combine to provide further confirmation of the possible contribution of comets to the origin of life.