Abstract: | The investigation of the volatile material in the coma of comets is a key to understanding the origin of cometary material,
the physical and chemical conditions in the early solar system, the process of comet formation, and the changes that comets
have undergone during the last 4.6 billion years. So far, in situ investigations of the volatile constituents have been confined
to a single comet, namely P/Halley in 1986. Although, the Giotto mission gave only a few hours of data from the coma, it has
yielded a surprising amount of new data and has advanced cometary science by a large step. In the present article the most
important results of the measurements of the volatile material of Halley's comet are summarized and an overview of the identified
molecules is given. Furthermore, a list of identified radicals and unstable molecules is presented for the first time. At
least one of the radicals, namely CH2, seems to be present as such in the cometary ice.
As an outlook to the future we present a list of open questions concerning cometary volatiles and a short preview on the next
generation of mass spectrometers that are being built for the International Rosetta Mission to explore the coma of Comet Wirtanen.
This revised version was published online in June 2006 with corrections to the Cover Date. |