Comets are thought to represent the most pristine samples of material left over from the formation of the solar system. Thus, their composition holds important clues about the physical processes at work during that time. Moreover, comets may well have supplied the early Earth with much of its water and organics. At millimeter and submillimeter wavelengths, it has become possible to observe the molecular constituents of cometary ices as they sublimate from the nucleus. Mapping, for which the LMT will be the premier instrument in the world, is key to distinguishing among the chemical and physical processes that take place in the cometary environment, such as direct sublimation from the icy nucleus, chemical processing in the coma, and photodissociation of larger molecules. The first detection of new cometary molecules has also been accomplished by our group.
Cometary observations have shown that there is a striking similarity between the composition of comets and the composition of the icy mantles observed on interstellar grains. This has led to an appreciation that the physical processes at work in the interstellar medium are similar to those that were operating during the formative states of the solar system. Some investigators even speculate that this similarity arises because interstellar grain mantles survived accretion into the solar system and were incorporated into the comets. In either case, study of the chemical and physical processes at work in interstellar clouds will lead to an improved understanding of the origins of the molecules observed in comets and the physical conditions under which they were formed.