Concluding Remarks

Despite the fact that comets are minor bodies in the solar system, they constitute an important link between molecules present in the interstellar clouds and, those that existed when the solar system formed. Their study is one of the most challenging objectives in the field of modern planetary science. Besides that, there is a theory that suggests that comets could have contributed to the prebiotic synthesis of molecules on the primitive Earth.

A variety of sources of energy are crucial for the processing and evolution of ice in comets and oher bodies. The form of deposition of this into the sample is different for each type of source. Evidently, the importance of a source is a complex combination of abundance, availability, and effectiveness. In reference to UV radiation, the most abundant source of energy in regions close the Sun, its effects could be restricted to the surface of comets. For other radiation sources such as ions, the interaction could be deeper and, as a consequence, the effects are not confined to a small layer on the surface, but, instead of that, they may be distributed.

The real and net contribution of each source of energy is not well understood nowadays. In fact, two key sources are considered as the main contributors to the modification of ice throughout the solar system: cosmic radiation (ions) and UV radiation. This is why, most of the time, the icy laboratory samples are studied irradiating with ions and UV radiation.

Evidently the complex nature of comets demands an integral study of those bodies. It this review, only one aspect has been considered, the generation of compounds from the irradiation of ices. There is a great deal of evidence that irradiation of simple ices produce a large amount of organic molecules. Many of the substances identified through IR detection techniques, match the signatures obtained from those of observations. However, not only the production of different compounds is important, but also the stability of molecules, the process of loss in mass (sputtering), the change in structure of the ice, and thermal annealing. It is difficult to follow all of the effects at the same time. However, many efforts are being carried out for the better understanding of comets.

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