Conclusions

The results reported in the present work give clear indication that the direct comparison of remote and in situ space measurements with laboratory data is a winning approach to interpret observations on cosmic materials. The new method is oriented at simulating formation and processing of cosmic materials in order to achieve the matching to observations by laboratory results complemented by a serious evaluation of the conditions and constraints that may (or may not) justify the presence of candidate compounds in various space environments. In this context, available elemental abundance seem to pose the most critical limitations [22].

Despite the many promising results, several astrophysical problems are still unsolved. The pathway for the amorphous-to-crystalline transition of silicates is still to be determined, accounting for the controversial indications coming from observations in comets, circumstellar and interstellar media. New experiments have been invoked to evaluate the capability that mechanisms, other then thermal annealing, may have in such a process, also depending on the chemical and structural status of the starting material.

The evolution of the aliphatic 3.4 p,m band from diffuse to dense ISM is another open issue. Efficiency of mechanisms that may contribute to the destruction (e.g., UV and ion processing) or the formation (hydrogenation) of the relevant C-H bonds are strongly related to detailed environment characteristics, such as density and temperature. Again, new experiments must demonstrate how the various factors combine in such a complex scenario.

Last but not least, the future in laboratory is also oriented at a more and more detailed comparison of data obtained on actual extraterrestrial samples, such as interplanetary dust particles, that can tell us a story not easily traceable by remote observations only. The next ambitious steps include long standing in situ analyses on comets (e.g., the ESA Rosetta mission) and cometary sample return (e.g., the NASA Stardust mission) by space missions.

These considerations evidence how the basis for a deeper investigation of cosmic materials has been traced and that the future will reserve new fascinating results in such a field.

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