Micrometeoroids as Carriers of Organics: Modeling of the Atmospheric Entry and Chemical Decomposition of Sub-Millimeter Grains

One of the most exciting perspectives in astrochemistry lies in the part played by molecules in space, since they might have a crucial role in the Earth's chemical evolution and origin of life. Life-related molecules may reach the Earth's surface embedded in solid particles: the mineral composition of these grains may provide a thermal protection against the high temperatures during the atmospheric entry process. While evaluating several mineral phases, the most interesting candidates are those present on the surface of several bodies of our Solar System and have an association with organics on Earth: carbonates, mainly of magnesium and calcium, and calcium sulfates. This chapter reviews recent studies performed using computer models: they include the dynamics of the atmospheric entry, the kinetics of the chemical reactions involved, and heat transfer processes. Results demonstrate that the thermal decomposition reaction of the materials considered provides a check of their feasibility as organics carriers and partially mitigates the heating in the first stage of the entry process. Another important aspect is the primordial atmospheric composition: the actual nature of the main atmospheric molecules affects significantly the grain heating, showing that this overlooked feature of meteoroid entry models may play an important role.