Thermal Reactivity Dynamics in Interstellar Ice

Ever more complex organic molecules are being observed in space. Star forming regions, planets and small bodies in our solar system exhibit a rich molecular diversity which culminates in the diverse molecular composition of meteorites. While many complex organic molecules can be formed through gas-phase reactions, solid-state chemistry on interstellar grains plays an important role. In this chapter, we discuss the specific case of purely thermal reactions in ice mantles, which do not require any extra energy input other than thermal energy. Thermal reactions are important because they are not limited by UV or cosmic rays fluxes or the scarcity of radicals on the surface because they involve only dominant mantle molecules. Thermal reactions represent an important step in the formation of complex organic molecules that constitute the primitive material of comets and asteroids.