In order to calculate global rate coefficients for atmospheric Martian entries situations, a detailed kinetic model using a state-to-state approach is developped for two important processes: dissociation/recombinaison of CO2 and ionization/recombinaison of Carbon. The behavior of the species involved is governed by the general balance equation including forward and backward elementary processes whose rate coefficients are in part based on experimental data. Extrapolation methods are used when necessary. During the population densities time-evolution, a quasi steady state can be identified: a global rate coefficient can be derived only during this state. The rates therefore obtained are fitted under a modified Arrhenius law and some of them are finally compared with experimental results.