The present work introduces and compares promising process concepts for in situ methanation on Mars based on an extensive simulation study. Specifically, we propose to optimize the H2/CO2 ratio and the recycle of unreacted H2 and CO2 species, to minimize the process complexity and product purification efforts. We found that H2/CO2 ratios above the stoichiometric value of 4 are beneficial, since practically full conversion and selectivity can be achieved. This minimizes the amount of unconverted reactants and byproducts for downstream processing and thereby the process complexity. The remaining separation of CH4 and H2 is feasible in principle and modelled by a thermodynamic approach.