Metal-CO2 propulsion is less known than in-situ resource utilization (ISRU) technologies. This concept, based on using Martian carbon dioxide as an oxidizer in jet or rocket engines, offers the advantage of no chemical processing for CO2 and thus requires less power consumption than ISRU alternatives. In this paper, we study the burning behavior of the Mg in a CO2 atmosphere to assess the feasibility of using Mg/CO2 reactions as an in situ resource utilization technology for rocket propulsion and energy generation on other planets. From the experimental results, we can see that the critical ignition temperature increases with increasing the particle size and decreases with increasing the ambient pressure. In the CO2 atmosphere, we found the complicated sequence of interaction modes including pulsating combustion in a wide range of ambient temperatures. The pulsation frequency is determined by the sample temperature at the phases of slow heterogeneous combustion between the flashes. The combustion mechanisms are discussed with consideration of processes in both a surface film and gas phase.