Abstract: The main component of the Martian atmosphere is CO2. If these CO2 can be efficiently converted into O2 and CO by low-temperature plasma for utilization, the launch load cost of life support system can be drastically reduced for deep space mission and the life support capabilities will be further improved. Low-temperature plasma shows a promising potential for CO2 dissociation and conversion. It can produce plenty of reactive species during the discharge, which enables the efficient CO2 conversion at a gas temperature of only a few hundred degrees. A DC microslit plasma reactor on submillimeter scale and with several Watts input power was designed, which can be used for the CO2 conversion at low gas temperature. The discharge parameters, such as discharge current and input power were measured. The optical emission spectroscopy (OES) method was adopted for identification of excited species and their variations with supply voltage and dilution gas content. The plasma vibrational and gas temperatures were measured based on the nitrogen vibrationrotation spectra. It is found that all of the three dilution gases (Ar, He, N2) can enhance the dissociation process, while adding helium gas can improve the CO2 ionization process. The excited species produced by dilution gases promote the CO2 dissociation through Penning dissociation channel because of their high energy. Since the excited state of helium (He*) has an energy higher than CO2 ionization threshold, it leads to an increase of CO2 ionization process. The nonequilibrium feature of microplasma was verified by large deviation between vibrational temperature (4400~4800 K) and gas temperature (450~600 K). Therefore, with reasonable plasma discharge and reactor structure design, the energy can be selectively injected into the vibrational species, which can further increase the CO2 vibrational dissociation.

Key words: CO₂ dissociation, optical emission spectroscopy, microplasma, in-situ resource utilization, Martian atmosphere