In recent years, NASA has conducted experiments aiming to develop ISRU technologies. In one such experiment, the Martian atmosphere was simulated with an Atmospheric Processing Module as part of the MARCO POLO (Mars Atmospheric and Regolith Collector/Processing for Lander Operations) project . The CO₂ was collected via a freezer and subsequently hydrogenated using 88 g of a 0.5 wt-% ruthenium on alumina catalyst to methane in a Sabatier reactor . During the initial start-up phase, hydrogen was supplied in excess of the stoichiometric ratio (4.5:1) . The unreacted hydrogen is recovered via a membrane and returned to the reactor with some methane. After the start-up phase, the system inlet composition is reduced to the stoichiometric H2/CO2 ratio of 4:1. Due to the recycling of unreacted H2, the reactor inlet H2/CO2 ratio exceeds the stoichiometric value of 4:1. However, no further specification is provided regarding the precise H2/CO2 ratio at the reactor inlet. With a CO2 conversion of 99.9% at a reaction temperature of 450°C the system demonstrates the production of 32 g h -1 methane with a purity of 99.9% . Apart from that, an investigation into the impact of the H2/CO2 ratios on CO2 conversion and product purity has not been included in the research's scope. Furthermore, a Sabatier reactor system is currently undergoing testing on the International Space Station (ISS) as part of the oxygen recovery system. This system is designed to convert the CO₂ produced by astronauts into methane and water . The details of the final version of the system are not yet available. Nonetheless, information pertaining to a developmental version has been made public by NASA .