Mars Simulation Facilities: A Review of Recent Developments, Capabilities and Applications

Understanding the habitability of both past and present Mars continues to evoke scientific interest, particularly now that there is growing evidence of previous, vastly available liquid water and a warmer Martian climate. While today the surface of the Red Planet is barren and dry, the presence of hydrated minerals like phyllosilicates and sulphate minerals may indicate that the planet was once much more conducive to the emergence of life. These observations are the driving force behind investigations into possible biomarkers and signs of extinct life in the context of Mars. While Mars orbiters, landers and rovers have significantly improved our understanding of the planet’s past, Earth-based experiments are necessary to support those missions technically and scientifically. Simulation facilities replicating the Mars climate are used to test instruments before flight and investigate interactions of biomarkers with the Martian environment. Here, we review some exemplary, modern ground-based facilities with a focus on sample species relevant to astrochemistry and astrobiology. The presented Mars simulation facilities utilize a variety of technical implementations and thus are capable of simulating all of the major environmental parameters on the Martian surface: atmosphere, temperature and electromagnetic solar radiation. Depending on the subject-specific requirements of each investigation, these setups integrate various simulation features and different measurement techniques. A few examples of particularly remarkable simulation facilities include: the Planetary Atmospheres and Surfaces Chamber and the MARTE Simulation Chamber at INTA's Centro de Astrobiologia, Spain, which are unique in terms of integrated measurement techniques and Martian dust simulation; the Mars Simulation Facility, one of several planetary simulation chambers based at the German aerospace center DLR, Germany, is specialized in humidity measurements and sample analysis using PAM fluorometry; the Mars Simulation Chamber/Planetary Atmosphere Chamber at the Kennedy Space Center, USA, integrates an optical filter system to simulate ultraviolet-light attenuation by Martian dust; the Mars Environmental Simulation Chamber at Aarhus University, Denmark, provides atmospheric cooling and the possibility to extract samples mid-experiment. Many state-of-the-art technologies used in Mars simulation chambers are also integral to space-based experimental platforms, such as the planned OREOcube/Exocube experiment on the International Space Station. In-situ space experiments are highly complementary to Martian simulations, particularly in providing supplementary knowledge about the influence of broad-range radiation exposure and the true solar spectrum.