The Michigan Mars Environmental Chamber: Preliminary Results and Capabilities

Introduction: We have developed the Michigan Mars Environmental Chamber (MMEC) to simulate the entire range of Martian surface and shallow subsurface conditions with respect to temperature, pressure, relative humidity, solar radiation and soil wetness. Our goal is to simulate the Martian diurnal cycle for equatorial as well as polar Martian conditions and test the hypothesis that salts known to exist in the Martian regolith can deliquesce and form brine pockets or layers by freeze-thaw cycles. Motivation: Liquid water is one of the necessary ingredients for the development of life as we know it. The behavior of various liquid states of H₂O such as liquid brine, undercooled liquid interfacial water, subsurface melt water and ground water has to be understood in order to understand the potential habitability of Mars for microbes and future human exploration. It has been shown that liquid brines are ubiquitous in the Martian polar regions [1, 2, 3] and microbial communities have been seen to survive under similar conditions in Antarctica's Dry Valleys [4]. Chamber Description: The MMEC is a cylindrical environmental chamber with an inside volume of 64 cm diameter by 160 cm length. The temperature range that can be simulated is 145 K to 500 K. The temperature is controlled through an automated control system using a thermal plate system with embedded cartridge heaters and a liquid nitrogen cooling loop. Furthermore, the temperature can be measured at eight variable locations inside the chamber. The pressure is controlled through an automated control system with attainable pressures ranging from 10 Pa to 10⁵ Pa of pure CO₂. Additionally, water vapor can be added to the chamber through a separate temperature and pressure controlled H₂O bath to change the relative humidity. The relative humidity is determined by measuring the frost point using a chilled mirror hygrometer and the full range of relative humidity values can be achieved. The soil wetness is measured using a microwave ring resonator soil wetness sensor [5]. Also, we can detect brine formation using a Raman spectrometer that measures spectral changes in the O-H stretching vibration region. Spectral reflectance measurements can be performed in the MMEC as well. A Xe-lamp will be used to simulate the solar radiation spectrum reaching the Martian surface and a camera will measure the spectral reflectance of the soil-ice mixture. The obtained soil wetness and spectral reflectance values are very important to support satellite estimations and numerical models. Acknowledgement: This research is supported by a grant from the NASA Astrobiology Program: Exobiology and Evolutionary Biology. Award #09-EXOB09-0050. References: [1] Renno, N. O. et al. (2009) JGR, 114, E00E03. [2] Zorzano, M.-P. et al. (2009) GRL, 36, L20201. [3] Möhlmann, D. and Kereszturi, A. (2010) Icarus, 207, 654-658. [4] Mikucki, J. A. et al. (2009) Science, 324, 397. [5] Sarabandi, K. and Li, E. S. (1997) IEEE GRS, 35, 1223-1231.