¹S. De Angelis, ¹C. Carli, ¹F. Tosi, ²P. Beck, ²B. Schmitt, ¹G. Piccioni, ¹M.C. De Sanctis, ¹F. Capaccioni, ³T. Di Iorio, ²Sylvain Philippe
Icarus (in Press) Link to Article [http://dx.doi.org/10.1016/j.icarus.2016.07.022]
¹Istituto di Astrofisica e Planetologia Spaziali, INAF-IAPS, Via del Fosso del Cavaliere 100, I-00133 Roma, Italy
²Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), 414 Rue de la Piscine, F-38400 St-Martin d’Hères (France), France
³ENEA Centro Ricerche Casaccia (ENEA SSPT-PROTER-OAC), Via Anguillarese 301, I-00123 Roma, Italy
Copyright Elsevier

We investigate two poly-hydrated magnesium sulfates, hexahydrite (MgSO4 • 6H2O) and epsomite (MgSO4 • 7H2O), in the visible and infrared (VNIR) spectral range 0.5÷4.0 μm, as particulate for three different grain size ranges: 20-50 µm, 75-100 µm and 125-150 µm. All samples were measured in the 93 K to 298 K temperature range. The spectra of these hydrated salts are characterized by strong OH absorption bands in the 1.0-1.5 μm region, and by H2O absorption bands near 2 and 3 μm. Other weak features show up at low temperatures near 1.75 μm (in both hexahydrite and epsomite) and 2.2 μm (only in hexahydrite). The spectral behavior of the absorption bands of these two minerals has been analyzed as a function of both grain size and temperature, deriving trends related to specific spectral parameters such as band center, band depth, band area, and band width. Hydrated minerals, in particular mono- and poly-hydrated sulfates, are present in planetary objects such as Mars and the icy Galilean satellites. Safe detection of these minerals shall rely on detailed laboratory investigation of these materials in different environmental conditions. Hence an accurate spectral analysis of such minerals as a function of temperature is key to better understand and constrain future observations.

¹Norbert Kömle,²Craig Pitcher,²Yang Gao,³Lutz Richter
Icarus (in Press) Link to Article [http://dx.doi.org/10.1016/j.icarus.2016.08.019]
¹Space Research Institute, Austrian Academy of Sciences, Schmiedlstraße 6, A-8042 Graz, Austria
²STAR Lab, Surrey Space Centre, University of Surrey, Guildford, GU2 7XH, UK
³OHB System AG, Manfred-Fuchs-Straße 1, 82234 Weßling – Oberpfaffenhofen, Germany
Copyright Elsevier

The Powdered Sample Dosing and Distribution System (PSDDS) of the ExoMars rover will be required to handle and contain samples of Mars regolith for long periods of time. Cementation of the regolith, caused by water and salts in the soil, results in clumpy material and a duricrust layer forming on the surface. It is therefore possible that material residing in the sampling system may cement, and could potentially hinder its operation. There has yet to be an investigation into the formation of duricrusts under simulated Martian conditions, or how this may affect the performance of sample handling mechanisms. Therefore experiments have been performed to create a duricrust and to explore the cementation of Mars analogues, before performing a series of tests on a qualification model of the PSDDS under simulated Martian conditions.

It was possible to create a consolidated crust of cemented material several millimetres deep, with the material below remaining powder-like. It was seen that due to the very low permeability of the Montmorillonite component material, diffusion of water through the material was quickly blocked, resulting in a sample with an inhomogeneous water content. Additionally, samples with a water mass content of 10% or higher would cement into a single solid piece. Finally, tests with the PSDDS revealed that samples with a water mass content of just 5% created small clumps with significant internal cohesion, blocking the sample funnels and preventing transportation of the material. These experiments have highlighted that the cementation of regolith in Martian conditions must be taken into consideration in the design of sample handling instruments.