Abstract
ExoMars is the European Space Agency (ESA) mission to Mars planned for launch in 2018, focusing on exobiology with the primary objective of searching for any traces of extant or extinct carbon-based micro-organisms. The on-surface mission is performed by a near-autonomous mobile robotic vehicle (also referred to as the rover) with a mission design life of 180 sols Patel et al. (2010). In order to obtain useful data on the tractive performance of the ExoMars rover before flight, it is necessary to perform mobility tests on representative soil simulant materials producing a Martian terrain analogue under terrestrial laboratory conditions. Three individual types of regolith shown to be found extensively on the Martian surface were identified for replication using commercially available terrestrial materials Patel (2011), sourced from UK sites in order to ensure easy supply and reduce lead times for delivery. These materials (also referred to as the Engineering Soil Simulants (ES-x) are: a fine dust analogue (ES-1); a fine aeolian sand analogue (ES-2); and a coarse sand analogue (ES-3). Following a detailed analysis, three fine sand regolith types were identified from commercially available products. Each material was used in its o -the-shelf state, except for ES-2, where further processing methods were used to reduce the particle size range. These materials were tested to determine their physical characteristics, including the particle size distribution, dry bulk density, particle shape (including angularity / sphericity) and moisture content. The results are analysed to allow comparative analysis with existing soil simulants and the published results regarding in-situ analysis of Martian soil on previous NASA missions. The findings have shown that in some cases material properties vary significantly from the specifications provided by material suppliers. It has confirmed that laboratory testing is necessary to determine the actual parameters and that standard geotechnical processes are suitable for doing so. The outcomes have allowed the confirmation of each simulant material as suitable for replicating their respective regolith types.