# Interface Direct Shear Tests on JEZ-1 Mars Regolith Simulant
## 2 Materials  
### JEZ-1 Mars Regolith Simulant  
A Mars Jezero Crater Delta simulant JEZ-1 was selected for the research of the Martian regolith-structure interface. The Jezero Crater Delta Simulant (JEZ-1) was designed by the CLASS Exolith Lab at the University of Central Florida to simulate anticipated materials in the Jezero Crater Deltas that are now being investigated by the NASA Mars 2020 Perseverance Rover. In general, the mineralogy, chemistry, and grain size distribution of the regolith throughout the Jezero deltas are likely variable. The simulant is made up of MGS-1 mineralogy [3], smectite clay, Mg-carbonate, and additional olivine (Table 1), which have been detected in the Jezero Crater Delta deposits by orbital remote sensing. The other mineral components and major bulk elemental chemistry are presented in Tables 1 and 2, respectively. The primary shape and particle size of the simulant JEZ-1 can be seen from photograph in Figure 1a. The particle size ranges between <0.04 \(\upmu\)m and 500 \(\upmu\)m, which is composed of angular and sub-angular shapes from SEM images that are provided in Figure 1b,c. The grain size distribution curves of JEZ-1 and another two previous stimulants (i.e., JSC \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Component** & **wt.\%** & **Component** & **wt.\%** \\ \hline Olivine & 32.0 & Plagioclase & 16.0 \\ \hline Glass-rich basalt & 13.5 & Pyroxene & 12.0 \\ \hline Mg-carbonate & 11.0 & Smectite & 6.0 \\ \hline Mg-sulfate & 2.4 & Ferrihydrite & 2.1 \\ \hline Hydrated silica & 1.8 & Magnetite & 1.1 \\ \hline Anhydrite & 1.0 & Fe-carbonate & 0.8 \\ \hline Hematite & 0.3 & - & - \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Mineralogy of JEZ-1 (results from Exolith Lab). \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Component** & **wt.\%** & **Component** & **wt.\%** \\ \hline SiO\({}_{2}\) & 44.2 & TiO\({}_{2}\) & 0.2 \\ \hline Al\({}_{2}\)O\({}_{3}\) & 11.3 & Cr\({}_{2}\)O\({}_{3}\) & 0.3 \\ \hline FeO\({}_{\text{T}}\) & 9.5 & MnO & 0.1 \\ \hline MgO & 25.9 & CaO & 3.5 \\ \hline Na\({}_{2}\)O & 1.9 & K\({}_{2}\)O & 0.3 \\ \hline P\({}_{2}\)O\({}_{5}\) & 0.6 & SO\({}_{3}\) & 2.1 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Bulk major element chemistry of JEZ-1 (CRF results from Exolith Lab). Mars-1 and MMS-1) are provided in Figure 2. From the grain size distribution test, the effective grain size (\(d_{10}\)) of JEZ-1 is 4.9 \(\upmu\)m and the coefficient of uniformity (\(C_{\rm u}\)) is equal to 14.3, indicating that JEZ-1 is a well-graded Martian simulant. The mean grain size (\(d_{50}\)) of JEZ-1 is 57.2 \(\upmu\)m, lower than the \(d_{50}\) values of JSC Mars-1 (200 \(\upmu\)m) and MMS-1 (120 \(\upmu\)m), according to the data from [7; 8]. This highlights that JEZ-1 has finer grains than the other two simulants (i.e., JSC Mars-1 and MMS-1), in agreement with the fact that the Jezero Crater Delta contains clays, as revealed by the Mars Reconnaissance Orbiter's CRISM instrument. Clays only form in the presence of water, it is the reason why Jezero Crater Delta can provide a great place for the scientific goal of the Mars 2020 mission. It aims at seeking a potentially habitable environment that may possess preserved signs of ancient microbial life. For example, scientists have found that clays exist in the Mississippi River Delta on Earth, where microbial life has been found embedded in the rock. Moreover, from other laboratory test results, the uncompressed bulk density of JEZ-1 is 1.54 g/cm\({}^{3}\). The maximum void ratio (\(\epsilon_{\rm max}\)) and minimum void ratio (\(\epsilon_{\rm min}\)) are 0.798 and 0.381, respectively. Figure 1: Photograph of Martian regolith simulant JEZ-1: (**a**) typical particles; and representative SEM images of JEZ-1 with magnification of: (**b**) \(\times\)50, (**c**) \(\times\)100. Figure 2: Grain size distribution curves of JEZ-1, JSC Mars-1 and MMS-1.