Introducing the First Greek Martian and Lunar Simulants

Introduction:

The interest for the Moon has risen with many missions being planned for the Moon surface culminating to the Artemis missions, spearheading a new era of human presence on the lunar surface. At the same time a recent paper (1) provided an overview of the current state of Martian research and understanding. A common theme on both of these endeavors is the requirement of extensive research across the fields of astrobiology, the frontier of ISRU technologies and habitability research under simulated conditions of those environments. A large number of Lunar and Martian Simulants has been developed over the past decades, often though produced rapidly with lower fidelity to satisfy demand  (2). Towards this purpose, our group made an effort to develop such materials, since in Greece only potentially analogue locations for simulated research exists. This research was initiated with the introduction of a new simulant classification system, after having highlighted a number of issues that pertain on the facet of Martian Simulants. We here report on the development of new simulants we produced for the Lunar and Martian surfaces.

Methodology:

Initially, we scrutinised the literature focusing on three focal points of research to collect data on the composition of Lunar and Martian surface location, the Lunar Curator Facility, the Analyst’s Notebook and the respective publications on simulant production, in order to identify which datasets have been already utilised. Based on these data, we selected one Lunar and two Martian locations to produce simulants. For the Moon we selected the 15260 Apollo Sample which has been extensively studied. (3) For Mars, we opted for the Rocknest and Gobabeb targets, which are 2 of the most cited and compared sites for simulant production. More specifically, for Moon we utilised the chemical analysis provided by (3) and for Mars those provided by (4).

For the simulant development we collected a number of igneous rock samples from the field, and acquire a number of pure mineral phases, for use as individual components, presented in table 1. All of the materials utilised by our team in the synthesis of the simulants have been firstly crushed and grounded to a grain fraction of under 1 mm. A portion of the material was further crushed in under 250 μm, and later refined for XRD analysis. Each sample was then scanned in three random locations via SEM-EDS and the average analysis was taken as the sample’s chemistry. Thus, via those two analytical techniques, the background of the chemical and mineralogical make up of our inventory of materials was established.

In order to establish the quality of our simulants we utilised the Figure of Merit (FOM) proposed by (5) and applied by (6). By using this system you can deduce the accuracy of your simulant based on how close the percentages of chemical oxides are to the reference sample.

Simulants:

Up to the point of writing, our team has produced a total of four simulants, two for the Moon and two for Mars. Initially a production of two prototypes for a Lunar and Martian simulant, Simulant #1 and #2 respectively, were made by mixing three individual mineral and rock components to verify the method of synthesis and correct any mistakes. However, even at that stage the theoretical FOM of our Simulant #1 was above 95% when compared to the Apollo 15260 sample, and Simulant #2 for Mars had FOM 90,7% and 89% for the Rocknest and Gobabeb targets respectively. (Table 1) 

Based on the preliminary results we produced refined simulants, Simulant #3 and #4 for Moon and Mars respectively, using additional components materials as showed in table 1. Thus, Simulant #3 for the Apollo 15260 sample reached FOM of almost 96% and Simulant #4 for Mars reached FOM of 94,6% and 91,6% for the Rocknest and Gobabeb targets, respectively. (Table 1) 

Future Goals:

The goal of this project is to try and make simulant materials for Moon and Mars more accessible to the scientific community, but also provide materials of higher fidelity and accuracy. Based on their chemistry, the FOM values on the martian simulants are higher than those presented in (6), suggesting that our endeavor has significant prospects compared with the fidelity of other simulants and providing the confidence that higher accuracy simulants can be synthesised. Furthermore, an additional number of analytical techniques will be used to verify their fidelity. Additionally, by the acquisition of additional mineral phases and rock samples we are targeting to increasing the FOM values. A short term requirement is also the availability of well-known simulants in order to be used in the OxR ESA project (7).

References:

• H. G. Changela et al., Mars: new insights and unresolved questions. International Journal of Astrobiology, 1-33 (2021).
• G. H. Peters et al., Mojave Mars simulant—Characterization of a new geologic Mars analog. Icarus 197, 470-479 (2008).
• A. Duncan et al. (1975) Interpretation of the compositional variability of Apollo 15 soils. in Lunar and Planetary Science Conference Proceedings, pp 2309-2320.
• C. Achilles et al., Mineralogy of an active eolian sediment from the Namib dune, Gale crater, Mars. Journal of Geophysical Research: Planets 122, 2344-2361 (2017).
• C. Schrader et al. (2009) Lunar regolith characterization for simulant design and evaluation using figure of merit algorithms. in 47th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition, p 755.
• L. E. Fackrell, P. A. Schroeder, A. Thompson, K. Stockstill-Cahill, C. A. Hibbitts, Development of Martian regolith and bedrock simulants: Potential and limitations of Martian regolith as an in-situ resource. Icarus 354, 114055 (2021).
• ESA (2022) https://www.esa.int/Enabling_Support/Space_Engineering_Technology/Moon_and_Mars_superoxides_for_oxygen_farming.

Table 1. Simulant components and Figure of Merit percentages.