Towards Representative Infrared Phobos Simulants: Design, Iteration, and Evaluation

The upcoming JAXA Martian Moons eXploration (MMX) mission aims to clarify key unknows about Phobos and Deimos and reveal the long-debated origin of Mars’ moons. The MMX Infra-Red Spectrometer (MIRS) will help to determine the surface structure, composition and mineralogy of Phobos. Through these and other observations, MMX represents the valuable opportunity to increase knowledge on small bodies, Mars and the early Solar System.The aim of the European Space Agency’s Vulcan Analogue Sample Facility is to support and de-risk exploratory missions through simulant research and testing, and is the driving force for this project. The incorporation of several European instruments onboard MMX, including the CNES-led MIRS, provides further motivation.Several Phobos simulants produced by academic and commercial groups have been utilized throughout the preparatory stages of the mission, including UTPS, OPPS and PCA/PGA [1,2,3]. However, gaps remain in the properties represented and there is yet to be a simulant which represents the spectral profile of the moon in full. Phobos is a spectrally dark and largely featureless body, although it has regions which differ in the spectral slope. Most of the surface is the steeply sloped red unit, except for the area around Stickney Crater, which is a flatter blue unit [4]. As most existing Phobos simulants are global, they also do not demonstrate the slope variation on the surface.At the Vulcan Facility, six preliminary simulants were created to assess the available candidate materials in their suitability in representing Phobos regolith in the near infrared, compared to observational data from orbiters. The core aim with these simulants was to display the spectral features present (~0.65µm and 2.7µm) and represent the mineralogy. The results from these are being used to develop an improved, more representative simulant following the initial design. Beyond this more general simulant, the goal of this work is to produce individual simulants for the red and blue units of Phobos’ surface. References: [1] Miyamoto et al., 2021. Earth Planets and Space, 73:1 [2] Wargnier et al., 2023. Monthly Notices of the Royal Astronomical Society, 524:3 [3] Landsman et al., 2021. Advances in Space Research 67:10. [4] Fraeman et al., 2014. Icarus, 229.