Determining a good Phobos simulant: An organic analysis based on spectral similarities between Phobos, Tagish Lake, and CM chondritic meteorites

The Japan Aerospace Exploration Agency (JAXA) is undertaking the Martian Moons Exploration Mission which presents a valuable opportunity to understand Phobos’ surface environments by landing spacecraft on its regolith to collect surface soil samples. Several Phobos simulations have been developed, such as the UTPS-TB (University of Tokyo Phobos Simulant, Tagish Lake based) to aid engineering and scientific evaluation experiments. This study evaluates the accuracy of the UTPS-TB by comparing its organic and elemental composition to that of planetary bodies spectrally similar to Phobos. UTPS-TB was not initially created to simulate organic content, but this study assesses its potential suitability for use in organic analysis. A comparative analysis is conducted based on previous literature detailing spectroscopic signatures at the visible-to-near-infrared and mid-infrared wavelengths of Phobos and other planetary bodies. It is concluded that its reflectance spectrum is overall most similar to that of CM2 chondrites, Tagish Lake meteorite, and D-type asteroids. Key characteristics are discussed in depth, such as a reduced hydrated band at 2.7 µm, an anhydrous nature, olivine and pyroxene content, as well as a dark component containing pyrite, magnetite, and iron-nickel content. The UTPS-TB exhibits characteristics of a pristine planetary body. Thermogravimetric mass loss experiments reveal low grade metamorphic profiles similar to that of Tagish Lake and CM chondrites. Derived ratios between molecular water, organic and hydroxide, phyllosilicate, and carbonate content are comparable to CM chondritic ratios, with a dominant phyllosilicate component. Elemental analysis of carbon, hydrogen, nitrogen, and sulphur content indicates that H and C content are consistent with expected low levels of alteration. The organic content ratio is notably very similar to that of CM2 Murchison. UTPS-TB, by this assessment, is a reliable simulation of Phobos. Amino acid analysis via ultra-performance liquid chromatography fluorescence detection and quadruple time-of-flight hybrid mass spectrometry (UPLC-FD/QToF-MS) of the UTPS-TB is currently being conducted.