In the first work package, we had a look at fragments of small bodies that were delivered to Earth, by setting up and developing a new analytical technique in Grenoble (Nano-infrared spectroscopy). We developped analytical protocols as well sample preparation protocols, in order to build and validate our approach (published in paper led by Solarys Postdoc Phan 2021,2022,2023). We could show that the technique can be used to study mixtures of silicates and organics, and applied this method to the most primitive samples we have from the Early solar system (Phan et al., 2024).
We also developed protocol to produce porous surfaces made of silicate and sub-µm particles of silicates, sulfides and organic materials. We have also set-up a methodology that enables to incorporate these small grains inside water-ice sphere, and produce hyper-porous samples by sublimation of the ice. This work led to several important results. First we showed that there is a small grains degeneracy for weakly absorbing material. In other words, when small grains are present (<1 µm), as expected in comets and primitive small bodies, the diagnostic signature of minerals decrease significantly (Sultana et al; 2020). We also show that the presence of elevated porosity maximize these effects. Last we added small opaque particles to the mixture and could reproduce all known optical properties of cometary matter and primitive asteroids (Sultana et al., 2023).
Our laboratory characterization have been used to compare and confront to available observations of the small bodies population. This is where the most striking results have been obtained. First we have used the sample preparation protocol designed to understand the presence of a peculiar absorption of comet 67P around 3-µm. We have shown that it is due to the presence of ammonium salts, with strong implications for the budget of nitrogen (Poch et al., 2020). Second, we have assessed how much water is present in the main-asteroid belt, based on reflectance spectra obtained on primitive extra-terrestrial samples. From this work we shown that main-belt asteroids appear dehydrated when compared to their asteroidal counterpart, and that the mass of water in the main-belt is of the order of the mass of Enceladus (Beck et al., Icarus 2021). Last, we have started to shade light on the links between primitives meteorites families and dark asteroids types. We have shown that many carbonaceous chondrites are not related to C-type asteroids, and proposed associations of asteroids spectral types to primitive meteorites groups (Eschrig et al., Icarus 2022, Prestgard et al., 2021,2023). Finally, we investigated how asteroid environmental conditions can impact reflectance spectra, with implication for the connection between meteorites and asteroids (Potin et al, 2019, 2020,2021).
Most of the results were shared through publication in peer review journals, conference participation, and last, through open access datasets.
