Reflectance and Raman spectroscopy of anhydrous carbonates for their identification at the surface of planetary bodies.

Introduction Carbonate minerals are ubiquitous on Earth, on all terrestrial planets and on many satellites and small bodies, in particular asteroids. These minerals are identified through remote sensing using either visible and near infrared reflectance spectroscopy but also since recently Raman spectroscopy. These techniques, as well as mid-infrared spectroscopy, are also very frequently used in the laboratory to identify the various anhydrous, hydroxylated and hydrated carbonates phases.In this talk we first report on an extensive ongoing experimental study of all types of carbonates by Visible, near and mir infrared and Raman spectroscopy of series of natural and synthetic samples, coupled with DRX and EPMA analysis to determine their mineralogical purity and their effective composition. We will focus here on the anhydrous calcite and dolomite groups including most of the rhombohedral carbonates.In the second part we report on the detailed analysis of their spectra in order to finely determine the band positions, width and intensity of the bands as a function of composition (Ca, Mg. Fe, ). We also provide a vibration mode attribution to all the bands. Coupled with an exhaustive compilation and a critical review of the literature on the spectroscopic properties of these carbonates, this allows us to build accurate band list data to be ingested in the new band list database of the SSHADE database infrastructure (www.sshade.eu). These absorption and Raman spectral information for individual minerals as well as for solid solutions (e.g. the magnesite-siderite solid solution) are invaluable for the community, and are a type of information still critically missing to easily interpret laboratory, field or astronomical spectra.Carbonate samplesA large set of samples (over 100) covering the anhydrous calcite and dolomite groups and including most of the rhombohedral carbonates (calcite, dolomite, ankerite, magnesite, siderite, rhodochrosite, smithsonite, sphaerocobaltite, kutnohorite, otavite and gaspeite) has been collected for this study. Most of the samples are of natural origin with a variety of composition, but a few pure minerals have been synthesized at ISTerre laboratory to complete the set, especially some hard-to-find natural end-members. They come from various sources, from the OSUG collection, from dealers and local collectors as well as from personal field collection in the mountain ranges around Grenoble. For the reflectance spectra part of the mineral have been grinded and sieved to either