An icy mineralogy package (IMP) for in-situ studies of Titan’s surface Original Research Article

We describe the scientific case for and preliminary design of an instrument whose primary goal is to determine the chemistry (element abundance) and mineralogy (compound identity and abundance) of Titan’s surface using a combination of energy dispersive X-ray fluorescence spectroscopy (EDXRF) and X-ray diffraction (XRD). XRD is capable of identifying any crystalline substance present on Titan’s surface at relative abundances greater than ∼1 wt%, allowing unambiguous identification of, for example, structure I and II clathrates (even in the presence of ice), and various organic solids, which may include C2H2, C2H4, C4H2, HCN, CH3CN, HC3N, and C4N2). The XRF component of the instrument will obtain elemental abundances for 16 < Z < 60 with minimum detection limits better than 10 ppm (including detection of atmospheric noble gas isotopes), and may achieve detection limits of 0.01–1% for lighter elements down to Z = 6 (carbon). The instrument is well suited to integration with other analytical tools as part of a light-weight surface chemistry and mineralogy package. Although considerably less sensitive to elemental abundance than GC–MS (10−2 vs. 10−8) it is likely to be significantly lighter (<0.5 kg vs. 10 kg).The instrument will be able to address the origin and evolution of Titan by measuring the mineralogy and chemistry of bulk crust (water ice/clathrates), excavated impact ejecta (possibly including XRD-identifiable high-pressure polymorphs of ice), and cryolava or ash (distinguishing between ammonia–methanol and sulfate–carbonate magmas). The instrument will also address atmospheric photochemistry and climate history by measuring the mineralogy and chemistry of organic sediments found in various environments, such as dunes, fluvial and peri-lacustrine areas (including possible evaporites), and possibly exhumed from deep reservoirs by mud volcanism. Lastly, the instrument will address Titan’s astrobiological evolution by enabling detection of more complex organic materials (crystalline carboxylic/amino acids or sugars) in areas where sediments have interacted with aqueous solutions.