Physical properties as indicators of liquid compositions: Derivation of the composition for Titan's surface liquids from the Huygens SSP measurements

We present a method for inferring the relative molar abundance of constituents of a liquid mixture, in this case methane, ethane, nitrogen and argon, from a measurement of a set of physical properties of the mixture. This problem is of interest in the context of the Huygens Surface Science Package, SSP, equipped to measure several physical properties of a liquid in case of a liquid landing on Saturn's moon Titan. While previous models emphasized the possibility of verifying a certain model proposed by atmospheric composition and equations of state, we use an inverse approach to the problem, i.e. we will infer the liquid composition strictly from our measurements of density, refractive index, permittivity, thermal conductivity and speed of sound. Other a priori information can later be used to improve (or reject) the model obtained from these measurements.