Calculation of Europa relevant solutions salinity using RLS-like data. A next step for Mars payload

With a growing interest on icy worlds and the exploration of the Outer Solar System different proposals for different missions have been considered in the last years. One the most interesting planetary bodies for a lander-kind mission is Europa, thanks to its astrobiological implications. The presence of an underlying liquid ocean, exchanging material with the surface of its ice crust, makes of great interest the use of a lander with capabilities to characterize the possible organics present in this icy world, but also to understand the environment in which those organics could be found. Raman spectroscopy has the unique capability to detect these organics and provide information about the aqueous environment and the different salts in play. In this work we focused in the analyses of different solutions using two different salts, one that can be directly detected in the solution (magnesium sulfate) and other that cannot be directly detected by Raman spectroscopy (magnesium chloride). Despite of not being directly detected, the presence of salts is known to affect the vibrational dynamics of the water, hence, this changes can be observed by Raman spectroscopy, more concisely in the OH vibrations region of its Raman spectrum. Through a process of band fitting to separate the five individual components of this spectral region and adding inputs from the features of the directly observed salt, we have developed a different models to calculate the salinity of different mixtures. Starting with univariate models useful for one component solutions, these models failed, as expected, to calculate the quantity of one of the salts when the other was also present in the solution. Using this band fitting process as dimensional reduction method for our data set, we trained a model using Artificial Neural Networks that successfully could calculate the cuantity of each salt in these binary solutions, and also characterize the ones with just one salt.