Deep neural networks for surface composition reconstruction from in-situ
exospheric measurements at Mercury
Abstract
Surface information derived from exospheric measurements at planetary
bodies complements surface mapping provided by dedicated imagers,
offering critical insights into surface release processes, dynamics of
various interactions within the planetary environment, erosion, space
weathering, and planetary evolution. This study explores a method for
deriving the elemental composition of Mercury’s regolith from in-situ
measurements of its neutral exosphere using deep neural networks (DNNs).
We present a supervised feed-forward DNN architecture—a network of
fully-connected neural layers, the so-called multilayer perceptron
(MLP). This network takes exospheric densities and proton precipitation
fluxes, derived from a simulated orbital run through Mercury’s
exosphere, as inputs and predicts the chemical elements of the surface
regolith below. It serves as an estimator for the surface-exosphere
interaction and the processes leading to exosphere formation, including
micrometeoroid impact vaporization, ion sputtering, photon-stimulated
desorption, and thermal desorption. Extensive training and testing
campaigns demonstrate the MLP DNN’s ability to accurately predict and
reconstruct surface composition maps from simulated exospheric
measurements. These results not only affirm the algorithm’s robustness
but also illuminate its extensive capabilities in handling complex data
sets for the creation of estimators for modeled exospheric generation.
Furthermore, the tests reveal substantial potential for further
development, suggesting that this method could significantly enhance the
analysis of complex surface-exosphere interactions and reduce
uncertainties in planetary exospheres models. This work anticipates the
analysis of data from the SERENA (Search for Exospheric Refilling and
Emitted Natural Abundances) instrument package aboard the BepiColombo
Mercury Planetary Orbiter, with its nominal phase starting in 2026.