Spectral Mixture Modeling with Laboratory Near-Infrared Data I: Insights into Compositional Analysis of Europa

A. Emran

doi:10.1016/j.icarus.2025.116841

paper

Spectral Mixture Modeling with Laboratory Near-Infrared Data I: Insights into Compositional Analysis of Europa

arXiv:2510.03436 · doi:10.1016/j.icarus.2025.116841

Abstract

Europa's surface composition and physical characteristics are commonly constrained using spectral deconvolution through linear mixture (LM) modeling and radiative transfer-based (RT) intimate mixture modeling. Here, I compared the results of these two spectral modeling- LM versus RT- against laboratory spectra of water (H $_{2}$ O) ice and sulfuric acid octahydrate (SAO; H $_{2}$ SO $_{4}$ $\cdot$ 8H $_{2}$ O) mixtures measured at near-infrared wavelengths ( $\sim$ 1.2-2.5 $μ$ m) with grain sizes of 90-106 $μ$ m (Hayes and Li, 2025). The modeled abundances indicate that the RT more closely reproduces the laboratory abundances, with deviations within $\pm$ 5% for both H $_{2}$ O ice and H $_{2}$ SO $_{4}$ $\cdot$ 8H $_{2}$ O with $\sim$ 100 $μ$ m grains. In contrast, the LM shows slightly larger discrepancies, typically ranging from $\pm$ 5-15% from the true abundances. Interestingly, both LM and RT tend to consistently overestimate the abundance of H $_{2}$ SO $_{4}$ $\cdot$ 8H $_{2}$ O and underestimate H $_{2}$ O ice across all mixtures. Nonetheless, when H $_{2}$ SO $_{4}$ $\cdot$ 8H $_{2}$ O either dominates (>80% as observed on Europa's trailing hemisphere; Carlson et al. 2005) or is present only in trace amounts ( $\sim$ 10% on areas in Europa's leading hemisphere; Dalton III et al. 2013; Ligier et al. 2016), both the LM and RT render acceptable results within $\pm$ 10% uncertainty. Thus, spectral modeling using the RT is preferred for constraining the surface composition across Europa, although the LM remains viable in specific compositional regimes.

19 pages, 4 figures, Published in Icarus

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