Photometrically-corrected global infrared mosaics of Enceladus: New implications for its spectral diversity and geological activity

TL;DR

This study creates a global infrared spectral mosaic of Enceladus using Cassini VIMS data, revealing spectral and geological diversity, especially around tectonized regions linked to potential internal activity.

Contribution

It introduces a new photometric correction method for hyperspectral data, enabling detailed analysis of Enceladus's surface composition and geological activity.

Findings

Heterogeneous spectral regions identified around Tiger Stripes and northern hemisphere.

Correlations between spectral variations and tectonized geological units.

Evidence suggesting endogenous activity possibly driven by seafloor hotspots.

Abstract

Between 2004 and 2017, spectral observations have been gathered by the Visual and Infrared Mapping Spectrometer (VIMS) on-board Cassini (Brown et al., 2004) during 23 Enceladus close encounters, in addition to more distant surveys. The objective of the present study is to produce a global hyperspectral mosaic of the complete VIMS data set of Enceladus in order to highlight spectral variations among the different geological units. This requires the selection of the best observations in terms of spatial resolution and illumination conditions. We have carried out a detailed investigation of the photometric behavior at several key wavelengths (1.35, 1.5, 1.65, 1.8, 2.0, 2.25, 2.55 and 3.6 ${\mu}$m), characteristics of the infrared spectra of water ice. We propose a new photometric function, based on the model of Shkuratov et al. (2011). When combined, corrected mosaics at different wavelengths reveal heterogeneous areas, in particular in the terrains surrounding the Tiger Stripes on the South Pole and in the northern hemisphere around 30{\deg}N, 90{\deg}W. Those areas appear mainly correlated to tectonized units, indicating an endogenous origin, potentially driven by seafloor hotspots.