Saturn's icy satellites investigated by Cassini - VIMS. IV. Daytime temperature maps

TL;DR

This study uses Cassini-VIMS spectral data to map daytime surface temperatures of Saturn's icy satellites by analyzing the 3.6 micron water ice absorption feature, revealing thermal anomalies and variations.

Contribution

It introduces a novel method to derive satellite surface temperatures from spectral peak positions, expanding previous ring temperature studies to icy satellites.

Findings

Identified thermal anomalies on Mimas and Tethys.

Mapped daytime temperature variations across satellite surfaces.

Demonstrated the effectiveness of spectral peak analysis for temperature estimation.

Abstract

The spectral position of the 3.6 micron continuum peak measured on Cassini-VIMS I/F spectra is used as a marker to infer the temperature of the regolith particles covering the surfaces of Saturn's icy satellites. This feature is characterizing the crystalline water ice spectrum which is the dominant compositional endmember of the satellites' surfaces. Laboratory measurements indicate that the position of the 3.6 micron peak of pure water ice is temperature-dependent, shifting towards shorter wavelengths when the sample is cooled, from about 3.65 micron at T=123 K to about 3.55 micron at T=88 K. A similar method was already applied to VIMS Saturn's rings mosaics to retrieve ring particles temperature (Filacchione et al., 2014). We report here about the daytime temperature variations observed on the icy satellites as derived from three different VIMS observation types. Temperature maps are built by mining the complete VIMS dataset collected in years 2004-2009 (pre-equinox) and in 2009-2012 (post equinox) by selecting pixels with max 150 km/pixel resolution. VIMS-derived temperature maps allow to identify thermal anomalies across the equatorial lens of Mimas and Tethys.