Spatially resolved near infrared observations of Enceladus’ tiger stripe eruptions from Cassini VIMS

Abstract

Particle properties of individual fissure eruptions within Enceladus’ plume have been analyzed using high spatial resolution Visible and Infrared Mapping Spectrometer (VIMS) observations from the Cassini mission. To first order, the spectra of the materials emerging from Cairo, Baghdad and Damascus sulci are very similar, with a strong absorption band around 3µm due to water-ice. The band minimum position indicates that the ice grains emerging from all the fissures are predominantly crystalline, which implies that the water-ice particles’ formation temperatures are likely above 130K. However, there is also evidence for subtle variations in the material emerging from the different source fissures. Variations in the spectral slope between 1–2.5µm are observed and probably reflect differences in the size distributions of particles between 0.5 and 5µm in radius. We also note variations in the shape of the 3µm water-ice absorption band, which are consistent with differences in the relative abundance of > 5µm particles. These differences in the particle size distribution likely reflect variations in the particle formation conditions and/or their transport within the fissures. These observations therefore provide strong motivation for detailed modeling to help place important constraints on the diversity of the sub-surface environmental conditions at the geologically active south-pole of Enceladus.