Sub-Micrometer Particles Remote Detection in Enceladus Plume Based on Cassinis UV Spectrograph Data

Enceladus is the Saturnian satellite known to have water vapor erupting from its south pole region called Tiger Stripes. Data collected by Cassini Ultraviolet Imaging Spectrograph during Enceladus transiting Saturn allow us to estimate water plume absorption from 1115.35 - 1912.50 Angstrom and compare it to the Mie solutions of Maxwell equations for particles with a diameter in the range from 10 nm up to 2 um. The best fit performed using Gradient Descent method indicates a presence of submicrometer particles of diameters: 120-180 nm and 240-320 nm consistent with Thermofilum sp., Thermoproteus sp., and Pyrobaculum sp. cell sizes present in hydrothermal vents on Earth.