Proposed Tasks of Enceladus Missions’ Instrumentation in the Context of Their Astrobiological Goals

Enceladus, Saturnian satellite, is a very significant object for astrobiologists due to the presence of liquid water that forms the ice-covered ocean. Water ice geysers escape from the south pole region through cracks in the ice shield. During the Cassini flight, the probe took samples of plumes matter recognizing besides other methane and molecular hydrogen. Since then, hypotheses have been formulated that life forms similar to those found in the Lost City Hydrothermal Field in the Atlantic ocean bottom may occur near Enceladus’ hydrothermal chimneys. In our work, we analyzed the possibility of a microbial factor detection in the Enceladus geysers. We used as model organisms selected extremophiles. We investigated multi-spectral cameras and mass spectrometers intended for use in mission proposals to Enceladus: Enceladus Orbiter, Enceladus Life Finder, The Explorer of Enceladus and Titan and THEO mission. The review pointed that the configuration of mass spectrometers and the proposed parameters of scientific orbits are appropriate for detecting volatile organic compounds corresponding to selected microorganisms such as aldehyde, ethanol, benzene, toluene, indole, or violacein. The possible presence of a microbiological component with physical dimensions in the order of several micrometres can only be observed for areas of geyser formation at their higher density (> 10 ppm) and with the occurrence of the “snowing microbes” phenomenon. We have found that particularly useful optical channels are 780–975 nm, 860–910 nm, and 5.0–5.3 µm.

Polarimetry of Saturnian satellite Enceladus

We present results of polarimetric observations of Saturn's moon Enceladus carried out from April 14, 2010 to April 13, 2013 in WR spectral band (550-750 nm). We used 2.6-m telescope equipped with a one-channel photoelectric photometer-polarimeter (Crimean Astrophysical Observatory). The measurements were performed at phase angles ranging from 1.65° to 5.71°. The phase-angle dependence of linear polarization of Enceladus was obtained using the results of our observations. Results obtained are discussed in terms of existing models of light scattering by regolith surfaces.