ITASEL

Italian Search for Extraterrestrial Life

A joint project INAF-IFSI, INAF-IRA, ASI

Saturnian system

The Cassini spacecraft has identified in the southern hemisphere of the satellite Enceladus, by using the UV-spectrometer, jets of ice particles carried by water vapour probably originated from liquid water sources below the satellite's surface. The water is thought to be supplied by volcanic activity on Enceladus. Since the temperature of the water vapour, as measured from IR observations, is sufficiently high to allow water molecules to escape from the gravitational field of Enceladus, the volcanic water supply is being suggested as a contribution to the material that forms the Saturn E-ring.

Jets of water erupting from Enceladus

Following this important discovery, observations of the Saturn system were carried out with the 32 m Medicina and the 14 m Metsahovi radio telescopes (HUT-TKK-MRO, Finland) during 2006-2008 campaigns. A direct FFT spectrometer was used at Medicina, and a locally developed software spectrometer at Metsahovi. About 300 hours of observational data were collected. Observational data were Doppler corrected before accumulation for a multitude of targets presented in the telescope beam. Statistically significant detections are associated with several Kronian satellites : Titan, Hyperion, Enceladus, Dione and Atlas.( Pogrebenko, S.V. et al., (2009), A&A ,494, L1-L4)

Several maser pumping models, based on water-neutrals, water-water and water - low energy electrons show the consistency of the detected radio lines with volume and column densities of water molecules in thr Enceladus plume and low-energy electron density in the Kronian environment. Since there is not enough infrared emission in the Saturnian system to provide a convenient IR pumping of the planetary maser at the required excitation level - as in case of the comet/Jupiter collision event - a pumping model based on the magnetohydrodynamics interaction of the satellite with the Saturnian magnetosphere and embedded water molecules can be considered as a plausible explanation, although such a model is subject to further developments which depend on the new observational results.