An article published in the journal “Icarus” reports a study on the frozen crust on the surface of Enceladus, the moon of Saturn which has an ocean of liquid water under its crust. A team of researchers analyzed data collected by the Cassini space probe’s Visible and Infrared Mapping Spectrometer (VIMS) instrument to obtain the most detailed infrared map of Enceladus’s surface. The map shows a clear correlation between reflected infrared emissions and geological activity, and in some areas, the surface ice turns out to be recent.
The Cassini space probe mission ended on September 15, 2017, leaving a wealth of data on the planet Saturn and its moons. Enceladus was one of the big surprises when mission scientists discovered that beneath its frozen crust there’s an ocean of liquid water and geysers were spotted emerging from cracks in the surface.
During the mission, Cassini passed flew by Enceladus 147 times, 23 of which at close distance. This allowed it to collect many measurements with its VIMS instrument, very useful to obtain information on the temperature and composition of the surface but also the characteristics of the ice grains such as size and crystallinity. That’s because ice with different characteristics reflects different visible and especially infrared frequencies. The image (NASA/JPL-Caltech/University of Arizona/LPG/CNRS/University of Nantes/Space Science Institute) shows various views of Enceladus, and you can better explore the map in this interactive version.
The new map of Enceladus created by putting together the data to have different colors depending on the characteristics of the ice shows their correlation with the geological activity existing on this moon. The red color indicates relatively fresh ice that was deposited on the surface as a result of geological events. That’s partly visible in the Northern Hemisphere, which was probably active in recent times from a geological point of view. It’s seen above all in the south pole area, where traces of the so-called tiger stripes, large tectonic faults present in that area, are evident. That’s no surprise because it’s an area where geysers were sighted, and could indicate the presence of hotspots on the ocean floor.
This analysis technique can also be applied in the future to other frozen moons to evaluate their activity, also to compare it with that of Enceladus. Europa is the other icy moon considered among the main candidates to host life forms in its underground ocean, so it could be a subject for similar research.
Europa Clipper is a NASA mission in preparation with Europa as its specific target while JUpiter ICy moons Explorer (JUICE) is an ESA mission in preparation that aims to study Europa but also Ganymede and Callisto, two of the other Jupiter’s Galilean moons. In the future, the data collected by these probes will be analyzed in the same way as Enceladus data.
