Water Parks around Jupiter?

NASA’s Galileo satellite has suggested underground lakes on Jupiter’s moon Europa; the smallest of four moons discovered by Galileo in 1610. It is also believed to have a saltwater ocean. In January 2000 the Galileo satellite found that near to Europa, Jupiter’s magnetic field changes direction rapidly. This indicates that an electric current is flowing through Europa. Since solid ice conducts electricity poorly, salty water (such as seawater on Earth) that conducts well was proposed as an explanation.

Europa is unique among the large icy satellites because its ocean is in direct contact with its rocky mantle beneath. The conditions of the mantle could be similar to those on Earth’s biologically rich sea floor, where hydrothermal fields provide excellent habitats, powered by energy and nutrients that result from reactions between the sea water and silicates. Consequently, Europa is the prime candidate in the search for habitable zones and life in the solar system.

However, the details of the processes that shape Europa’s ice shell, and the fundamental question of its thickness have proved difficult to understand.

Now, Britney Schmidt and her team at the University of Austin, Texas have put forward evidence of Europa’s icy surface communicating with the structure below, hinting at evidence for giant underlying lakes. The team focused on Galileo images of two roughly circular, bumpy features on Europa’s surface called chaos terrains. Based on similar processes seen on Earth - on ice shelves and under glaciers overlaying volcanoes - they developed a four-step model to explain how the features form.

  Here, due to geothermal activity, water rises from below the surface and as a lake forms the icebergs start to float and eventually break up due to collisions, creating matrix material consisting of crushed ice as shown in the diagram. Salt rich water then fills up fractures in the matrix and over time the entire structure refreezes. This explains the dome-like structures observed in topographic studies of the moon. Similar processes have been well documented in the case of Antarctic ice shelves, where Hydrofracture of tidal cracks by melt water allows for the production of large tabular icebergs and granular brash ice with minimal melting of the shelf, a process analogous to chaos formation on Europa.    

This recent analysis shows that the chaotic features on Europa’s surface may be formed by exchange between this and the underlying lake. It allows transfer of nutrients and energy between the surface and a possible vast global ocean below the thick ice shell. This is thought to increase the potential for life there.