Researchers are keen on exploring Jupiter's icy moons, which may resemble some of the planets found orbiting stars beyond our solar system, to assess their suitability for life.





Europa, Callisto and Jupiter's largest moon, Ganymede, are all believed to have liquid oceans beneath their icy shells, as well as organic chemistry and possible sources of energy beyond the dim amount of sunlight that reaches their distant surfaces.



These are all conditions that may be required for life in much more distant planetary bodies.



"We thought for quite some time these were dead icy bodies, but we have recently actually discovered a fabulous collection of very geologically active things there," planetary scientist Athena Coustenis, with the Paris Observatory in France, said.



A newly proposed mission, The Jupiter Icy Moons Explorer, nicknamed JUICE, would send a spacecraft to study the three moons and their habitability.



Mission planners selected Ganymede as an archetype of an exoplanet water world like GJ 1214b, a super-Earth discovered last year circling a star about 40 light-years from Earth.



"We think it is the best example of a liquid environment trapped between icy layers," JUICE science study team member Olga Prieto Ballesteros, with the Center of Astrobiology in Madrid , Spain, said.



Europa poses an intriguing model to those exploring the possibility of alien life because its buried ocean is believed to be in direct contact with the moon's silicate mantle, a source of salts and other elements. Europa is thought to be like exoplanets that are between water worlds and Earth-like bodies.



"The icy planetary bodies have opened the possibility to find habitats in deeper environments. We can say that these will expand the classical concept of habitability," which previously was limited to places with liquid water on surface , Prieto Ballesteros said.