As NASA’s Curiosity rover beamed back its first pictures from the Martian surface earlier this month, a landmark in the search for extraterrestrial life was reached. The search for extraterrestrial life is not confined to Mars, though. Jupiter’s ice encrusted moons, Callisto, Europa and Ganymede may hide subterranean oceans beneath their outer shells that could provide a hospitable environment for alien life forms. These vast underground seas are thought to contain organic compounds and conditions similar to those found on exoplanets and could be key to a new understanding of how life develops beyond our
Solar System.

Once thought to be dead and icy, planetary scientists at the Observatoire de Paris now believe Jupiter’s moons to be geologically active, and therefore potentially habitable. The Jupiter Icy Moons Explorer, or JUICE, as it is affectionately known, is a space program, which was announced in April 2012 by the European Space Agency. JUICE will explore these moons and characterize them, particularly Ganymede, as potential habitats and archetypes of exoplanets. Proposed timescales estimate the spacecraft to launch some time around June 2022, reaching Jupiter’s orbit in 2030 and performing observations for three years.

While the mission is still years away, analysis of such planetary archetypes will greatly improve our understanding of extraterrestrial life. The probability of another form of life elsewhere in the Universe is incredibly high and, as of August 2011, the number of exoplanets discovered is 777 and counting. Scientists believe that the conditions on moons like Ganymede could be extremely similar to planetary bodies GJ 1214 b, a large water-world exoplanet around 40 light years away. It lies in the habitable zone of its parent star, the red dwarf GJ 1214. For now, at least, the JUICE program may be our best shot at getting a glimpse of how life exists in planetary systems elsewhere in the Universe.