Europa: as the human eye might see it (colors adjusted, Credit:
NASA/JPL/Ted Stryk) by Caleb Scharf Jupiter’s enigmatic moon
Europa has long been thought to contain a huge ocean beneath its
icy crust, but what is in that ocean and does it ever come to
the surface? Since the Voyager and Galileo probes explored the
Jovian system, its moons have presented an extraordinary and
fascinating puzzle. The largest of the 67 known moons are the
ones that Galileo Galilei watched wend their way around
Jupiter’s bulk back in the early 1600′s – Io, Europa, Ganymede,
and Callisto. These bodies are remarkable both for their size
(Ganymede is 8% larger in diameter than the planet Mercury,
Callisto is 99% Mercury’s size) and their diversity.