Those of us who follow such things are quite used to the steady stream of incredible images of Saturn and its moons sent back to us by the Cassini spacecraft over the past few years.  But did you know that Cassini snapped a few images of Jupiter while still en route to Saturn?  This image, taken in December 2000, shows the galilean moon Io, with giant Jupiter as a backdrop and I strongly recommend clicking it to see the larger version.  Io shares a few features with our own Moon:  It’s about the same size, and orbits at about the same altitude above its planet’s surface.  Bearing this in mind, have another look at that picture and think about how when we’ve told you that Jupiter is “big”, we totally failed to convey just how enormous it really is.