In May 2001
NASA's Galileo spacecraft took the highest resolution images of any of
Jupiter's satellites. The images were of the southeastern perimeter of Callisto's
massive Asgard impact basin and what they revealed was unlike anything seen
before in the Solar System: numerous bright, icy spires rising from an
otherwise relatively flat, cratered terrain. The spires may consist of
material thrown outward from a major impact billions of years ago.
In this image dozens of knobby spires rise into the airless void to twice
the height of the Statue of Liberty. Over the eons the dirty ice in the
spires has slowly eroded, leaving the non-ice materials to slide down and
collect around the base of the spires. As this location is on the side of
Callisto that always faces away from Jupiter (the "anti-Jupiter" side), its
jovian host would never appear above the horizon.
While the Galileo images of Callisto's surface were of relatively high
resolution, they still could not discern anything smaller than 10 feet, so
what exactly these spires would look like from ground level, or what the
colors would be, is open to conjecture. Here I've taken some liberty by
giving the darker, non-icy materials a tan color and by depicting flecks of ice
scattered on the ground and at the bases of the spires.