This is how
Jupiter and its Galilean satellites may appear from the surface of Jupiter's tiny
moon Themisto. At a distance of 4.7 million miles, Jupiter subtends an angle
of 1.1 degrees (the moon subtends an angle of 0.5 degrees in Earth's
sky). The Galilean satellites are, left to right, Ganymede, Europa, Io, and on
the far right Callisto.
Not much is known about Themisto. It was first discovered in 1975, then
lost, then rediscovered in 2000. Themisto is the next significant body orbiting Jupiter beyond Callisto.
Beyond Themisto are another 54 known jovian satellites, the
furthest of which has an orbital radius of 19 million miles.
With a mean diameter of only 5 miles and an albedo (surface brightness)
about half that of the moon, no earthbound telescope or interplanetary
probe has yet revealed any details of Themisto's surface. In this image I'm
suggesting that Themisto has an ancient, dusty and heavily cratered surface
with the occasional--and fanciful--outcropping of dirty water ice. This satellite is
far too small to host an atmosphere, and too small even for its own gravity
to pull it into a spherical shape like its relatively massive Galilean
cousins. An visiting astronaut could easily propel him/herself into orbit
with a single jump.