  We report the discovery of soft (0.25--2 keV) x-ray emission from the
Galilean satellites Io and Europa, probably Ganymede, and from the Io Plasma
Torus (IPT). Bombardment by energetic (>10 keV) H, O, and S ions from the
region of the IPT seems the likely source of the x-ray emission from the
Galilean satellites. According to our estimates, fluorescent x-ray emission
excited by solar x-rays, even during flares from the active Sun,
charge-exchange processes, previously invoked to explain Jupiter's x-ray aurora
and cometary x-ray emission, and ion stripping by dust grains fail to account
for the observed emission. On the other hand, bremsstrahlung emission of soft
X-rays from non-thermal electrons in the few hundred to few thousand eV range
may account for a substantial fraction of the observed x-ray flux from the IPT.
