  We report the discovery of 12 new satellites of Jupiter, giving Jupiter 79
known satellites. The new finds are between 23rd-24th mag in the r-band and 1-3
km in diameter assuming dark albedos. Nine of the discoveries are in the
distant retrograde satellite groupings. Two of the new satellites are in the
closer Himalia prograde group near 28 degrees in inclination. S/2016 J2,
nicknamed Valetudo, has an orbit unlike any other known outer satellite and is
the most distant prograde satellite around any planet at 0.36 Hill radii.
Numerical simulations show S/2016 J2 is very stable, with average and range of
i=34.2+-3 deg, e=0.216+-0.125, and a=18.9+-0.7 million km over 100 Myrs. Our
stability simulations show a S/2016 J2 like orbit would be stable out to a=21.8
million km or 0.41 Hill radii, but no further, unlike more distant and
eccentric retrograde satellites. S/2016 J2's large semi-major axis means it
significantly overlaps the orbits of the distant retrogrades. A
prograde-retrograde moon-moon collision between outer satellites of Jupiter has
likely happened over the age of the solar system.
