CNET - "We found that the Galilean moons of Jupiter, one of which is the largest moon in our solar system, would very quickly destroy any large rings that might form," Stephen Kane, an astrophysicist from the University of California, Riverside, who led the research, said in a statement. "As a result, it is unlikely that Jupiter had large rings at any point in its past."
In other words, Kane and colleagues believe the gravitational pull and sheer force of Jupiter's orbiting moons -- especially the four largest Galilean ones -- would've obliterated any and all matter attempting to produce Saturn-like rings around the gas giant.