Jupiter, along with its beautiful ringed sister planet, Saturn, are the gas-giant duo of our Sun's family of eight major planets. The other two giant planets--that dwell in our Solar System's outer limits--are Uranus and Neptune. Uranus and Neptune are classified as ice giants, because they carry within them larger cores than Jupiter and Saturn, as well as thinner gaseous envelopes. Jupiter and Saturn may (or may not) contain small, hidden cores, that are heavily veiled by extremely massive, dense gaseous envelopes.
The very productive Cassini mission might attain some indirect information by analyzing the ring arc material--however, it is unlikely to come close to the little moon again before the mission ends in 2017.
Discovering the little moon also reinforces the theory that most dwarf planets have moons.