|For generations, astronomers have argued over how the planets in our solar system were formed. Today, most theories assume that planets were formed in a nebula of gas and dust that condensed around what eventually became our sun, but there is still great disagreement over details, particularly for gas giant planets like Jupiter: Did a small core form first around which each planet condensed, or did instability in the nebula cause pockets to collapse directly into planets?
Eight years from now, if all goes as planned, a spacecraft will enter orbit around Jupiter that should provide insight into planet formation.
Juno, the first solar-powered mission to the outer planets (it will carry no nuclear materials), will be inserted into a polar orbit that will approach the gas giant world much more closely than any previous mission. It will carry several instruments intended to determine the structure of Jupiter's atmosphere.
Source - http://www.spacedaily.com/reports/Studying_A_Giant_Planet_999.html