Toward the end of Cassini's mission at Saturn, it will enter a highly inclined orbit, allowing the spacecraft to study Saturn's gravitational and magnetic fields in the same way that Juno will study Jupiter's. This final phase of Cassini's mission happens in 2017, when Juno is exploring Jupiter--offering an unusual opportunity for two spacecraft to study similar aspects of the two biggest gas-giant planets simultaneously. Studying the interiors of both planets--for instance, measuring the size of their cores--will help scientists better understand how exactly the outer solar system formed and evolved. For example, scientists can determine whether Jupiter and Saturn migrated early in the solar system's history, in which the planets formed far from the sun, moved inward, and then went back out.