Both Jupiter and Saturn, the largest gas giants in the solar system, have been explored by robotic probes. Galileo orbited Jupiter for a number of years, exploring the planet and its many moons, for several years before plunging into its atmosphere in 2003. Cassini is currently orbiting Saturn, unlocking the secrets of the ringed planet and its moons. Now, according to Science News, scientists are looking at similar expeditions to Uranus and Neptune, the two ice giants that lay beyond Jupiter and Saturn. Each planet and its moons have interesting features that bear studying further. They were last visited by the Voyager 2 spacecraft decades ago.
Uranus, for example, has been knocked on its side with its polar axis residing where its equator should be. As a result, weather on the planet must be positively weird. Looking at a sideways planet close up might be a great way to test theories about the formation of planets.
However, Neptune is a more typical ice giant, with storms wracking its gassy surface, and therefore might be a better target. Besides, it has a large moon, Triton, which it captured billions of years ago and may be similar to Pluto in size and composition. It also might be like Enceladus or Europa in that it has an ice crust covering a subsurface ocean.
Planetary scientists also are about to have a powerful launch vehicle that could get a #Space prove to either Uranus or Neptune in a few years in the form of the heavy lift Space Launch System. New Horizons took nine and a half years to get to Pluto using a gravity assist maneuver past Jupiter. The SLS could cut that time considerably and get to either Uranus or Neptune directly.
Of course, a mission to either planet, especially using the SLS, will cost a lot of money. NASA has a lot on its plate right now, including the woefully underfunded Journey to Mars program. On the other hand, New Horizons and other robotic expeditions such as the Mars Curiosity have shown that planetary science can be not only illuminating, but exciting. The government could do worse things than fund an expansion of the frontiers of science.