NASA's Jet Propulsion Laboratory is considering a new mission to Uranus and possibly Neptune after successfully flying by Pluto and, if all goes according to plan, the Europa moon orbiting Jupiter. The proposed mission could cost less than $2 billion, researchers said, and would be NASA's first trip to Neptune in more than 26 years.

With NASA's Cassini mission to Saturn expected to be complete by 2017 and another mission to study Jupiter's atmosphere likely over by 2018, the space agency will soon be short on plans for deep space exploration. The Europa Multiple-Flyby Mission isn't scheduled to launch until 2025. Jim Green, NASA's head of planetary sciences, announced Monday that the Jet Propulsion Lab will next study a flagship mission to Uranus or Neptune, or both, as a way of filling that gap.

The planets are known as "the ice giants."

“The composition and chemistry of ice giant atmospheres provides clues about their formation, evolution and current state,” explained a research paper referenced as part of NASA's Outer Planets Assessment Group Meeting in Laurel, Maryland. “Migration of the ice giants early in our solar systems history may be responsible for the late heavy bombardment of the inner solar system, though to have provided many of the volatiles (such as water) found on the terrestrial planets today.”

Both planets are also surrounded by moons and dwarf planets with distinct characteristics. The Triton moon orbiting Neptune, for instance, is nearly as large as Earth's moon, though ice volcanoes dispersed throughout the celestial body give off nitrogen frost, giving the moon a smoky appearance.