An influential panel of scientists says NASA should put exploration of Uranus at the top of its to-do list. The US National Academies of Sciences, Engineering, and Medicine (NAS) made the recommendation in its report on "the next decade of planetary science and astrobiology." The only visit thus far to the seventh planet in the solar system occurred in 1986 when the Voyager-2 probe made a brief fly-by, the BBC reports. Now that objects sized similarly to Uranus are being discovered around other stars, scientists are hoping for a better understanding of the ice giant. "We think we understand how something gets as big as Jupiter, and we think we understand how something gets to be the size of Earth and Venus. But in the middle, in that kind of sweet spot between those end-members—we don't fully understand how a world can start to grow and grow and not just carry on to become Jupiter-mass in size," one expert explains. "A mission to Uranus could help us answer that." More: