Uranus up close: What proposed NASA 'ice giant' mission could teach us

A mission to Uranus is now the top future-mission priority of NASA planetary scientists, and exploration of this mysterious ice giant may shed light on a kind of planet now known to be one of the most common in the universe, researchers say.
Since astronomers discovered the first exoplanets orbiting distant stars more than 30 years ago, one of the most common kinds of alien worlds that scientists have detected are ice giants. Whereas gas giants such as Jupiter and Saturn are, as their name suggests, mostly gas, ice giants such as Uranus and Neptune are rich in heavier elements.
Much remains unknown about Uranus and Neptune. Whereas the solar system's six innermost planets — Mercury, Venus, Earth, Mars, Jupiter and Saturn — have all had spacecraft in orbit around them collecting insights for scientists, to date Uranus and Neptune have only experienced flybys more than 30 years ago, both from NASA's Voyager 2 probe in 1986 and 1989. These brief encounters yielded tantalizing views of the planets that left behind more questions than previously imagined, Kathleen Mandt, a planetary scientist at The Johns Hopkins University Applied Physics Laboratory in Maryland, told Space.com.
Uranus up close: What proposed NASA 'ice giant' mission could teach us