Mission to Uranus
With no spacecraft visiting the ice giants for over 30 years, Anthony King speaks to the planetary scientists planning a return visit
Uranus was discovered in March 1781 by astronomer William Hershel from his garden in Bath. More than 200 years later, the Nasa spacecraft Voyager 2 flew past Uranus in January 1986, our first ever close encounter with the seventh planet of our solar system. It remains the only visit to a planet that is around 20 times more distant from the sun than Earth.
But plans are afoot to return. A once-in-a-decade report from the National Academies of Sciences in the US, released last April, recommends Uranus as the highest priority flagship mission of the US space agency, Nasa. The report advised that an orbiter and probe should take off in the early 2030.
Uranus is an ice giant, along with the similarly sized but even more distant Neptune. The description conjures images of a frozen world, but the name mostly distinguishes them from the gas giants, Jupiter and Saturn. Their true nature is surprisingly obscure, much more so than the gas giants dominated by hydrogen and helium, which have been explored more recently by probes and orbiters.