NASA should explore Uranus and Enceladus, say planetary scientists

A major report on priorities for the next decade of US planetary science calls for the first dedicated Uranus probe and an orbiter-lander combo for Saturn’s ocean moon Enceladus

By Leah Crane

US planetary scientists have put together a huge report on the state of our knowledge of the solar system and priorities for the next decade of exploration. They recommend two big new missions: a Uranus probe to launch in the early 2030s and a mission to Enceladus, one of Saturn’s moons, to take off in the late 2030s or early 2040s.

Once every 10 years, the top research priorities of the entire US planetary science community are identified by the US National Academies of Sciences, Engineering, and Medicine in a process called a decadal survey. This document makes recommendations to the government agencies that fund most of the country’s planetary research – primarily NASA and the National Science Foundation (NSF) – and is often used as a sort of blueprint for the next decade of exploration.

The report laying out the goals for 2022 to 2032, released on 19 April, is titled Origins, Worlds, and Life. The process of creating it included 527 white papers submitted by planetary scientists around the US and nearly two years of discussions among a group of 97 experts.

The highest priority laid out in the new decadal survey is the completion of NASA’s Mars Sample Return initiative, which began with the Perseverance rover. The rover has been collecting samples as it explores Mars that it will later leave behind for a planned 2028 mission to pick up and return to Earth for analysis. Even if the mission goes significantly over budget, “NASA should work with the Administration and Congress to secure a budget augmentation to ensure the success of this strategic mission,” the report says.

It also recommends two large new missions. The first is the Uranus Orbiter and Probe (UOP), which would ideally launch in 2031 or 2032. The last – and only – time we visited Uranus was with the Voyager 2 probe in 1986, and the planet’s inner workings remain mysterious.

UOP’s orbiter would circle Uranus for years, while the probe would sink into the atmosphere to measure its composition, temperature and circulation. “This would be the first ever mission focused on one of the ice giants, which is particularly important now that we think ice giants might be the most common type of planet in the universe,” says Robin Canup at the Southwest Research Institute in Colorado, one of the report’s chairs.

The second major recommended mission is the Enceladus Orbilander, in which a single spacecraft would serve as both an orbiter and a lander. It would orbit the icy moon for 1.5 years and collect samples from the plumes of liquid water that blast from Enceladus’s buried ocean, then land, take more samples and analyse them for signs of life.

There were several smaller recommended missions, including a lunar rover called Endurance-A to collect samples from the moon’s south pole for astronauts to bring back to Earth. “One of the major themes here is a desire to more closely integrate NASA’s science goals with its human exploration goals, and that’s what Endurance-A was designed to do,” says Canup.

The survey set out two possible paths to realising its recommendations: the Recommended Program, described as “aspirational and inspirational”, and the Level Program, which assumes that funding for planetary science will remain roughly the same over the next decade. What happens next is up to NASA, the NSF and the US Congress to decide.

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