NASA’s Next Decade: Building an Ice Giant Mission

Late 2021, the astronomy community Issued a nodal survey, a roadmap of scientific priorities for the next ten years, which describes the devices we need to build in order to achieve them. This survey focused on distant objects and recommended projects such as the large, broad-spectrum space telescopes.

This week sees the release of a Second nodal survey, this focused on the needs of astronomers and planetary scientists who focus on things in our solar system. The big recommendations for this survey are the orbiters of Uranus and Enceladus, while the smaller missions include preparations for the return of samples from Mars, the moon and Ceres. As usual, what we get done will depend on whether planetary science budgets are better than keeping pace with inflation.

big priorities

The survey identifies the overarching science topics behind the priorities, but is broad enough that it covers pretty much everything. As mentioned, it includes a look at the materials found in small bodies within the Solar System to infer details of planet formation from the protoplanetary disk, and observations of planets to track their evolution since then. Also a priority: the formation of the moon. study of the atmosphere and interior of the planets; And the role of influences in shaping the evolution of the planet. Finally, there is the possibility of life in the present or in the past on a body other than Earth.

This appears to cover just about everything in the solar system, which means that these research priorities can justify any mission. So what devices has the scientific community chosen to pursue?

The big-ticket item is the Uranus Orbiter and Probe, or UOP, which will undoubtedly get a better name before launch. Much like the previous Galileo and Cassini missions, the UOP would consist of an orbiter that stays in place to study the system, and an atmospheric probe making a one-way trip to the planet (or, in Cassini’s case, the atmosphere of the moon Titan). Ideally, a UOP would be created within the next decade in order to use the gravity assist from Jupiter that would be available if it were launched within a window that ends in 2032.

Why Uranus? We have already made an extensive study of gas giants Jupiter and Saturn, but the ice giants of the outer solar system, Neptune and Uranus, have only been visited by Voyager two decades ago. Surveys of exoplanets have revealed that planets the size of Neptune are very common elsewhere in our galaxy, so studying them will generally be useful. Uranus in particular is interesting because it appears to have been hit so hard early in its history, causing its axis of rotation to shift nearly 90 degrees. It also has moons that appear to have been geologically active and could harbor oceans. Aside from all of that, it’s much closer to Neptune.

Should the budget exceed inflation, the survey recommends a second major mission, this one to Enceladus, one of Saturn’s moons. Enceladus appears to have an icy ocean and a portion of hot water that releases some of its contents into space. Enceladus Orbilander will fly through the plumes of these geysers to analyze their content and then land for two years of operation on the lunar surface. The goal would be to launch it in time to reach the Moon by the 1950s, when orbital differences will provide more sunlight in the southern hemisphere than Enceladus, where the hot springs are located.