Should NASA send a mission to explore Uranus and its moons? It’s been on NASA’s to-do list for a decade and scientists warn that if a spacecraft doesn’t leave soon, the next best window will be the 2090s.
We will know soon. On April 19, 2022, recommendations from the Decadal Survey for Planetary Science and Astrobiology, a report compiled by the National Academy of Sciences, will define NASA’s priorities for the next 10 years.
Although there are plans to greenlight a sample return mission to Mars, much of which is already planned by NASA, there’s a good chance it will also task the space agency with investigate one of the solar system’s “ice giant” planets, Neptune. and Uranus. After all, 10 years ago a mission to Uranus was the third highest priority lighthouse mission. Nothing was done.
Which planet should NASA favor? The advantages and disadvantages of missions on the two ice giant planets can be summarized as follows:
- The seventh planet Uranus has five moons that could be “ocean worlds”, which could harbor life.
- The eighth planet Neptune has a moon called Triton, which is thought to be a captured dwarf planet – much like Pluto – so a mission would be a two-for-one deal.
The case for Uranus, the third largest planet in our solar system in a slow orbit of 84 Earth years around the Sun, is featured in two proposals being considered by the Decadal Study –Quest to Uranus to Explore Solar System Theories (QUEST) and A New Frontiers-class mission for the Uranian system.
“Uranus is the only example in our solar system that we have of what a giant system of ice would look like,” said Erin Leonard of NASA’s Jet Propulsion Laboratory and lead author of both proposals. “It’s the only place where we have moons around an ice giant that have always been there, where it’s not Kuiper Belt intruders that were later captured, which is Triton.”
Leonard’s proposals are for New Frontiers missions – which cost no more than $900 million, or about a third of the cost of a full-fledged Flagship mission – to send an orbiter to Uranus, which would launch 2032 and arrive at Uranus in 2045.
The Juno-style QUEST orbiter would study Uranus’ oddly shaped and chaotic magnetic field and its extreme axial tilt (orbits Uranus sideways). Update long-standing theories of planetary formation and valuable data on the ice giant planets, which appear to be the most abundant in our galaxy.
QUEST would also investigate why Uranus appears to be cooler than it should be.
“What is interesting about Uranus is that Voyager 2 did not detect any internal heat emission. It’s very different from the other three giant planets, which radiate more heat than they receive from the Sun because they’re huge balls of compressed gas,” said Dr Kunio Sayanagi from the School of Science at Hampton University. “They all have interiors with very high temperatures slowly escaping, but not at Uranus. Something interesting is going on that cannot be explained.
Meanwhile, the other concept focuses on Uranus’ rings, its magnetic field, and an investigation – via flybys – of possible subterranean oceans on some of its 27 moons. There’s tantalizing evidence from Voyager 2 that the deepest and largest of the moons – Miranda, Ariel, Umbriel, Titania and Oberon – may harbor subterranean oceans. They also have surfaces that are geologically young (read: free of many craters) and therefore appear to be geologically active.
Humanity has only visited Uranus once. A short flyby on January 24, 1986 by NASA’s Voyager 2 spacecraft gave us our only close-up images of Uranus and discovered 10 new moons. The only other images we have of Uranus come from the Hubble Space Telescope and ground-based telescopes like Keck.
Planetary scientists are desperate to examine them more closely. A “Moons of Uranus” project is already on the agenda for the James Webb Space Telescope’s (JWST) very first installment of science work later in 2022. It will spend 21 hours closely studying Ariel, Umbriel, Titania and Oberon at the search for traces of ammonia, organic molecules, carbon dioxide ice and water.
Any discoveries made by JWST will inform any mission to study them closely, of course, although time is running out. If NASA wants to send a mission, gravitational assistance from Jupiter is needed, which is only possible every 12 years or so. It will be available from 2029 to 2034.
“When the planets line up correctly, we can use Jupiter to get to Uranus, which means we can throw more mass and also get there a little faster, which makes everything a little cheaper,” he said. Leonard.
However, there is another seasonal reason why now is the time for a mission to Uranus. It is essential that a mission arrive in the Uranian system in the early 2040s, when the high northern latitudes of its moons would still be visible. This opportunity will disappear once the system enters the southern spring in the late 2040s, and won’t return until the 2090s. “We don’t want it to be a full Uranus year since Voyager was around because everyone Uranus system is tilted sideways,” Leonard said. “When we were there with Voyager, only the southern hemispheres of the moons were illuminated. We would really like to see other parts of the moons.
There are now plans for flagship and New Frontiers missions to Uranus, but regardless of preference, such a mission must be launched between 2030 and 2032, regardless of size or cost.
Could NASA prepare a mission in 10 years? “For a flagship mission, it’s pretty close, but you can do it,” Leonard said, citing that flagship missions are inherently more complicated because they have more science instruments. “But I would definitely say for a New Frontiers mission – it’s easier to do it a little faster, but as always, it’s all on the budget.”
Any mission would take 10 years to build and launch and another 13 years to get there. So anyway, it will be a quarter of a century before anyone does any new science on the seventh planet in the solar system.
I wish you clear skies and big eyes.