We Need a Dedicated Mission to Uranus, Scientists Say

With its strange rings and inclinations, surprising seasonal variations, and 27 moons, Uranus is the craziest planet in the solar system. The enigmatic ice giant has much to teach us, which is why astronomers are clamoring for a mission to explore the planet up close.

The first special mission to Uranus is long overdue, argues Kathleen Mandt, a planetary scientist at the Johns Hopkins Applied Physics Laboratory, in Science Perspectives essay released today.

In fact, a minute has passed since our only brief visit to the distant ice giant. NASA’s Voyager 2 probe flew past Uranus on January 24, 1986, taking remarkable views of the planet and its moons before continuing its journey to Neptune – the Solar System’s other ice giant – and then into interstellar space.

Like Saturn and Jupiter, Uranus and Neptune are packed with hydrogen and helium, the two lightest elements in the universe. “We call Uranus and Neptune ice giants because they have more of the other, heavier elements compared to hydrogen than either Saturn or Jupiter,” Mandt explained in an email. “Because Saturn and Jupiter are composed mostly of hydrogen, we call them the gas giants.”

The images Voyager 2 captured left us wanting more, but it’s now three decades later and we still haven’t bothered to return. In her essay, Mandt advocates exactly that: a special NASA Uranus orbiter and a probe called UOP. Parked in orbit around Uranus, the spacecraft would take unprecedented measurements of the planet, its many moons and rings, and also deploy a probe to study the chemical cocktail that makes up its dim atmosphere.

G/O Media may receive a commission

Pre-order now

Galaxy Book 3 series

Available February 24th
Every new laptop model comes with a free memory upgrade. The 1TB version of each is priced the same as the 512GB version, which basically means the 1TB version is $200 cheaper.

The urgent need for a special mission to Uranus is hardly new. A key shortcoming identified in the most recent Decade review, in which NASA commissions the Academies of Science, Engineering and Medicine to compile a list of priorities for the coming decade, was the “lack of knowledge about the ice giants.” The review identified UOP as a high-priority planetary mission, a conclusion reached in previous decennial reviews, Mandt points out. The 2013 decennial review listed the Mars Sample Return Mission and the Europa Clipper as high priorities, and these missions are now in full development mode. A special mission to Uranus, Mandt argues, appears to be next in line.

Related story: Whoa, Uranus looks all messed up right now

Such a mission would help unlock the many mysteries of Uranus (stop giggling, this is serious). Planetary scientists are trying to learn more about the ice giants and how they formed, as well as the extent to which Uranus has migrated from its original, formative place. According to Mandt, close-up studies of Uranus could reveal the history of our immediate surroundings and show how small celestial bodies were able to distribute water and other building blocks of life to the inner solar system. These investigations could also shed light on distant exoplanets and “their system architectures,” writes Mandt in her paper. Such assessments would require detailed measurements of isotopic ratios and the amounts of noble gases present in the ice giant — data that an atmospheric probe could easily collect, the planetary scientist says.

Other questions that need to be answered include the reason for the planet’s sharp tilt, a 90-degree tilt that causes “extreme atmospheric seasonality over its 84-year Earth orbit,” writes Mandt, adding that “observations of haze and clouds from Earth may not provide enough information to explain atmospheric circulation and wind patterns.”

UOP could probe Uranus’ magnetosphere and provide new insights into the planet’s internal structure (is the core solid or diffuse?). And then there are the many moons of Uranus to consider.

“The moons of Uranus are much smaller than the four large moons of Jupiter and Saturn’s moon Titan. They should be solid and inactive because they are small, and the surfaces should show only impact craters,” Mandt wrote to me. “Excitingly, Voyager 2’s images didn’t show many craters, instead showing features that could have been formed by geological activity. We want to study the internal structure of these moons to find out why the surfaces are so young, and we hope to find evidence of liquid water.”

In fact, Uranus may host a moon or two with liquid water hidden beneath an icy shell. Astrobiologists should lick their fingers to study the Uranus system up close.

The mission plan, Mandt argues, could draw on pre-existing work, including the Origins, Worlds and Life (OWL) document released as part of the 2022 Decadal Planetary Science Survey. The plan calls for UOP to launch by 2032 to take advantage of Jupiter’s immense gravity, which would allow the gas giant to catapult the spacecraft to its final destination. UOP would reach Uranus around 2050. These are rough estimates, but this is generally the timeframe that this mission will likely take place if approved.

I asked Mandt about the types of instruments she would like to see on the orbiter and probe.

“For the probe, the most important instrument is a mass spectrometer. This instrument is able to measure what elements and molecules are in the atmosphere based on their mass,” she replied. “We need this information to find out where Uranus formed and how much it migrated after it formed. The orbiter requires a combination of instruments, including cameras that measure different wavelengths and sensors that detect electrons, ions and the magnetic field.”

The mission would also present some unique challenges, as no orbiter has worked so far from home. At distances nearly 20 times the Earth’s distance from the Sun, signals from UOP would take over three hours to reach ground stations on Earth; This “will make planning important when sending commands and will require patience while waiting for new results,” Mandt told me. Collecting enough solar energy could also prove to be a challenge. She said the spacecraft “will require radioisotope power sources like the ones the Cassini mission had and like what’s still powering the two Voyager spacecraft and New Horizons.”

If given the opportunity to work on this mission, Mandt said she would be happy to help plan the probe’s observations and make plans for studying the composition of the moons and rings of Uranus. “We eagerly await hearing from NASA on what the next steps will be,” she said.

More: Why Uranus is a different shade of blue than Neptune