Uranus’ moon Ariel is covered with incomprehensible grooves and trenches. Scientists suspect that on it, as on many others, the ocean hides under the ice. And the mysterious objects are really windows to it.

Ariel’s mid grooves
Last year, a study led by planetary scientist Richard Cartwright of the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, suggested that ice deposits of carbon dioxide and other carbon molecules on Uranus‘ moon Ariel probably originated from terrestrial processes.
New research may shed light on how these materials reached (or even still reach) the surface. A new study led by APL planetary geologist Chloe Beddingfield points to median grooves — trenches cutting through Ariel’s massive canyons — as possible conduits for this exchange.
The results of the study, published on February 3 in the Planetary Science Journal, suggest that these grooves are spreading centers similar to those that create new oceanic crust on Earth’s seafloor by lifting up internal material that forms a new surface.
Formation of amazing geologic structures
Among the youngest known features of Ariel’s surface, grooves have long been suspected to be the product of a complex interplay of tectonic and volcanic activity. Using images taken by NASA’s Voyager-1 spacecraft (the only mission to fly past Uranus and its moons), the research team hypothesized that the grooves could have been formed by fissures or volcanic channels.
But the new analysis leans heavily toward centers of distribution. For example, the flanking grooves of a canyon wall fit together like puzzle pieces when their center floors are digitally removed. And the canyon floor in some places shows evenly spaced ridges — similar to construction excavator tracks — consistent with a series of material deposits.
Beddingfield explained that spreading centers arise from convection cells beneath the Earth’s crust. The heat from Ariel’s bowels forces the material upward, splitting the surface and pushing it apart as the material is placed and gradually cooled.
Geologic activity cycles on moons
Interestingly, Ariel and several other moons of Uranus have experienced several periods of geologic activity, probably caused by tidal forces. These forces, derived from the resonance of the moons’ periods when their orbital periods are aligned in exact ratios, caused their icy interior to cycle between phases of heating and, in some cases, melting and freezing.
Scientists believe these resonances helped sustain the oceans beneath Ariel and its younger neighbor Miranda. For example, the 2024 study co-authored by APL’s Tom Nordheim, suggested that such resonances formed the ocean in Miranda’s interior, and that the ocean may still exist today.
Subsurface Ocean
A thin residual ocean may also exist on Ariel, although Beddingfield remains careful to establish direct links between this ocean and the medial grooves.
“The size of Ariel’s possible ocean and its depth beneath the surface can only be estimated, but it may be too isolated to interact with spreading centers,” she said. “There’s just a lot we don’t know. And while carbon oxide ices are present on Ariel’s surface, it’s still unclear whether they’re associated with the grooves because Voyager 2 didn’t have instruments that could map the distribution of ices.”
To find the answer, Cartwright emphasized the need for further research and the importance of a special mission to Uranus. “We need an orbiter that can make close passes of Ariel, map its medial grooves in detail, and analyze their spectral signatures for components like carbon dioxide and carbon monoxide,” he said. If carbon molecules are concentrated along these grooves, it would strongly support the idea that they are windows to Ariel’s inner world.
As Uranus rises in the ranks of exploration priorities, Ariel and its enigmatic median grooves may soon come under scrutiny, offering an unprecedented glimpse into the past month and perhaps even its present.
According to phys.org