Miranda, Uranus’s smallest major moon, looks like someone took a planetary blender to it and hit “pulse” a few times. The surface is a chaotic mess of ridges, cliffs, and valleys that shouldn’t exist on something only 470 kilometers across. For decades, planetary scientists assumed this tortured landscape was ancient history—scars from a cosmic collision that happened billions of years ago, frozen in time like a particularly ugly geological photograph.
Turns out that assumption might be spectacularly wrong.
When Ice Moons Decide They’re Not Actually Dead After All
In 2024, researchers at Johns Hopkins University published data suggesting Miranda might still be geologically active. Not “active” in the tame academic sense, but actually-maybe-right-now active. The evidence comes from analyzing Voyager 2 images from 1986—the only spacecraft that’s ever visited the Uranian system. Using computer models that didn’t exist in the 1980s, scientists discovered that Miranda’s surface features could only form if the moon had liquid water beneath its icy crust within the last 100 million years. That’s practically yesterday in geological terms.
Here’s the thing: liquid water on a moon orbiting Uranus is bonkers. The planet is so far from the Sun that solar heating is essentially irrelevant—we’re talking about a place where the average temperature is negative 224 degrees Celsius. So where’s the heat coming from?
The answer involves something called tidal heating, which sounds boring but is actually one of the universe’s most elegant torture mechanisms. When a moon orbits a planet on an elliptical path, gravitational forces squeeze and stretch its interior like a cosmic stress ball. This flexing generates heat through friction. Jupiter’s moon Io is the poster child for this process—it has over 400 active volcanoes because Jupiter’s gravity is essentially kneading it like pizza dough.
Miranda experienced something similar, possibly as recently as 10 million years ago.
The Problem With Calling Anything on These Moons Actual Volcanoes Though
Wait—maybe “volcano” is the wrong word entirely. When we think volcanoes, we picture Mount Etna spewing molten rock at 1,200 degrees Celsius, or Paricutin emerging from a Mexican cornfield in 1943, growing 336 meters in just one year. Those are magma volcanoes, driven by silicate rock melting under extreme temperatures and pressures. What happens on icy moons is fundamentally different, even if it looks similar.
Cryovolcanoes erupt water, ammonia, methane, or nitrogen instead of molten rock. The mechanics are comparable—pressure builds beneath the surface until something gives and material explosively vents into space—but the chemistry is alien. Scientists discovered evidence of cryovolcanism on Saturn’s moon Enceladus in 2005, when Cassini spotted enormous geysers shooting ice particles 500 kilometers above the surface. Those plumes contain organic molecules and hint at a subsurface ocean that could potentially harbor life.
Uranus’s moon Ariel shows even weirder features. Its surface has smooth regions that look suspiciously like they were resurfaced by flowing cryolava within the past few hundred million years. The Kachina Chasmata—a series of enormous valleys—might be the remnants of cryovolcanic eruptions that happened when the solar system was already middle-aged.
But proving current activity is brutally difficult. Voyager 2 spent exactly six hours studying the Uranian moons before hurtling off into interstellar space. That’s like trying to understand Earth’s entire geological history by looking at it for the length of a work meeting. We have pixelated images from 1986 and a lot of educated guessing.
The evidence for active cryovolcanism on Miranda specifically remains circumstantial. The moon’s bizarre terrain—including Verona Rupes, a cliff face 20 kilometers high that makes the Grand Canyon look like a ditch—suggests recent geological activity. Computer simulations indicate Miranda might have had a subsurface ocean as recently as 100 to 500 million years ago, kept liquid by tidal heating from gravitational resonances with other Uranian moons. If that ocean still exists, cryovolcanic eruptions are not just possible but likely.
NASA’s proposed Uranus Orbiter and Probe mission, which might launch in the 2030s if funding materializes, could finally answer these questions. The spacecraft would spend years studying the Uranian system, watching for plumes, measuring surface temperatures, and analyzing the moons’ compositions. Until then, we’re stuck with decades-old data and increasingly sophisticated computer models that keep suggesting these icy worlds are far stranger than we imagined.
Titania, Uranus’s largest moon, adds another wrinkle to the story. Its surface shows evidence of past tectonic activity and possible cryovolcanic flows, but everything looks old—maybe two billion years old. Did these moons have a volcanic youth and then fall silent? Or do they erupt sporadically across geological timescales, and we just happened to miss the show?
The frustrating reality is that studying volcanoes on Uranian moons requires being there, watching, waiting. Volcanic eruptions—whether magma or cryogenic—are ephemeral events. You can’t understand them from a single snapshot taken nearly 40 years ago from thousands of kilometers away. It’s like trying to determine if someone’s interesting by glancing at them across a crowded room in terrible lighting.
So are there volcanoes on Uranus’s moons? Maybe. Probably. Almost certainly in the past, possibly right now. The evidence leans toward yes, but the “yes” comes with asterisks, footnotes, and a desperate need for new data. These aren’t volcanoes like we have on Earth—they’re colder, stranger, and potentially harboring subsurface oceans beneath crusts of ice light-years from the Sun. Which, honestly, might be even more interesting than the regular molten-rock variety.
