This zoomed-in image of Uranus, captured by Webb’s Near-Infrared Camera (NIRCam) Feb. 6, 2023, reveals stunning views of the planet’s rings. The planet displays a blue hue in this representative-color image, made by combining data from two filters (F140M, F300M) at 1.4 and 3.0 microns, which are shown here as blue and orange, respectively (Credits: NASA, ESA, CSA, STScI. Image processing: J. DePasquale (STScI))
AUSTIN — Imagine a spacecraft dancing with distant moons, detecting tiny wobbles that could reveal vast hidden oceans beneath thick layers of ice. This isn’t science fiction; it’s a cutting-edge approach researchers are taking to explore one of the solar system’s most mysterious planets: Uranus.
Scientists at the University of Texas are pioneering a new method to detect liquid water oceans on the moons of Uranus — potentially opening up exciting possibilities for finding life beyond Earth. Their innovative computer model, described in the journal Geophysical Research Letters, could help NASA’s upcoming mission determine if these distant moons harbor the most fundamental ingredient for life: water.
“Discovering liquid water oceans inside the moons of Uranus would transform our thinking about the range of possibilities for where life could exist,” says planetary scientist Doug Hemingway, who developed the groundbreaking model, in a university release.
The research focuses on a remarkable phenomenon: moon wobbles. Unlike stationary objects, moons aren’t perfectly rigid. They subtly sway as they orbit, and these movements can reveal what’s happening beneath their icy surfaces. A moon with a liquid ocean inside will wobble more than a completely solid moon — think of how a water-filled balloon moves differently from a solid rubber ball.
By analyzing these microscopic movements, the researchers can estimate the size and depth of potential oceans. For instance, they calculated that if Uranus’s moon Ariel wobbles just 300 feet during its orbit, it likely contains a 100-mile-deep ocean protected by a 20-mile-thick ice shell.
This technique isn’t entirely new. Scientists previously used a similar approach to confirm that Saturn’s moon Enceladus has a global ocean. Now, they’re applying this method to Uranus’s moons, which are particularly intriguing because they belong to a class of planets called “ice giants” — a type of planet more common in the galaxy than previously thought.
The potential implications are profound. If Uranus’s moons contain liquid water, it suggests that similar ocean-bearing worlds might be far more prevalent throughout the universe than we currently understand. Each discovered ocean represents another potential habitat for life, expanding our cosmic perspective.
NASA is currently in the early stages of planning a mission to Uranus, and this research will help mission designers optimize their approach. By providing a predictive model for ocean detection, the University of Texas team is essentially creating a sophisticated “slide rule” to maximize the mission’s scientific potential.
“It could be the difference between discovering an ocean or finding we don’t have that capability when we arrive,” says Krista Soderlund, a research associate professor involved with NASA mission concepts.
The next steps involve refining the model by integrating measurements from multiple instruments, which could provide an even more detailed picture of these distant, icy worlds. One thing is certain: our understanding of potential life in the universe is about to get a lot more interesting.
Paper Summary
Methodology
The study investigated whether subsurface oceans exist in the icy moons of Uranus by examining the relationship between libration amplitudes (wobbling during rotation) and internal structures. Researchers modeled each moon as having either two layers (an ice shell and a rocky core) or three layers (ice, ocean, and core).
They calculated how the thickness of the ice shell and the presence of a liquid ocean influence measurable quantities like libration amplitude and gravitational fields. Using known densities, radii, and orbital parameters, they predicted libration behaviors with and without oceans to understand the moons’ structures.
Key Results
The researchers found that some Uranian moons, like Miranda, Ariel, and Umbriel, are more likely to show large libration amplitudes if they have thin ice shells and underlying oceans. For these moons, ice shells thinner than 30 kilometers would result in noticeable librations.
In contrast, moons like Titania and Oberon, with larger orbits and thicker shells, would have libration amplitudes too small to detect easily. Their findings suggest that thick oceans are more detectable, while thin ones might go unnoticed without precise instruments.
Study Limitations
Detecting small librations requires instruments with extremely high precision, which might not be feasible with current spacecraft designs. The study assumed hydrostatic equilibrium (uniform layers) and specific material properties, which may oversimplify the moons’ actual complex structures. Factors like past heating events, non-uniform shell thicknesses, and varying chemical compositions of oceans could significantly affect the results.
Discussion & Takeaways
The research highlights that libration measurements could provide critical insights into whether subsurface oceans exist and the thickness of the ice shells. This information is essential for understanding the energy and thermal history of these moons, which impacts their habitability.
However, detecting thin oceans will require highly accurate measurements, particularly for the smaller moons. The findings encourage future missions to prioritize instruments capable of measuring small librations and gravitational fields to improve the chances of confirming subsurface oceans.
Funding & Disclosures
The study was supported by the University of Texas Institute for Geophysics and the Jackson School of Geosciences. The authors disclosed no conflicts of interest, and data utilized were freely available in published literature.
