In 1986, NASA’s Voyager 2 whizzed past Uranus, capturing images of its large, ice-laden moons. Now, four decades later, NASA is planning to revisit Uranus, this time with advanced equipment designed to probe whether these icy moons conceal liquid water oceans.

While this mission is in its early stages of planning, researchers from the University of Texas Institute for Geophysics (UTIG) are already laying the groundwork. They are developing a computer model that could detect subterranean oceans using only the spacecraft’s onboard cameras.

The significance of this research lies in the quest to determine the best method to detect oceans on Uranus. The presence of liquid water is a vital factor in the search for life, making it crucial to ascertain its existence on these moons.

The newly-formulated computer model analyses minor oscillations or wobbles in the moon’s rotation as it orbits Uranus. Based on this analysis, it estimates the composition of water, ice, and rock within the moon. A smaller wobble suggests a solid moon, while a larger wobble indicates that the icy surface might be overlying a liquid water ocean. With the addition of gravity data, the model can compute the ocean’s depth and the thickness of the ice above it.

Uranus, along with Neptune, belongs to a category of planets known as ice giants. There are more bodies of similar size to these ice giants detected outside our solar system than any other type of exoplanet. If the moons of Uranus are found to harbor sub-surface oceans, this could imply a multitude of potential life-bearing worlds across the galaxy, stated Doug Hemingway, UTIG planetary scientist and the model’s developer.

“Unearthing hidden oceans within Uranus’s moons could redefine our understanding of where life could potentially exist,” Hemingway said.

The UTIG research, which was featured in the journal Geophysical Research Letters, aims to aid mission scientists and engineers in enhancing their ocean detection capabilities.

All large moons, including those belonging to Uranus, are tidally locked, meaning they always present the same face to their parent planet due to gravity. However, these moons still oscillate slightly as they orbit. Understanding the extent of these wobbles is crucial in determining the existence and size of oceans on Uranus’s moons.

Moons with internal liquid water oceans will wobble more than entirely solid ones. Nevertheless, even a massive ocean will cause only a minor wobble, with a moon’s rotation deviating by a few hundred feet during its orbit. However, this slight deviation can still be detected by passing spacecraft, as demonstrated in the case of Saturn’s moon Enceladus.

Hemingway carried out theoretical calculations for five of Uranus’s moons, resulting in several plausible scenarios. For instance, if Uranus’s moon Ariel wobbles by 300 feet, it likely houses a 100-mile-deep ocean beneath a 20-mile-thick ice shell.

According to UTIG Research Associate Professor Krista Soderlund, detecting smaller oceans will require either closer proximity or more powerful cameras. However, the model provides mission designers with a guide to what might work.

“The difference could be between discovering an ocean and realizing we lack the capability to do so upon arrival,” said Soderlund, who was not part of the current research but has collaborated with NASA on Uranus mission concepts.

The next step, Hemingway suggests, is to expand the model to incorporate measurements from other instruments, which could provide a clearer picture of the moons’ interiors.

This research, co-authored by Francis Nimmo from the University of California, Santa Cruz, was funded by UTIG.