A newly developed computer model can detect and evaluate hidden oceans beneath the icy surfaces of Uranus’s moons. This model achieves this by studying the subtle orbital variations that would be apparent to a spacecraft passing by. This research provides valuable tools for engineers and scientists as they prepare for NASA’s future Uranus Orbiter and Probe mission.
In 1986, when NASA’s Voyager 2 made its flyby of Uranus, it captured fuzzy images of sizable icy moons. Nearly four decades later, NASA is planning to dispatch another spacecraft to Uranus, this time equipped to investigate whether these frozen moons conceal liquid water oceans beneath their surfaces.
The mission is still in its initial phases. However, researchers from the University of Texas Institute for Geophysics (UTIG) are proactively developing a new computer model capable of identifying underwater oceans through the spacecraft’s cameras.
This research is crucial as scientists are uncertain about the most effective method for detecting oceans at Uranus. Identifying the presence of liquid water is important because it is essential for life.
The innovative computer model analyzes small movements, or wobbles, of a moon as it rotates around its planet. From this analysis, it can determine the volumes of water, ice, and rock present inside the moon. A small wobble indicates a mostly solid moon, while a larger wobble suggests that the icy outer layer floats above a substantial liquid ocean. When combined with gravitational data, this model can also deduce the ocean’s depth and the thickness of the ice above it.
Uranus, along with Neptune, belongs to a group of planets known as ice giants. Astronomers have observed more ice giant-like bodies outside our solar system than any other category of exoplanets. If Uranus’s moons are found to harbor internal oceans, it could imply that numerous potentially habitable worlds exist throughout the galaxy, as stated by UTIG planetary scientist Doug Hemingway, who created the model.
“Uncovering liquid water oceans within the moons of Uranus would drastically alter our understanding of where life could potentially exist,” he noted.
The findings from UTIG, published in the journal Geophysical Research Letters, will aid mission scientists and engineers in enhancing their chances of discovering oceans. UTIG is part of the Jackson School of Geosciences at The University of Texas at Austin.
All of the large moons in our solar system, including those of Uranus, are tidally locked, which means their rotation is synchronized with their orbit, always displaying the same side toward the planet. However, their rotation is not entirely static; all tidally locked moons experience some oscillation as they orbit. Understanding the degree of these wobbles is essential for determining whether Uranus’s moons possess hidden oceans, and if so, how extensive they may be.
Moons with internal liquid water oceans will wobble more than solid moons. Even the largest oceans, however, lead to only minimal wobble: the moon’s rotation may vary by just a few hundred feet during its orbit.
This slight deviation is still detectable by passing spacecraft. In fact, this method was previously applied to confirm the existence of a global ocean within Saturn’s moon Enceladus.
To assess whether this method could be effective for Uranus, Hemingway projected theoretical models for five of its moons, producing various plausible scenarios. For instance, if the moon Ariel wobbles 300 feet, it likely has an ocean about 100 miles deep, surrounded by a 20-mile-thick layer of ice.
Identifying smaller oceans will require spacecraft to get closer or have more powerful cameras. Nevertheless, the model provides mission planners with a framework to understand what approaches will be effective, according to UTIG Research Associate Professor Krista Soderlund.
“This could be the crucial factor in determining whether we discover an ocean or realize our tools are insufficient upon arrival,” said Soderlund, who was not part of this specific study.
Soderlund has collaborated with NASA on various Uranus mission concepts and is also part of the science team for NASA’s Europa Clipper mission, which recently launched and carries a radar imager developed by UTIG that penetrates ice.
The next step, according to Hemingway, is extending the model to incorporate measurements from additional instruments to gain a better understanding of the moons’ interiors.
The journal article was co-authored by Francis Nimmo from the University of California, Santa Cruz. The research received funding from UTIG.
