It is highly probable that the four biggest moons of Uranus might harbor a vast ocean layer, spanning several miles beneath their icy coverings and far-reaching cores. NASA has released a recent study in the Journal of Geophysical Research, which not only helps in outlining the course of a potential Uranus mission but has wider implications transcending beyond the planet itself.
There are a minimum of 27 moons revolving around Uranus, with the biggest four being roughly two to three times smaller than our Moon for Earth, with Ariel measuring around 720 miles in diameter and the largest, Titania, measuring 980 miles. Due to its size, researchers have long speculated that Titania is the most probable satellite to sustain internal heat caused by radioactive decay. It was believed that Uranus’ other moons were too petite to maintain the warmth required to prevent an internal ocean from freezing, as the heating caused by Uranus’ gravitational pull is insignificant.
Using data from Voyager 2 and new computer modeling, a recent analysis examined all five of Uranus’ major moons: Ariel, Umbriel, Titania, Oberon, and Miranda. Titania and Oberon, the moons farthest from Uranus, may harbor oceans as deep as 30 miles beneath their surface, while Ariel and Umbriel could have oceans up to 19 miles deep.
In a statement, Julie Castillo-Rogez, a planetary scientist at NASA’s Jet Propulsion Laboratory and co-author, expressed that “When it comes to small bodies – dwarf planets and moons – planetary scientists previously have found evidence of oceans in several unlikely places, including the dwarf planets Ceres and Pluto, and Saturn’s moon Mimas.”
“So there are mechanisms at play that we don’t fully understand. This paper investigates what those could be and how they are relevant to the many bodies in the solar system that could be rich in water but have limited internal heat.”
After analyzing the data gathered from Voyager 2’s flybys of Uranus in the 1980s and recent ground-based research, the new study utilized additional discoveries from NASA’s Galileo, Cassini, Dawn, and New Horizons missions (which all explored ocean worlds), along with knowledge of the chemistry and geology of Saturn’s moon Enceladus, Pluto and its moon Charon, and Ceres to construct computer models. These moons situated around Pluto and Saturn are icy bodies of similar size to Uranus’ moons.
By utilizing modeling techniques, the team was able to determine the porosity of the Uranian moons’ surfaces, concluding that they are adequately insulated to preserve internal heat required for an ocean to exist. Furthermore, the models unveiled that the moons’ rocky mantles could serve as a viable heat source, producing hot liquid that would contribute to sustaining a warm environment for the ocean. The potential for such warming is particularly high in the cases of Titania and Oberon, where the oceanic temperatures may even be conducive to supporting life forms.
Scientists can gain insight into the substances present on the icy moons’ surfaces by examining the composition of these oceans, provided that any underlying materials were displaced by internal geological processes. Data obtained through telescopes suggests that material recently flowed onto the surface of Ariel, one of the moons, potentially originating from icy volcanoes.
Miranda, the fifth largest moon orbiting Uranus and positioned closest to it, possesses surface characteristics that could be relatively new, indicating that it might have had enough warmth to maintain an ocean at certain moments. Nonetheless, according to recent thermal simulations, Miranda possibly did not harbor the water body for a considerable length of time, as its capacity to retain heat is low, causing the ocean to freeze.
The new study reveals that chlorides and ammonia are probably plentiful in the oceans, which could serve as a means of regulating temperature and maintaining the internal oceans of organisms. Additionally, the modeling conducted by the author indicates that the salts present in the water could provide another form of temperature control, due to ammonia’s ability to act as an antifreeze.
Exploring the underlying mechanisms of the surface of a moon may assist scientists and engineers in selecting suitable tools for future missions, yet there are numerous uncertainties surrounding the vast moons of Uranus that require further attention.
Castillo-Rogez noted that “We need to develop new models for different assumptions on the origin of the moons in order to guide planning for future observations.”