Four out of five of Uranus’ moons have the probability of hosting oceans, says a recent study by a team of researchers from the California Institute of Technology, USA, SETI Institute, USA, Massachusetts Institute of Technology (MIT), USA, and University of Maryland, USA, published in Journal of Geophysical Research.
Their study involved modeling the internal evolution, present-day physical structures, and geophysical as well as geochemical signatures, which could be recorded by the spacecraft. The four moons of Uranus that could have water on their surface include Ariel, Titania, Umbriel, and Oberon. The team revisited data obtained from Voyager 2.
The researchers predicted that, if at all the moons contained liquid, it would be present as residual oceans, which would be less than 30 kilometers in thicken on Ariel and Umbriel, and would be less than 50 kilometers in thickness on Titania as well as Oberon. The fifth moon of Uranus, Miranda, is unlikely to have water bodies on it, claim the researchers.
Along with this, they believe that the water bodies might be hypersaline (saltier than seawater), and that the magnetic fields induced by these liquid bodies can be detected by spacecraft-based magnetometers in the future.
The scientists also believe that if the water is maintained by certain elements—ammonia and chloride—it would be nearly impossible to detect magnetic fields induced by the water bodies, as the electrical conductivity of these elements is close to zero.
In their study’s results, the researchers provide thermal evolution (refers to the consequence created due to the competition between heat-producing internal energy sources and its removal due to mantle convection) models of the Uranus’ moons. Along with this, they assess and present the properties of the water bodies that might be there currently on few of the moons of Uranus.
The thermal evolution models for Miranda show that its interior mostly compacts but partially melts and differentiates (a process where the layers of the planet or moon separate based on their density) , whereas those of Ariel and Titania experience near global melting of their volatile phase. For Titania, its rocky core can undergo more differentiation due to thermal metamorphism (transformation of original rock due to high temperatures), states the article. Umbriel and Oberon can be represented by the thermal models of Ariel and Titania, respectively.
Their results also show that Miranda’s interior was not able to get warm enough for the interior to evolve, whereas Titania’s and Ariel’s ice could melt partially, which could lead to partial differentiation. In addition, the researchers say that the preservation of a porous lid on Ariel and Titania facilitates the preservation of a liquid layer (approximately 10–20 kilometers) until the present.
These five moons of Uranus have a two-layer interior, a mean hydrosphere density of 1,000 kilograms per cubic metres, and a rock density not more than 3,400 kilograms per cubic metres, the paper reports.
Based on their analysis, the researchers point out that Umbriel, Ariel, Titania, and Oberon could have preserved liquid until now, which is sustained by radioisotope decay heat and decreased thermal conductivity of the moon’s outer shell. These water bodies could be residual or ‘relict’ rather than being thick, confirm the researchers.
Furthermore, the researchers believe that studying the presence of deep oceans in Uranus’ moons would enable them to better understand the process involved in preserving water bodies in icy moons, which are less than 1,000 kilometers in diameter, and determine the probability of environments being habitable in the outer solar system.