Scientists talked about a possible ancient ocean on the moon of Uranus

In the past, an ocean about 170 km thick could have been located under the icy surface of Ariel, one of Uranus' moons. Planetary scientists came to this conclusion after studying the faults on the surface of the satellite and modeling the effect of tidal forces. About how scientists have reconstructed Ariel's possible past and why it is not yet possible to talk about the ocean on it today, see the "Izvestia" article.

What was discovered on the surface of Ariel

Scientists mapped large faults, and then calculated what stresses could occur in the crust of Ariel as it moved around Uranus. The gravity of the planet slightly changes the shape of the satellite: when the distance between them changes, its icy shell experiences repeated stretching and compression.

According to the researchers' calculations, in the past, Ariel's orbit could have been noticeably less circular than it is now. Its eccentricity, an indicator of the deviation of the orbit from the circle, should have reached about 0.04. This is about 40 times the current value. Such an orbit would enhance tidal deformations and could create stresses sufficient to form faults.

What could be the depth of the ocean

The model assumes the existence of an ocean about 170 km thick under the icy crust. For comparison, the average depth of the Pacific Ocean is about 4 km. At the same time, the number 170 km is the result of a calculation for the possible past state of Ariel, and not a measurement of the water layer by the spacecraft.

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The authors examined different combinations of ice thickness, ocean size, and the shape of the orbit. As explained by co-author Alex Pattoff, senior researcher at the Planetary Science Institute, the observed cracks could occur with a thin ice shell over a vast ocean or with a more elongated orbit and a smaller ocean. In both scenarios, the liquid layer helps explain the fault pattern.

This is still indirect evidence. Researchers are reconstructing the conditions under which existing structures could have formed, but they don't know exactly when the proposed ocean originated, how long it lasted, or whether liquid water remains under the surface of Ariel today.

Why do scientists talk about two oceanic worlds?

Earlier, the same group explored Miranda, another moon of Uranus with a highly rugged surface. Their calculations also pointed to the possibility of a subglacial ocean in the past. Thus, Ariel may not be the only satellite of the planet whose history is connected with liquid water. Currently, these studies do not confirm the presence of oceans on both satellites.

New observations will help verify the models. The images of Ariel's southern hemisphere were obtained by Voyager 2 during a flyby of Uranus in 1986, while the northern hemisphere remains virtually unexplored. The researchers hope that a future mission will be able to verify their predictions about the location of faults and ridges there. According to study co-author Tom Nordheim, to answer these questions, scientists need to return to the Uranian system.