NASA says 4 of the largest Uranus moons could have oceans

The study published in the Journal of Geophysical Research details the evolution of the makeup and structure of all five large Uranus moons—Ariel, Umbriel, Titania, Oberon, and Miranda. The study suggests that four of these moons could hold oceans that could potentially be dozens of kilometres deep.

Uranus and its moons

A total of 27 moons orbit Uranus. Among the four biggest, their sizes range from 1,160 kilometres across (Ariel) to 1,580 kilometres across (Titania).

For a long time, scientists believed that the planet’s biggest moon, Titania, would be the most likely to retain internal heat. They generally considered the other moons to be too small to retain the heat necessary to keep an ocean from freezing. This retention of internal heat from radioactive decay will be an important factor because Uranus is only a minor source of heat.

“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,” said Julie Castillo-Rogez, lead author of the paper, in a press statement.

Looking for the Uranus moon oceans

The research re-analysed the findings from when NASA’s Voyager 2 flew by Uranus in the 1980s. It also studied ground-based observations. Using this data, the researchers built computer models that included additional data from the Galileo, Cassini, Dawn and New Horizons spacecraft.

Based on this modelling, the researchers gauged how porous the surfaces of the Uranian moons are. With this, they found that they are insulated enough to retain the amount of internal heat that would be needed to host an internal ocean.

They also found what could be a potential source of heat in the moons’ mantles, which releases hot liquid. This heat source could help an ocean maintain a warm environment, and according to NASA, it is a scenario that is especially likely for Titania and Oberon, where the oceans could even be warm enough to support life.

But internal heat is not the only factor that could contribute to a Moon having a subsurface ocean. The study also suggests the abundance of chlorides and ammonia in the oceans of the four largest Uranian moons. Ammonia is known to act as antifreeze. The salts present in the water could also act as an antifreeze.

Future space missions, like any involving NASA’s envisioned SWIM concept swimming robots, could investigate subsurface oceans to see what they are made of and whether they can be habitable.