Something ‘we don’t understand’ is happening on Uranus’s moons, scientists say

Moons could hold oceans that could be dozens of miles deep

Vishwam Sankaran
Friday 05 May 2023 11:27 BST
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Four of Uranus’s largest moons may contain an ocean layer beneath their icy crusts, according to a new study.

Uranus has at least 27 moons circling it.

And the first insights into the interior makeup and structure of five of the largest ones – Ariel, Umbriel, Titania, Oberon and Miranda – have been offered by scientists from Nasa’s Jet Propulsion Laboratory.

Four of these moons could hold oceans that could be dozens of miles deep, according to the research published in the journal Journal of Geophysical Research: Planets.

Data from Nasa’s Voyager 2 spacecraft launched in 1977 was revisited along with new computer modeling for the study.

Astronomers have long thought Titania, due to its size, could likely be able to retain its internal heat to keep an internal ocean from freezing.

But the other moons were previously widely thought to be too small to retain heat – with temperature changes created by the gravitational pull of Uranus being only a minor source.

“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,” study co-author Julie Castillo-Rogez said.

“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,” she explained.

In the latest study, researchers revisited findings from Nasa’s Voyager 2 flybys of Uranus in the 1980s and from ground-based observations.

They built computer models using additional findings from Nasa’s Galileo, Cassini, Dawn and New Horizon space probes, which each discovered ocean worlds, as well as data on other icy bodies such as Saturn’s moon Enceladus.

The new findings suggest Uranus’s large moons are likely insulated enough to retain internal heat needed to host an ocean.

Researchers also found what could be a potential heat source in the moons’ rocky mantles that release hot liquid which could help an ocean maintain a warm environment.

They said this is especially likely for Titania and Oberon, where the oceans may even be warm enough to potentially support habitability.

Scientists also found that chlorides and ammonia are likely abundant in the oceans of Uranus’ largest moons.

The salts in the water, especially ammonia, could be another source of antifreeze that maintains the moons’ internal oceans, they suspect.

“We need to develop new models for different assumptions on the origin of the moons in order to guide planning for future observations,” Dr Castillo-Rogez said.

Understanding what lies beneath and on the surfaces of these moons will help astronomers and engineers develop the best science instruments to study them in future missions.

The new findings, they said, can also help design instruments that future probes can use to look for liquid water in the deep interiors of these moons.

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