A view of Ariel composed by NASA/JPL-Caltech, December 12, 2016.
| Photo Credit: Kevin M. Gill

The Solar System has many mysteries. We don’t know why the Sun’s corona is so hot. We don’t know why Saturn’s moon Titan has such a significant atmosphere. We don’t know why Triton rotates in the direction opposite to its host planet, Neptune, although a recent study found an answer: Triton and Pluto had a common origin before Neptune pulled Triton to itself.

Another mystery in the Solar System may be coming to a similar close. Astronomers have been curious why the surface of Uranus’s moon Ariel has frozen carbon dioxide (CO₂). At that distance from the Sun, the CO₂ should have already vaporised into space — yet the ice covers the moon’s surface. On July 24, NASA’s James Webb Space Telescope (JWST) reported evidence of a liquid ocean buried under Ariel’s surface, supplying CO₂ to the world above.

The people behind the finding came to this conclusion when they found carbon monoxide. If Ariel has to have this compound, it has to have a surface temperature around 18 degrees C less than what it is or it could have a subsurface water ocean producing carbon oxides. One side of Ariel has cracks and grooves through which icy slop and these compounds could be gushing out to the surface. JWST also found signs of carbonite minerals, which could be formed when water interacts with rocks.

More studies and space missions will be needed to confirm these details. If they are, we’ll have yet another water-bearing moon out there.