A moon of Uranus could have a hidden ocean, James Webb Space Telescope finds

Using the James Webb Space Telescope (JWST), astronomers discovered that Ariel, a moon of Uranus, could be hiding in a buried liquid water ocean. 

The discovery could supply an answer to a mystery surrounding this Uranian moon that has perplexed scientists: the fact Ariel's surface is covered with a significant amount of carbon dioxide ice. This is puzzling because at the distance Uranus and its moons exist from the sun, 20 times further out from the sun than Earth, carbon dioxide turns to gas and is lost to space. This means some process must refresh the carbon dioxide at the surface of Ariel.

Previous theories have suggested this happens as a result of interactions between Ariel's surface and charged particles trapped in Uranus' magnetosphere that provide ionizing radiation, breaking down molecules and leaving carbon dioxide, a process called "radiolysis."

However, new evidence from the JWST suggests the source of this carbon dioxide could come not from outside Ariel but from its interior, possibly from a buried subsurface ocean.

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Because chemical elements and molecules absorb and emit light at characteristic wavelengths, they leave individual "fingerprints" on spectra. The team behind this discovery used the JWST to gather spectra of light from Ariel, which helped them paint a picture of the chemical makeup of the Uranian moon. 

Comparing this to simulated spectra from a chemical mix in the lab here on Earth revealed to the team that Ariel has some of the most carbon dioxide-rich deposits in the solar system. Not only did this add an extra 10 millimeters (0.4 inches) of thickness to the ice on the side of the tidally locked Ariel that permanently faces away from Uranus, but it also revealed clear deposits of carbon monoxide for the first time.