Ariel, Uranus’ fourth-largest moon, may have an internal ocean, a discovery that has puzzled scientists. The discovery was made thanks to the James Webb Space Telescope by a team of more than 20 scientists from various international institutions. … It was just published in “Astrophysical Journal Letters‘.
The presence of an underground ocean on Ariel may be the answer to a long-standing mystery surrounding this Uranian moon: the fact that its surface is covered in a large amount of carbon dioxide ice. This is troubling because at that distance from the sun, 20 times farther away than Earth, carbon dioxide turns into gas and is lost to space. So some other process must be able to accumulate it on Ariel’s surface.
Previous theories suggest that the buildup of this compound is the result of interactions between the moon’s surface and charged particles trapped in Uranus’ magnetosphere. These interactions produce ionizing radiation, which in turn breaks apart the molecules and leaves behind carbon dioxide, in a process called “radiolysis.”
But new data from James Webb suggests that the source of this carbon dioxide cannot be external, but rather within the moon, perhaps in the form of an underground ocean.
ocean of liquid water
The researchers’ analyses revealed that not only is there carbon dioxide on Ariel, but that deposits of this compound are the richest in the entire solar system, forming a layer on the surface ice that reaches a thickness of 10 mm. For the first time, the researchers also found carbon monoxide on the surface of Ariel.
“Simply put,” says Richard Cartwright, of the Johns Hopkins University Applied Physics Laboratory and the first signatory to the article, “all this shouldn’t be there. The temperature would have to drop to -207 degrees Celsius for carbon monoxide to settle (however, the temperature on Ariel’s surface is up to 18 degrees warmer). The only explanation, without a doubt, is that something is regenerating the carbon monoxide.”
Cartwright acknowledges that radiometric analysis could explain some of this substitution. But not all of it, which could mean that most of the carbon and oxygen compounds seen on Ariel’s surface were created by chemical processes in an ocean of liquid water trapped beneath the surface’s ice layer.
Scientists have long suspected that Ariel’s cracked, fissured “skin” may be due to active cryovolcanoes, volcanoes that erupt instead of lava, spewing tall plumes of frozen mud so powerful that they shoot material into the magnetic field of Uranus itself.
Most of the cracks and grooves on Ariel’s surface are on the side of the moon that doesn’t face the planet, which may have something to do with the fact that carbon dioxide and carbon monoxide are mostly found on this side of the moon.
Another idea, carbonates.
But Webb found more evidence that the ocean was underground. In fact, spectroscopy indicated the presence of carbonite minerals, salts that form when rock interacts with liquid water.
“If our interpretation is correct, this result is important because it suggests that these carbonates must have formed inland,” Cartwright says. “It’s something we definitely need to confirm, whether through future observations, modeling, or a combination of techniques.”
Uranus and its moons have not been visited by a spacecraft since Voyager 2, which passed by nearly four decades ago on its way to the outer solar system. For some time now, experts have been insisting on the importance of a mission dedicated exclusively to the Uranian system.
Cartwright believes it would be an opportunity to gather valuable information about Uranus and Neptune, the other ice giants in our planetary system. Such a mission could provide vital data about other moons of both planets that could also harbor oceans. An unexpected amount of water is found throughout our solar system.
“Beer enthusiast. Subtly charming alcohol junkie. Wannabe internet buff. Typical pop culture lover.”