- Ariel, a moon of Uranus, may have an underground oceanadding it to the list of possible ocean worlds in our solar system.
- Unexpected ice deposits of carbon dioxide and carbon monoxide On Ariel's surface, mainly on the trailing hemisphere, the side opposite the direction in which the Moon moves in its orbit, there is evidence of the presence of an ocean. These deposits indicate that the ocean is replenishing inside.
- Ariel shows signs of geological activity, perhaps even ice volcanoes.Future missions are expected to further explore and confirm these findings.
Does Uranus' Moon Ariel Have a Hidden Ocean?
He Webb A space telescope has made new observations of Ariel, a moon of the outer planet Uranus, suggesting that Ariel could harbor an ice-covered subsurface ocean. Icy ocean worlds in our outer solar system are a What a thingScientists are so fascinated by the possibility that they are sending a Space mission to another possible ocean moon, Jupiter's moon Europa. Why? Because they think these ocean moons could harbor life! On July 24, 2024, a research team led by the Johns Hopkins University Applied Physics Laboratory (JHUAPL) in Laurel, Maryland, He pointed out The surprising presence of carbon dioxide on Ariel's surface, they said, could be offset by a hidden liquid ocean deep inside Ariel.
The researchers published His new peer reviewed to study in The letters of the astrophysical journal July 24, 2024.
The mystery of Ariel's carbon dioxide ice
The main clue to the existence of a subsurface ocean comes from Ariel's icy surface. Ariel's surface is geologically the youngest of Uranus's. 28 known moonsIt is largely covered by water, carbon dioxide and ammonia ice.
The carbon dioxide ice surprised astronomers. Ariel has no detectable atmosphere, so even in the extreme cold in which Uranus orbits the Sun, it should sublimate (turn into gas). But since there's a fair amount of ice on the Moon's surface, something must be continually replenishing it. Plus, most of the ice is on Ariel's trailing hemisphere. That's the hemisphere that always faces away from the Moon's orbit.
Scientists have proposed two main theories over the years. One is that charged particles in Uranus's interior… magnetosphere either solar radiation interact with the surface of Ariel. This could create carbon dioxide through a process called radiolysis.
The other possibility is that primordial carbon dioxide is trapped in water ice inside Ariel. Outgassing could leave deposits of carbon dioxide ice on the surface.
Carbon monoxide that shouldn't be there
The new Webb observations suggest the second option is more likely. The researchers found that Ariel has some of the richest carbon dioxide deposits in the entire solar system. On the moon's trailing hemisphere, they are about 10 mm thick.
But Webb detected something else that puzzles scientists: carbon monoxide. Scientists didn't expect to find it on Ariel. And, like carbon dioxide, it's found mostly in Ariel's trailing hemisphere. As lead author Richard Cartwright from JHUAPL noted:
It just shouldn't be there. You have to get down to 30 kelvin (-405 degrees Fahrenheit) for the carbon monoxide to stabilize. The carbon monoxide would also have to be actively replenished, no doubt.
The problem is that Ariel's surface is, on average, 65 degrees Fahrenheit warmer (36 C warmer). So how can there be carbon monoxide there? As Cartwright said, it would have to be replenished somehow.
Researchers said radiolysis could explain some of the replenishment, but it is unlikely to explain all of it. Other research has suggested the process would be limited on Ariel. This is because the axis of the moon's magnetic field and the orbital plane Uranus' moons are about 58 degrees out of phase, so interactions with the magnetic field would not produce enough carbon dioxide or carbon monoxide to explain the observed amounts.
An underground ocean in Ariel?
So only gases originating from Ariel's interior remain. Researchers say this is the most likely scenario to explain most of the ice deposits on the surface. In fact, carbon dioxide and carbon monoxide may have their origin in a subsurface ocean.
The processes involved may be ancient, and the gases are simply still seeping to the surface. Or they may be leaking now. This means that Ariel likely had a hidden ocean in the past, or still has one today.
Another tentative discovery – carbonate minerals – would also support the ocean explanation. The formation of such minerals requires the interaction of rock and liquid water. Cartwright said:
If our interpretation of that carbonate feature is correct, then it's a pretty important result because it means it had to have formed inland. That's something we absolutely need to confirm, either through future observations, modeling, or some combination of techniques.
Is Ariel an active world?
So far, only Traveler 2 On January 24, 1986, the probe visited Ariel, Uranus' fourth-largest moon. The flyby was brief, but the spacecraft saw a world with many deep grooves and cracks on its surface. There were also other smooth areas that may have been the result of cryovolcanic (ice volcano) eruptions. All this indicates that Ariel was – and perhaps still is – geologically active. There could even be plumes, reminiscent of those of Enceladus and maybe EuropeA different study in 2023 suggested that Ariel or the moon Miranda, or even both, are release of plasma particles in the magnetosphere of Uranus.
If that's the case with Miranda, then it could also have an underground ocean, the scientists said.
Scientists also noted that the canyons and grooves are found mostly on the trailing side of Ariel. It's possible that carbon dioxide and carbon monoxide leak through them toward the surface. They could provide an easy conduit for gases to escape from Ariel's interior. But researchers don't know for sure, since Voyager 2 only saw part of Ariel's surface — about 35 percent — during its flyby on Jan. 24, 1986. There could also be more canyons and grooves on the leading hemisphere. Cartwright said:
It's a bit of an exaggeration because we haven't seen much of the moon's surface yet. We won't know until we make more specific observations.
The Uranian system is fascinating
The findings, however, show that Ariel is a more complex world than we thought. This probably applies to Uranus and its other moons as well. Ian Cohen At JHUAPL they commented:
All of this new knowledge underscores just how fascinating the Uranus system is. Whether it's unlocking clues about how the solar system formed, better understanding the planet's complex magnetosphere, or determining whether these moons are possible ocean worlds, many of us in the planetary science community are eager for a future mission to explore Uranus.
Bottom line: Researchers using NASA's Webb Space Telescope have discovered that Uranus's fourth-largest moon, Ariel, may have an underground ocean, similar to Europa, Enceladus and others.
Through the Johns Hopkins Applied Physics Laboratory
Read more: New moons! Uranus is now 28 and Neptune 16
Read more: Signs of life on ocean moons could be just beneath the surface
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