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- Uranus and Neptune are the ice giant planets in our solar system<\/strong>. They have deep atmospheres of hydrogen, helium and methane. But what are they like on the inside?<\/li>\n
- Scientists thought Uranus and Neptune contain an unusual form of water<\/strong> that is part liquid and part solid, as well as methane and ammonia. Intense pressures might also turn carbon atoms into diamond material that rains down in the planets\u2019 atmospheres.<\/li>\n
- Instead, Uranus and Neptune might have deep oceans<\/strong> of water below their atmospheres, a new study suggests. Another layer rich in carbon would be below that, and the two layers can never mix together, like oil and water.<\/li>\n<\/ul>\n
Are Uranus and Neptune water worlds?<\/h3>\n
Scientists have long thought that the ice giants \u2013 Uranus and Neptune \u2013 have a hot, dense fluid of icy water, methane and ammonia around their cores. But on November 25, 2024, scientists at the University of California, Berkeley, suggested a different scenario. Instead, they said the interiors of the two giant planets may be more layered, with deep global oceans of water beneath their atmospheres. This could also explain why both planets have unusually disorganized magnetic fields.<\/p>\n
The researchers published their peer-reviewed findings in Proceedings of the National Academy of Sciences<\/em> (PNAS) on November 25, 2024.<\/p>\n
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The ice giants Uranus and Neptune<\/h3>\n
Uranus and Neptune are the two ice giants in our solar system. Unlike the gas giants Jupiter and Saturn, their interiors are thought to contain more icy water, methane and ammonia. The water may be in the form of superionic water, which is actually part solid and part liquid. This region is below the planets\u2019 deep, thick atmospheres. Below that is a solid core.<\/p>\n
Scientists have also theorized that their interiors contain superionic water ice, which is actually hot<\/em> and part solid and part liquid. Or diamond rain, where pressures are so great that carbon atoms get squeezed into diamond and rain down in the atmosphere. Wild!<\/p>\n
![\"Uranus](\"https:\/\/earthsky.org\/upl\/2024\/11\/Uranus-Neptune-Voyager-2-1980s.jpg\")
View larger. | NASA\u2019s Voyager 2 spacecraft captured these views of Uranus and Neptune during its flybys of the planets in the late 1980s. A new study suggests both giant planets could have deep layers of water below their atmospheres. Image via NASA\/ JPL-Caltech\/ B. J\u00f3nsson\/ NOIRLab.<\/figcaption><\/figure>\n A layered interior with oceans?<\/h3>\n
But now, researcher Burkhard Militzer at UC Berkeley has proposed an alternative possibility. The interiors of both planets may be more distinctly layered. In this scenario, a global ocean of water is below each planet\u2019s atmosphere. And below that would be a highly compressed fluid of carbon, nitrogen and hydrogen.<\/p>\n
But just like oil and water, the two layers don\u2019t mix and remain separate.<\/p>\n
Previous studies have suggested the interiors of both planets contain icy water, methane and ammonia. The new study suggests that instead of remaining as one layer, this region divided into the two distinct layers. Essentially, hydrogen would be squeezed out of the methane and ammonia.<\/p>\n
The study estimates that the water\/ocean layer on both Uranus and Neptune is about 5,000 miles (8,000 km) thick. The carbon layer would be a similar thickness.<\/p>\n
![\"2](\"https:\/\/earthsky.org\/upl\/2024\/11\/Uranus-Neptune-interiors-new-model-water-carbon.jpg\")
View larger. | Diagram depicting the interiors of Uranus and Neptune, based on the new model. The light blue on top is the thick atmosphere and the darker blue is the water-hydrogen ocean. Image via Burkhard Militzer\/ UC Berkeley.<\/figcaption><\/figure>\n Lack of magnetic fields<\/h3>\n
Scientists have also long known that both Uranus and Neptune lack magnetic fields similar to Earth\u2019s. The new study could explain why. Militzer said:<\/p>\n
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We now have, I would say, a good theory why Uranus and Neptune have really different fields, and it\u2019s very different from Earth, Jupiter and Saturn. We didn\u2019t know this before. It\u2019s like oil and water, except the oil goes below because hydrogen is lost.<\/p>\n<\/blockquote>\n
Voyager 2 found that both planets lack a dipole magnetic field, and instead only have disorganized magnetic fields. A dipole magnetic field is like what you see with a bar magnet. Earth\u2019s dipole magnetic field is created by convection \u2013 the movement of heat through a fluid like air or water \u2013 in its interior, in the liquid outer iron core.<\/p>\n
But since neither Uranus or Neptune have a dipole magnetic field, that means there\u2019s no convection in their interiors. If there are two layers that don\u2019t mix, that would prevent convection from occurring.<\/p>\n
Simulating the planets\u2019 interiors<\/h3>\n
Previously, Militzer used computer simulations of 100 atoms to try to figure out why the layers wouldn\u2019t mix. The atoms had the same proportions of carbon, oxygen, nitrogen and hydrogen as the known composition of elements in the early solar system. The interiors of the two planets had an estimated 3.4 million times Earth\u2019s atmospheric pressure and were 4,750 Kelvin (8,000\u00b0F) in temperature. But even in those simulations, he couldn\u2019t determine what the layers would be composed of.<\/p>\n
Then, last year, Militzer ran new simulations, but this time with 540 atoms. He found that in similar conditions in the interiors of Uranus and Neptune, the layers formed naturally. Militzer explained:<\/p>\n
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One day, I looked at the model, and the water had separated from the carbon and nitrogen. What I couldn\u2019t do 10 years ago was now happening. I thought, \u2018Wow! Now I know why the layers form: One is water-rich and the other is carbon-rich, and in Uranus and Neptune, it\u2019s the carbon-rich system that is below. The heavy part stays in the bottom, and the lighter part stays on top and it cannot do any convecting.\u2019<\/p>\n
I couldn\u2019t discover this without having a large system of atoms, and the large system I couldn\u2019t simulate 10 years ago.<\/p>\n<\/blockquote>\n
Water on top, carbon on bottom<\/h3>\n
So basically, it was like the oil and water analogy. Except in this case, the water layer stayed on top instead of the bottom. Convection could occur in the upper water-hydrogen ocean layer, but not in the lower carbon-rich layer. Therefore, the water layer could produce the disorganized magnetic field, but not a full dipole magnetic field like Earth.<\/p>\n
In addition, the gravity fields of Uranus and Neptune in the layered model matches what Voyager 2 actually measured decades ago.<\/p>\n
The new model could explain the interior behavior of both Uranus and Neptune without the need for diamond rain or superionic water. As Militzer said:<\/p>\n
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If you ask my colleagues, \u2018What do you think explains the fields of Uranus and Neptune?\u2019 they may say, \u2018Well, maybe it\u2019s this diamond rain, but maybe it\u2019s this water property which we call superionic.\u2019 From my perspective, this is not plausible. But if we have this separation into two separate layers, that should explain it.<\/p>\n<\/blockquote>\n
Similarities to mini-Neptunes<\/h3>\n
The findings are reminiscent of some mini-Neptune type exoplanets, which are also thought to have deep water layers beneath thick hydrogen atmospheres. Others \u2013 called hycean worlds \u2013 might have solid surfaces, with deep global oceans and thick hydrogen atmospheres.<\/p>\n
Bottom line: Uranus and Neptune might have deep water oceans beneath their thick atmospheres, with a carbon layer below them. Like oil and water, the two layers never mix.<\/p>\n
Source: Phase separation of planetary ices explains nondipolar magnetic fields of Uranus and Neptune<\/p>\n
Via University of Berkeley<\/p>\n
Read more: True colors of Uranus and Neptune in newly processed images<\/p>\n
Read more: New Hubble images show storms on Uranus and Neptune<\/p>\n
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\n - Scientists thought Uranus and Neptune contain an unusual form of water<\/strong> that is part liquid and part solid, as well as methane and ammonia. Intense pressures might also turn carbon atoms into diamond material that rains down in the planets\u2019 atmospheres.<\/li>\n