Not Ice Giants at All? Neptune and Uranus Possibly More Rocky Inside
The two outermost planets in the solar system are generally considered ice giants, yet we know little about their interiors. This is highlighted by a new study.
The interior of Uranus as an ice giant (left) or as a rock giant
(Image: Keck Institute for Space Studies/Chuck Carter)
Contrary to common assumptions, the two outermost planets in the solar system might be rocky rather than icy: Uranus and Neptune would then not be ice giants, but rock giants. This is suggested by a study by two researchers from the University of Zurich, which has now been presented. Luca Morf and Ravit Helled conclude from this that previous physical models of the composition of the two celestial bodies were too simplistic, and their interiors are by no means limited to ice. They had already suspected this, but only now have they found computational evidence for it. The finding would therefore also fit with the fact that the dwarf planet Pluto, which is not far from both, also consists predominantly of rock.
No Final Certainty
As the two researchers explain, they combined physical and empirical models of the two planets for their analysis. The result was "new, neutral, and physically consistent models." Starting from a random density profile, they then calculated a gravitational field that matched the observations. From this, they derived a possible composition. They repeated this often enough to achieve the best possible agreement between the model and the measurement data. The result was that the possible composition of Uranus and Neptune is by no means limited to ice.
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Furthermore, the work revealed that Uranus's magnetic field might lie deeper than Neptune's. For both, they differ enormously from Earth's because they are not only more chaotic but also have more than two poles. They are currently limiting their hypothesis about the composition of the two planets. The results are promising, but "some uncertainty remains." We do not yet understand well enough how materials behave inside planets, and that could influence the results. However, their work could pave the way for a fundamentally new picture of the solar system. Besides the rocky planets and the gas giants, it would then not consist of ice giants. The work has been published in Astronomy & Astrophysics.
(mho)
