New Delhi: The weirdest planets in the Solar System may just be stranger than previously imagined. Uranus and Neptune are conventionally both considered
to be ice giants. The Earth has a metallic core, surrounded by a mantle of molten rock or magma, with a solid rocky crust. The ice giants on the other hand have an atmosphere of hydrogen, helium and methane as their outermost layer, with an icy mantle, made up of water, ammonia and methane ices, with a rocky core. New interior models of the ice giants indicate that a range of possibilities fit the observations.
The researchers examined previous assumptions of these ice giants, that are based on theoretical predictions of the process of planet assembly around a newborn star, and reconciled them with observations. The scientists started with a random density profile for the interior of the ice giants, then calculated the planetary gravitational field based on observations to infer the possible compositions of the interior. The researchers discovered that Uranus and Neptune may be ice-rich or water-rich.
The mystery of non-dipolar magnetic fields
A paper describing the research has been published in Astronomy and Astrophysics. Lead author of the study, Luca Morf explains, “The ice giant classification is oversimplified as Uranus and Neptune are still poorly understood. Models based on physics were too assumption-heavy, while empirical models are too simplistic. We combined both approaches to get interior models that are both “agnostic” or unbiased and yet, are physically consistent.”
Uranus and Neptune have puzzling magnetic fields, that are not dipolar like the Earth. The complex magnetic fields on the ice giants have more than two poles. The new models explain these complex, tangled magnetic fields because of layers of ionic water, that generate magnetic dynamos in locations that explain these magnetic fields. Uncertainties remain in the composition of the remote interiors of these ice worlds, with the study highlighting the need for new interplanetary missions to explore these exotic worlds.
