Friday, June 3, 2022

Uranus and Neptune are similar and different

Uranus and Neptune have much in common. Their mass, size and even atmospheric compositions are similar. Furthermore, the two planets are the outermost of the Solar System, suggesting a similar formation mechanism.

However, within the wavelengths of visible light Neptune appears dark blue, while Uranus has a more blue colouring. Until now this difference had remained partly a mystery, but today thanks to a new study published in the Journal of Geophysical Research we may have an answer.

The researchers of this study have in fact managed to build a first unique model for the atmosphere of the two planets. Previous studies had always focused on monochromatic wavelengths, while this study was based on observations obtained over the entire range of visible and near-infrared light. Researchers have theorized that in the atmospheres of the two planets there are three states of aerosols located at different heights. The central layer, which according to the model is the one that affects color, is more often on Uranus than on Neptune. It has been suggested that methane ice particles in the atmosphere precipitate and condense on the aerosols of this layer, forming something like methane snow. 

The atmosphere of Neptune, however, is much more active than that of Uranus, as evidenced by the speed of the winds. The turbulence on Neptune would then be able to remove the methane snow from the layer, keeping it thin. These suspended particles would thus be responsible for the intense blue color.

On Uranus, where this does not happen, the color is instead blue.

Credit: NASA, JPL.

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