LET it snow, but forget the powdery white stuff. Instead, snow is warm and black on hot Jupiters - scorching worlds that sit close to their sun.
Hot Jupiter HD 209458b has one side that always faces its star and reaches 2000 °C, while the other is in perpetual night at 500 °C. Older models suggested that titanium oxides would be gaseous on the day side but condense if blown to the night side, falling into the lower atmosphere, where they would become trapped.
Now Vivien Parmentier of the Côte d'Azur Observatory in Nice, France, and colleagues have a model that suggests the snow turns to a gas again as it falls and pressure and temperature rise. Draughts then blow the titanium oxides back to the upper atmosphere, creating a snow cycle (arxiv.org/abs/1301.4522). The snow would be black thanks to trapped silica oxides.
This article appeared in print under the headline "World where snow is hot and black"
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