Like Diamonds In The Sky
Comme des diamants dans le ciel (réf. à la chanson Diamonds de Rihanna, 2012)
Diamonds are probably available in embarassing abundance in the cosmos.
Des diamants comme s’il en pleuvait. Littéralement. C’est ce qu’ont démontré des scientifiques en recréant les conditions atmosphériques d’Uranus et de Saturne. A l’aide de polystyrène et d’un laser, ils sont parvenus à confirmer l’hypothèse formulée par les chercheurs depuis longtemps : il pleut des pierres précieuses sur ces deux planètes.
In the marketplaces of planet Earth diamonds are both desirable and scarce, and that makes them expensive. Both the demand and the rarity are, however, largely artificial. Diamonds were made desirable in the 20th century mainly by a marketing campaign from De Beers, a big South African producer of the stones. The scarcity was, until recently, a result of the same company—which at one point controlled about 90% of the world’s production— ensuring that the number of stones which found their way into the world’s jewellery shops was well regulated.
2. In nature, though, diamonds are unremarkable. They are simply crystals of carbon, albeit crystals of a type that needs a fair amount of pressure to form. And carbon is the fourth-most abundant element in the universe. For that reason, as demonstrated in a paper just published
in Nature Astronomy, they are probably available in embarrassing abundance in the cosmos.
3. Dominik Kraus, a physicist at the Helmholtz Centre in Dresden, and his colleagues, are interested in ice-giant planets, such as Uranus and Neptune. Ice giants are rich in heavy elements such as oxygen, nitrogen and, crucially, carbon. That carbon is locked up in compounds, mostly hydrocarbons such as methane and ethane.
4. Ice giants, as the name suggests, are also big. This means that, in the depths of their thick atmospheres, temperatures are high enough to split those hydrocarbons into hydrogen and
carbon, and pressures are sufficient to compress the carbon into diamonds. The consequence, 10,000km or so beneath the top of the atmosphere, is a constant rain of diamonds.
5. This research will be of interest to more than gem-cutters of the distant future looking for new sources of supply. Knowing the temperature and pressure at which parts of an ice giant’s atmosphere start to decompose into their elementary constituents can help astronomers fix the relationship between the radius and mass of such planets. Knowing how they relate will help catalogue just how many more diamond-encrusted planets are lurking out there in the cosmos.