Like Dia­monds In The Sky

Comme des dia­mants dans le ciel (réf. à la chan­son Dia­monds de Ri­han­na, 2012)

Vocable (Anglais) - - Édito / Sommaire -

Jack­pot cos­mique.

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.

COSMIC JACK­POT

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.

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