On A Diamond Sea

Next Big Future reports on Diamond Oceans. Apparently the Lawrence Livermore National Lab has been doing ultra-pressure experiments on diamond, getting up to 4 TPa (40 Mbar) then dropping the pressure and temperature to examine what phase changes occur. Seems the stuff becomes a liquid in a pressure/temperature range of relevance to the cores of Uranus and Neptune. Interestingly diamond stays crystalline over the range of P-T normally seen in Uranus/Neptune models. However if there’s a strong, stable thermally stratified region, then heat loss from the core might be lower and the core temperature much, much higher, heading towards liquid diamond conditions.

Abstract of the work that inspired the news, at Nature…

Nature Physics 6, 40 – 43 (2009)
Published online: 8 November 2009 | doi:10.1038/nphys1438

Melting temperature of diamond at ultrahigh pressure

J. H. Eggert1, D. G. Hicks1, P. M. Celliers1, D. K. Bradley1, R. S. McWilliams1,2, R. Jeanloz2, J. E. Miller3, T. R. Boehly3 & G. W. Collins1

Which makes me wonder: has the carbon formed a natural “diamond sphere” around a hot core? Could we terraform the ocean above the diamond layer? And what happened to the excess hydrogen after methane decomposition?

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