Could there be oceans of diamond in the outer solar system?
Although diamond is a common material on Earth, its melting point is very difficult to measure—as it’s heated to high temperatures, it physically changes into graphite before melting into liquid. In order to stop this change and find the actual melting point of diamond, researchers raised the pressure as well as the temperature. An experiment led by Jon Eggert of Lawrence Livermore National Laboratory used the powerful Omega laser to blast tiny diamonds just two millimeters in diameter, raising them to temperatures of 110,000 Kelvin and pressures of 4,000 giga Pascals—40 million times the pressure you feel at sea level on Earth. They found that liquefied diamond acts like water. When they reduced the temperature and pressure again, microscopic diamond chunks formed and floated atop the liquid—the solid was less dense than the liquid, just like ice and water. Such ultrahigh temperatures and pressures are found in Neptune and Uranus on the outskirts of our solar system, which are composed of approximately 10% carbon, so it’s plausible that these huge gas giants could contain oceans of liquid diamond. This could help explain the strange orientation of the planets’ magnetic fields, which are out of alignment with the planets’ rotation by up to 60 degrees—it’s the equivalent of moving Earth’s magnetic south pole to Central Australia. Seas of internal liquid diamond in Neptune and Uranus would affect their magnetic fields and therefore could be responsible for the mismatched poles. Eggert suggests that they could have “liquid carbon core surrounded by floating diamond or possibly ‘diamond-bergs’”, but it’s a speculative scenario.