Mixtures of planetary ices at extreme conditions

Abstract

The interiors of neptune and uranus are believed to be primarily composed of a fluid mixture of methane and water. The mixture is subjected to pressures up to several hundred gigapascal, causing the ionization of water. Laboratory and simulation studies so far have focused on the properties of the individual components. Here we show, using first-principle molecular dynamic simulations, that the properties of the mixed fluid are qualitatively different with respect to those of its components at the same conditions. We observe a pressure-induced softening of the methane-water intermolecular repulsion that points to an enhancement of mixing under extreme conditions. Ionized water causes the progressive ionization of methane and the mixture becomes electronically conductive at milder conditions than pure water, indicating that the planetary magnetic field of uranus and neptune may originate at shallower depths than currently assumed.

Carbon precipitation from heavy hydrocarbon fluid in deep planetary interiors

“…These planets are postulated to have mantles consisting of mixture of fluid methane, water and ammonia, where these compounds have a role similar to that of minerals in the Earth's mantle 1 . The effects of possible formation of mixtures between methane, water and ammonia 30,31 and ionization 3 were shown to occur at higher temperatures than those studied in this work. Notwithstanding this, our study offers evidence for chemical reactivity of C-H component of planetary ices, which may also affect positions of planetary isentropes.…”

One-step electric-field driven methane and formaldehyde synthesis from liquid methanol

“…The first experimental evidence that an electric field can control chemical reactions has been recently provided. 25 On the other hand, recent ab initio molecular dynamics (AIMD) studies have succeeded in describing complex chemical reactions of small organic molecules under extreme conditions of confinement 26 and pressure, 27,28 and, more specifically, in the case of strong electric fields in water, 29 quantitatively confirmed by experiments, 30,31 including a study mimicking in silico the historical Miller experiment. 32 …”

Dynamical Screening and Ionic Conductivity in Water fromAb InitioSimulations

“…Microscopic analyses show that large fluctuations in the effective charge of the protons occur on a femtosecond timescale that play a crucial role in the charge transport in water. Most important, the real power of the method presented here is its direct applicability to more complex systems than water, such as strongly reacting chemicals [17] and molecular mixtures in the deep inte-rior of giant planets [13,18].…”