Speaker
Marco Guarguaglini
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P1.2032.pdf
Equation of state and optical reflectivity
of shock-compressed C-H-N-O planetary ices
M. Guarguaglini1, J.-A. Hernandez1, Y. Fujimoto2, K. Miyanishi2, P. Barroso3, F.
Lefevre1, A. Benuzzi-Mounaix1, N. Ozaki2, T. Vinci1, E. Brambrink1, A. Ravasio1
1Laboratoire LULI - CNRS, École Polytechnique, CEA: Université Paris-Saclay,
Palaiseau, France
2Graduate School of Engineering, Osaka University, Suita, Osaka, Japan
3Observatoire de Paris, Paris, France
Water, ethanol, and ammonia are amongst the key components of Uranus and Neptune.
Knowing their equation of state, conductivity, and transport properties at planetary interiors
conditions (a few Mbar and a few 1000 K) is required for developing precise structure and
evolution models of the two planets as well as for explaining their puzzling magnetic fields
and luminosities. The physical and chemical behaviour of such mixtures at extreme
pressures and temperatures is not only important for planetology but also interesting on its
own, since those conditions are characterised by the coexistence of dissociated atoms,
atomic clusters and chains. This regime is very difficult to study via ab initio simulations
and experimental verifications are required.
We studied pure water, a C-H-O and a C-H-N-O mixture, compressed up to 3 Mbar via
laser-driven shock loading. The principal Hugoniot has been explored using the decaying
shock technique. Moreover, off-Hugoniot states have been reached via a double-shock
technique and through coupling of dynamic and static compression in diamond anvil cells.
The experiments were performed at the GEKKO XII and LULI 2000 laser facilities using
standard rear-side optical diagnostics (VISARs, SOP, reflectometer) to characterise the
equation of state (a relation between density, pressure, internal energy, and temperature)
and optical reflectivity of the shocked state.
The results show that water and C-H-N-O mixtures share the same equation of state with a
trivial density scaling, while the reflectivity behaves differently in both the onset pressure
and the saturation value. From the reflectivity measurements an estimation of a
conductivity will be given using a Drude model. The consequences for the icy giants
interiors will be addressed.
