Laura R. Benedetti
Experimental Geophysics Group
Lawrence Livermore National Laboratory
Testing Solar System Astronomy in a Physics Laboratory
Monday, March 3, 2008, 4:00 p.m.
Refreshments at 3:45 p.m.
ABSTRACT
The deep interiors of the planets in our solar system cannot be directly observed by any method, yet the physical and chemical properties of the materials in a planet's interior contribute strongly to those parameters that we can observe such as magnetic and gravitational fields. However, under the high temperatures and pressures present in planetary interiors, the physical and chemical properties of many materials are vastly different from at ambient conditions. Thus scientists must rely on laboratory experiments and theory to infer the compositions and structures of planets and to constrain theories of solar system evolution. To this end, the laser-heated diamond cell is an experimental tool that can be used to reproduce in the laboratory the extreme thermodynamic conditions that are present deep inside planets.
In this talk I will describe experiments we have done with the laser-heated diamond cell to experimentally probe the interiors of Uranus and Neptune. We have found that methane, CH4, decomposes to its pure elements, hydrogen and carbon at high temperatures for pressures greater than 20 gigapascals. Also, we have developed new techniques for identifying the onset of melting, and we will present our measurements of the melting curve of oxygen at 50 gigapascals.