To be properly understood and simulated, complex Earth and Planetary Science processes need to be studied at a realistic range of elevated pressure (P) and temperature (T). Therefore, the main objective of the PLANEX project (i.e., Experimental planet: simulation and in-situ analyses under extreme conditions1) was to develop a high pressure – high temperature (HP-HT) analytical platform dedicated to in situ measurements of various geological materials.

The experimental axis based on the so called transparent Internally Heated Pressure Vessel (t-IHPV) is the key element of this platform. The t-IHPV equipped with three windows and an inner sample container, transparent in the desired range of electromagnetic radiation, allows a coupling to different analytical techniques. The use of sapphire enables in situ Raman or Infrared emission spectroscopy studies, while a combination of beryllium and glassy carbon is employed for in situ radiography, small-/wide-angle X-ray scattering (SAXS/WAXS) and X-ray absorption spectroscopy (XAS) measurements. Solid or liquid samples (range ~mg/mL) can be heated up to 1200 °C and pressurised up to 200 MPa under He gas; temperature and pressure can be independently regulated. These intermediate conditions successfully fill the P-T gap not available with commonly used optical cells, fused silica capillary capsules and diamond anvil cells.

After a technical overview of each t-IHPV - based in situ setup developed under PLANEX (e.g. Raman, FTIR, SAXS/WAXS and radiography), we will present the proof of concept measurements: i) speciation of C-O-H-N-S volatile elements and metals in hydrothermal magmatic fluids, ii) hydrothermal transformation of nebular organic matter, iii) phase identification of hydrothermal synthesis, iv) clay mineral structure during dehydration reactions. The results demonstrate the high scientific potential of the platform to address key questions in Earth and Planetary sciences, such as the origin of life, planet formation, genesis of ore deposits, fault zones mechanics.