Purpose and Goals The generation and diagnostics of extreme states of matter as appearing in the interior of planets, brown dwarfs and stars is one of the key scientific challenges in a number of scientific fields. These include: - Generation of such conditions at FLASH and the future free electron laser facility (European XFEL). - Generation of higher pressures in static experiments both in the laboratory and at synchrotron facilities (PETRA III). - Development of new diagnostic tools. - Predictions of high pressure and temperature properties of materials from ab-initio methods. - Application of such results to the study of interior of planetary and astrophysical bodies. To bring together researchers from these different fields in the physical sciences a workshop series has been established by DESY, XFEL GmbH, DLR Berlin, the University of Rostock and Bayerisches Goinstitut to discuss related topics and problems. Earlier workshops were held at DESY Hamburg (2012), DLR Berlin (2013), University of Rostock (2014), Bayerisches Geoinstitut at the University of Bayreuth (2015), and European XFEL/DESY in Hamburg (2016). The aim of the upcoming workshop is to continue the discussion of scientific questions with relevance for extreme planetary environments in terms of high pressure (HP) and high temperature (HT). The conditions prevalent in the deep interiors and atmospheric envelopes of solar system planets, their satellites as well as massive solid and gas giant extrasolar planets, respectively, and are not fully accessible by conventional experimental and theoretical methods. New and enabling techniques to be used in the HP/HT regime are based on the combination of intense pulsed x-ray sources with pulsed sample excitation, in particular but not exclusively related to high energy optical lasers. Simultaneously, ab initio simulations for matter under extreme conditions provide a more and more predictive data set for planetary interiors in this HP/HT regime. The following topics will be part of the workshop: - Evolution and structure of giant planet interiors - Interior structure, bulk composition, and internal geodynamics of solid planets - Deep volatile cycles and exchange processes between geochemical reservoirs - Physics and chemistry of impact processes - Equations of state, petrology, and geochemistry of planetary materials - Melting relations and phase transformations of materials at extreme states - Dynamic and ultrafast processes in strongly excited solids or similar, - Compression experiments using high-power optical and free electron lasers - Laboratory experiments using multi-anvil and diamond-anvil cells - Ab-initio simulation studies for matter under extreme conditions Abstracts and contributions are welcome to the above subject areas that represent an initial outline and are open to further suggestions. The workshop will include a mix of solicited, contributed and poster presentations. This meeting is also intended to inspire new projects and offer a discussion space to foster collaboration between workshop participants from the various research fields. Time and Location The workshop will start on October 4th (noon) and end on October 6th (noon) 2017. It will be held at the Max-Planck-Campus in Göttingen. Deadline for registration and abstract submission: August 20th, 2017. There is no registration fee.