Periodic Reporting for period 4 - PICKLE (Planetary Interiors Constrained by Key Laboratory Experiments)
Reporting period: 2022-04-01 to 2023-09-30
The knowledge of interiors of rocky planets of our solar system (Mercury, Venus, Earth and Mars) is important for understanding their formation, present state, and evolution. The comprehension of differences and similarities in the internal constitution will shed a new light on the origin and evolution of the solar system.
Space missions are invaluable to this planetary quest. Yet, constraints on planetary interiors have been largely limited to geodesy data, with seismic observations on planetary bodies other than Earth limited to the Apollo records for the Moon. In this context the InSight mission, operational on Mars from November 2018 till December 2022, has been a true game changer. Indeed, InSight has been the first extra-terrestrial seismology mission to probe the interior of a planet other than Earth.
However, the interpretation and full exploitation of the observations to produce accurate models of planetary structure and dynamics heavily rely on the knowledge of properties of constituent materials at relevant pressures and temperatures.
PICKLE aimed at developing techniques and methodologies, combining innovative laboratory and synchrotron measurements, to acquire much-needed physical properties of planet-forming materials at high pressure and high temperature. We related bulk chemistry assessed from meteorites to mineralogy, we measured sound velocities and acoustic attenuation of rocks making the mantle of telluric planets, providing data enabling the interpretation of Martian seismic records collected by InSight. We determined the phase diagram of iron alloys forming telluric planetary cores and provided an unprecedented determination of the thermo-elastic properties of liquid iron alloys under the conditions of the core of the Moon and Ganymede. The ensemble of the data on iron alloys including melting curves and phase relations, equation of state of solid and liquid phases, has been implemented in a consistent thermodynamic model used to guide the inversion of geophysical observations collected on Mars by the InSight and to propose crystallization scenarios for the core of Mercury.
In summary, this interdisciplinary project has provided important datasets used to model the interior of telluric planetary bodies, including the Earth, but with a main focus on the Moon, Mercury and Mars. Ultimately, PICKLE led to an improved understanding of planetary constitution, addressing similarities and diversity.
Space missions are invaluable to this planetary quest. Yet, constraints on planetary interiors have been largely limited to geodesy data, with seismic observations on planetary bodies other than Earth limited to the Apollo records for the Moon. In this context the InSight mission, operational on Mars from November 2018 till December 2022, has been a true game changer. Indeed, InSight has been the first extra-terrestrial seismology mission to probe the interior of a planet other than Earth.
However, the interpretation and full exploitation of the observations to produce accurate models of planetary structure and dynamics heavily rely on the knowledge of properties of constituent materials at relevant pressures and temperatures.
PICKLE aimed at developing techniques and methodologies, combining innovative laboratory and synchrotron measurements, to acquire much-needed physical properties of planet-forming materials at high pressure and high temperature. We related bulk chemistry assessed from meteorites to mineralogy, we measured sound velocities and acoustic attenuation of rocks making the mantle of telluric planets, providing data enabling the interpretation of Martian seismic records collected by InSight. We determined the phase diagram of iron alloys forming telluric planetary cores and provided an unprecedented determination of the thermo-elastic properties of liquid iron alloys under the conditions of the core of the Moon and Ganymede. The ensemble of the data on iron alloys including melting curves and phase relations, equation of state of solid and liquid phases, has been implemented in a consistent thermodynamic model used to guide the inversion of geophysical observations collected on Mars by the InSight and to propose crystallization scenarios for the core of Mercury.
In summary, this interdisciplinary project has provided important datasets used to model the interior of telluric planetary bodies, including the Earth, but with a main focus on the Moon, Mercury and Mars. Ultimately, PICKLE led to an improved understanding of planetary constitution, addressing similarities and diversity.
We built a unique experimental setup, combining femtosecond laser pump-probe techniques with resistively heated and laser heated diamond anvil cell, which has proved capable of probing the acoustic properties of materials over a very wide pressure range, exceeding one million times atmospheric pressure, and at temperatures up to 4000 degrees. Upon further optimization of the experimental protocol we will be able to probe the acoustic properties of a variety of planet-forming materials at the pressure and temperature conditions existing in planetary deep interiors.
Setup for experimentation in multi-anvil press was optimized by the use of newly developed materials and innovative technical solutions enabling to retain liquids at high pressure and high temperature conditions, minimizing the risk of chemical reaction, but as well the contribution of the sample’s environment to the collected signal. These technological advances, together with an improved data collection protocol, which combines angular and energy dispersive X-ray diffraction, absorption and X-ray imaging, allowed to obtain data of unprecedented quality on liquid metals at the conditions of the core of the Moon and Ganymede, and on solid and partially molten rocks at the conditions of the Martian mantle.
Multiple synchrotron campaigns for x-ray diffraction and absorption measurements at simultaneous high pressure and high temperature conditions, complemented with electron microscopy analysis of the recovered samples, have allowed studying the phase diagram of the binary Fe-S, Fe-Si, Fe-O and Fe-C systems. Equation of states have been determined for several Fe-Si and selected Fe-Si-C solid alloys. Local structure, density and thermo-elastic parameters, including thermal expansion, have been determined for liquid Fe-S, Fe-Si and Fe-S-C alloys at record pressure and temperature conditions.
The ensemble of the results obtained on the iron alloys expected to form the core of the telluric planets allowed us to propose compositional and crystallization models for the core of several bodies of the Solar system, including the Moon and other satellites such as Ganymede, small planets such as Mercury and Mars, and larger objects, from Earth to exoplanets. In particular, collected data have been used to provide the thermodynamic model of liquid iron alloys currently used as the reference for the thermo-elastic properties of the Mars’ core.
Phase equilibria experiments allowed relating bulk chemical composition to mantle mineralogy, addressing the effects of pressure, temperature and redox conditions. Experiments by x-ray diffraction, radiography and ultrasonic interferometry, have been carried out to determine solidus and liquidus of rocks representative of the Martian mantle, as well as the pressure- and temperature-dependent melt fraction. Velocity measurements on analogues of the Martian mantle have been performed at pertinent pressure and temperature conditions providing guidance for the interpretation of the seismic data collected by the InSight mission.
Obtained results have been disseminated to the scientific community via technical and scientific papers (29 papers published so-far, including 1 Nature, 2 Science, 1 Nature Communications and 2 PNAS) and by presentation to international conferences. Dissemination towards general public has been systematically pursued, via presentation in science festivals and interventions at schools (pre-schools, elementary schools, observation courses and short internships proposed to middle and high school students).
Setup for experimentation in multi-anvil press was optimized by the use of newly developed materials and innovative technical solutions enabling to retain liquids at high pressure and high temperature conditions, minimizing the risk of chemical reaction, but as well the contribution of the sample’s environment to the collected signal. These technological advances, together with an improved data collection protocol, which combines angular and energy dispersive X-ray diffraction, absorption and X-ray imaging, allowed to obtain data of unprecedented quality on liquid metals at the conditions of the core of the Moon and Ganymede, and on solid and partially molten rocks at the conditions of the Martian mantle.
Multiple synchrotron campaigns for x-ray diffraction and absorption measurements at simultaneous high pressure and high temperature conditions, complemented with electron microscopy analysis of the recovered samples, have allowed studying the phase diagram of the binary Fe-S, Fe-Si, Fe-O and Fe-C systems. Equation of states have been determined for several Fe-Si and selected Fe-Si-C solid alloys. Local structure, density and thermo-elastic parameters, including thermal expansion, have been determined for liquid Fe-S, Fe-Si and Fe-S-C alloys at record pressure and temperature conditions.
The ensemble of the results obtained on the iron alloys expected to form the core of the telluric planets allowed us to propose compositional and crystallization models for the core of several bodies of the Solar system, including the Moon and other satellites such as Ganymede, small planets such as Mercury and Mars, and larger objects, from Earth to exoplanets. In particular, collected data have been used to provide the thermodynamic model of liquid iron alloys currently used as the reference for the thermo-elastic properties of the Mars’ core.
Phase equilibria experiments allowed relating bulk chemical composition to mantle mineralogy, addressing the effects of pressure, temperature and redox conditions. Experiments by x-ray diffraction, radiography and ultrasonic interferometry, have been carried out to determine solidus and liquidus of rocks representative of the Martian mantle, as well as the pressure- and temperature-dependent melt fraction. Velocity measurements on analogues of the Martian mantle have been performed at pertinent pressure and temperature conditions providing guidance for the interpretation of the seismic data collected by the InSight mission.
Obtained results have been disseminated to the scientific community via technical and scientific papers (29 papers published so-far, including 1 Nature, 2 Science, 1 Nature Communications and 2 PNAS) and by presentation to international conferences. Dissemination towards general public has been systematically pursued, via presentation in science festivals and interventions at schools (pre-schools, elementary schools, observation courses and short internships proposed to middle and high school students).
We developed a unique experimental setup that combines the use of pump-probe laser acoustic techniques together with laser heating diamond anvil cell to probe a large variety of samples, be these powders, single crystals, glasses or liquids, under unprecedentedly large pressure and temperature ranges.
We performed the first sound wave velocity measurements of model Martian rocks under actual Martian mantle conditions and the first in situ determination of melt relations.
We pushed ahead our capabilities of performing measurements on liquids under extreme conditions. We have been able for the first time to probe both compressibility and thermal expansion of liquid metals at conditions of the interiors of the Moon and Ganymede.
Within this project we have been developing techniques and methodologies, combining innovative laboratory and synchrotron measurements, to probe a variety of physical properties currently unknown or poorly constrained, at actual conditions of planetary interiors. These groundbreaking measurements allowed us to start collecting the database required to establish reliable planetary models and needed to guide interpretation and full exploitation of observations, be these Earth based or from space missions (e.g. the InSight mission on Mars).
We performed the first sound wave velocity measurements of model Martian rocks under actual Martian mantle conditions and the first in situ determination of melt relations.
We pushed ahead our capabilities of performing measurements on liquids under extreme conditions. We have been able for the first time to probe both compressibility and thermal expansion of liquid metals at conditions of the interiors of the Moon and Ganymede.
Within this project we have been developing techniques and methodologies, combining innovative laboratory and synchrotron measurements, to probe a variety of physical properties currently unknown or poorly constrained, at actual conditions of planetary interiors. These groundbreaking measurements allowed us to start collecting the database required to establish reliable planetary models and needed to guide interpretation and full exploitation of observations, be these Earth based or from space missions (e.g. the InSight mission on Mars).