Current projects

Crustal magnetic source depths on Mars:


The dawn of high-resolution observations with the James Webb Space Telescope will enable spatially resolved observations of ultrashort-period rocky exoplanets. Some of these planets orbit so closely to their host star that they lack an atmosphere, which gives direct access to their surfaces and opens a window to infer their geodynamics. GJ 367 b has been observationally constrained to a planetary radius of about 0.72 to 0.75 Earth radii and a mass between 0.48 and 0.55 Earth masses, which puts this planets in a Mercury-like interior regime with a thin mantle overlying a large core. The dayside temperature ranges between 1500 and 1800 K, suggesting a permanent magma ocean or dayside magma pond on the surface, induced by stellar irradiation. We perform global 2D spherical annulus StagYY simulations of solid-state mantle convection and surface melting with the goal to constrain the geometric and compositonal properties of the planet. The combination of observations and numerical models offers a unique opportunity to constrain the compositional fractionation during magma ocean epochs and provides avenues to constrain the delivery and loss cycle of atmophile elements on strongly irradiated exoplanets.

Collaborators: T. Lichtenberg / Univ. Groningen, T. G. Meier / Univ. Oxford, D. J. Bower, P. J. Tackley / ETH Zurich


Explaining the peculiar separation of metal and troilite pockets in acapulcoites:

Acapulcoites are primitive achondrites that are derived from a partially differentiated parent body that experienced peak temperatures above the Fe-Ni-S solidus. Their textures reflect annealing driven by the minimization of surface energy, yielding smoothly curved silicate grain boundaries, common 120 degrees triple junctions and an equiaxial shape of Fe-Ni and FeS pockets. However, one peculiar obervation is not easily explained: Fe-Ni and FeS pockets are often spatially separated and seldom form common boundaries in acapulcoites. Static annealing experiments were performed in a Walker-type multianvil press using a model system of olivine with 5 wt% gold. The mixed powders were compressed to 2.5 GPa and equilibrated at 1300 degrees C before rapidly decreasing to 1000 degrees C, below the Au and FeS solidi. At this temperature the samples were statically annealed for durations between three hours and one month to mimic slow cooling of planetesimals. Our experiments successfully simulate the phase separation and the decrease of Fe-Ni-FeS boundary length observed in H3-H6 chondrites and acapulcoites.

Collaborators: A. Neri / Univ. Lille, E. Kubik, A. Bouvier / BGI Bayreuth, N. P. Walte / TU Munich

Completed projects

Probing the viscosity of Venus' mantle:

The Baltis Vallis channel on Venus preserved a record of long-wavelength deformation generated by a convecting mantle, offering a unique window into the planet's geodynamics. We statistically compare the observed dynamic topography of Baltis Vallis with dynamic topography generated by a suite of 3D stagnant-lid mantle convection models. Baltis Vallis' relatively young age and low topography indicate vigorous convection in Venus' mantle, implying a mantle viscosity 1-2 order of magnitude lower than Earth's. This difference may arise from either a water-rich, less degassed interior or a higher-temperature mantle beneath the insulating lid.

N. J. McGregor, F. Nimmo, C. Gillmann, G. J. Golabek , A. M. Plattner and J. W. Conrad (2025). Probing the viscosity of Venus's mantle from dynamic topography at Baltis Vallis. J. Geophys. Res. Planets 130, e2024JE008581.

Coverage:  EGU Blog


Tungsten isotope evolution during Earth's formation:

The Hf-W isotopic system is the reference chronometer for determining the chronology of Earth's accretion and differentiation. However, its results depend strongly on uncertain parameters, including the extent of metal-silicate equilibration and the siderophility of tungsten. Here we show that a multistage core-formation model based on N-body accretion simulations, element mass balance and metal-silicate partitioning, largely eliminates these uncertainties. We considered smoothed particle hydrodynamics estimates of the depth of melting caused by giant impacts and the isotopic evolution of ¹⁸²W. We applied two metal-silicate fractionation mechanisms: (i) the metal delivered by the cores of large impactors equilibrates with only a small fraction of the impact-induced magma pond and (ii) metal delivered by small impactors emulsifies in global magma oceans before undergoing progressive segregation. The latter is crucial for fitting the W abundance and ¹⁸²W anomaly of Earth's mantle. In addition, we show that the duration of magma ocean solidification has a major effect on Earth's tungsten isotope anomaly. Depending on the characteristics of the giant impacts, results predict that the Moon formed either 143-183 Myr or 53-62 Myr after the start of the solar system. Thus, independent evaluations of the Moon's age provide an additional constraint on the validity of accretion simulations.

D. C. Rubie, K. I. Dale, G. Nathan, M. Nakajima. E. S. Jennings, G. J. Golabek, S. A. Jacobson and A. Morbidelli (2025). Tungsten isotope evolution during Earth's formation and new constraints on the viability of accretion simulation. Earth Planet. Sci. Lett. 651, 119139.

Grain size evolution in Earth's lower mantle:

Recent experimental investigations of grain size evolution in bridgmanite-ferropericlase assemblages have suggested very slow growth for these bimodal phases. We develop self-consistent 2-D spherical half-annulus geodynamic models of Earth's evolution using the finite volume code StagYY to assess the role of grain size on lower mantle viscosity. We are considering three scenarios: (i) uniform grain growth throughout the entire mantle with a composite rheology, (ii) different grain growth in the upper and lower mantle with a composite rheology, and (iii) different grain growth in the upper and lower mantle with purely diffusion creep rheology. In the case of different grain size evolution, the upper mantle's grain size evolution law is controlled by forsterite-enstatite grain growth, while the lower mantle's grain size evolution law is controlled by bridgmanite-ferropericlase grain growth. Our results suggest that mantle viscosity is primarily controlled by temperature, whereas grain size has a minor effect compared to the effect of temperature. To establish the robustness of this finding we vary several other model parameters, such as surface yield strength, phase transition grain size reset, different transitional stresses for creep mechanisms, pressure dependence on grain growth, and different grain damage parameters. For all our models, we consistently find that grain size has a very limited effect on controlling lower mantle viscosity in the present-day Earth. However, large grain size may have affected the lower mantle viscosity in the early Earth as larger grains of single phase bridgmanite could increase the viscosity of the early mantle delaying the onset of global convection.

J. Paul, G. J. Golabek, A. B. Rozel, P. J. Tackley, T. Katsura and H. Fei (2024). Effect of bridgmanite-ferropericlase grain size evolution on Earth's average mantle viscosity: Implications for mantle convection in early and present-day Earth. Prog. Earth Planet. Sc. 11, 64.

Combined impact and interior evolution models for Mars:

Here we use a coupled SPH-thermochemical approach to first simulate an impact event, and then use the result of this realistic model as the initial condition for the long-term mantle convection model. We find that both the impact scenario and the mantle properties affect the geometry of impact-induced crust and the subsequent state of the interior, and that the impact-induced crust extends beyond the initial magma pond. We show that a near head-on impact event with impactor radius of 750 km can best reproduce the southern highlands of Mars with a geometry similar to that of present-day Mars observations.

K. W. Cheng, H. A. Ballantyne, G. J. Golabek, M. Jutzi, A. B. Rozel & P. J. Tackley (2024). Combined impact and interior evolution models in three dimensions indicate a southern impact origin of the Martian Dichotomy. Icarus 420, 116137.

Mantle depletion after martian giant impact:

Previous giant impact models coupled with simulations of mantle convection have shown that the martian crustal dichotomy can be explained by post‐impact melt crystallization that emplaced a thick crust in the southern hemisphere. In this study, we show that the depleted residue left behind by the original post‐impact crustal formation can spread laterally, potentially persisting beneath the northern hemisphere to the present‐day. Such a large‐scale mantle province would concurrently explain both the prevalence of long‐term magmatism on Mars and its strong preference for localized equatorial regions.

K. W. Cheng, A. B. Rozel, G. J. Golabek, H. A. Ballantyne, M. Jutzi & P. J. Tackley (2024). Mars's Crustal and Volcanic Structure Explained by Southern Giant Impact and Resulting Mantle Depletion. Geophys. Res. Lett. 51, e2023GL105910.

Animation:  Movie

Induction heating of planets orbiting white dwarfs:

Recently a number of planets have been discovered that orbit white dwarfs. We investigate whether electromagnetic induction heating due to the extremely strong magnetic fields of some white dwarfs can drive volcanic activity even on small bodies orbiting such white dwarfs on short-period orbits. Our results show that induction heating can indeed rapidly partially melt the mantle of lunar-mass objects orbiting white dwarfs with strong magnetic fields. The related volcanism drives outgassing that could be observed in the future around white dwarfs.

K. G. Kislyakova, L. Noack, E. Sanchis, L. Fossati, G. G. Valyavin, G. J. Golabek & M. Guedel (2023). Induction heating of planetary interiors in white dwarf systems. Astron. Astrophys. 677, A109.


Investigating the feasibility of an impact-induced Martian Dichotomy:

Most studies attempting to explain the martian dichtomy focus on two theories; either the dichotomy formed solely through geodynamic processes or a giant impact occurred that imprinted the crustal cavity in the northern hemisphere we observe today. Recent work has proved the importance of coupling these hypotheses, introducing a hybrid exogenic-endogenic scenario with crust formation from the impact-generated melt. We model the impact using a suite of SPH simulations that explore a large parameter space. For the outcome of the simulation outcomes we apply a newly developed scheme to estimate the thickness and distribution of new formed or re-distributed post-impact crust.

H. A. Ballantyne, M. Jutzi, G. J. Golabek, L. Mishra, K. W. Cheng, A. Rozel & P. J. Tackley (2023). Investigating the feasibility of an impact-induced Martian dichotomy. Icarus 392, 115395.


Fluid flux determination for serpentinites in subduction zones:

We present a new method to determine fluid flux at subduction zone conditions. Orientated drill cores of antigorite starting material were placed into a MgO sleeve. Fluid released upon serpentine dehydration are fixed in the MgO sleeve by the formation of brucite, thus the amount and distribution of brucite in the run product serves as a proxy for fluid flux. The experiments show that dehydration results in an isotropic fluid flux. The timescales of fluid flux indicate that a large fluid pressure can build up during dehydration. Intermediate-depth earthquakes caused by brittle fracturing are thus likely to be caused by dehydration reactions in subducted serpentinites.

L. Eberhard, M. Thielmann, P. Eichheimer, A.