Mark A. Wieczorek

Institut de Physique du Globe de Paris
Planetary and Space Sciences group

Senior research scientist

About me

My scientific research focuses on deciphering the interior structure and geologic evolution of the terrestrial planets and moons. As a geophysicist, I mostly use planetary topography, gravity, and magnetic field data that have been acquired from orbiting spacecraft, but I also rely on remote sensing data, seismic data, thermal evolution modeling, and impact crater formation models. I have worked with several lunar missions, including NASA’s lunar gravity mapping mission GRAIL and the upcoming Lunar Vertex mission that will investigate one of the largest magnetic anomalies on the Moon. I am also a co-investigator on NASA’s geophysical mission to Mars, Insight, the laser altimeter on ESA’s BepiColombo mission to Mercury, the laser altimeter on the JUICE mission that will investigate the moons of Jupiter, and NASA’s mission to the asteroid 16 Psyche.

I am currently at the Institut de Physique du Globe de Paris, where I have been since 2023. Prior to this I was at the Observatoire de la Côte d’Azur as a member of the Laboratoire Lagrange (2017-2022), and before this I was the leader of the Planetary and Space Sciences group at IPGP. I was the editor-in-chief of the Journal of Geophysical Research Planets from 2011-2015 and I am currently a member of the Icarus editorial advory board. In addition to my scientific activities, I am the lead developer of the shtools software package that is used for analyzing global data expressed in spherical harmonics.

Recent Publications

Surface Waves and Crustal Structure on Mars

D. Kim, W B Banerdt, S Ceylan, and 42 more authors

Science, 2022.

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We detected surface waves from two meteorite impacts on Mars. By measuring group velocity dispersion along the impact-lander path, we obtained a direct constraint on crustal structure away from the InSight lander. The crust north of the equatorial dichotomy had a shear wave velocity of approximately 3.2 kilometers per second in the 5- to 30-kilometer depth range, with little depth variation. This implies a higher crustal density than inferred beneath the lander, suggesting either compositional differences or reduced porosity in the volcanic areas traversed by the surface waves. The lower velocities and the crustal layering observed beneath the landing site down to a 10-kilometer depth are not a global feature. Structural variations revealed by surface waves hold implications for models of the formation and thickness of the martian crust.
The Mantle Viscosity Structure of Venus

J. S. Maia, M. A. Wieczorek, and A.-C. Plesa

Geophysical Research Letters, 2023.

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The long-wavelength gravity and topography of Venus are dominated by mantle convective flows, and are hence sensitive to the planet’s viscosity structure and mantle density anomalies. By modeling the dynamic gravity and topography signatures and by making use of a Bayesian inference approach, we investigate the viscosity structure of the Venusian mantle by constraining radial viscosity variations. We performed inversions under a wide range of model assumptions that consistently predicted the existence of a thin low-viscosity zone in the uppermost mantle. The zone is about 235 km thick and has a viscosity reduction of 5–15 times with respect to the underlying mantle. Drawing a parallel with the Earth, the reduced viscosity could be a result of partial melting as suggested for the origin of the asthenosphere. These results support the interpretation that Venus is a geologically active world predominantly governed by ongoing magmatic processes.
InSight Constraints on the Global Character of the Martian Crust

Mark A. Wieczorek, Adrien Broquet, Scott M. McLennan, and 23 more authors

Journal of Geophysical Research: Planets, 2022.

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Analyses of seismic data from the InSight mission have provided the first in situ constraints on the thickness of the crust of Mars. These crustal thickness constraints are currently limited to beneath the lander that is located in the northern lowlands, and we use gravity and topography data to construct global crustal thickness models that satisfy the seismic data. These models consider a range of possible mantle and core density profiles, a range of crustal densities, a low-density surface layer, and the possibility that the crustal density of the northern lowlands is greater than that of the southern highlands. Using the preferred InSight three-layer seismic model of the crust, the average crustal thickness of the planet is found to lie between 30 and 72 km. Depending on the choice of the upper mantle density, the maximum permissible density of the northern lowlands and southern highlands crust is constrained to be between 2,850 and 3,100 kg m\mkern1mu-3. These crustal densities are lower than typical Martian basaltic materials and are consistent with a crust that is on average more felsic than the materials found at the surface. We argue that a substantial portion of the crust of Mars is a primary crust that formed during the initial differentiation of the planet. Various hypotheses for the origin of the observed intracrustal seisimic layers are assessed, with our preferred interpretation including thick volcanic deposits, ejecta from the Utopia basin, porosity closure, and differentiation products of a Borealis impact melt sheet.
Lunar Magnetism

Mark A. Wieczorek, Benjamin P. Weiss, Doris Breuer, and 14 more authors

Reviews in Mineralogy and Geochemistry, 2023.

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Magnetic Signatures of Lunar Impact Craters

Xi Yang, and Mark Wieczorek

Icarus, 2024.

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The Moon almost certainly had an internally generated magnetic field in its past, but the duration of the dynamo, its temporal stability, and the surface field intensity are poorly known. Impact cratering events heat portions of the crust above the Curie temperature, allowing the ambient magnetic field strength to be recorded as the crater cools. We systematically analyzed the magnetic signatures of lunar impact craters with diameters greater than 90 km using recent magnetic field models and crater databases. Craters were classified as having evidence for impact-related central magnetization or demagnetization, and synthetic magnetic field models were used to estimate the number of incorrect identifications. In total, about 15% of craters were found to have impact-related magnetized or demagnetized signatures. The proportion of pre-Nectarian and Nectarian aged craters in the magnetized class is about 2%–3%, and there is little evidence for magnetized craters in the Imbrian and younger periods. The percentage of craters in the demagnetized class is about 0.3%–3% in the pre-Nectarian and Nectarian periods and abruptly increases to 16% in the Imbrian period. Our observations are consistent with the presence of strong dynamo fields during portions of the older pre-Nectarian and Nectarian periods, with a weakening (or cessation) of the dynamo at the beginning of the younger Imbrian period. These results differ from paleomagnetic analyses of lunar samples that imply the existence of strong dynamo field strengths from the pre-Nectarian up until at least the first half of the Imbrian period.