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.
Lithospheric Structure of Venusian Crustal Plateaus

J. S. Maia, and M. A. Wieczorek

Journal of Geophysical Research: Planets, 2022.

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Crustal plateaus are Venusian highlands characterized by tectonized terrains. It is commonly interpreted that their topography is isostatically supported and that they represent fossils of an extinct tectonic regime. Using gravity and topography we perform a comprehensive investigation of the lithospheric structure of six crustal plateaus. We computed the admittance (gravity to topography wavelength-dependent ratio) for each region and compared them to modeled admittances. Three compensation scenarios were tested: Airy isostasy, a surface-loading flexural model, and a flexural model with surface and subsurface loads. Our results show that the topography of most plateaus is supported by crustal thickening and that the addition of a mantle support component is not necessary at the investigated wavelengths. The elastic thickness was constrained to be less than 35 km with a best-fitting average of 15 km, confirming that these regions are consistent with an isostatic regime. The average crustal thickness of the plateaus ranges from 15 to 34 km, and if they are in Airy isostasy, this implies that the global average crustal thickness of Venus is about 20 km. Phoebe Regio is the sole exception of our analysis in that crustal thicknesses that are compatible with the other plateaus are obtained only when a buoyant layer is included. Heat flow estimations computed from the elastic thickness indicate that the plateaus formed under higher heat flow conditions compared to the current global average and could have caused localized melting. Present-day heat flow predictions suggest that eclogitization could occur where the crust is thickest.
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, 2022.

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Analyses of lunar rocks and magnetic field data from orbit show that the Moon once had a global magnetic field generated by an internal dynamo. Magnetization of the deep crust implies that a dynamo operated during the first 100 million years following crust formation and magnetization of some impact basins implies that the dynamo continued into the Nectarian period. Paleomagnetic analyses of Apollo samples provide evidence for dynamo activity from about 4.25 billion years ago (Ga) until at least 1.92 Ga, ceasing thereafter by ~0.80 Ga. The field strength was Earth-like until about 3.56 Ga (from ~40 to 110 μT), after which it decreased by more than an order of magnitude. Several mechanisms have been proposed to account for the long duration of the lunar dynamo. These include thermal convection in the core that could power a dynamo for a few hundred million years, core crystallization that could power a dynamo until about 1.5 Ga, mantle and/or inner core precession that could power a dynamo beyond 2 Ga, impact-induced changes in the rotation rate of the mantle that could power several short-lived dynamos up until when the last basin formed at ~3.7 Ga, and a basal magma ocean that could have potentially powered a dynamo over much of lunar history. Magnetohydrodynamic simulations have shown that the amplification of pre-existing fields by impact generated plasmas are insufficient and too short lived to have played an important role in crustal magnetization. Some of the magnetic carriers responsible for crustal magnetization, such as those responsible for the magnetization of the deep highland crust and mare basalts, are of lunar origin. Other magnetic carriers may instead be derived from meteoritic materials that were accreted to the Moon during large impacts. Outstanding questions in lunar magnetism include the geometry of the internally generated magnetic field, the exceedingly high surface field strengths implied by some paleomagnetic analyses, whether dynamo activity was continuous or episodic, the origin of strong crustal magnetic anomalies that have no correlation with surface geology, and the mechanisms that powered the lunar dynamo through time.