The scientific return of these geophysical datasets is greatly enhanced when combined with complementary surface observations, laboratory experiments, and numerical modeling. Multi-spectral and hyperspectral imaging, together with experimental analyses, link remote sensing data to mineralogical and physical properties, offering insights into the composition of outer and internal layers. Altimetry measurements provide independent constraints on tidal responses and rotational dynamics, complementing gravity and magnetic data and offering key insights into the rheology and differentiation of the deep interior. Joint analyses of gravity and topography provide information regarding the thickness, density, and elastic properties of interior layers, while thermochemical evolution models connect present-day structures through space and time to long-term geophysical and geological processes. Together, these approaches provide a more integrated understanding of how planetary bodies formed, differentiated, and evolved.
This session will focus on the instruments, measurement techniques, modeling approaches, and laboratory studies that enable robust constraints on the evolution of surfaces and interiors of planetary bodies. Contributions are invited that address both achievements and limitations of current methods, as well as innovative strategies to overcome existing challenges or combine disparate methodologies. Results from past, ongoing, and forthcoming missions, integrative analyses across multiple datasets, and forward-looking exploration concepts are all welcome. By bringing together diverse perspectives, the session aims to provide a broad and technically rigorous overview of the methods by which we can infer the processes shaping planetary bodies and to outline pathways for major discoveries in the coming decades.
Solicited presenter: Adrien Broquet - On the Crustal Architecture of the Terrestrial Planets
Orals: Thu, 7 May, 16:15–18:00 | Room 0.16
The crust is the outermost solid layer of a rocky body with a composition that substantially differs from the deeper interior (mantle and core). Due to its lower thermal conductivity, the crust thermally insulates the interior, and thus the thickness of the crust controls the rate at which a planet cools in time (Plesa et al., 2022). The crust preserves a record of a planet’s geologic history, hosting remanent magnetization from interior dynamos (e.g., Langlais et al., 2010), and has been scarred by tectonic (e.g., Andrews-Hanna & Broquet, 2023), impact (e.g., Melosh et al., 2013), volcanic (e.g., Carr & Head, 2010) and erosional processes (e.g., Hynek et al., 2010). For these reasons, understanding the structure and composition of the crust is fundamental for uncovering the diverse geologic pathways of rocky bodies in the solar system.
In this work, we provide a broad overview of our current knowledge of the composition and structure of planetary crusts following Broquet et al. (2025). We summarize the different geophysical approaches to characterize the shape of the crust and propose improvements to existing inversions of observed gravity and topography for crustal thickness from both conceptual and theoretical perspectives. In particular, we discuss how the gravity field resolution, data filtering, crustal density as well as the elastic and dynamic support of topography all affect crustal thickness inversions. Based on these improvements, we propose refined crustal thickness models for Mercury, Venus, Mars, and the Moon.
Andrews-Hanna, J.C., & Broquet, A. (2023). The history of global strain and geodynamics on Mars. Icarus 395. doi: 10.1016/j.icarus.2023.115476.
Broquet, A., Maia, J., & Wieczorek, M.A. (2025). On the crustal architecture of the terrestrial planets. J. Geophys. Res. Planets 130, e2025JE009139. doi: 10.1029/2025JE009139
Carr, M.H., & Head, J.W. (2010). Geologic history of Mars. Earth Planet. Sci. Lett. 294. doi: 10.1016/j.epsl.2009.06.042.
Hynek, B.M., Beach, M., Hoke, M.R. (2010). Updated global map of Martian valley networks and implications for climate and hydrologic processes. J. Geophys. Res. Planets 115(E9). doi: 10.1029/2009JE003548.
Langlais, B., Lesur, V., Purucker, M. et al. (2010). Crustal Magnetic Fields of Terrestrial Planets. Space Sci. Rev. 152, 223–249. doi: 10.1007/s11214-009-9557-y.
Melosh, H.J., Freed, A.M., Johnson, B.C., et al. (2013). The Origin of Lunar Mascon Basins. Science 340. doi: 10.1126/science.1235768.
Plesa, A.-C., Wieczorek, M.A., Knapmeyer, M., Rivoldini, A., Walterová, M., Breuer, D. (2022). Chapter Four - Interior dynamics and thermal evolution of Mars - a geodynamic perspective. Adv. Geo. 63. 10.1016/bs.agph.2022.07.005.
How to cite: Broquet, A., Maia, J., and Wieczorek, M. A.: On the Crustal Architecture of the Terrestrial Planets, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3845, https://doi.org/10.5194/egusphere-egu26-3845, 2026.
Mercury experiences periodic radial surface deformation, quantified by the Love number h2, due to tidal forces exerted by the Sun. Existing measurements come from processing of the Mercury Laser Altimeter (MLA ) profiles using independent approaches: (1) the cross-over analysis (1.55±0.65; Bertone et al., 2021), the self-registration techniques (0.92±0.58; Xiao et al., 2025), and (3) the direct altimetry (1.05±0.29; Stenzel et al., 2025). Unfortunately, the associated uncertainties are still too large to offer meaningful insights into Mercury’s interior (Stenzel et al., this meeting).
We base our study on Xiao et al. (2025a), but focus on a more polar region of 80°N to 84°N. We permit more reference profiles during the self-registration iterations, adopt higher spatial resolution for the reference terrain model, and minimize projection-induced distortions. To improve the geolocation of MLA footprints, we refine the MESSENGER orbits by carefully modeling non-conservative forces experienced by the spacecraft (Andolfo et al., 2024). Trajectory uncertainty stability is assessed using two independent precise orbit determination frameworks, based on the GEODYN II and MONTE software, respectively.
The derived tidal deformation time series are shown in Figure 1 and their general trends resemble well that of the tidal signal. After removing the outliers, the inverted tidal h2 converges to between 1.3 and 1.4. Bootstrappings by subsamplings and perturbations considering measurement errors indicate a 3-sigma uncertainty of around 0.1.
Figure 1. Measured radial tidal deformation against Mercury's mean anomaly (black dots). Theoretical tidal deformation is shown for comparison (blue curves).
We use the Markov Chain Monte Carlo (MCMC) to infer plausible Mercury interior structure that are consistent with the measured annual libration (Xiao et al., 2025b), tidal Love number k2 (Konopliv et al., 2020), and polar Moment of Inertia (Bertone et al., 2021). We assume a forsterite/enstatite mantle and a Fe-S-Si core, and consider pressure/temperature dependent properties of the materials. Besides, we take into account the gravitational-pressure couplings at the layer boundaries when estimating the annual libration (Rivoldini and Van Hoolst, 2013). The tidal h2 prediction is around 0.9, which is much smaller than our measurement.
Currently, we are examining factors that may possibly bias our estimate. We should also note that the study region is extremely limited to within the northern smooth plains which are caused by massive flood volcanism in the past. The large tidal h2 may point to lingering interior heterogeneties, for example, a softer or warmer mantle beneath.
These activities also stand as a preparation for the upcoming data collected by the BepiColombo Laser Altimeter (BELA) onboard ESA/JAXA’s BepiColombo mission to Mercury (Hussmann and Stark, 2020).
Acknowledges
AG acknowledges the California Institute of Technology (Caltech) and the Jet Propulsion Laboratory (JPL) for the license of the software MONTE Project Edition.
References
Andolfo et al., 2024. JGCD, 47(3), 518-530. Bertone et al., 2021. JGR: Planets, 126(4), e2020JE006683. Hussmann and Stark, 2020. EPJ ST, 229(8), 1379-1389. Konopliv et al., 2020. Icarus, 335, 113386. Rivoldini and Van Hoolst, 2013. EPSL, 377, 62-72. Stenzel et al., 2025. Authorea Preprints. Xiao et al., 2025a. GRL, 52(7), e2024GL112266. Xiao et al., 2025b. EPSC-DPS2025-325.
How to cite: Xiao, H., Rivoldini, A., Stark, A., Genova, A., Torrini, T., Briaud, A., Tosi, N., Andolfo, S., Van Hoolst, T., Hussmann, H., Lara, L., and Gutiérrez, P.: Refining Mercury's tidal Love number h2 through self-registration of MESSENGER laser profiles, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15443, https://doi.org/10.5194/egusphere-egu26-15443, 2026.
Considering a laterally variable crustal thickness has important effects on modeling the 3D geodynamical evolution of terrestrial bodies (e.g., Plesa et al., 2016; Fleury et al., 2024; Santangelo et al., 2025). On the one hand, it provides an orientation for the geodynamic model by correlating subsurface regions with surface features such as craters and volcanic centers. On the other hand, it improves the geodynamic model, allowing it to capture temperature fluctuations induced by thickness variations in a radiogenically enriched and low-conductivity crust.
Asymmetries in the subsurface temperature predicted by geodynamical models at present-day will induce gravity field anomalies that can, in turn, affect crustal thickness inversions. In the case of the Moon, a present-day thermal asymmetry between near- and far-side has been predicted by several studies (e.g., Laneuville et al., 2013, 2018; Park et al., 2025; Santangelo et al., 2025), possibly induced by the concentration of radioactive isotopes underneath the nearside crust. This 100–200 K temperature anomaly in the mantle translates to a large-scale and prominent negative density anomaly, which is yet to be accounted for by inversions of gravity data for the crustal thickness of the Moon (e.g., Wieczorek et al., 2013).
In this work, we couple geodynamic models together with gravity and topography inversions of crustal thickness to provide self-consistent estimates of the lunar mantle and crustal structure. We convert subsurface thermal anomalies predicted by the thermal evolution model into density anomalies using a pressure- and temperature-dependent parameterization of the thermal expansivity (Tosi et al., 2013). The density anomalies are used as input to invert for the crustal thickness distribution. The crustal thickness inversion model used in this study has been adapted from the setup described in Broquet et al., (2024).
For self-consistency, we iterate between the crustal thickness and the geodynamic model, as the density anomalies obtained in the geodynamic model result from crustal thickness variations and associated distribution of radiogenic isotopes, while the crustal thickness inversion itself depends on the density anomalies and associated density contrast at the crust-mantle boundary. Convergence is reached within a couple of iterations.
We find that a positive temperature anomaly associated with the enrichment of radiogenic isotopes beneath the lunar near side, as required to explain the Apollo 15 and Apollo 17 heat flux measurements (Langseth et a., 1976), induces a crustal thinning up to 8.5 km in the Procellarum KREEP Terrane (PKT) region. Conversely, the positive density anomaly associated with a colder lunar interior underneath the thin-crust South-Pole Aitken basin produces a crustal thickening of ~3 km.
Our coupled geodynamic crustal thickness models show that the effects of subsurface temperature anomalies can lead to changes in crustal thickness estimates comparable to the uncertainty in the seismically derived crustal thickness measurements (~8 km; Chenet et al., 2006). Thus, considering temperature anomalies on crustal thickness modeling has important implications for our understanding of the crustal structure of the Moon. Upcoming seismic and heat flow measurements will, therefore, be critical to discriminate between different interior structure models.
How to cite: Santangelo, S., Plesa, A.-C., Broquet, A., Breuer, D., and Grott, M.: The effect of present-day mantle temperature anomalies on crustal thickness inversions for the Moon, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1113, https://doi.org/10.5194/egusphere-egu26-1113, 2026.
More than 50 years after Apollo, the Moon deep interior structure is still not well known. Several seismic experiments are expected on the Moon surface in the coming year (Chang’e 7, Chandrayan, Artemis III, FSS and SPSS). All of those seismometers are not expected to resolved the seismic background of the Moon and their performances are not meeting the International Lunar Network requirements (10-11 m.s-2/sqrt(Hz)).
To meet this requirement, IPGP is developing an optical seismometer operated in open loop. Its mechanical oscillator is a 1Kg proof mass suspended by a 4 cross blades hinge and a leaf spring with extremely low damping. Its displacement sensor is a Michelson interferometer, associated to a narrow bandwidth laser source and an optical phase readout electronic inherited from fiber optics gyroscope. This instrument will be candidate for all flight opportunities around 2030 (launch date).
The first prototypes performances tests demonstrated the potential of this technology. But it also revealed that stray light inside the interferometer is limiting its performance. Different techniques of characterization of the stray light are compared: in situ coherent detection, characterization using a delay line and short coherency length light source. Tests results are compared to simulation.
Analysis of the stray light impact on the performances through the optical phase readout electronic modulation scheme shows the impact on performances. Expectation and performances potential of the next prototypes generation is discussed.
How to cite: de Raucourt, S., Guattari, F., Chabaud, G., Drilleau, M., Kawamura, T., Lognonné, P., Nebut, T., Robert, O., and Tillier, S.: Lunar Optical Very Broad Band: a high-performance seismometer for Moon deep interior study, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13434, https://doi.org/10.5194/egusphere-egu26-13434, 2026.
In the absence of structural asymmetry, the lunar tidal Love numbers should be order independent. Through careful analysis of GRAIL’s non-static gravity field, a recent study by Park et al. (2025; Nature) extracted statistically different ordered Love numbers for the monthly Moon tides, indicative of large scale laterally varying internal structure. In their study, they inverted for variations in shear modulus within the lunar mantle and interpreted these variations in the context of temperature variations. In a complementary, though distinct vein, we jointly invert these new Love numbers, augmented with the same Love numbers for the yearly tides, in tandem with the free-air gravity field and the center-of-mass to center-of-figure offset, to produce a long-wavelength tomographic model of the Moon’s mantle density, elastic, and anelastic properties. To do this, we adapted a normal mode perturbation theory able to predict tidal deformation derived for the Earth that incorporates the Moon's rotation, lateral variations in density, shear and bulk moduli, attenuation, and boundary topography such as the crustal-mantle interface and the core-mantle boundary (Lau et al., 2015; GJI). Since we self-consistently solve for density, shear modulus and attenuation, we are able to interpret our results in the context of both temperature and compositional variations, finding a lower contribution to variations in temperature than in Park et al.’s work and independent density variations within the nearside-farside mantle asymmetry.
How to cite: Wagner, N., Berne, A., Lau, H., and Frankenberg, N.: The Lopsided Moon: Tidal Signals of a Heterogeneous Interior, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15471, https://doi.org/10.5194/egusphere-egu26-15471, 2026.
The South Pole-Aitken basin (SPA) is the oldest and largest known impact basin on the Moon. We use gravity, topography, and surface remote sensing data together with impact simulations to reveal new details of the structure and formation of the basin and to place new constraints on the structure, differentiation, and early evolution of the Moon. The geophysical expression of SPA reveals an elongated, tapered basin formed in a southward-directed oblique impact. Impact simulations show that the downrange excavation from the core of a differentiated impactor can explain the tapered shape of the basin. Remote sensing reveals an asymmetric ejecta blanket rich in thorium, consistent with asymmetric excavation of late-stage lunar magma ocean liquids enriched in incompatible elements such as potassium, rare earth elements, and phosphorus (KREEP). The distribution of Th-rich ejecta can be explained in the context of models of magma ocean crystallization, in which progressive solidification of the magma ocean caused it to become concentrated beneath regions of thinner crust, eventually pinching out to zero thickness beneath the farside highlands and finally concentrating within the nearside Procellarum KREEP terrane. At an intermediate stage, a thin and discontinuous layer of late-stage magma ocean liquids would have been present beneath the southwestern half of the basin extending onto the nearside, which explains the observed distribution of Th-rich SPA ejecta. Material excavated by SPA on the farside and the younger Imbrium basin on the nearside reveal the evolution of the late-stage magma ocean products in space and time. The ages of these basins and Th concentrations of their ejecta match the modeled compositional evolution of the magma ocean. Thus, the ejecta of SPA provides a means to sample the late-stage magma ocean as well as the lunar mantle. High-resolution gravity data reveals an annulus of large-amplitude, short-wavelength gravity anomalies surrounding the basin, consistent with the predicted distribution of material excavated from the lunar mantle. Remote sensing observations of craters excavating into this material indicate a heterogeneous mantle at the time of impact, containing both orthopyroxene-rich and clinopyroxene-rich material. Experimental work predicts that these distinct compositions should form early and late in the magma ocean crystallization sequence, respectively. Thus, the observed compositions are consistent with partial or ongoing overturn of the lunar mantle at the time of the SPA impact. Together, these analyses show how the Moon’s oldest known impact basin provides a key constraint on the interior structure, differentiation, and early evolution of the Moon. This work provides context for recent, ongoing, and future missions exploring the lunar farside that offer the opportunity for in situ exploration of materials derived from the SPA impact.
How to cite: Andrews Hanna, J. C., Gowman, G., Wakita, S., Johnson, B. C., Alexander, A., Bill, C. A., Bottke, W. F., Broquet, A., Collins, G. S., Davison, T. M., Evans, A. J., Keane, J. T., Levin, J. N., Mallik, A., Marchi, S., Moriarty III, D. P., Moruzzi Fresenius, S. A., and Roy, A.: The South Pole-Aitken basin constrains the early evolution and differentiation of the Moon, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16091, https://doi.org/10.5194/egusphere-egu26-16091, 2026.
Lava tubes and other subsurface cavities represent key targets for planetary exploration, as they could provide shelter from radiation for astronauts during future exploration missions and are high-priority astrobiology sites. While these structures have been identified on Mars and the Moon, characterization requires conducting geophysical surveys that may first be proven on terrestrial analogs. Among available geophysical methods, magnetic surveys using aerial platforms (e.g., drones or helicopters) offer a cost-effective and easily deployed approach.
The island of Lanzarote (Canary Islands, Spain) is renowned for its volcanic structures—including volcanoes, calderas, and lava tubes—similar to those found on other planetary bodies, particularly Mars. In May 2023, the NASA Goddard Instrument Field Team acquired vector fluxgate and scalar magnetic measurements over three lava tubes in Lanzarote: La Corona, Los Naturalistas, and Tahiche. Previous analyses of the data collected over the Corona lava tube demonstrated the feasibility of using fluxgate magnetic measurements to detect and characterize subsurface cavities. This study focuses on the Naturalistas and Tahiche tubes, which are significantly shallower, shorter, and narrower than La Corona. Specifically, Tahiche exhibits a complex geometry with abrupt changes in size and trajectory. These varied tube geometries provide complementary case studies for validating magnetic surveys for cavity detection, a critical step before conducting magnetometer surveys on other planetary bodies.
We processed our measurements and calculated magnetic anomalies of both the total magnetic field and each of the fluxgate Cartesian vector components. We also applied several enhancement techniques to constrain the location, size, and depth of the two lava tubes. Lastly, we built 2D magnetic forward models for each magnetic transect to reconstruct the geometry and trajectory of the Naturalistas and Tahiche tubes using magnetic data alone. Those geometries will be compared with LiDAR data collected from the tube interiors during the same field campaign. These results provide important guidelines for designing future magnetic surveys on the surfaces of Mars and Moon.
How to cite: Martin de Blas, J., Martos, Y. M., Espley, J., Sheppard, D., Scheidt, S., Richardson, J., and Connerney, J.: Detection and characterization of the Naturalistas and Tahiche lava tubes (Lanzarote, Canary Islands) using vector fluxgate and scalar magnetometer measurements, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13716, https://doi.org/10.5194/egusphere-egu26-13716, 2026.
The Tajogaite eruption provides a recent example of the construction of a volcanic edifice and an opportunity to track the evolution of the volcano and its products. The eruption was active from 19 September to 13 December 2021, making its surface incursion into the Cumbre Vieja volcanic rift. Over the months, there were several eruptive vents that built a main edifice. Among its main products were tephritic and basanitic lava flows, some reaching the coast; pyroclastic materials near the cone, such as bombs; and ash ejection throughout the process.
The aim of this work is to study the mineralogical composition through the magnetic characterisation of the rocks. The lavas from the 2021 eruption have similar compositions, ranging from tephrites to basanites, emitted in the early and late stages of the eruption, respectively, with the former being richer in amphibole and the latter richer in olivine. Rocks emitted by the Tajogaite volcano are compared with those from other eruptions on the island, such as San Juan (1949) and Tacande (1480).
To this end, a methodology is employed which consists, firstly, of collecting field samples for magnetic characterisation. With the aid of a Vibrating Sample Magnetometer, the natural remanence of the samples, the first magnetisation curves and the hysteresis loops are measured.
An original contribution of this work is the use of a normalisation of the first magnetisation curves. Depending on their shape and changes in slope, compositional differences in the samples can be identified due to variations in their magnetic carriers. Therefore, we associate different curves with different rock compositions.
How to cite: Melguizo Baena, Á., Rivero Rodríguez, M. Á., López Escolano, A., Fernández Romero, S., Ntelakrous Karnavas, L., Oliveira, J. S., and Díaz Michelena, M.: Magnetic characterisation of volcanic rocks from the Tajogaite eruption., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1845, https://doi.org/10.5194/egusphere-egu26-1845, 2026.
The Isidis Planitia impact basin on Mars is located on the north-south dichotomy boundary, bordered by Utopia Planitia and the Syrtis Major volcanic province. The basin records a long geological history of global and regional events of impact-induced, volcanic and sedimentary processes. This is evident in the presence of a high-density subsurface mass concentration, the strongest on Mars outside the major volcanic provinces. The nature of this interior structure remains poorly understood despite modelling efforts (e.g., [1-3]). Isidis Planitia’s surface also hosts the densest clustering of pitted cones [4,5]. The formation mechanism of these landforms, characterised by a conical mound with a central depression, remains debated as volcanic [6], sedimentary [4] or glacial [7].
We present an integrated approach to Isidis Planitia, showing that pitted cones are topographically constrained by surface wrinkle ridges driven by its subsurface structure. The subsurface is modelled using impact scaling laws combined with geological context to formulate a multi-layered model, which is fit to the local gravity field. Resultant structural elements are consistent with impact theory [8-10], estimated structures below Lunar basins [11,12], as well as mapped basins [13]. However, the gravity field cannot be constrained using infill, scaling laws and realistic density values. The models require mantle-like materials in the innermost parts of the basin. This element does not reconcile with expectations of impact theory nor basin infill, and is interpreted as significant post-impact plutonic intrusions.
This intrusive element is linked to a set of wrinkle ridge surface expressions with anomalous direction and dip. Two distinct formations of ridges are identified: an initial radial set of ridges and a latter concentric inward-dipping formation. This anomalous concentric set is not mirrored in Lunar basins [14,15] nor in Martian basins Utopia and Hellas [16,17]. The initial set is likely driven by regional compressive effects. The latter formation is driven by a stress field in the inner basin, which could be achieved during pluton inflation.
The pitted cones are shown to correlate with the basin topography dominated by the wrinkle ridges. The population conforms to both sets of pre-existing wrinkle ridges in distinct surface flow patterns. They are most consistent with volcanic rootless cones formed by lavas interacting with near-surface volatiles. The lava could be sourced from the intrusive magmatism, addressing the lack of other sources [6]. Overall, this study links Isidis Planitia’s subsurface structure to surface morphology. It could redefine the complex and dynamic basin, offering new insights into the active geological evolution of Mars.
References: [1] Wieczorek et al. (2022). [2] Ding et al. (2024). [3] Zhong et al. (2022). [4] Mills et al. (2024) Icarus 418. [5] Chen et al. (2024). [6] Ghent et al. (2012). [7] Guidat et al. (2015). [8] Freed et al. (2014). [9] Johnson et al. (2018). [10] Potter (2015). [11] Runyon et al. (2022). [12] Spudis et al. (2014). [13] Christeson et al. (2021). [14] Collins et al. (2023). [15] Tariq et al. (2024). [16] Carboni et al. (2025). [17] Head et al. (2002).
How to cite: Bijlsma, J., Root, B., and de Vet, S.: Insights into pitted cones at Isidis Planitia through synthesis of interior and surface, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16905, https://doi.org/10.5194/egusphere-egu26-16905, 2026.
The dwarf planet Pluto and its largest moon Charon represent a fully tidally evolved system: their orbital eccentricity is almost zero and their respective rotational periods are equal to the mutual orbital period. According to a widely accepted hypothesis, Charon as well as other Pluto moons originated in a giant oblique impact (e.g., Canup et al., 2005; Arakawa et al., 2019), forming on a tight orbit above the synchronous radius, and evolved by tidal recession from the primary, which was endowed with a large angular momentum and thus fast rotation. A recent, alternative scenario proposes formation by collisional capture (Denton et al., 2025), resulting in Charon’s emplacement on an initially circular close-in orbit and a primordial synchronisation at high spin rate.
A tidally evolving binary is subjected to surface stresses that are strongly dependent on the mutual distance and, for small orbital separations, may lead to the formation of tidally-oriented fractures in the ice shell similar to those on Enceladus or Europa. The orientation of fractures identified on images from the New Horizons mission is, however, not correlated with expected tidal stresses and has instead been attributed to ocean freezing, which would have postdated the full orbital evolution (Rhoden et al., 2020). Moreover, an initially quickly rotating Pluto (and Charon) consistent with the giant impact scenarios would lead to a considerable rotational bulge that would only be able to relax before present in the case of a thin lithosphere and a weak ice shell above a subsurface ocean (McKinnon et al., 2025).
Here, we present a model of the Pluto-Charon synchronisation that predicts lower tidal stresses and does not require initial fast rotation of the partners, thus potentially alleviating some of the challenges posed by the standard tidal recession scenario. We propose that the binary was formed by a capture of a highly inclined retrograde minor planet (proto-Charon) by a prograde-rotating Pluto and subsequently evolved by tidal approach. Following this line, we perform numerical simulations of the binary’s orbital evolution, studying the effect of various initial spin rates, eccentricities, and interior properties. During the evolution, Pluto acquires its present-day retrograde rotation and, depending on ice viscosity, Charon may experience episodes of higher spin-orbit resonances (such as 3:2 or 2:1). Since the evolution of a planet with a retrograde moon proceeds at distances greater than the present-day semi-major axis, both Pluto and Charon experience tidal heating and stresses two orders of magnitude lower than in the tidal recession scenario.
How to cite: Efroimsky, M., Walterova, M., Gevorgyan, Y., Bagheri, A., Makarov, V. V., and Khan, A.: Synchronisation of the Pluto-Charon binary by inward tidal migration., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6046, https://doi.org/10.5194/egusphere-egu26-6046, 2026.
Tectonic activity from global contraction and its influence on the location of volcanic eruptions (i.e. faculae) continues to elicit diverse interpretations, with the underlying structural controls of many faculae still poorly constrained [1;2]. At the boundary of the Rachmaninoff basin area and the northern smooth plains lies a large 800 km long, 100km wide, and 1000-3500 km high elevation structure which terminates at the 200 km diameter Copland crater. 400 km north of this boundary is a parallel structure of similar dimensions, implying a shared formation mechanism. Topographic profiles perpendicular to these structures reveal that both have asymmetric positive relief indicative of thrust fault scarps (i.e. lobate scarps and rupes), with a steep sloping forelimb followed by a more gently sloping backlimb. Although these structures are generally taller and wider than even the largest thrust fault scarps on Mercury (e.g. Enterprise Rupes with <2500 m of relief), we present evidence that these structures contain a significant amount of shortening and may be unidentified thrust faults which strike east and dip to the south. Specifically, they outline the rims of relic craters (b50 and b72, [3]), meaning that crustal shortening utilized preexisting crater wall bounding normal faults. This shortening is identified from the deformation induced on Copland crater where its southern rim is elevated 1,250 m respect to its northern rim. Mapped faults in the area have noted smaller lobate scarps in the area, and one which passes through the center of Copland and offsets its floor by 400 m [4], however this is dwarfed by the deformation caused by the deflected large thrust which has uplifted the southern rim of Copland crater. Furthermore, the presence of volcanic eruptions (Neidr and Nathair Faculae, [5]) along the southern edge of the scarp, the hanging wall, is typical of thrust fault activity on Earth [6]. The parallel trend shared with the long-wavelength topography (broad troughs and crests, [7]) may also indicate a shared formation mechanism. Revelations from the BepiColombo mission, particularly the updated high-resolution topography, will facilitate more interpretation of the local tectonic regimes on Mercury and may reveal many undetected shortening structures and faculae, and in turn a full appreciation of their geospatial relationships can be achieved.
References
[1] Banks, M. E. et al. (2015). JGR: Planets, 120(11), DOI: 10.1002/2015JE004828
[2] Jozwiak, L. M., et al. (2018). Icarus, 302, 191-212. DOI: 10.1016/j.icarus.2017.11.011
[3] Orgel, C., et al. (2020). JGR: Planets, 125(8), e2019JE006212. DOI: 10.1029/2019JE006212
[4] Bernhardt, H., et al. (2025). (No. EPSC-DPS2025-2108). Copernicus Meetings. DOI: 10.5194/epsc-dps2025-2108
[5] Wright, J., et al. (2024). Earth and Space Sci., 11(2). DOI: 10.1029/2023EA003258
[6] Gaffney, E. S., et al. (2007). Earth and Planet. Sci. Let., 263(3-4), 323-338. DOI: 10.1016/j.epsl.2007.09.00
[7] Schmidt, G. W., et al. (2026). JGR: Planets, 120(11). DOI: 10.1029/2025JE009233
Acknowledgements: We gratefully acknowledge funding from the Italian Space Agency (ASI) under ASI-INAF agreement 2024-18-HH.0.
How to cite: Schmidt, G., Buoninfante, S., Galluzzi, V., and Palumbo, P.: Structural Controls on Volcanic Eruptions: Insights from the Copland-Rachmaninoff Tectonic Regime on Mercury, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-23097, https://doi.org/10.5194/egusphere-egu26-23097, 2026.
Impact basins on terrestrial planets have been thoroughly investigated from imagery and topography data. Previous work has already shown the presence of peak-ring basins on terrestrial planets and estimated their size (e.g., [1]), utilising topography and morphological data. However, the modelling of gravity and crustal thickness data can be a powerful approach in detecting hidden impact basins and estimating the diameters of their rim and inner rings. This is also useful in updating the basin catalogue of terrestrial planets and provides valuable constraints to accurately estimate the impact rate during the early Solar System.
NASA’s MESSENGER mission provided most datasets used in the last decade to model the internal structure of Mercury and characterize its surface. Image products derived after MESSENGER have been widely used to detect impact basins and provide a consistent database [2, 3]. More recently, Mercury’s gravity anomalies have also been used to re-update this catalogue [4].
Here we model Bouguer gravity anomalies of Mercury using the MESS160A gravity field model [5] to properly estimate the size of inner rings. We first quantify a regional value of the Bouguer gravity anomaly, which is defined as the average value obtained from azimuthally averaged profiles in the spatial range 1.5D to 2D, where D is the basin diameter. The size of the Bouguer gravity high is derived as the radius where the profiles first intersect the regional values. The uncertainties represent the ±1σ values of the regional values taken in the same spatial range. We performed tests on filtered GRAIL gravity data, consistently with the spatial resolution of Mercury’s gravity field, to understand how the resolution affects the size estimates of certain lunar basins [6]. The used approach can be reliable for inner ring diameters ≳ 70 km when considering the highest gravity resolution for Mercury.
We present preliminary results for selected certain impact basins [2, 3, 7] in the northern hemisphere where the current gravity data is characterized by higher resolution, and for putative or uncertain basins [2, 3]. The results confirm the existence of the investigated certain and putative basins, and provide updated inner ring sizes.
This approach will be first used to identify potential unknown impact basins, re-evaluate the existing databases of impact basins on Mercury, and it can be valuable in assessing the existence and number of multi-ring basins on Mercury. Though our current database focuses on basins in the northern hemisphere, the approaching ESA-JAXA BepiColombo mission will provide higher-resolution gravity data in the southern hemisphere, allowing us to better quantify the impact basins size at these latitudes.
References
[1] Baker D. M. H. et al. (2011). Planet. Space Sci., 59(15).
[2] Fassett C. I. et al. (2012). JGR: Planets, 117(E12).
[3] Orgel C. et al. (2020). JGR: Planets, 125(8).
[4] Szczech C. C. et al. (2024). Icarus, 422.
[5] Konopliv A. S. et al. (2020). Icarus, 335.
[6] Neumann, G. A. et al. (2015). Sci. Adv., 1(9).
[7] Hall G. P. et al. (2021). JGR: Planets, 126(9).
Acknowledgements: We gratefully acknowledge funding from the Italian Space Agency (ASI) under ASI-INAF agreement 2024-18-HH.0.
How to cite: Buoninfante, S., Wieczorek, M. A., Galluzzi, V., Schmidt, G. W., and Palumbo, P.: Computing the size of Mercury’s impact basins and ring systems through gravity data modelling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10257, https://doi.org/10.5194/egusphere-egu26-10257, 2026.
This study presents a novel Bayesian framework for the three-dimensional characterization of the internal structure of planetary bodies, accounting for their irregular layering. The interior model inversion is formulated within a Markov Chain Monte Carlo (MCMC) approach and relies on three-dimensional model equations linking the physical properties of the internal layers to the spherical harmonic coefficients of the gravity field. The method produces statistically consistent posterior distributions of parameters that define the internal structure of each accepted model that match the target distributions of the observed gravity coefficients and complementary geophysical constraints (e.g., Love number k2, librations).
Each interior model consists of concentric uniform ellipsoidal layers defined by size, density, and rheological properties. Crustal thickness variations are represented as deviations from a reference ellipsoid, providing a computationally efficient alternative to fully voxel-based representations while retaining sensitivity to lateral heterogeneities. Gravity coefficients are computed as the sum of a hydrostatic contribution, determined by the ellipsoidal shape of each layer, and a non-hydrostatic contribution derived from degree-dependent admittance.
The framework yields global grids of the crustal thickness together with the corresponding gravity spectra and associated residuals. These outputs provide constraints that cannot be captured by 1-D (spherical) or 2-D (ellipsoidal) interior models commonly adopted in the literature. The proposed approach is particularly suited to small bodies of the Solar System, including icy moons and dwarf planets, for which shape irregularities exert a first-order control on internal structure and geological evolution.
How to cite: Boccacci, G., Ciambellini, M., Gargiulo, A. M., and Genova, A.: A Generalized Method for the three-dimensional characterization of the internal structure of planetary bodies based on Markov Chain Monte Carlo (MCMC) techniques, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17615, https://doi.org/10.5194/egusphere-egu26-17615, 2026.
Accurate estimation of geophysical parameters, including total mass, moment of inertia and rotational state of planetary bodies is essential for understanding their degree of differentiation, constraining their internal structure, and gaining insights into their evolutionary path. To improve the accuracy of these key estimates, we have developed an integrated framework that combines Earth-based radio tracking data with navigation measurements based on the observation of relevant surface features on the body’s surface.
Two-way Doppler and range measurements provide robust constraints on the spacecraft motion along the line of sight and are traditionally used for gravity and geophysical investigations. Surface imagery of the central body offers complementary information, supporting the estimation of the target body’s spin vector and deviations from uniform rotational state, such as longitudinal librations.
The proposed approach leverages the tracking of relevant surface features to jointly reconstruct the spacecraft trajectory and estimate geophysical parameters of the target body. Features tracked across partially overlapping images acquired sequentially during closely spaced orbital passes improve the internal consistency of the trajectory reconstruction, whereas features observed across different mission phases contribute to the refinement of the body’s rotational state. To address challenges arising from variable illumination conditions and resolution discrepancies in planetary images, hybrid strategies are adopted for feature tracking, combining conventional computer vision with Artificial Intelligence-based feature detection and matching.
The framework is validated using data from the MESSENGER spacecraft during its science orbital phase around Mercury. The novel approach improves estimation accuracies with respect to single-instrument solutions and provides a flexible, effective tool for maximizing the scientific return of deep-space missions.
How to cite: Gargiulo, A. M., Andolfo, S., Torrini, T., Re, C., and Cremonese, G.: Integration of Radio Tracking and Feature-based Optical Measurements for Geophysical Investigations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22989, https://doi.org/10.5194/egusphere-egu26-22989, 2026.
Recent reprocessing of NASA's GRAIL mission gravimetric data in the work of Park et al. (2025) allowed for the estimation of the third-degree lunar tidal Love number, k3, at a monthly tidal period of 27.3288 days. The obtained value, k3 = 0.0163 ± 0.0007, is significantly higher than predictions based on spherically symmetric models of the lunar interior. This same study suggests that this high k₃ value could be explained by the presence of a degree-1, order-1 anomaly in the lunar mantle shear modulus, with an amplitude of approximately 3%.
In this work, we investigate the tidal response of laterally heterogeneous lunar interiors using 3-D viscoelastic modeling and considering not only elastic framework but also viscoelastic rheology. Using CitcomSVE – a finite-element code initially developed for modeling glacial isostatic adjustment deformations – we model the lunar interior as suggested in the results of Park et al. (2025), i.e., for degree-1, order-1 mantle anomaly in shear modulus. We further quantify tidal dissipation at both monthly and yearly (365.260 days) forcing periods to assess whether the dissipation predicted by this model is consistent with current observational constraints on lunar tidal dissipation.
How to cite: Guinard, A., Abreu-Torres, J., Fienga, A., Zhong, S., and Mémin, A.: Exploration of Degree-1 Heterogeneities in the Lunar Mantle Using CitcomSVE, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3345, https://doi.org/10.5194/egusphere-egu26-3345, 2026.
This study systematically analyzes the composition and origin of materials in the Chang’e-4 landing area (Von Kármán crater) using 131 in-situ lunar soil spectra from the first 60 lunar days obtained by Visible and Near-infrared Imaging Spectrometer onboard Yutu-2 rover and spectral data from the Moon Mineralogy Mapper (M3). Results show that the 2μm absorption center of the landing area aligns with that of Finsen ejecta, while the 1μm absorption center shifts toward longer wavelength, suggesting an enrichment in olivine or glass of the landing area. The surface materials at the landing area might originate from the distal ejecta of Finsen crater.
Based on the Chang'e-2 Digital Orthophoto Map(DOM) data and the geological characteristics along the traverse area of Yutu-2 rover, we found that the rock types in and around the Von Kármán crater can be classified into three categories. (1)Basalts formed in two different periods. The late-stage basalt is flood lava (approximately 320m thick), originating from Leibniz crater. The old basalts represent the basement rock at the bottom of Kármán crater; (2)Widely distributed weathered deposits. Although their spectra are similar to those of Finsen ejecta, these deposits are located at the distal end of the ejecta rays, exhibit variable thickness, and reveal local fragmented blocks beneath them. This suggests that the deposits likely represent a mixture of ejecta material and local substrate; (3) Highland rocks. The basement rocks that predate the Von Kármán and Von Kármán M craters are represented by a large number of highland rocks, which form the rim plateau around the Von Kármán crater. The distal position and heterogeneous thickness of the Finsen ejecta at the landing area indicate that the Finsen-forming impact event only modified the composition of landing area surface regolith at millimeter- to centimeter-scale depths, without causing significant topographic alteration.
How to cite: Zhang, H., Liu, D., Li, Z., Zhang, Z., and Li, C.: Composition and Provenance of the Chang’e-4 Landing Area, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3738, https://doi.org/10.5194/egusphere-egu26-3738, 2026.
High-precision radio tracking from a future Uranus orbiter may provide key constraints on Uranus’ internal structure and dynamics, provided suitable instrumentation and an optimized orbital tour. We present the results of radio science simulations to evaluate gravity field recovery performance across different orbital configurations.
We run numerical simulations of the gravity experiment by using NASA/JPL MONTE orbit determination software, assuming the orbiter to be equipped with high-end radio tracking system capable of generating accurate Doppler and range observables at both X- and Ka-band, supporting triple-link plasma calibration. Two representative mission scenarios are analyzed: (i) southern-hemisphere periapses at an altitude of ~7000 km, passing outside the ring system, and (ii) low-altitude periapses at ~1000 km, passing inside the rings. The results show indeed a strong dependence of gravity field recovery on orbital geometry. In the higher-altitude scenario, only the J2 and J4 zonal harmonics can be estimated with sufficient accuracy, whereas the lower-altitude configuration enables the reliable determination of J6.
In parallel, we investigate the effect of Uranus’ normal modes of oscillation on the spacecraft dynamics. The free oscillation spectrum is computed assuming a simplified internal structure model, adapted from approaches developed for the Juno and Cassini missions. Although individual mode frequencies are unlikely to be resolved, their cumulative effect produces time-variable perturbations on the low-degree zonal harmonics that may act as a source of noise in gravity field estimation.
These results highlight the critical role of high-end radio tracking instrumentation and orbital design in maximizing the scientific return of gravity science at Uranus and provide a quantitative framework for evaluating the observability of its interior and dynamical processes.
How to cite: Durante, D. and di Stefano, I.: Uranus gravity field investigations from an orbiter mission, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21183, https://doi.org/10.5194/egusphere-egu26-21183, 2026.
The M-MATISSE mission, currently in Phase A with ESA as an M7 candidate, is a dual-spacecraft concept designed to investigate the coupled Martian magnetosphere, ionosphere, and thermosphere (MIT coupling) under varying space-weather and lower-atmosphere conditions. Two identical spacecraft, “Henri” and “Marguerite,” will fly complementary orbits with apocenters of 3,000 km and 10,000 km and common pericenters at 250 km, enabling highly diverse radio occultation geometries through an inter-satellite crosslink.
This contribution focuses on the M-MATISSE Crosslink Radio Science (MaCro) instrument, a dedicated mutual radio occultation payload optimized for Mars ionospheric and atmospheric profiling. MaCro employs software-defined radios based on the AD9361 transceiver, dual-band omnidirectional antenna assemblies (UHF/S-band), and ultrastable master reference oscillators with Allan deviation on the order of 10⁻¹³ at 100 s. Simultaneous UHF and S-band links allow separation of dispersive ionospheric effects from neutral atmospheric contributions, while flexible SDR filtering and automatic gain control accommodate large signal dynamics during occultation ingress and egress.
We present the MaCro instrument architecture and its expected performance, highlighting design challenges specific to crosslink radio occultation instruments. We provide bounds on the achievable frequency and refractivity retrieval accuracy and its sensitivity to the carrier-to-noise ratio, integration time, and clock stability, and discuss the implications for high-resolution profiling of Mars’ ionosphere and neutral atmosphere.
How to cite: Vorderobermeier, T., Andert, T., Pätzold, M., Tellmann, S., Plettemeier, D., Laabs, M., Budroweit, J., Imamura, T., Ando, H., Genova, A., Hahn, M., Noguchi, K., Oschlisniok, J., Peter, K., Schäfer, W., Sanchez-Cano, B., and Leblanc, F.: Design and Performance of the MaCro Crosslink Radio Science Instrument for M-MATISSE, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19577, https://doi.org/10.5194/egusphere-egu26-19577, 2026.
Posters virtual: Mon, 4 May, 14:00–18:00 | vPoster spot 4
EGU26-23072 | ECS | Posters virtual | VPS27
A data-driven approach to multi-ring basin identification on MercuryMon, 04 May, 14:39–14:42 (CEST) vPoster spot 4
Multi-ring impact basins represent some of the oldest and most degraded large-scale structures on terrestrial planetary bodies, making their identification and characterization particularly challenging. Only a few well-preserved examples are known, such as the Orientale basin on the Moon, commonly regarded as the archetype of multi-ring basins. On Mercury, several multi-ring basins were initially proposed based on Mariner 10 imagery (Spudis & Guest, 1988); however, most of these candidates were not confirmed by subsequent analyses using MESSENGER data (e.g., Fassett et al., 2012; Orgel et al., 2020), highlighting the difficulty of recognizing ancient, highly modified basin architectures. Here we present a semi-automatic workflow aimed at the systematic characterization of multi-ring basins on Mercury. The workflow combines manual structural mapping with quantitative, data-driven analyses and consists of four main steps: (1) construction of a structural map of tectonic features; (2) determination of the basin center using concentric deviation analysis (Karagoz et al., 2024); (3) estimation of the multi-ring geometry through a newly developed tool that analyzes the radial distribution of mapped structures using one-dimensional kernel density estimation (KDE). In this step, dominant concentric rings are identified as statistically robust density maxima obtained with a Gaussian kernel and an objectively defined Silverman bandwidth, while ring uncertainty is quantified through the interquartile range (IQR) of associated structures; and (4) comparison of the inferred ring geometry with the basin’s median radial topographic profile, derived from 360 azimuthally distributed radial profiles, to assess geometric and morphological consistency. We apply this workflow to two basins of different confidence levels. For the Orientale basin on the Moon, the method identifies three concentric rings corresponding to the Inner Rook Ring, Outer Rook Ring, and Cordillera Ring, consistent with previous studies (Spudis et al., 2013). For the Andal–Coleridge basin on Mercury, a probable multi-ring basin, the workflow retrieves a four-ring geometry that broadly coincides with rings II–V proposed by Spudis & Guest (1988). These results demonstrate that the combined use of structural mapping, KDE-based ring detection, and radial profile analysis provides a robust and reproducible framework for investigating degraded multi-ring basins. Future work will apply this workflow to additional candidate basins on Mercury to reassess their multi-ring nature and improve constraints on the planet’s early impact and tectonic history.
Acknowledgements: We gratefully acknowledge funding from the Italian Space Agency (ASI) under ASI-INAF agreement 2024-18-HH.0.
How to cite: Sepe, A., Ferranti, L., Galluzzi, V., Schmidt, G. W., and Palumbo, P.: A data-driven approach to multi-ring basin identification on Mercury, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-23072, https://doi.org/10.5194/egusphere-egu26-23072, 2026.
