BepiColombo is a joint mission between the European Space Agency (ESA) and the Japanese Aerospace Exploration Agency (JAXA), which will carry out the comprehensive exploration of planet Mercury. The mission was launched on 20 October 2018 from the European spaceport Kourou in French Guiana, and is currently on a eight-year-long cruise to Mercury. BepiColombo consists of two orbiters, the Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (Mio). In late 2026, these orbiters will be put in orbit around the innermost planet of our Solar System. Once in orbit, BepiColombo with its state of the art and very comprehensive payload will perform measurements to increase our knowledge on the fundamental questions about Mercury’s evolution, composition, interior, magnetosphere, and exosphere. BepiColombo successfully completed the last of its 6 flybys of Mercury in January 2025, and will continue its cruise during the rest of 2025 and much of 2026. Although the two BepiColombo orbiters are in a stacked configuration during the cruise, during which only some of the instruments can perform scientific observations, the mission has already produced some very valuable results, as well as striking observations of the planet using its three engineering monitoring cameras. We shall provide a summary of the mission status, a preview of the remaining plans for the mission up to and after arrival in orbit around Mercury, a broad overview of scientific results to date, and observations by the mission's monitoring cameras from the Mercury flybys.
How to cite: Jones, G. H. and Murakami, G.: BepiColombo Mission Update, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19385, https://doi.org/10.5194/egusphere-egu25-19385, 2025.
Introduction: Mercury, the innermost planet in the Solar System, remains an enigma due to significant gaps in our understanding of its internal structure. Recent advancements in planetary science have highlighted the potential of tidal Love numbers, specifically k2 and h2, to provide critical insights into the size of Mercury's inner core [1]. The Love number k2 represents a gravitational parameter, while h2 characterizes the radial deformation of the planet's surface. The determination of h2 can be achieved through techniques such as laser altimetry. The upcoming BepiColombo mission, set to arrive at Mercury in late 2026 [2], will enhance our understanding of Mercury's interior. A key instrument aboard BepiColombo, the Laser Altimeter (BELA), will enable the mapping of time-dependent surface elevations, providing crucial data for calculating h2 [3,4].
This study simulates BepiColombo's measurements using an orbit, observation, and tides model [5,6,7] to examine how the uncertainty in h2 decreases over the observation period. The BepiColombo Mercury Planetary Orbiter (MPO) offers significantly better coverage of Mercury's tidal potential compared to the MESSENGER mission [8,9], suggesting that the BepiColombo mission will yield more precise measurements of the h2 parameter. However, the simulation kernels used in this study are based on outdated mission parameters due to the revised arrival schedule of BepiColombo. To ensure the accuracy and relevance of our findings, we plan to update the simulations with the most recent kernel data.
To further explore the potential of the BepiColombo mission in constraining Mercury's internal structure, we will employ a simulation-based approach using planning kernels provided by the European Space Agency (ESA). Our model will simulate observations of Mercury's surface topography, incorporating tidal signals to model the planet's response to external gravitational forces. Additionally, observational errors and potentially different rotation states of Mercury will be introduced to reflect the expected noise levels from the BELA laser altimeter. These simulated observations will be used to calculate the Love number h2 and its associated uncertainty for different observation durations. This will allow us to assess how the mission's length influences the precision of the h2 measurement.
Acknowledgments: This work is supported by DLR under grant 50QW2301. PDS data used in this work: Neumann G. (2016), urn:nasa:pds:mess_mla_calibrated::1.0, 10.17189
References: [1] Steinbrügge G. et al. (2018), JGR, 123, 2760-2772. [2] Benkhoff J. et al. (2010), PSS, 58, 2-20. [3] Thomas N. et al. (2007), PSS, 55, 1398-1413. [4] Thomas, N. et al. (2021), Space Sci. Rev., 217. [5] Koch C. et al. (2010), PSS, 58, 2022-2030. [6] Thor R. N. et al. (2021), J. Geod., 95. [7] Thor R. N. et al. (2020), A&A, 633, A85. [8] Santo A.G. et al. (2001), PSS 49, 1481-1500. [9] Cavanaugh J.F. et al. (2007) Space Sci. Rev., 131, 451-479
How to cite: Stenzel, O., Hilchenbach, M., Arghavanian, A., and Xiao, H.: Mercury's Love number h2: Expected error range throughout the BepiColombo mission, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11985, https://doi.org/10.5194/egusphere-egu25-11985, 2025.
Mercury, the innermost planet in our solar system, offers a unique natural laboratory for planetary science, particularly with its unexpectedly high concentration of volatile elements and the presence of volatile-related geological features. This study investigates the morphology and ages of craters at Mercury's north and south poles to understand the distribution of water ice within these regions. Utilizing high-resolution images from the MESSENGER mission and various digital elevation models, we measured crater depth and diameter and conducted crater size-frequency distribution analyses. Our findings reveal significant differences in the depth-to-diameter (d/D) ratios and absolute ages of craters between the poles. North Pole craters are generally younger, deeper, and smaller in diameter, while South Pole craters are older, shallower, and larger in diameter. The Northern Smooth Plains at the North Pole, formed by extensive volcanic activity, exhibit fewer impact craters, suggesting a younger surface. In contrast, the South Pole's heavily cratered terrain displays significant weathering and thicker regolith layers. The study also highlights the uneven distribution of water ice, likely influenced by crater morphology and the presence of insulating layers. This research provides insights into the geological history of Mercury and the processes shaping its polar regions, enhancing our understanding of the planet's volatile content and its implications for habitability in the inner solar system.
How to cite: Wang, X.: Asymmetry distribution of craters on north and south poles of Mercury, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7516, https://doi.org/10.5194/egusphere-egu25-7516, 2025.
The recognition of pyroclastic deposits on Mercury surface was driven by the presence of central pit (vent) surrounded by a spectrally bright and red deposit (facula) (Head et al, Science, 2008). In particular, the Visible to Near-InfraRed (VNIR) spectral properties permitted them to differentiate it from the surrounding terrains and defining the putative border of the deposits (e.g. Head et al, Science, 2008), since there is no morphological evidence that permits to limit their areal extension. Consequently, to improve our understanding of how the spectral properties of the effusive material extruded during the pyroclastic activity can change, considering variations in composition or textural properties of the material could improve our understanding of the pyroclastic deposits itself.
In this work we planned spectral analysis in reflectance and emittance of a systematic variation of samples with a silicate component as an example of pyroclastic extruded lava mixed with graphite or sulfide suitable for product formed with interaction of volatiles components during the pyroclastic activity at very reduced condition on Mercury (e.g., Cartier&Wood, Elements, 2019).
The pyroclastic endmember was prepared considering different variations among a crystalline mafic material and an amorphous component. We take into account variations in abundance as well as variation of particle size for the endmembers and for the mixtures.
All the samples have been measured in bidirectional reflectance in the VIS+VNIR+MIR spectral range, with particular attention to the 0.4-2.0 mm and 7-14 mm, spectral ranges where SIMBIO-SYS and MERTIS, onboard to Bepicolombo (Benkhoff et al., Spa.Sci.Rev., 2021), will operate. Moreover, for selected samples, emissivity (at Tsample = 150°, 250°, 350°, 450° C) in the MIR spectral range will be carried on. All the spectroscopic measurements are done at the PSL of DLR in Berlin.
This research was supported by the International Space Science Institute (ISSI), through International Team project #552 (Wide-ranging characterization of explosive volcanism on Mercury: origin, properties, and modifications of pyroclastic deposits).
How to cite: Maturilli, A., Carli, C., Galiano, A., Penttilä, A., and Landi, A. I.: Laboratory Spectral Measurements to Simulate Pyroclastic Material on Mercury, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15727, https://doi.org/10.5194/egusphere-egu25-15727, 2025.
Volcanic and magmatic processes have played a significant role in shaping Mercury’s surface and contributing to its mineral diversity. Areas such as smooth plains, which cover 27% of the planet, are thought to have formed from effusive volcanic events. Explosive volcanism is also suggested by the presence of depressions surrounded by high-reflectance halos, calderas, and vents linked to impact structures or faults. The BepiColombo mission, a collaboration between ESA and JAXA, was launched in 2018 to explore Mercury. It consists of two orbiters, MIO (JAXA) and MPO (ESA), with a focus on studying the planet's interior, surface, exosphere, and magnetosphere. The MPO carries instruments such as SIMBIO-SYS and MERTIS, which are designed to acquire spectral data.
Interpreting planetary surface data often requires understanding complex factors like mineral composition, elemental abundance, temperature, and particle size. This study investigates the mid-infrared (MIR) spectral response of silicate glasses with a range of grain sizes and chemical compositions, aiming to build a database to support future spectral analyses of Mercury’s surface, where volcaniclastic materials are expected to be abundant.
Three compositions resembling the Northern Volcanic Plains (NVP) on Mercury were prepared: NVP, NVP_Na, and NVP_Mg, each with varying amounts of Na and Mg. These compositions were created by melting pure oxides at 1400°C, then crushing the resulting glass into powder and re-melting it to ensure homogeneity. The glass was sieved into various grain size fractions, with some samples mixed to create new samples with Gaussian-like distributions to explore how fine-grained fractions affect spectral responses, particularly in relation to volcanic ash.
Spectroscopic analysis was performed using a Bruker Invenio-X FT-IR spectrometer. The VNIR spectra (400-2000 nm) showed typical features of silicate glasses, with an absorption peak at around 1100 nm and a weaker one at 1900 nm, related to Fe-O bonds. The slope of the spectra did not vary much with increasing grain size in NVP samples, but there was a noticeable increase in the NIR slope (1200-1800 nm) for NVP_Na and NVP_Mg.
In the MIR region (7-14 µm), the spectra revealed a correlation between the shape of the spectra and the chemical and granulometric characteristics of the samples. A local maximum at 10000 nm was observed for all spectra, associated with tetrahedral silicate units, and the NVP_Mg spectra showed distinct features due to the network-modifying role of Mg. The spectra also exhibited the Christiansen Feature at around 8 µm, a diagnostic feature for igneous products, and a transparency feature around 12 µm, which appeared in spectra of finer-grained samples.
These spectra will be made available on the SSDC-ASI portal and will be crucial for interpreting data from the BepiColombo mission, particularly from SIMBIO-SYS and MERTIS. This research will help in identifying potential unknown igneous materials on Mercury’s surface.
How to cite: Pisello, A., Fastelli, M., Scricciolo, E., Baroni, M., Musu, A., Comodi, P., and Perugini, D.: Spectral characterization of lab-made silicate glasses as analogues for Mercury: influence of grain size and chemical composition., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17874, https://doi.org/10.5194/egusphere-egu25-17874, 2025.
Mercury’s intrinsic magnetic field is remarkably weak, resulting in a small magnetosphere. Due to the proximity of Mercury to the Sun and lack of a protective ionosphere, Mercury’s magnetosphere endures the most intense solar wind flux and severe space weather in the solar system. The interaction between the solar wind and Mercury’s magnetosphere is dominated by dynamic kinetic processes, such as exceptionally high magnetic reconnection rates. Mercury’s magnetosphere is also closely coupled to its surface, making it highly susceptible to extreme solar events, including Coronal Mass Ejections (CMEs). To explore this complex and dynamic environment, we utilize Amitis (https://www.amitiscode.com), an advanced 3D hybrid-kinetic plasma model, to simulate the interaction between the solar wind and Mercury’s magnetosphere under conditions of extreme solar activity. Our study reveals how Mercury’s magnetosphere dynamically responds to intense solar events and provides detailed insights into the energy and flux of solar wind plasma impacting the planet’s surface. By examining these interactions, we aim to better understand the mechanisms governing Mercury’s unique space weather environment and their implications for surface processes.
How to cite: Fatemi, S., Szabo, P. S., Poppe, A. R., Raines, J. M., and Millilo, A.: Extreme Space Weather at Mercury: Investigating Magnetospheric and Surface Interactions Using Hybrid Simulations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8218, https://doi.org/10.5194/egusphere-egu25-8218, 2025.
Plasma high-speed jets are common in Earth’s magnetosheath, and they significantly perturb the magnetosheath and affect the magnetosphere. The space environment of Mercury, characterized by the bow shock, magnetosheath, and magnetosphere, shares many similarities with that of Earth, so high-speed jets may also be formed in Mercury’s magnetosheath. Here we examine the formation of magnetosheath jets using a three-dimensional global hybrid simulation. The simulation results demonstrate that magnetosheath jets may be formed by the passage of upstream compressive structures through the bow shock. The number and size of the jets are significantly smaller than those at Earth because of Mercury’s smaller magnetosphere size. Under the impact of magnetosheath jets, Mercury’s magnetopause undergoes significant deformation up to 0.19 RM(RMis Mercury’s radius). These simulation results are expected to be tested by the BepiColombo mission.
How to cite: Guo, J., Lu, S., Lu, Q., Slavin, J., Sun, W., and Zhong, J.: Three-dimensional Global Hybrid Simulation of Magnetosheath Jets at Mercury , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9676, https://doi.org/10.5194/egusphere-egu25-9676, 2025.
The MESSENGER spacecraft, which orbited Mercury from 2011 to early 2015, provided crucial insights into the structure and dynamics of Mercury's magnetosphere, including the identification of the Low Latitude Boundary Layer (LLBL). LLBL forms a mixed region of the magnetospheric and magnetosheath plasma, playing a crucial role in transferring mass and energy from the solar wind into the planetary magnetosphere. A statistical study by Liljablad et al. (2015) examined the properties of the LLBL during MESSENGER's first orbital year. More recently, the BepiColombo spacecraft crossed the LLBL in Mercury's duskside magnetosphere during its third Mercury flyby in 2023. Using the Mercury Plasma Particle Experiment (MPPE) instruments, specifically the ion analyzer (MIA) and mass spectrum analyzer (MSA), clear ion energy dispersion ranging from a few eV/e to 40 keV/e was observed (Harada et al., 2024; Hadid et al., 2024).
This study aims to build on these findings by conducting a comprehensive analysis of the LLBL using all MESSENGER data collected throughout its orbital period. The Magnetic field (MAG) and ion data (FIPS) revealed 351 LLBL cases. Considering the energy variation of the maximum differential flux of protons from the magnetopause toward the magnetosphere, 38 cases exhibited decreasing H⁺ energy dispersion, while 88 showed increasing H⁺ energy dispersion. Notably, the average H⁺ temperature is higher in LLBLs with increasing dispersion compared to those with decreasing or no dispersion. A clear dawn-dusk asymmetry was observed: 85% of H⁺ decreasing cases occurred on the duskside, while 89% of H⁺ increasing cases were on the dawnside. Interestingly, in many LLBL cases, the energy dispersion of He²⁺ ions differed from that of H⁺, particularly in the majority of increasing cases, though He²⁺ data is limited. Following orbit insertion, the 3D distribution functions measured by the ion sensors (MIA and MSA) aboard the BepiColombo magnetospheric orbiter will enable a more detailed analysis.
How to cite: Wang, X., Hadid, L., Aizawa, S., Sahraoui, F., Raines, J., and Lavraud, B.: Investigation of the Low-Latitude Boundary Layer (LLBL) in Mercury's Magnetosphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11550, https://doi.org/10.5194/egusphere-egu25-11550, 2025.
Ultralow frequency (ULF) waves are found in certain parts of the upstream region of planetary bow shocks. These waves are believed to be driven by the interaction of solar wind ions reflected from the bow shock with the original solar wind beam. The region where ULF waves can possibly be observed is then determined by the regions accessible to the reflected ions within the foreshock (defined as the region magnetically connected to the bow shock). The boundary of the region where ULF waves are observed at Earth is known to also depend on the growth rate of the waves and on the direction of the interplanetary magnetic field (IMF). To identify the ULF foreshock boundary at Mercury, we use MESSENGER observations to investigate the presence or absence of clear ULF wave activity upstream of the bow shock. The boundary of regions where ULF waves are present, as parametrized by the angle θBn between the IMF and the bow shock normal, is identified and the dependence on the IMF is studied. The connection to higher-frequency whistler waves emissions is also investigated. The results are compared to results from other planets, and their connection to other upstream phenomena is discussed. Finally, open questions that can be addressed by the upcoming BepiColombo mission are discussed.
How to cite: Karlsson, T., Blanco-Cano, X., Hietala, H., Bergman, S., Plaschke, F., and Wong Chan, T. K.: Investigation of the Ultralow Frequency (ULF) foreshock boundary at Mercury, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1275, https://doi.org/10.5194/egusphere-egu25-1275, 2025.
The solar wind significantly shapes and influences planetary magnetospheres, driving their structure and dynamics. Mercury, with its weak intrinsic magnetic field and close proximity to the Sun, is particularly sensitive to solar wind variations and adapts quickly to solar wind changes. Understanding solar wind characteristics, such as flow speed, is essential for fine-tuning magnetospheric models and eventually for interpreting Mercury’s magnetospheric response to solar wind changes. The solar wind speed affects both the aberration angle, which tilts the magnetosphere relative to the Mercury-Sun line, and the subsolar standoff distances from the internal dipole center of both the bow shock as well as the magnetopause.
This study reconstructs solar wind speeds from various bow shock and magnetopause crossings observed in-situ by MESSENGER’s magnetometer. We fit empirical bow shock and magnetopause models to the aberration angle and treat the subsolar standoff distances as additional parameters. For single crossings, a strong correlation between the parameters emerges. Thus, they cannot be independently determined, resulting in an infinite set of possible solutions for solar wind speed. To alleviate this problem, we combine multiple crossings to find a common aberration angle. Here, we present and discuss the first statistical results from the analysis and compare them to average boundary shapes and positions.
How to cite: Heyner, D., Klingenstein, L., Pump, K., Aizawa, S., Schmid, D., and Plaschke, F.: Solar wind velocity reconstruction at Mercury using MESSENGER bow shock and magnetopause crossings. , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15352, https://doi.org/10.5194/egusphere-egu25-15352, 2025.
The ESA-JAXA joint mission BepiColombo is still on the track to Mercury. The two spacecraft for BepiColombo, Mio (Mercury Magnetospheric Orbiter: MMO) and Mercury Planetary Orbiter (MPO), are combined with MMO Sun Shield (MOSIF) and Mercury Transfer Module (MTM) during the cruise phase. BepiColombo will arrive at Mercury in November 2026, and it has 8-years cruise with the heliocentric distance range of 0.3-1.2 AU. The long cruise phase also includes 9 planetary flybys: once at the Earth, twice at Venus, and 6 times at Mercury. On 8 January 2025 we completed the last (6th) Mercury flyby successfully. Even before arrival, we already obtained fruitful science data from Mercury during the Mercury flybys. We performed science observations with almost all the instruments onboard Mio and successfully obtained comprehensive data of Mercury’s magnetosphere such as magnetic fields, plasma particles, and waves. Here we present the overview and initial results of the science observations during the Mercury flybys.
How to cite: Murakami, G. and Jones, G.: Overview and initial results of BepiColombo Mercury flybys, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18018, https://doi.org/10.5194/egusphere-egu25-18018, 2025.
BepiColombo, launched in October 2018, is currently en route to Mercury. Although its planned orbit insertion is set for November 2026, BepiColombo continuously gathers new measurements during Mercury flybys. Throughout the cruise phase, the two spacecraft remain docked, with Mio protected behind the MOSIF sun shield, resulting in a limited observation for many instruments. Despite of such constraints, thanks to the smaller Larmor radii of electrons, wider range of electrons (from a few eV to a few hundreds of keV) got detected during the 3rd Mercury flyby by Mercury Electron Analyzer (MEA) onboard Mio and Solar Intensity X-ray and Particle Spectrometer (SIXS) onboard the Mercury Planetary Orbiter (MPO). Both instruments show quite similar variations indicating that they are observing same populations of electrons with wider energy range, and small differences in time indicate there are time-of-flight of electrons related to the drift motion of particles in the magnetosphere. Together with Plasma Wave Investigations (PWI) onboard Mio, the possible electron accelerations and transport will be discussed.
How to cite: Aizawa, S., Kilpua, E., Vainio, R., Rojo, M., Andre, N., Grande, M., Sanchez-Cano, B., Pinto, M., Saito, Y., and Sahraoui, F. and the MEA-SIXS-PWI of BepiColombo: Accelerated electrons in Mercury’s magnetosphere observed during the 3rd Mercury flyby of BepiColombo, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11787, https://doi.org/10.5194/egusphere-egu25-11787, 2025.
Mercury hosts a dynamic and highly variable magnetosphere shaped by its weak intrinsic magnetic field and the intense pressure of the solar wind. Previous observations from spacecraft sent to the planet have provided key insights into Mercury’s magnetospheric structure and energetic particle populations, revealing transient and highly variable energetic electron enhancements within the planet’s magnetosphere. We present BepiColombo/SIXS observations of energetic electron populations in Mercury’s magnetosphere during the spacecraft’s first three flybys of the planet. Although no such populations were observed during the first flyby, strong energetic electron signatures were observed during the second and third flybys. These observations are discussed in the context of observations by MESSENGER (Lawrence et al., 2015) in the invariant latitude-MLT plane, showing good agreement between the two data sets. Additionally, we present the highest time resolution energy spectra (> 70 keV) produced at Mercury during the second and third flybys.
How to cite: Edwards, L., Grande, M., Lawrence, D., Kilpua, E., Vainio, R., Lehtolainen, A., and Esko, E.: Energetic Electron Observations During BepiColombo’s First Three Mercury Flybys, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15163, https://doi.org/10.5194/egusphere-egu25-15163, 2025.
The closest planet to the Sun, Mercury, is subject to particularly intense fluxes of solar energetic particles (SEPs). Its relatively weak magnetic field and small magnetosphere offer some protection againts these particles, deflecting them away before they can reach the surface. The effectiveness of this shielding could be probed in detailed during BepiColombo’s fourth (4 September 2024) and sixth (8 January 2025) flybys when and SEP events happened to be ongoing and the planet was immersed in high fluxes of energetic particles. During the fourth flyby, BepiColombo reached only 165 kilometres from the Mercury’s surface. In this presentation we analysis high energy electron and proton observations provided by the Solar Intensity X-ray and Particle Spectrometer SIXS. The data reveal a deep drop out in energetic particles fluxes due planetry shadowing. In addition, these unique measurements reveal that variations in particle fluxes depend clearly on particle type, direction and energy.
How to cite: Kilpua, E., Vainio, R., Grande, M., Edwards, L., Esko, E., Laurenza, M., Lehtolainen, A., Oleynik, P., Palmroos, C., Liu, S. J., Massetti, S., and Heyner, D.: Planetary shadowing and Solar Energetic Particles during the fourth and sixth BepiColomo Mercury Flybys, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17383, https://doi.org/10.5194/egusphere-egu25-17383, 2025.
On 8 January 2025, the ESA/JAXA BepiColombo mission flew by Mercury for the sixth time at an altitude of 295 km. The spacecraft took on a unique route through Mercury’s magnetic and particle environment, crossing the equator opposite the Sun on Mercury’s night side before flying over the planet’s north pole. During eclipse, in the cold shadow of the planet, as well as above the northern pole the spacecraft passed through regions where charged particles precipitate from the planet’s magnetic tail and from the solar wind towards its surface. We will detail the original electron observations obtained by the Mercury Electron Analyzer during Mercury’s sixth flyby, and compare and contrast them with electron observations obtained during previous BepiColombo flybys. All together, these new observations will provide new insights into the diversity of structures observed in these regions and the underlying mechanisms responsible for their formation and dynamics.
How to cite: André, N., Sauvaud, J.-A., Saito, Y., Rojo, M., Aizawa, S., Fedorov, A., Penou, E., Barthe, A., Yokota, S., Nemecek, Z., Safrankova, J., Marcucci, M. F., Liu, Z.-Y., Persson, M., Hadid, L., Delcourt, D., Harada, Y., Fraenz, M., Krupp, N., and Murakami, G.: Observations from the Mercury Electron Analyzer onboard BepiColombo during its sixth Mercury flyby, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6945, https://doi.org/10.5194/egusphere-egu25-6945, 2025.
How to cite: Hadid, L., Harada, Y., and Saito, Y. and the MSA/MPPE and MIA/MPPE teams: Ion observations and composition from MSA and MIA during BepiColombo's final gravity assist maneuver at Mercury, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11718, https://doi.org/10.5194/egusphere-egu25-11718, 2025.
BepiColombo made its sixth and final swing-by of Mercury on January 8, 2025, crossing from the nightside over the north pole to the dayside near the noon-midnight plane. The Miniature Ion Precipitation Analyzer (MIPA), an ion analyzer in the Search for Exospheric Refilling and Emitted Natural Abundance (SERENA) instrument suite on the Mercury Planetary Orbiter (MPO), made observations throughout the swing-by, observing positive ions in the range from 30 eV – 14 keV with a hemispherical field of view. This swing-by gives a unique snapshot of the state of Mercury’s magnetosphere, as MIPA observed several magnetospheric regions within a short period, some of them for the first time. We observe the plasma sheet and plasma sheet horns, as well as plasma upwelling from the northern polar cusp to the dayside magnetopause. Passing through the dayside magnetosheath shows high anisotropic fluxes, as the magnetosheath bulk flow was in the MIPA FOV, unlike previous swing-bys. Following the bow shock crossing, we see a distinct foreshock population, followed by a half an hour gap in signal before a second foreshock detection at +5 RM. We then compare the MIPA observations to modeled magnetic fields and environment. The combination of all the swing-bys highlights the versatility of planetary swing-by trajectories, which allow for observations of regions that may not be accessible after orbit insertion.
How to cite: Williamson, H., Barabash, S., Wieser, M., Nilsson, H., Futaana, Y., Milillo, A., Aronica, A., Kasakov, A., Orsini, S., Varsani, A., and Laky, G.: A snapshot of Mercury’s magnetosphere seen by MIPA in BepiColombo’s MSB6, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21593, https://doi.org/10.5194/egusphere-egu25-21593, 2025.
The BepiColombo mission to Mercury consists of two spacecraft MPO and MIO and was launched in 2018. During the cruise phase towards the target the spacecraft performed its last close flyby near Mercury on 8 Jan 2025 (MSB6). This was the last flyby before going into orbit around the innermost planet at the end of 2026. We report on particle results from the Mass Spectrum Analyzer MSA on MIO and the Planetary Ion Camera PICAM onboard MPO together with magnetic field data MAG and hybrid simulation during this flyby. PICAM measured solar wind upstream and recorded the magnetospheric and magnetosheath plasma at various energies while MSA recorded the ion composition during the flyby including H+, He++, He+, Na+ and other heavy ions. Most of Na+ was seen near closest approach in the shadow of the planet which agrees well with AIKEF hybrid model results.
How to cite: Krupp, N., Fränz, M., Teubenbacher, D., Exner, W., Heyner, D., Hadid, L. Z., Varsani, A., Harada, Y., Aizawa, S., Andre, N., Milillo, A., Saito, Y., Delcourt, D., Prencipe, F., Krüger, H., Laky, G., Katra, B., Verdeil, C., Yokota, S., and Fiethe, B.: Observations of Mercury’s plasma environment along BepiColombo’s sixth swingby on 8 Jan 2025, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8338, https://doi.org/10.5194/egusphere-egu25-8338, 2025.
The BepiColombo mission, a cornerstone of the European Space Agency's (ESA) Cosmic Vision program in collaboration with the Japan Aerospace Exploration Agency (JAXA), represents an ambitious endeavor to deepen our understanding of Mercury. It uniquely combines the Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (Mio) to investigate Mercury’s interaction with the solar wind, its geological history, and its magnetic environment. The mission seeks to address fundamental questions about the evolution of terrestrial planets, including Mercury’s formation, internal structure, and enigmatic magnetic field.
BepiColombo’s operational phase at Mercury will prioritize the implementation of a meticulously designed strategy to maximize the scientific potential of its complementary payload. The dual-spacecraft configuration enables synchronized observations of the planet’s surface, exosphere, and magnetosphere, offering unprecedented insights into the planet’s complex environment. Key mission strategies include utilizing the spacecraft’s elliptical orbits to optimize coverage during perihelion passes, supporting high-resolution investigations of regions of particular scientific interest, and facilitating comprehensive global mapping. These efforts aim to provide a holistic understanding of Mercury’s geological and magnetic properties, as well as its interactions with the solar wind, making significant contributions to planetary science.
This presentation will highlight the broader implications of BepiColombo’s mission design, the operational strategies planned for the science phase, and the valuable insights gained from its Venus and Mercury flybys. Particular focus will be placed on how these lessons refine the mission’s science objectives and influence future exploration initiatives targeting Mercury and other inner Solar System bodies.
How to cite: Kotsiaros, S., Jones, G., Benkhoff, J., Martinez Sanmartin, S., Besse, S., Frew, D., Cappuccio, P., Belgacem, I., and Geiger, B.: BepiColombo's Journey to Mercury: Lessons from Cruise Operations and Plans for Orbital Science, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18729, https://doi.org/10.5194/egusphere-egu25-18729, 2025.
Cooling and crystallization of Mercury's magma ocean likely formed a layered mantle composed of various proportions of minerals such as olivine, orthopyroxene, clinopyroxene, sulfides, and plagioclase, each with distinct thermal properties (e.g. thermal diffusivity, thermal conductivity, heat capacity, and melting temperature). Planetary thermal evolution models often consider an homogeneous mantle and treat these properties as constant or only varying with pressure and/or temperature. Their dependence on composition and modal proportions is usually neglected, but can have a large impact on the modeled evolution.
Recent experimental studies gave access to the thermal conductivity and diffusivity of olivine, orthopyroxene and clinopyroxene. We calculated the thermal conductivity and diffusivity profiles of Mercury’s mantle assuming it is made of the Mg-rich endmembers forsterite, enstatite or diopside (i.e. the most likely phases occurring in the reduced interior of Mercury). We used a 1D parameterized model to simulate the thermal evolution of the planet with conductivity values varying from 1 to 4 Wm-1K-1, covering the above range of different mineralogies. We investigated several scenarios with (1) homogeneous conductivity over the whole mantle; (2) two layers characterized by different conductivity values. We then analyzed the results in terms of crust production and duration of mantle melting.
At pressures and temperatures relevant for Mercury's mantle, enstatite and diopside have higher conductivities and diffusivities than forsterite. This has a direct impact on the thermal evolution of the planet and on the melting of a fertile layer. Indeed, the more conductive the mantle is, the shorter its melting duration. Therefore, a mantle characterized by the conductivity of enstatite or diopside would promote a shorter melting time than one with conductivity of forsterite. In a two-layer mantle, melting duration is lower when conductivity of the top layer is higher compared to the bottom layer. The melting duration would thus be shorter for a mantle with a refractory olivine-like mantle conductivity at the base and an enstatite- and diopside-bearing fertile mantle-like conductivity in the upper part of the stratigraphic column. Besides the thermal conductivity, other parameters such as solidus temperature and heat production rate will be taken into account to obtain a consistent picture of the influence of mineralogical-dependent parameters on Mercury's evolution.
Accounting for variations in thermal conductivity and diffusivity due to heterogeneity in the mantle is therefore crucial in modeling planetary interiors. These factors significantly affect key parameters like crust thickness and the duration of volcanism.
How to cite: Lécaille, M., Tosi, N., Namur, O., Rivoldini, A., and Charlier, B.: The role of mantle layering and mineralogical-dependent thermal properties on the evolution of Mercury's interior, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17082, https://doi.org/10.5194/egusphere-egu25-17082, 2025.
On Mercury, faculae are high-albedo, spectrally red, deposits originating from explosive volcanic eruptions (Kerber et al., 2009) whose source are likely rimless depressions. These depressions are usually located in the center of the facula and interpreted to be volcanic vents. In this work we analyzed the Agwo facula, sited in the western margin of Caloris basin (22.39°N, 146.16°E). We performed a detailed geomorphological map of the area using MDIS derived mosaics with a spatial resolution ranging from 20 m/pixel to 28 m/pixel and with different illumination conditions. Additionally, a BDR (Basemap reduced Data Record) MDIS mosaic, with a resolution of 166 m/pixel, was used as a basemap. MDIS WAC color maps, based on the reflectance at 750 nm and the VIS slope between 480 and 830 nm, respectively, were also used as part of the analysis. These latter maps helped determine the areal extent of the pyroclastic deposits. Finally, a DTM of the region, derived from MDIS images using the technique of stereophotoclinometry (SPC) and with a spatial resolution of 20 m/pixel, helped us to better characterized the facula’s topography. The geomorphological map highlights that Agwo facula experienced several explosive episodes. In particular, through the cross-cutting relationship observed among the pits, at least eight eruptive events have been distinguished. The terrain within the pits shows different surface texture and albedo, that allowed the distinction of several geological units: from the oldest and smoother surfaces to the younger and rougher textured surfaces. Therefore, the morphological and spectral characteristics of pits suggest that Agwo facula is the result of multiple eruptions, which likely occurred at different times, contributing to the better understanding of the formation of this feature.
References:
Kerber, L., Head, J.W., Solomon, S.C., Murchie, S.L., Blewett, D.T., Wilson, L., 2009. Earth Planet. Sci. Lett. 285, 263–271. https://doi.org/10.1016/j.epsl.2009.04.037.
Acknowledgment
This research was supported by the International Space Science Institute (ISSI) in Bern, through ISSI International Team project #552 (Wide-ranging characterization of explosive volcanism on Mercury: origin, properties, and modifications of pyroclastic deposits). Contributions by D. Domingue and J. Weirich were also supported by NASA’s Solar System Working’s grant 80NSSC21K0165.
How to cite: Giacomini, L., Galiano, A., Galluzzi, V., Munaretto, G., Rothery, D. A., Domingue, D., Weirich, J., Jozwiak, L. M., D' Amore, M., and Carli, C.: High resolution geomorphological analysis of Agwo facula (Mercury), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8261, https://doi.org/10.5194/egusphere-egu25-8261, 2025.
Analyses of topographic roughness at various baselines are useful for studying surface evolution on airless bodies. Using data from the Mercury Laser Altimeter (MLA) onboard Space ENvironment, Geochemistry, and Ranging (MESSENGER) mission, roughness distribution on Mercury has been investigated at baselines down to sub-km scale [e.g., 1]. However, due to the eccentric orbit of MESSENGER and the limited ranging distance of MLA, laser ranging observations are limited to the north polar region. In addition, previous image-based digital elevation cannot be used to quantify roughness at km scale due to limited spatial resolution [2]. Therefore, roughness at km-scale baselines has not been mapped below 45°N latitude on Mercury.
To complement the lack of roughness data in the equatorial region, this study analyzes the latest global DEM (version 20240927) produced as described in Preusker et al. [3]. The effective resolution of this DEM has been estimated to be 5 km [e.g., 3]. Focusing on topographic curvatures at baselines of 5–10 km and their interquartile ranges at each latitude and longitude, we mapped roughness distribution at latitudes of 66°N–66°S to examine correlations between roughness and geologic features.
Our new roughness map shows several anomalous features correlated with Mercury’s geology. The most obvious feature is a clear distinction between smooth plains and rough intercrater plains. Our roughness map shows roughness differences similar to those reported by previous works for the northern hemisphere [1]. In addition, our analysis shows a certain variation in roughness among the smooth plains. For example, the Caloris smooth plains show higher roughness than other smooth plains due to superposing grabens in the Caloris basin. Another characteristic is high-roughness anomalies around young basins. The areas of continuous ejecta have higher roughness than the surroundings due to their freshness. The roughness values do not simply decrease with increasing distance from the basin centers but show local minima adjacent to their rims, originating from coverage of impact melt and/or deficit of secondary craters.
Furthermore, a comparison with the latest catalog of tectonic landforms [4] shows an absence of contractional landforms at high roughness anomalies. The lobate scarps and ridges tend to be distributed outside rough regions like the young basin ejecta. This correlation may suggest superposition of younger basin ejecta on older tectonic features, difficulty of tectonic landform detection on rough terrains, and/or less efficient formation of contractional landforms due to possibly high crustal porosity. These possibilities imply that the extent of Mercury’s radial contraction may have been underestimated due to the obscuration of old contractional landforms. In the presentation, we will discuss possible extent of corrections to global contraction estimates to account for the roughness effect.
References:
[1] Kreslavsky M. A. et al. (2014) GRL, 41, 8245–8251.
[2] Florinsky I. V. (2018) Planetary and Space Science, 151, 56–70.
[3] Preusker F. et al. (2017) Planetary and Space Science, 142, 26–37.
[4] Klimczak C. et al. (2023) 54th LPSC, Abstract #1122.
Acknowledgment: This work was supported by JSPS KAKENHI Grant Number JP22K21344 and JSPS Overseas Research Fellowship.
How to cite: Nishiyama, G., Preusker, F., Broquet, A., Stark, A., and Hussmann, H.: Roughness map for the equatorial region of Mercury and its implication to surface evolution, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4305, https://doi.org/10.5194/egusphere-egu25-4305, 2025.
The surface of Mercury has been extensively altered by space weathering and impact processes, making it challenging to identify the boundaries of geological units. We analyzed the Glinka crater in the Beethoven quadrangle (H-07), a region characterized by notable spectral and geological variability, including impact craters, a possible pyroclastic vent, hollows, and compressive structures. To delineate morphological boundaries, we integrated high-resolution imaging, spectral data, and topographic products.
For morphological mapping, we produced monochromatic mosaics at 121 m/px, 56 m/px, and 14 m/px resolutions using MESSENGER MDIS/NAC data. Spectral investigations utilized an eight-filters MDIS/WAC-derived multispectral image (268 m/px). Additional datasets including Digital Elevation Model (DEM, 222 m/px), roughness and shading maps, and gravity data. Data processing involved the Integrated Software for Imagers and Spectrometers (ISIS3), applying the Kaasalainen-Shkuratov photometric correction model considering the parameters derived by Domingue et al. (2016). Spectral unit identification relied on four parameters: Reflectance at 750 nm (R750), Global Spectral Slope between 430 and 1000 nm (S430-1000), IR Slope ranging between 750 and 1000 nm (S750-1000), and UV Slope between 430 and 560 nm (S430-560). Threshold values for these parameters were determined through supervised k-means clustering (k=4), resulting in maps showing Regions of Interest (ROIs) for each spectral parameter. To combine all threshold values of the four parameters, an automated process generated a composite map with over 400 ROIs. Smaller ROIs (<15% of the average pixel count per ROI) were excluded, and those with similar values (∆10%) were merged iteratively, yielding seven final spectral units.
We are producing a geological map of the area by integrating data from the spectral map and high-resolution imagery. The spectral map highlights spectral variations and, in some cases, compositional differences. This integration enables a more precise definition of the boundaries between geological units. involves detailed geological and chronostratigraphic interpretations involves the exploration of various RGB combinations to extract additional information. This analysis includes spectral parameter values for each unit, taking into account surface morphology and texture, which may influence spectral responses without necessarily indicating compositional differences.
Domingue D. L. et al. (2016) Icarus 268, 172-203. https://doi.org/10.1016/j.icarus.2015.11.040
Acknowledgements: M.I. and G.M. acknowledges support from the Italian Space Agency (2022-16-HH.1-2024).
How to cite: Ianiri, M., Mitri, G., and Zambon, F.: Glinka crater on Mercury: a spectral and morphological analysis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17959, https://doi.org/10.5194/egusphere-egu25-17959, 2025.
Mercury has a surface-bound exosphere that mediates transport of ion and netural species on the surface and within the Hermean environment. When precipitating solar wind particles impact the planet’s regolith, ions may be neutralised and backscattered, form chemical reactions with surface species, or induce sputtering processes. The SERENA (Search for Exospheric Refilling and Emitted Neutral Abundances) instrument onboard BepiColombo aims to study these surface-exosphere-magnetosphere interactions, using a suite of particle detectors and mass spectrometers.
At INAF/IAPS, the Ion and Energetic Neutral Atom (I-ENA) laboratory facilitates controlled experiments on the interaction of ion/neutral beams with diverse surface analogues and detectors for planetary space weather investigation. ELENA (Emitted Low Energy and Neutral Atoms) one of the SERENA instruments, is devoted to detect backscattered ENA and possibly magnetospheric and solar wind ions with an energy range of 10 eV-5 keV, and its Flight Spare (FS) is tested and calibrated in the laboratory. The ELENA FS is intended to be used for future investigations of backscattering process with Mercury analogues. Laboratory experiments involving irradiation of Mercury analogues aim to provide ground truth to the data provided by this instrument.
We present a test for simulating Solar Wind interactions with Mercury surface analogues. Mercury analogues are placed in a bespoke vacuum system which achieves working pressures of 10-7 mbar. A particle beam of energies between 0.5-5 keV (Helium-Argon), that can be modulated in intensity, area and direction, is used to irradiate samples. The charged particle beam (ions) can also be made into a beam of ENA with a neutralisation cell for charge exchange effect.
We plan to investigate a variety of diverse samples, including slabs of meteorite and pellets similar in composition and grain size to Mercury’s surface.
This work will provide a detailed description of the facility and experimental framework, while identifying open questions and fostering discussions on interdisciplinary collaborations needed to advance Mercury science. Such experiments are pivotal for improving our understanding of Mercury’s environment and directly support the goals of the BepiColombo mission.
How to cite: Brin, A., Richards, G., De Angelis, E., Rispoli, R., Moroni, M., Sordini, R., Colasanti, L., Vertolli, N., Nuccilli, F., Mura, A., Mangano, V., Orsini, S., Plainaki, C., and Massetti, S.: Laboratory simulation of ion impact and back-scattering on Mercury surface analogues for planetary space weather investigation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19661, https://doi.org/10.5194/egusphere-egu25-19661, 2025.
Mercury’s tenuous atmosphere leaves its surface exposed to continuous meteoroid bombardment, which vaporizes surface material and enriches the exosphere with various species. Ground-based observations (Bida et al., 2000; Killen et al., 2005) first detected calcium in Mercury’s exosphere; subsequent measurements by the MASCS spectrometer onboard MESSENGER confirmed that these Ca atoms can reach remarkably high temperatures (12,000–20,000 K, and occasionally up to ~70,000 K) despite Mercury’s surface being only a few hundred K (Killen et al., 2005). The Ca corona also displays distinct temporal and spatial patterns, suggesting that meteoroid impact vaporization—especially from the 2P/Encke meteor stream—is a significant source of these superthermal Ca atoms. It has been proposed that Ca-bearing molecules, such as CaO, are vaporized by impacts and subsequently dissociated into Ca atoms. In this work, we employ a time-dependent Monte Carlo model to simulate the expansion of gases released by impact vaporization, incorporating multiple species and photodissociation processes to determine the spatial distribution of fragments. These results will aid in interpreting future observations by the BepiColombo mission.
How to cite: Lai, I.-L., Hsu, C.-Y., and Ip, W.-H.: Impact Vaporization and Mercury’s Superthermal Exosphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3985, https://doi.org/10.5194/egusphere-egu25-3985, 2025.
Between 1974 and 1975, the Mariner 10 spacecraft investigated Mercury's environment during three flybys. By using its ultraviolet spectrometer, it identified helium, atomic oxygen, and hydrogen atoms in Mercury’s exosphere. Interestingly, no H2 molecules were detected during these flybys. Based on data from the occultation instrument, an upper limit for H2 surface density was established from the detection threshold of about 1.4 x 107 cm-3. Here, we present the first in-situ detection of H2 molecules in the Hermean Exosphere, identified through magnetic field and plasma measurements obtained from the MESSENGER spacecraft. The data was analyzed for ion cyclotron waves produced by H2+ pick-up ions. Our findings reveal a much lower dayside surface density of approximately 2000 cm-3, significantly below the Mariner 10 detection threshold. Furthermore, the observed atomic hydrogen in the exosphere cannot be entirely attributed to H2 dissociation. Instead, it likely arises from a combination of thermal hydrogen atoms, charge exchange processes, space weather effects, H2 dissociation and micrometeorite impacts.
How to cite: Weichbold, F., Schmid, D., Lammer, H., Volwerk, M., Scherf, M., Erkaev, N., Varsani, A., and Simon-Wedlund, C.: Insights into Mercury's Hydrogen Exosphere: Characterization and First Detection of H₂ Molecules, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6716, https://doi.org/10.5194/egusphere-egu25-6716, 2025.
Mercury's magnetosphere is more dynamic than Earth's due to its proximity to the Sun, and it is subject to a lower Mach number solar wind. Regarding the solar wind interaction with Mercury, we are interested in the configurations of Mercury’s magnetosphere and the energy transport under various solar wind conditions. First, this study examines the potential impact of low Mach number solar wind on Mercury's bow shock and the resulting effects on the magnetosphere. To analyze the variability of Mercury's bow shock in response to solar wind properties, this study combines observations by the Helios data with theoretical solutions and MHD simulations. The results show that when Mercury encounters solar wind with an extremely low Mach number, its bow shock is expected to become more flattened, further from the planet, and may even disappear completely. Our other focus is on the Kelvin-Helmholtz instability (KHI) that occurs at the magnetopause, which plays a crucial role in the energy transfer and momentum coupling process between the solar wind and Mercury's magnetospheres. We conducted MHD simulations based on boundary conditions and plasma parameters from a global hybrid simulation of the MESSENGER’s first flyby in 2008. Given the lack of comprehensive plasma observations of Mercury's magnetosphere, we examined two scenarios: one with a heavily mass-loaded magnetosphere and another with a weakly mass-loaded magnetosphere. Our findings show that the KHI in a heavily loaded magnetosphere results in a more turbulent magnetopause, with nonlinear fast-mode plane waves expanding away from the magnetopause. The momentum and energy flux quantified from our simulations reveals that the KHI with a heavily loaded magnetosphere can efficiently transport momentum and energy away from the magnetopause in the presence of the fast-mode plane waves. In such a scenario, observed in the inner magnetosphere, the momentum flux can reach about 0.5 % of the initial solar-wind dynamic pressure; the energy flux can be 10-2 erg/cm2/s, and the energy density is about 1.5 %-3.0 % of the initial solar-wind energy.
How to cite: Lai, S.-H., Wang, Y.-C., Yang, Y.-H., and Ip, W.-H.: Solar wind- Mercury's magnetosphere interaction by data exploration and MHD simulations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-124, https://doi.org/10.5194/egusphere-egu25-124, 2025.
Upstream region of the Mercury magnetosphere is of great interest in advancing our knowledge on the plasma waves and instabilities. The interplanetary magnetic field is nearly aligned with the solar wind stream at the distances of Mercury to the Sun with a Parker spiral angle of only about 20 degrees. A one-dimensional beam plasma system is likely realized ahead of or around the Mercury. The solar wind plasma streams away from the Sun and the beam ions (either shock-reflected ions or pickup ions) stream against the sola wind, forming a naturaly laboratory of head-on beam collider experiments at an energy scale of keV (through the electromagnetic interactions without binary collisions). We study the dielectric response of the beam plasma and develop various scenarios of beam instabilities relevant to the Mercury upstream waves in a systematic way including the right-hand resonant instability and the pickup ion cyclotron waves. Our wave model has the potential to serve as an analysis tool to estimate the beam velocity and the flow speed from the resonance frequency, particularly useful to in-situ magnetic field data analyses for MESSENGER and BepiColombo measurements.
How to cite: Narita, Y., Schmid, D., and Motschmann, U.: Mercury upstream region as a natural laboratory of beam plasma experiments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2481, https://doi.org/10.5194/egusphere-egu25-2481, 2025.
Abstract
Anomalous reconnection layer (ARL) usually appears near the magnetopause when the solar wind is in low Alfvén Mach number. The structure of an ARL is similar to the magnetic reconnection outflow region, i.e., a decrease in the total magnetic field and an increase in the high-energy ion flux. The ARL is seldom observed in the Earth’s magnetospheric environment because the solar wind at Earth is mostly in high Alfvén Mach number regime. According to previous observations, the solar wind at Mercury is usually in low Alfvén Mach number. Therefore, we assume that such an ARL can be observed frequently near Mercury’s magnetopause. To test this assumption, we examined the magnetic fields and ion fluxes obtained at the Mercury’s magnetosheath by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft. With 120 events of ARLs we identified from MESSENGER’s data, we validate the assumption that ARLs frequently appear on Mercury. These ARL events were extracted from the list of MESSENGER bowshock and magnetopause crossing times compiled by Winslow et al. [2013]. The number of the ARL events found on Mercury is much larger than those found on Earth. The thickness of each ARL was estimated from the data, finding that the ARLs occupy, on average, one-fifth the thickness of the magnetosheath for Mercury. This work helps deepen our understanding of the comparative magnetospheric environment of Mercury and Earth.
References
Winslow, R. M., B. J. Anderson, C. L. Johnson, J. A. Slavin, H. Korth, M. E. Purucker, D. N. Baker, and S. C. Solomon (2013), Mercury's magnetopause and bow shock from MESSENGER Magnetometer observations, J. Geophys. Res. Space Physics, 118, 2213–2227, doi:10.1002/jgra.50237.
How to cite: Chiu, I.-H., Shue, J.-H., Hasegawa, H., Zhong, J., and Hirahara, M.: A Survey of the Anomalous Reconnection Layer on Mercury, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3409, https://doi.org/10.5194/egusphere-egu25-3409, 2025.
Kelvin-Helmholtz (K-H) instability plays an important role in transporting mass, momentum and energy at the magnetopause of planetary magnetospheres. Previous studies have shown that the K-H waves on Mercury’s magnetosphere exhibit clear dawn-dusk asymmetry, i.e., they are frequently observed on the duskside magnetopause but rarely on the dawnside. In this presentation, we first present a case study of K-H waves on the dawnside of Mercury’s magnetosphere and a statistical study of K-H waves from 2014 to 2015 based on MSEEENGER’s observations.
In the case study, the K-H waveforms on the dawnside side were divided into linear waves and nonlinear waves by modeling the magnetopause as Harris current sheet. The 30mHz compressional ultra-low-frequency waves and ion-Bernstein modes were observed in the magnetosphere adjacent to these K-H waves, which are interpreted as the evidence of energy and mass transport by K-H waves. However, only a few magnetopause oscillations were observed on the duskside during the same MESSENGER’s orbit under similar interplanetary magnetic field conditions. No compressional waves or ion-Berstein modes were observed associated with these oscillations.
Our statistical study found that K-H waves were equably prevalent on both the dawnside and duskside, which are different from the previously reported dawn-dusk asymmetry. We categorized our cases into linear and nonlinear stages and analyzed their interplanetary magnetic field conditions. Our results provide insights into the study of K-H instability at Mercury, especially the mechanism of asymmetry and transport of plasma and energy.
How to cite: Li, R., Sun, W., and Fu, S.: Kelvin-Helmholtz Instability Observations on Mercury’s magnetopause: MESSENGER Study, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7859, https://doi.org/10.5194/egusphere-egu25-7859, 2025.
Planetary magnetospheres exhibit significant twisting of the magnetotail with increasing downstream distances.
However, Mercury's tail twist observed by MESSENGER indicate a rather small twist of up to 3 degrees.
Here, we model Mercury's magnetotail response to different Interplanetary Magnetic Field (IMF) directions and determine what MPO and Mio might observe in their orbital phase with the hybrid model AIKEF.
Our hybrid model results indicate that Mercury's magnetotail topology exhibits a similar small twist at MPO altitudes, comparable to MESSENGER results.
The tail twist observed by Mio, however, indicates a strong dependency on the upstream IMF direction, becoming much more Earth-like.
In addition, kinetic effects warp and bend the neutral sheet significantly, disallowing easy determinations of the twist angles.
How to cite: Exner, W. and Romanelli, N.: Mercury's Nightside Magnetosphere: Predictions for Mercury's Magnetotail Twist at the Orbits of MPO and Mio, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6978, https://doi.org/10.5194/egusphere-egu25-6978, 2025.
The relationship between Mercury’s magnetic cusp and variations in the solar wind has been investigated in several prior studies. Building on this foundation, we developed an integrated approach that combines two independent detection algorithms: one that identifies cusp signatures using magnetic field data—based on magnetic anisotropy and angular variations relative to the KTH reference model (without the cusp)—and another that analyzes particle data, utilizing a method established by Jim Rains. A key aspect of this work is the comparison of these two independent detection methods to gain deeper insights into cusp behavior. Using this combined approach, we conducted a statistical analysis that reveals how the structure and occurrence of Mercury’s magnetic cusp vary under different solar wind conditions.
How to cite: Zywczok, R. and Heyner, D.: Statistical Analysis of Mercury’s Magnetic Cusp and its Dependence on Solar Wind Conditions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21600, https://doi.org/10.5194/egusphere-egu25-21600, 2025.
The BepiColombo mission, a collaboration between the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA), aims to explore Mercury and its space environment. This mission is the first multi-spacecraft endeavor beyond Earth, comprising the Mercury Planetary Orbiter (MPO), managed by ESA, and Mio, led by JAXA. Launched in 2018, BepiColombo is still in cruise phase and recently completed its sixth and final swing-by maneuver at Mercury before its arrival in December 2026. This study provides a comparative analysis of magnetic field observations during the mission's Mercury flybys, utilizing data from the Magnetometer (MGF) onboard the Mio spacecraft. We aim to characterize the observed space environment and solar wind conditions for each flyby. The distinct flyby trajectories enable the exploration of extended regions around Mercury, encompassing the distant magnetotail, bow shock, and both hemispheres along the terminator. These observations provide valuable insights into the magnetospheric and solar wind conditions during each of the six flybys, significantly enhancing our understanding of the dynamic behavior of the solar wind in the inner heliosphere and the complex structure of Mercury's magnetosphere.
How to cite: Schmid, D., Baumjohann, W., Matsuoka, A., Fischer, D., Magnes, W., Heyner, D., Auster, H.-U., and Nakamura, R.: Comparative Analysis of Magnetic Field Observations during BepiColombo Mercury Flybys, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17931, https://doi.org/10.5194/egusphere-egu25-17931, 2025.
Thanks to MESSENGER observations, we know that Mercury’s magnetosphere is highly dynamic, and it can be fully reconfigured in a few minutes, with strong influences of external conditions.
BepiColombo mission includes a comprehensive payload for the investigation of the environment. During the cruise phase, not all the sensors can operate for science measurements, however, during the swing-bys the magnetic field and particles in Mercury’s magnetosphere are successfully measured by the MPO and Mio payloads. In this presentation, we will focus on Mercury’s swing-by 2 (MSB2) observations in comparison with other swing-bys. During the MSB2, BepiColombo passed from dusk in the tail toward dawn in the dayside in a nearly equatorial path. The IMF turned from northward to southward during the crossing. The dayside magnetopause boundary was clearly observed, while the bow shock crossing was not clearly distinguishable. Close to the planet signatures of circulating high energy ions have been seen. While upstream the bow shock, foreshock ions have been observed.
How to cite: Milillo, A., Varsani, A., Heyner, D., Hadid, L. Z., Baumjohann, W., Barabash, S., and Andrè, N. and the MPO/SERENA, MPO-MAG, Mio-MGF, Mio/MPPE-MEA and MSA teams: Mercury’s Environment Observed by BepiColombo during the Second Mercury’s Swing-by, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10436, https://doi.org/10.5194/egusphere-egu25-10436, 2025.
BepiColombo, the joint ESA-JAXA mission on route to the planet Mercury, was launched in 2018. After eight successful planetary flybys, the spacecraft had its final Mercury flyby on 08 Jan 2025. The PICAM (Planetary Ion Camera) instrument, part of the SERENA package, was operational from 48 hours prior to the closest encounter, until 48 hours afterwards. This ion sensor successfully monitored the upstream solar wind, as well as the magnetospheric and planetary ions at the vicinity of Mercury. Near the planet, PICAM operated in mass spectrometry mode using its Hadamard Time-of-Flight gating, which is a novel technique to improve the observations of low-density ions. We present the analysis of the ion species detected at Mercury’s environment.
How to cite: Varsani, A., Lammer, H., Milillo, A., Schmid, D., Heyner, D., Raines, J., Laky, G., Krupp, N., Jeszenszky, H., Giono, G., Volwerk, M., Teubenbacher, D., Nakamura, R., Orsini, S., Livi, S., Barabash, S., Fraenz, M., Krueger, H., Aronica, A., and Kazakov, A.: Ion species of Mercury’s 6th flyby, detected by PICAM's Hadamard mass spectrometry, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11316, https://doi.org/10.5194/egusphere-egu25-11316, 2025.
