Mercury Surface Research Articles

Estimating Interplanetary Magnetic Field Conditions at Mercury's Orbit From MESSENGER Magnetosheath Observations Using a Feedforward Neural Network

AbstractMercury's small magnetosphere is embedded in the dynamic and intense solar wind environment characteristic of the inner heliosphere. Both the magnitude and orientation of the interplanetary magnetic field (IMF) significantly influence the solar wind‐magnetospheric interaction at Mercury, driving phenomena such as magnetic reconnection. The MErcury Surface, Space Environment, Geochemistry and Ranging (MESSENGER) spacecraft provided in‐situ magnetic field measurements of the solar wind, the magnetosheath, and the magnetosphere along each orbit. However, it is a challenge to directly assess the IMF's impact on Mercury's plasma environment due to the temporal separation between observations within the solar wind and the magnetosphere, especially in the absence of an upstream monitor. Here, we present a feedforward neural network (FNN) trained on a subset of magnetosheath observations to estimate the strength and orientation of the IMF upstream of the bow shock. Utilizing magnetosheath magnetic field, cylindrical spatial coordinates, and heliocentric distance measurements, the FNN predicts upstream IMF conditions with an score of 0.70 and mean averaged error of 5.3 nT, thereby greatly decreasing the temporal separation between IMF estimates and magnetospheric measurements throughout the MESSENGER mission. This approach yields IMF estimates for all magnetosheath data measured by MESSENGER, providing a useful tool for future investigations of the IMF impact on Mercury's magnetosphere. This method will be integrable with the dual‐spacecraft BepiColombo magnetosheath measurements, providing useful estimates of upstream IMF conditions particularly during the extended periods in which neither spacecraft sample the solar wind. Our results demonstrate the utility of machine learning techniques on advancing space science research.

On Anomalous Dissipation in Plasma of Dusty Mercury’s Exosphere

The anomalous dissipation related to the effect of charging of dust particles that gives rise to new physical phenomena, effects, and mechanisms represents one of the main specific features of dusty plasma that makes it different from conventional plasma containing no charged dust particles. We analyze the process of anomalous dissipation in the context of description of the dynamics of dust particles in dusty plasma of the Mercury’s exosphere. An analytical description of oscillations of a dust particle above the surface of Mercury is presented. The frequency of charging of dust particles that characterizes the anomalous dissipation determines the damping of such oscillations. It is demonstrated that the anomalous dissipation is important for substantiation of the model of levitating dust particles that is used for description of dusty plasma above Mercury. The results of numerical simulations that justify the use of the discussed model are presented.

Mg Exosphere of Mercury Observed by PHEBUS Onboard BepiColombo During Its Second and Third Swing‐Bys

AbstractMercury's exosphere is an important target for understanding the dynamics of coupled systems in space environments, tenuous planetary atmospheres, and planetary surfaces. Magnesium (Mg) is especially crucial for establishing methods for estimating the surface chemical composition distribution through observations of the exosphere because its distribution in the exosphere and on the surface is strongly correlated. However, owing to its low radiance, the Hermean Mg exosphere has only been detected by the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) onboard the Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) spacecraft. Thus, we have few observation data for areas other than low latitude regions in addition to few detection cases of short‐term or sporadic fluctuations, resulting in a poor understanding of ejection and transportation mechanisms of the Mg exosphere. In this study, we analyzed the distribution of the Hermean Mg exosphere by the Probing of Hermean Exosphere by Ultraviolet Spectroscopy (PHEBUS) onboard the Mercury Planetary Orbiter of the BepiColombo mission during its second and third Mercury swing‐bys (MSBs). First, we constructed a calibration method including background subtraction and calibration using stellar observations. Mg light curves at two true anomaly angles were obtained, which were in agreement with the Chamberlain model and a three‐dimensional numerical calculation. Comparing the Mg and calcium (Ca) radiances obtained by PHEBUS during the MSBs, the exospheric Mg atoms have a lower energy than the exospheric Ca atoms. This is consistent with the lower energy necessary for producing the Mg atoms produced by molecular photodissociation than for Ca atoms.

Optimizing Transdermal Patch Design: A Quality by Design Approach for Dysmenorrhea Relief.

This study explores the potential of transdermal patches as a systemic delivery system for donepezil (DPZ), aiming to circumvent hepatic first-pass metabolism and mitigate oral administration-associated side effects. DPZ, known for its poor solubility and adverse effects, is formulated into transdermal patches using a matrix-type approach with PVP K30 and HPMC K100 polymers alongside dimethyl sulfoxide as a plasticizer. Through solvent casting on a mercury surface, the patches are prepared and assessed for physical properties and drug-excipient interactions using FTIR analysis. The results demonstrate satisfactory physical characteristics, including appearance, weight variation, and tensile strength. Notably, formulations containing HPMC K100 (400 mg) and PVP K30 (300 mg) exhibit enhanced DPZ discharge, signifying their potential as an effective drug delivery system for mitigating DPZ-associated side effects.

Synthesis and Characterization of Fe-Poor Olivine with Applications to the Surface of Mercury

Synthesis and Characterization of Fe-Poor Olivine with Applications to the Surface of Mercury

Impact structures on Mercury from MESSENGER data: Implications on their formation processes and crustal structure

In this study high-resolution stereo images and Digital Terrain Models (DTMs) from MErcury Surface, Space ENvironment, Geochemistry and Ranging (MESSENGER) mission were utilized to detect impact structures in regions not covered by Mercury’s Laser Altimeter (MLA), while gravitational data was utilized as a supported data set. We have established an inventory of 314 impact structures ≥150 km, classified on their morphological and gravitational characteristics. 24 basins ≥300 km have been newly discovered. Additionally, we have identified significant surface modifications in impact structures of smooth material infill, which can be either impact-induced or volcanic in origin. The Bouguer anomaly and crustal thinning in the center are displaying an interplay of predominant change of crustal structure in impact basins. Further, this study reveals a common impact history of Mercury and the Moon. Nevertheless, cumulative density distributions suggest the possibility of either a divergence in impactor populations responsible for forming large basins on both celestial bodies or a significant shift in impactor rates. This work holds important implications not only for understanding impact structure formation and evolution processes but also for interpreting the crustal structure. It presents an updated and expanded catalog of impact structures on Mercury, encompassing buried basins, and identifies new areas of interest, potentially serving as target sites for the forthcoming BepiColombo mission.

Deep Entry of Low‐Energy Ions Into Mercury’s Magnetosphere: BepiColombo Mio’s Third Flyby Observations

AbstractAlthough solar wind‐driven convection is expected to dominate magnetospheric circulation at Mercury, its exact pattern remains poorly characterized by observations. Here we present BepiColombo Mio observations during the third Mercury flyby indicative of convection‐driven transport of low‐energy dense ions into the deep magnetosphere. During the flyby, Mio observed an energy‐dispersed ion population from the duskside magnetopause to the deep region of the midnight magnetosphere. A comparison of the observations with backward test particle simulations suggests that the observed energy dispersion structure can be explained in terms of energy‐selective transport by convection from the duskside tail magnetopause. We also discuss the properties and origins of more energetic ions observed in the more dipole‐like field regions of the magnetosphere in comparison to previously reported populations of the plasma sheet horn and ring current ions. Additionally, forward test particle simulations predict that most of the observed ions on the nightside will precipitate onto relatively low‐latitude regions of the nightside surface of Mercury for a typical convection case. The presented observations and simulation results reveal the critical role of magnetospheric convection in determining the structure of Mercury's magnetospheric plasma. The upstream driver dependence of magnetospheric convection and its effects on other magnetospheric processes and plasma‐surface interactions should be further investigated by in‐orbit BepiColombo observations.

The formation of volatile‐bearing djerfisherite in reduced meteorites

AbstractEnstatite meteorites, both aubrites and enstatite chondrites, formed under exceptionally reducing conditions, similar to the planet Mercury. Despite being reduced, the MESSENGER mission showed that the surface of Mercury is more enriched in volatiles (e.g., S, Na, K, Cl) than previously thought. To better understand the mineral hosts of these volatiles and how they formed, this work examines the chemistry and petrographic settings of a rare, K‐bearing sulfide called djerfisherite within enstatite chondrites and aubrites. The petrographic settings of djerfisherite within aubrites suggest this critical host of Cl formed after both the crystallization of troilite and exsolution of daubréelite. Djerfisherite is commonly observed as a rim on other sulfides and in contact with metal. We present an alteration model for djerfisherite formation in aubrite meteorites, whereby troilite and Fe‐Ni metal are altered through anhydrous, alkali‐ and Cl‐rich fluid metasomatism on the aubrite parent body to produce secondary djerfisherite. Moreover, we observe a loss of volatiles in djerfisherite within impact melted regions of the Miller Range 07139 EH3 chondrite and the Bishopville aubrite and explore the potential for impact devolatilization changes to sulfide chemistry on other reduced bodies in the Solar System. Vapor or fluid phase interactions are likely important in the formation of volatile‐rich phases in reduced systems. While most Na and K on the mercurian surface is expected to be hosted in feldspar, djerfisherite is likely a minor, but critical, reservoir for K, Na, and Cl. Djerfisherite present on reduced bodies, such as Mercury, may represent sulfides formed via late‐stage, primary metasomatism.

Formation and growth of nanophase iron particles on the surface of Mercury revealed by experimental study

Formation and growth of nanophase iron particles on the surface of Mercury revealed by experimental study

A statistical evaluation of the morphological variability of shortening landforms on Mercury

Observations of Mercury from both the Mariner 10 and MESSENGER missions showed that Mercury has a global population of shortening landforms, with several thousands of individual structures identified to date. The accommodation of widespread tectonic shortening is widely regarded to be the result of global contraction—the long, sustained cooling of the interior that has caused the planet to shrink. Shortening landforms on Mercury have been traditionally categorized into three distinct categories: lobate scarps, wrinkle ridges, and high-relief ridges. Although the clearest examples of shortening landforms at the time were used to describe and define these categories qualitatively, later studies showed that shortening landforms on Mercury display morphological characteristics that do not make for a ready classification into one of these “traditional” groups. More recently, other studies have classified shortening landforms based on the terrain that those landforms reside in to avoid generalizing morphology. In this study, we quantitatively assess the shape of shortening landforms by measuring and compiling a suite of 12 morphological parameters for 100 such structures across the planet. These parameters were evaluated for their importance in defining categories using two multivariate statistical analyses, a Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA). These methods allow us to assess any correlation that the traditional categories, terrain types, or alternative classification schemes have with the variation observed across our set of measurements. Our results show that the morphologic characteristics of shortening landforms on Mercury are not accurately captured by traditionally recognized groups. Instead, shortening landforms fall along a morphological spectrum, where only a few ideal examples of lobate scarps or wrinkle ridges provide clear endmembers. Therefore, despite the frequent use of the terms “lobate scarps” and “wrinkle ridges” in works regarding planetary tectonics, we find that such terminology does not appropriately define the morphology of shortening landforms found on Mercury and may lead to the generalization, or misinterpretation of landforms described as accommodating shortening on Mercury's surface. Future studies should test if a distinction between the landforms is found in the underlying thrust fault systems.

Short large-amplitude magnetic structures (SLAMS) at Mercury observed by MESSENGER

Abstract. We present the first observations of short large-amplitude magnetic structures (denoted SLAMS) at Mercury. We have investigated approximately 4 years of MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) data to identify SLAMS in the Mercury foreshock. Defining SLAMS as magnetic field compressional structures, with an increase in magnetic field strength of at least twice the background magnetic field strength, when MESSENGER is located in the solar wind, we find 435 SLAMS. The SLAMS are found either in regions of a general ultra-low frequency (ULF) wave field, at the boundary of such a ULF wave field, or in a few cases isolated from the wave field. We present statistics on several properties of the SLAMS, such as temporal scale size, amplitude, and the presence of whistler-like wave emissions. We find that SLAMS are mostly found during periods of low interplanetary magnetic field strength, indicating that they are more common for higher solar wind Alfvénic Mach number (MA). We use the Tao solar wind model to estimate solar wind parameters to verify that MA is indeed larger during SLAMS observations than otherwise. Finally, we also investigate how SLAMS observations are related to foreshock geometry.

Dynamics of Sputtered Neutral Sodium Atoms in the Near‐Mercury Space

AbstractThe solar wind sputtering in the magnetospheric polar cusp is an important source of heavy atoms in Mercury’s exosphere and magnetosphere. However, the majority of ejected atoms are neutral, undergoing an extended period before photoionization occurs. In this study, we employ an ab initio simulation to investigate the behavior of sodium (Na) atoms prior to their photoionization. Our results reveal that overall only approximately 2.7% of the sputtered atoms contribute to magnetospheric ions, while the vast majority of these ions (∼82.9%) escape into interplanetary space. The remaining fraction (14.4%) eventually returns to the planetary surface. For Na atoms ionized inside the magnetosphere, a larger proportion of Na+ (53.5%) is supplied to the magnetotail compared to the polar cusp (39.4%), which is due to the tailward acceleration caused by solar radiation. Additionally, the remaining Na+ (7.1%) contributes to the dayside ring current region, as demonstrated by the observation of the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft. Our research introduces a perspective on Na+ transport in the magnetosphere that complements and coexists with traditional mechanisms.

The Descartes Code (Spin Orbital Rotation of Photons)–IV. The Harress-Sagnac Color Excess in the Rotation Curves of Galaxies

In 1933, Zwicky formulated the significant bifurcation point in the history of astrophysics. Zwicky postulated an unknown dark matter in order to explain the color excess in the observed Doppler effect in the rotation curves of galaxies. However, until now we have not detected these dark matter particles. In this contribution, we propose to come back to this bifurcation point and to interpret the observed color excess as the Harress-Sagnac effect known in the rotating interferometers. We have described photon properties in those rotating interferometers based on the old color theory of Descartes—rotating light globules (spin-orbital rotation of photons). Therefore, the color excess observed in the rotation curves of galaxies can be interpreted as the additional color excess of photons emitting from distant rotating stars. Formulae for these color excesses are given for different locations of the rotating galaxy inspired by Zwicky’s core-shell model of galaxies. A part of Zwicky’s enigma is an unknown influence of the Solar gravitational field at 1 AU on the distant photon properties. From the forgotten Gerber’s retarded potential formula we have derived an expression for the acceleration of distant photons towards the Sun at 1 AU as ax = 1.171 × 10⁻¹⁰ ms⁻². This is a very surprising coincidence with the Milgrom empirical value a0 = (1.2 ± 0.1) × 10⁻¹⁰ ms⁻². Therefore, we propose to test this new formula at the surface of Mercury and Mars in order to reveal if our gravitational models are universal or “geocentric”, valid for the surroundings of the Earth only.

Laboratory reflectance spectra of enstatite and oldhamite mixtures for comparison with Earth-based reflectance spectra of asteroid 2867 Šteins and Mercury

The reflectance spectra of synthetic oldhamite (CaS), synthetic enstatite (Mg2Si2O6), and their mixtures have been studied in the spectral range from 0.3 μm to 16 μm. The spectrum of enstatite is very bright, with a steep slope in the ultraviolet (UV) and an almost neutral slope in the visible (VIS) and near-infrared (NIR). The mid-infrared (MIR) region is characterized by the Christiansen feature, Reststrahlen bands and the Transparency feature. The oldhamite spectrum shows a red slope in the UV and VIS and an absorption band at 0.41 μm. The absorption band has a relative depth of 11.4%. In the MIR, the oldhamite spectrum is much brighter than the enstatite spectrum and shows several broad absorption bands. The spectra of the mixtures show an intermediate behavior between the two endmembers. The absorption band at 0.41 μm is visible in the spectra of all mixtures, even in the spectrum of the mixture with only 1 vol% oldhamite. In the MIR, the spectra of the mixtures with ≤10 vol% oldhamite are very similar to the spectrum of pure enstatite. Changes in the spectral characteristics such as reflectance or band depths do not follow simple linear trends but show two distinct trends: One for mixtures with ≤10 vol% oldhamite and one for mixtures with ≥20 vol% oldhamite. Changes occur significantly faster in the spectra of mixtures with ≤10 vol% than in those with ≥20 vol% oldhamite.Reflectance spectra of the E[II]-type asteroid 2867 Šteins are flat and almost featureless but show an absorption band at 0.49 μm, which is attributed to oldhamite. Comparison of the laboratory spectra in the VIS and MIR with spectra of Šteins gives an upper limit for the oldhamite content on its surface of 40 %vol. Hence, Šteins probably consists of aubrite-like material with virtually FeO-free enstatite as the major constituent and an oldhamite abundance of <40 vol%. Šteins and other E[II]-type asteroids likely formed through igneous processes on a larger now destroyed body, where an immiscible CaS-melt formed within a silicate melt.The surface of Mercury is also linked to FeO-poor silicates like enstatite. Oldhamite and other sulfides are linked to the formation of hollows on Mercury. Mixtures of enstatite and oldhamite could therefore serve as suitable model analog for the surface of Mercury. Contrasting trends at ∼7–8.5 μm in the MIR reflectance spectra of oldhamite and enstatite could be used as an indicator for the presence of oldhamite in spectral data that will be collected by the MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer) instrument onboard the ESA/JAXA BepiColombo mission to Mercury.

Cysteamine Chemisorption at Mercury-Solution Interfaces in the Context of Redox and Microdissociation Equilibria.

The redox behavior and chemisorption of cysteamine (CA) at a charged mercury surface are described, with an emphasis on its acid-base properties supported by molecular dynamics and quantum mechanical calculations. It was found that CA forms chemisorbed layers on the surface of the mercury electrode. The formation of Hg-CA complexes is connected to mercury disproportionation, as reflected in peaks SII and SI at potentials higher than the electrode potential of zero charge (p.z.c.). Both the process of chemisorption of CA and its consequent redox transformation are proton-dependent. Also, depending on the protonation of CA, the formation of typical populations of chemisorbed conformers can be observed. In addition, cystamine (CA disulfide dimer) can be reduced on the mercury surface. Between the potentials of this reduction and peak SI, the p.z.c. of the electrode used can be found. Furthermore, CA can serve as an LMW catalyst for hydrogen evolution. The mechanistic insights presented here can be used for follow-up research on CA chemisorption and targeted modification of other metallic surfaces.

The parts of the meteoroid stream originating in comet 109P/Swift-Tuttle crossing the orbits of Mercury, Venus, and Mars

The nucleus of comet 109P/Swift-Tuttle is the source of meteoroids which frequently impact the Earth as the well-known, most powerful meteor shower Perseids, #7. In addition, the stream splits into several other filaments corresponding to few other meteor showers. In this work, we investigated, if the meteoroids of 109P’s stream also impact the other three terrestrial planets. It appeared that there are meteor showers at Venus and Mars, two with the radiants in the northern and one in the southern ecliptic hemisphere of sky. Interestingly, the positions of the radiant areas of 109P’s showers are almost the same at all three planets, Venus, Earth, and Mars. Any shower being so active as the Perseids was predicted neither at Venus nor at Mars, however. Some meteoroids of one filament of the 109P’s stream also impacts the surface of Mercury, but the corresponding shower is predicted so low in number that it can scarcely be detected.

Understanding the Dust Environment at Mercury: From Surface to Exosphere

We provide an overview of our understanding of the dust environment at Mercury and the role that dust plays in shaping the planet's surface and exosphere. Our understanding of the role that dust impacts play in the generation of Mercury's atmosphere has evolved considerably with continued analysis of results from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission. Recent models have provided evidence for the probable release of refractory species into Mercury's exosphere via impacts. However, there remain significant questions regarding the relative contributions of atoms released via impacts versus other mechanisms (e.g., photon-stimulated desorption) to the overall exospheric budget. We also discuss the state of observational and modeling efforts to constrain the dust environment at Mercury, including sources from the zodiacal cloud, cometary trails, and interstellar dust. We describe the advancements that will be made in our characterization of dust at Mercury with BepiColombo, providing observational constraints on the dust clouds themselves and the role that impacts play in exospheric generation. On Mercury's surface, there remain outstanding questions regarding the role that dust impacts play in the regolith cycling and development. We review how improved modeling efforts to understand grain lifetimes as a function of impactor flux will further our understanding of Mercury's regolith. Finally, there are few constraints on the role of dust impacts on the space weathering of Mercury's surface, particularly the expected chemical, physical, and spectral alterations to the regolith. Here we discuss the importance of laboratory experiments to simulate these processes for the interpretation of data from MESSENGER and BepiColombo.

An Empirical Model for Mercury’s Field‐Aligned Currents Derived From MESSENGER Magnetometer Data

AbstractMercury is the only planetary magnetosphere which does not possess a significantly conducting ionosphere, yet magnetic field observations by the Mariner 10 and MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) missions revealed a stable presence of large‐scale field‐aligned currents (FACs). Several empirical magnetic field models have been developed to describe Mercury’s magnetospheric currents and their associated magnetic fields, but none attempted to include an explicit description of large‐scale FACs. Here, we describe a dynamic FAC magnetic field model for Mercury based on the analytical solution to conical currents, which are shielded by a dynamic magnetopause boundary. The model contains free parameters setting the FACs' latitudinal extent and amplitude as functions of magnetospheric activity. The parameters are fit by minimizing the root‐mean‐square (RMS) differences between the model and MESSENGER Magnetometer data. During magnetically quiet conditions, the modeled FACs have an intensity of ∼10 nA/m2 and extend in latitude from ∼83°N to ∼40°N. They intensify to ∼20 nA/m2 and expand equatorward to ∼28°N during the most active times. The inclusion of the FAC model reduces low‐altitude RMS residuals by 8.1% when compared to prior models. The model effectively captures the azimuthal component of the magnetic field present in the MESSENGER low‐altitude data, but largely misses the radial and co‐latitudinal components, indicating other large‐scale physics remain missing in the mathematical descriptions of Mercury's magnetosphere.

Statistical Analysis of Mercury's Magnetotail Lobe Field Using MESSENGER Observations

AbstractThe magnetotail lobe region at Mercury is characterized by low plasma density and low magnetic field variability compared to the nightside magnetosheath and central plasma sheet. At Mercury, as well as other planets, lobe magnetic fields play a crucial role in storing and releasing magnetic flux in response to changing upstream solar wind conditions such as interplanetary magnetic field (IMF) orientation and solar wind dynamic pressure (Pdyn). This makes the region significant for studying the magnetospheric interaction with the intense solar wind conditions at Mercury's orbit. Here, we identify and analyze magnetotail lobe observations made by the Mercury Surface, Space Environment, Geochemistry and Ranging (MESSENGER) spacecraft during its 4 years orbital phase. We empirically determined a set of criteria using magnetometer (MAG) and the Fast Imaging Plasma Spectrometer instruments onboard MESSENGER to identify lobe magnetic field intervals. From 3,332 MESSENGER orbits, we identify 1,242 lobe field intervals. We derive an expression for the average lobe magnetic field strength in nanotesla with respect to radial distance downtail: Blobe(r) = (135 ± 8) * r(−2.1±0.3) + (31 ± 8). The lobe magnetic field exhibits both small‐scale (∼3 min) and orbit‐to‐orbit (∼8–12 hr) variability in magnetic field strength compared to this averaged field strength expression. The orbit‐to‐orbit variability in lobe field strength is not significantly correlated with estimated IMF orientation, but is directly correlated with Pdyn. Thus, our findings provide evidence for the pressure balance between the inward facing Pdyn on the nightside magnetopause and the outward facing magnetic pressure supplied by the lobes.

Less than one weight percent of graphite on the surface of Mercury

Less than one weight percent of graphite on the surface of Mercury