Journal of Geophysical Research: Planets

The Mars Science Laboratory rover, Curiosity, has been examining strata from a period of Martian history where extensive clay mineral formation transitioned to sulfate mineral formation. This mineralogic change corresponds to a change from a wetter to a more arid climate. Among the tools used by Curiosity to study the rocks that recorded this transition is the multispectral capability of its Mast Camera (Mastcam). The Mastcam filter wheel, in combination with its Bayer Pattern filter focal plane array has provided multispectral scenes recorded in 12 spectral bands over the 445–1,013 nm spectral range. Here, Mastcam multispectral results from the rover's exploration of predominantly sulfate‐bearing strata that bracket a distinct dark‐toned resistant stratigraphic marker unit, now referred to as the Amapari Marker Band (AMB), are presented in association with supporting information from some of Curiosity's other instruments. Using an agglomerative hierarchical clustering approach, six spectral classes were derived. These classes included three stratigraphic classes plus a class indicating more intense diagenetic alteration and classes of dark‐toned float rocks and a set of Fe‐Ni meteorites. These spectral classes were compared to the spectra of analogous terrestrial materials. Among the observations, a distinct tonal and color unit was observed directly below the Amapari Marker Band. Several lines of evidence suggest this narrow interval is an alteration horizon. The alteration could have resulted from diagenesis, exposure as a weathering surface, or from introduction of water associated with the deposition of the lower AMB.

Whether or not there is a particulate layer in the lowest 10 km of the Venusian atmosphere is still an open question. Some of the past in situ experiments showed the presence of a detached particulate layer, and a few suggested the existence of finely dispersed aerosols, while other instruments supported the idea of no particulate matter in the deep atmosphere. In this work, we investigate the presence of a near‐surface particulate layer (NSPL) using in situ data from the Venera 13 mission. While the original spectrophotometric data from Venera 13 were lost, we have reconstructed a part of this data by digitizing the old graphic material and selected the eight most reliable Venera 13 downward radiance profiles from 0.48 to 0.8 μ {\upmu }m for our retrievals. The retrievals suggest the existence of the particulate layer with a peak in the altitude range of 3.5–5 km. They further indicate a log‐normal particle size distribution with a mean radius between 0.6 and 0.85 μ {\upmu }m. The retrievals constrain the real refractive index of the particles to lie around the range of 1.4–1.6, with the imaginary refractive index of a magnitude of 10−3 ${10}^{-3}$. Based on refractive index retrievals, uplifted basalt particles or volcanic ash could be responsible for near‐surface particulates. In comparison, volatile condensates appear less likely to be behind the formation of NSPL.

Europa's surface exhibits many regions of complex topography termed “chaos terrains.” One set of hypotheses for chaos terrain formation requires upward migration of liquid water from perched water bodies within the icy shell formed by convection and tidal heating. However, consideration of the behavior of terrestrial ice sheets suggests the upwards movement of water from englacial water bodies is uncommon. Instead, rapid downwards hydrofracture from supraglacial lakes—unbounded given a sufficient volume of water—can occur in relatively low tensile stress states given a sufficiently deep initial fracture due to the negative relative buoyancy of water. I suggest that downwards, not upwards, fracture may be more reasonable for perched water bodies but show that full hydrofracture is unlikely if the perched water body is located beneath a mechanically strong icy lid. However, full hydrofracture is possible in the event of lid break up over a perched water body and likely in the event of a meteor impact that generates sufficient meltwater and a tensile shock. This provides a possible mechanism for the transfer of biologically important nutrients to the subsurface ocean and the formation of chaos terrains.

A regional dust storm was observed in the northern spring of Martian Year 35, characterized by a relatively cold and clear atmosphere. Satellite observations and general circulation model simulations show that the atmospheric temperature response to this early regional dust storm is significant, both in the dust lifting region and in remote areas. Atmospheric heating in the dust‐lifting region was primarily driven by shortwave radiative heating of dust particles. Anomalous cooling in the northern mesosphere and heating responses in the southern troposphere were associated with dust‐modulated gravity waves and planetary waves, respectively. Inhomogeneous heating from dust distribution during the storm generated anomalous atmospheric waves, significantly enhancing southward meridional circulation and lifting water vapor in the lower tropical troposphere. This dust storm substantially increased meridional water transport from the Northern Hemisphere to the Southern Hemisphere, with pronounced longitudinal asymmetry underscoring the influence of tropical topographic features on water vapor transport.

Over the past decade, the Tunable Laser Spectrometer (TLS) on NASA's Curiosity rover has reported several detections of methane on Mars, attracting attention due to the potential astrobiological implications of its presence. Here, we re‐analyze published TLS data, identifying issues in data robustness and reduction. We find that the TLS foreoptics chamber typically contained methane abundances that were 3–4 orders of magnitude greater than those reported in the sample cell, alongside unexpected and rapidly varying pressure changes inside the instrument. Using information from unreported experiments where methane diffusion into the cell was observed, we estimate a gas transport coefficient and develop a model to simulate gas exchanges between the two compartments in typical experiments, investigating the implications for methane measurements. We find that tiny leaks (<0.1% of foreoptics methane) would suffice to explain the reported atmospheric methane measurements—leaks that are otherwise undetectable from housekeeping data. Furthermore, in an analysis of five experiments where more complete data are available, we find that the TLS retrieval method—which averages discrepant methane levels from the three lines of the R3 triplet as if the three lines were independent, rather than fitting the spectrum to the distinctive pattern of the triplet itself—likely underestimates uncertainties. The probability that three methane levels from individual triplet lines are disparate in all five experiments is typically ∼10⁻³, suggesting the presence of systematic errors that are unaccounted for in previously reported methane levels. Finally, we propose a constructive two‐step experiment to further investigate our findings.

Measurements of the lunar surface have revealed a variable presence of hydration, which has contributions from both hydroxyl (OH) and molecular water (H2O). Recent observations of the lunar hydration suggest that a component of this signature is comprised of molecules that are readily mobile and actively migrate across the lunar surface over the course of a lunar day due to surface temperature variations. However, exospheric measurements of H2O suggest very low abundances above the dayside surface which previous work has argued is in conflict with the surface abundances and the putative occurance of ballistic migration. Here, we use a ballistic transport model to quantify the amounts of OH and H2O in the lunar exosphere and to characterize patterns in the transportation and retention of hydration across the lunar surface. We find that ∼0.5% of a monolayer of hydration on the surface, with 99% OH and 1% H2O contribution to hydration signatures, matches observational upper limits for the presence of hydration in the exosphere. We conclude that there is no discrepancy between the low exospheric measurements and ballistic migration. However, the previously observed day‐time recovery of the hydration signal cannot be explained by this ballistic migration, suggesting that OH/H2O production is also occurring on timescales less than a lunar day. Additionally, we find that ballistic transport results in the transportation of ∼2% of the hydration sourced from surface desorption to the polar regions of the Moon.

Noachian‐aged Jezero crater, the landing site of the Perseverance rover, recorded a fan‐delta system associated with fluvial‐lacustrine features, indicating the past presence of a paleolake. However, the collected targets at the Jezero crater floor indicate that igneous units exhibit distinctive mineralogical features, including the co‐occurrence of different hydrated salts as evidence of later alteration by fluids. In this work, we analyzed the SHERLOC Raman spectra and micro‐images of seven targets in the upper fan unit at Jezero crater during the third science campaign. Mineral detection in these abraded patches consists of carbonate, sulfate, perchlorate or phosphate, and silicate phases (including olivine and pyroxene). The widespread distribution of carbonate minerals in this region indicates a prominent sedimentary deposit potentially related to the Martian paleolakes or transport and deposit processes of rivers or water flows. In four targets, sulfate phases containing anhydrite and hydrous Ca‐sulfate were also identified. These phases were possibly formed from sulfate‐rich low‐temperature fluids. An alternative mechanism for sulfate formation involves the interaction between sedimentary rocks and fluids in either dilute brines under high‐temperature conditions or concentrated brines in low‐temperature environments. The prolonged processes of fluvial, flooding, and eolian sedimentation have significantly reshaped the lithified sediments of Jezero crater, contributing to mineralogical diversity between the crater floor and delta.

NASA's Curiosity rover has found widespread evidence of alteration in sedimentary rocks in Gale crater, Mars driven by interactions with fluids both before and after lithification (early and late diagenesis). Most notably, Curiosity observed distinctive color, chemical, and mineralogical changes interpreted as evidence of diagenesis at the unconformity between Mt. Sharp group fluvial/lacustrine mudstones and Siccar Point group (SPg) aeolian sandstones, a part of the larger Mound Skirting Unit (MSU) that mantles Mt. Sharp. However, the distribution of diagenesis across Mt. Sharp beyond Curiosity's traverse is poorly constrained. In this study, we use orbital color images and spectroscopy to characterize diagenesis‐driven alteration at the MSU unconformity elsewhere in Gale. We find that color variations similar to those observed by Curiosity appear at the MSU unconformity across Mt. Sharp and exhibit spectral properties consistent with hydrated silica, suggesting that some of the alteration observed by Curiosity below the MSU unconformity was extensive across Mt. Sharp. We hypothesize that fluid flow was extensive throughout the MSU, but diagenesis was locally enhanced by permeability differences across the unconformity. In this model, more permeable SPg/MSU sandstones provided a conduit for subsurface fluids that stagnated within and altered the upper few meters of less permeable (e.g., clay‐bearing) Mt. Sharp group strata below. The extensive diagenesis observed in Gale implies that subsurface fluids were long‐lived and widespread. Gaining a better understanding of what rock properties control and influence diagenetic fluid flow will help us improve the search for ancient aqueous environments and possible biosignatures on Mars.

Since its detection by Mariner 10, helium has been a key focus in studies of Mercury's exosphere. Recently, Weichbold et al. (2025), https://doi.org/10.1029/2024je008679 provided the first in situ helium measurements, inferring density from Ion Cyclotron Wave (ICW) events observed by the MESSENGER spacecraft. This approach enables, for the first time, a helium density profile across a broad altitude range without relying on prior models. We present an ab‐initio model for a steady state, solar wind‐driven helium exosphere, which informed the interpretation of these ICW measurements. We discuss helium release processes and evaluate whether meteoroid impacts could account for specific instances of elevated helium measurements. We developed a global, semi‐analytical model based on a helium‐saturated regolith and an average helium source flux of 2.5−1.25+2.5×1023 ${\mathrm{2.5}\,}_{-\mathrm{1.25}}^{+\mathrm{2.5}}\times {\mathrm{10}}^{23}$ He/s from solar wind ion implantation. We calculate the helium flux distribution using an analytical lateral transport model and then generate local radial density profiles from a numerical (Monte Carlo) radial transport model. Additionally, we applied the radial transport model to estimate the scale and duration of large, sporadic helium release events and assess the likelihood of detecting these events in situ. The strong agreement between our model and the novel measurements confirms that the measurable helium exosphere is dominated by thermally recycled particles. We show that elevated helium measurements can result from the vaporization and release of helium from large (1 m) meteoroid impacts, but it is statistically unlikely that more than one impact event is captured in the given set of measurements.

Previous studies have demonstrated that magnetic reconnection can cause ionospheric ions to escape from Mars. Using data from the Mars Atmosphere and Volatile Evolution (MAVEN) mission, we observed a dayside magnetic reconnection event with a jet speed of approximately 1.1 km/s, which is below Mars' escape velocity of 5 km/s. This event, characterized by a clear Hall magnetic field between draped interplanetary magnetic fields and open crustal field lines, was detected in the dayside ionosphere of the southern hemisphere. Due to the high density of heavy ions, the inflow Alfvén speed is low, around 2 km/s. Consequently, the reconnection jet, moving approximately at the inflow Alfvén speed, cannot escape Mars despite moving towards space. However, the reconnection significantly heated the ionospheric ions. Our findings may offer valuable insights into the study of similar processes, such as failed eruptions in the solar corona.

The surfaces of airless bodies are constantly exposed to high‐energy particles and ionizing radiation, which interact with surficial materials, inducing crystal defects and modifying spectral characteristics. In this study, a series of irradiation experiments were performed to simulate different types of space radiation, including H⁺ ion irradiation, high‐energy electron (HE) irradiation, X‐ray irradiation and ultraviolet (UV) irradiation. Their visible and near‐infrared (VNIR) reflectance spectra exhibit characteristic absorption features centered <1.0 μm, indicating the formation of various types of color centers in NaCl. In H⁺ ion irradiation and HE irradiation experiments, the irradiated NaCl samples showed a broad Raman envelope in the range of ∼50–300 cm⁻¹, indicating the formation of color centers. However, the Raman spectra of NaCl samples before and after X‐ray irradiation seem identical. In addition, the UV irradiation experiment did not induce the formation of color centers. Currently, color centers have already been detected on airless bodies. Our results enhance their credibility by demonstrating that various types of space radiation can induce the formation of color centers in NaCl under simulated conditions. In future orbital and in situ missions, the colored NaCl can be identified via VNIR spectral and Raman spectral surveys, aiding in the analysis of radiation‐induced processes on celestial bodies. Our experiments provide insights into the interaction mechanisms between space radiation and surface materials, helping to interpret spectral observations and evaluate the effects of space radiation.

Plain Language Summary Landslides, or mass movements, have been known to occur on the surface of Venus, though were not initially believed to be relatively abundant compared to other planetary bodies. Most of these landslides occur in the continent‐like region of Atla Regio. These landslides have similar characteristics to landslides on Earth and Mars, though the massive size of most of these landslides is more comparable to those on Mars. Some causes of the Venusian landslides might be different compared to Earth, though, due to the lack of tectonic plates and liquid water on the surface of Venus. For example, a landslide that is caused normally by a combination of soil and water on Earth is likely caused by a mix of atmospheric gases with the loose soil on the surface of Venus, though this was not the most common cause. Landslides are most commonly composed of rocks and are located within deep canyon‐like regions near volcanoes. Studying these landslides is important for understanding the overall surface processes on the planet. The quantity of landslides was limited due to the resolution of the data, but future work plans to expand upon the global quantity of known landslides.

Halite minerals, widespread across Mars, have captured significant attention from geologists and astrobiologists for their potential to preserve biosignatures. Here, we report the preservation of organic matter within primary fluid inclusions in a halite duricrust, dated to 197.8 ± 36.2 ∼ 226.0 ± 29.0 ka BP, obtained from the Mars‐analog Qaidam Basin, NW China. Employing transmitted and fluorescent light microscopy alongside Raman spectroscopy, we identified abundant β‐carotene, lipids, and kerogen within these fluid inclusions. Notably, lipids were detected in situ and non‐destructively within fluid inclusions in salts. The presence of genes associated with microbial synthesis of carotenoids, such as β‐carotene, across diverse prokaryotes suggests that these microorganisms could be a potential source of β‐carotene preserved in halite salts. The consistent spatial co‐occurrence of β‐carotene and anhydrite within all identified anhydrite‐containing inclusions in this study implies potential interactions between carotenoid‐producing microorganisms and sulfate minerals. This study underscores the significance of the preservation of biosignatures in near‐surface salts in the search for life on Mars.

Helium (He) was first detected by remote spectroscopic observations of the Ultraviolet Visible Spectrometers (UVVS) instrument in Mercury's exosphere during the three Mariner 10 flybys in 1974 and 1975. Here, we derive the first in situ radial density profile of He in Mercury's extended exosphere by analyzing magnetic field and plasma measurements from 2011 to 2015 obtained by the MErcury Surface, Space ENvironment, Geophysics, and Ranging (MESSENGER) spacecraft. Our results indicate that most of the exospheric He follows a thermal trend. Interestingly, some events show density enhancements compared to the thermal profile which might be caused by sporadic (micro‐)meteorite impact events. These energetic He population events yield average He surface densities of ≈ ${\approx}$150 cm⁻³. The thermal He population on Mercury's day side can be reproduced with a surface density of ≈ ${\approx}$1,100 cm⁻³. The main exospheric He source can be identified as thermal release and thermal recycling of solar wind implanted He particles that agree well with the observations made by the Probing Of Hermean Exosphere By Ultraviolet Spectrometer (PHEBUS) instrument on board BepiColombo during its first Mercury fly by and exospheric simulations.

The formation of Mg‐/Alkali‐suites represents the most pronounced and oldest process in the magmatic evolution of the Moon. Fragments of these rocks have been identified among the samples collected by almost all lunar missions. In addition, remote observations indicate widespread distribution of these rocks on the Moon. However, collected samples remain restricted to the locations around the south‐eastern boundary of the Procellarum KREEP Terrane (PKT), limiting the ability to confirm information provided by remote observations and to investigate relationships between Mg‐/Alkali‐suites in different parts of the Moon. An important feature of these rocks delivered by Apollo missions is enrichment in incompatible elements, resulting in a frequent appearance of accessory zircon, which can be considered as one of the identifiers of rocks belonging to these suites. Consequently, the age of 4,311 ± 35 Ma and chemical characteristics of a zircon grain found in an agglutinate from Chang'e‐5 soil are interpreted as evidence of an origin in an Alkali or most likely Mg‐suite rock. The zircon grain is exotic to the landing site surrounded by the young ca. 2.0 Ga basaltic flows and was most likely delivered to the site as a distal impact ejecta. The location of the collected sample at the Chang'e‐5 landing site to the west of the Imbrium basin, remote from all other sample collection sites, confirms the wide distribution of Mg‐suite rocks, at least within PKT. The age of the zircon also provides the first indication that this early magmatism could have been contemporaneous across the nearside of the Moon.

Multiple lines of evidence indicate that liquid water‐rock interactions occurred on ancient Mars, particularly within the crust, where hydrothermal systems have been hypothesized. Such hydrothermal circulation (HC) can significantly lower temperatures in the crust, thereby restricting the viscoelastic relaxation of impact craters. Craters with minimal relaxation are characterized by their large depth‐to‐diameter ratio and prominent Bouguer gravity anomalies. Additionally, HC can induce magnetic anomalies through chemical remanent magnetization (CRM). Consequently, if HC was widespread on Mars, the gravitational signatures of unrelaxed craters may correlate with their magnetic signatures. To investigate how HC influenced the magnetic characteristics of the Martian crust, we focus on the region surrounding several unrelaxed craters in the southern highlands, where hydrothermal activity was likely prevalent. We use a newly developed joint inversion approach and model magnetization and density in such regions to investigate how hydrothermal systems affect those parameters. The inversion approach makes use of a mutual information term in which models with a parameter relationship are favored, that is, models in which magnetization and density distributions are correlated. Despite showing large Bouguer gravity anomalies and forming over 3.75 billion years ago, when the Martian dynamo was most likely active, investigated craters and surrounding regions exhibit minimal magnetic anomalies. We propose that this lack of magnetic signatures is most likely due to demagnetization of the crust through CRM, induced by HC long after the Martian dynamo ceased. Our findings suggest that deep, long‐lived hydrothermal systems—likely fueled by heat‐producing elements—were present, potentially creating habitable conditions on early Mars.

Mars may have had an ancient ocean filling its northern lowlands until around 3.5 billion years ago. The existence or lack of such a large body of water would have important implications on the ancient martian climate, landscapes, and habitability. One proposed piece of evidence is preserved paleoshorelines on the martian surface along the dichotomy boundary. Paleoshorelines on Earth are often recognized as subtle breaks in slopes that are laterally persistent and at consistent elevations. Is it probable, or even possible, that paleoshoreline topography on Mars might persist for 3.5 billion years, even at the slow erosion rates estimated for the martian surface? Here, we use topographic data showing well‐preserved Earth‐analog erosional paleoshorelines from Lake Bonneville in modern day Utah and numerically model their erosion at Mars‐like rates for 3.5 billion years. Depending on the chosen diffusivity value and scale of the terrain used in each experiment, identifiable paleoshoreline features may or may not persist after the modeled erosion; higher diffusivities and smaller scales favor paleoshoreline erosion and smaller diffusivities and larger scales favoring paleoshoreline preservation.

Titan is the only icy satellite in the solar system with a dense atmosphere. This atmosphere is composed primarily of nitrogen with a few percent methane, which supports an active, methane‐based hydrological cycle on Titan. The presence of methane, however, is intriguing, as its lifetime is likely much shorter than the age of the solar system due to its irreversible destruction by UV photolysis. To explain Titan's current atmospheric methane abundance, it is hypothesized that a replenishment mechanism is needed. One such mechanism may be crater forming impacts; a methane‐clathrate layer potentially covering the surface of Titan may act as a reservoir that releases methane when disrupted by impacts. Here, we perform impact simulations into methane‐clathrate layers to investigate the amount of methane released via impacts. Our simulations show that the amount of methane released into the atmosphere depends on both the impactor size and the methane‐clathrate layer thickness. A single 20‐km‐diameter impactor releases up to 1% of Titan's current atmospheric methane mass; the effect of impact obliquity and surface porosity may further increase the released mass by a factor of 2–3. The release rate from impacts is lower than the net loss rate by photolysis, but the released methane mass via impacts can enhance the lifetime of methane in Titan's atmosphere by up to 3%. Menrva‐sized (> ${ >}$400 km diameter) crater‐forming impacts directly liberate ∼ ${\sim}$15% of Titan's current atmospheric methane. The direct heating of the atmosphere by the impactor might contribute to additional crustal heating and methane release.

A fundamental constraint on the Moon's interior mass distribution is the 1.935‐km lunar center of mass (COM)–center of figure (COF) offset. Extant constraints on the mass asymmetry that generates the COM‐COF offset—commonly attributed to a crustal thickness asymmetry wherein the nearside crust is thinner than that of the farside—do not permit a unique solution for the lunar interior structure. Using simple analytical models of isostasy and porosity evolution, we quantify potential contributions to the lunar mass asymmetry from nearside‐farside asymmetries (specifically, spherical harmonic degree‐1 variations) in porosity, crustal basalts, and dense late‐stage magma ocean cumulates. We demonstrate that these asymmetries could simultaneously explain the COM‐COF offset and allow for a lunar crust that formed with globally uniform thickness and porosity. Scenarios with an excess of ∼10–44 km of late‐stage cumulates in the nearside relative to the farside allow for full ranges of 5%–12% nearside anorthosite porosity, 1–2 km of excess nearside basalts, and nearside crustal thickness of either 30 km or 38 km. Furthermore, under specific conditions (30‐km nearside crust with low porosity and high late‐stage cumulate density of ∼3,600 kg/m³), the COM‐COF offset permits an initially uniform crust as well as a present‐day crust with uniform thickness. While observational constraints do not favor perfectly symmetric present‐day crustal thickness, our analyses highlight the importance of higher fidelity characterization of the lunar interior structure and the use of caution in investigations that fundamentally rely on lunar crustal thickness constraints.

The Mars Exploration Rovers (MER) Spirit and Opportunity, sent to Gusev crater and Meridiani Planum, respectively, determined the chemical composition of martian materials with their Alpha Particle X‐ray Spectrometers (APXS). The MER APXS was effective at routinely quantifying major, minor, and select (Ni, Zn, Br) trace elements at levels down to ∼50 ppm but often reached detection limits for other trace elements (e.g., Ga and Ge during typical individual analyses of a single sample). To enable precise quantification of additional trace elements, a database of MER APXS target properties (e.g., location, feature, target, formation, target type, sample preparation) was created, enabling the construction of a library of composite (i.e., summed) spectra with improved statistics. Composite spectra generated from individual spectra with shared characteristics have a higher potential for resolving and thus quantifying trace element peaks. Analyses of composite spectra from Meridiani Planum and Gusev crater indicate that the molar Ga to Al ratio is relatively constant throughout both regions and is in line with predicted values for the martian crust and measured values in martian meteorites. Gallium and aluminum likely do not volatilize and instead remain together during volcanism and aqueous alteration. In contrast, Ge is enriched at least an order of magnitude relative to martian meteorites, and the molar Ge to Si ratio is much more variable across Meridiani Planum and Gusev crater. Enrichment of Ge may be a global phenomenon resulting from volcanic outgassing of volatiles and subsequent overprinting by local mobilization and enrichment via hydrothermal fluids.

The observed geochemical heterogeneity on the surface of Mercury is key to understanding the planet's volcanic activity and mantle conditions. The Caloris basin shows a diversity in elemental composition, spectral properties, and geomorphology, both within and around it. However, the relationship among these characteristics has not been well understood due to the mismatch in spatial resolutions of the available observation data. This study investigates the geochemical end‐members around the Caloris basin, overcoming the limitation of the low spatial resolution of MESSENGER's X‐Ray Spectrometer (XRS) data. End‐member units are defined using spectral and geomorphological units from MESSENGER's VIS‐NIR spectral data and high‐resolution images, with the assumption of homogeneous elemental compositions within each unit. A mixing model is constructed to reproduce the XRS data by mixing the end‐members, and we solve the inverse problem to calculate the respective end‐member compositions. Five end‐member compositions were determined, including those corresponding to the post‐Caloris volcanic smooth plains interior and exterior to the basin and surrounding pre‐Caloris crust. Two smooth plains units, which are geomorphologically indistinguishable but spectrally distinct, showed a compositional variation consistent with magma evolution through fractional crystallization. This suggests that they originated from parent magmas with a common composition. The pre‐Caloris crust units showed a large compositional variation, ranging from low‐ to high‐Mg content, implying the potential existence of high‐Mg crusts comparable to the HMR. The observed crustal diversity could be explained by relatively minor heterogeneity in source mantle compositions and/or conditions of partial melting within the mantle.

In volcanically active planetary bodies, the depths and longevity of crustal magma storage critically control eruptibility and crustal composition. A paucity of relevant observations and models has challenged our understanding of the development of crustal magma storage systems on Mars and their role in the apparent lack of evolved compositions. Here, we use numerical modeling, together with recent results from the InSight mission, to study the evolution of crustal magma chambers on Mars and conditions that promote their growth and eruptibility. We find that the martian crust can be divided, by depth, into three major domains. For Elysium Planitia (the InSight landing site), at depths ≤15 km (∼1.5 kbar), trapped magma pods are small, short‐lived, with high diking potential, hindering the production of evolved compositions. While depths >25 km (∼2.5 kbar) can host long‐lived magma chambers, 15–25 km (∼2 ± 0.5 kbar) marks a transition where magma chambers could grow while concurrently expelling magma. Interestingly, this narrow depth window overlaps with the depth of an intra‐crustal discontinuity reported by InSight, suggesting a possible magmatic origin for the discontinuity. We further show that the crustal thermal gradient strongly controls this transition depth, indicating the possible variability of the domain depths in different terrains. Our results also support the likelihood of deep‐seated magmatism beneath the seismically active Cerberus Fossae, suggesting that magmatism continues to play a major role in shaping the martian crust.

One of the central questions to be addressed by the NASA Psyche mission is the composition and origin of the asteroid (16) Psyche. In preparation of the mission's planned arrival in 2029, in this work we explore how different internal structures may be expressed on (16) Psyche. We model the core size and shape that may exist at (16) Psyche given currently available constraints. We find that if Psyche has compositional layering, then tectonic features accommodating large amounts of compression from pore closure and a freezing core may be present. We also find that because of (16) Psyche's elongated shape and fast rotation, it is important to properly reference the elevations to the geoid (i.e., the accelerations a particle will feel) when interpreting possible mass wasting effects.

Plain Language Summary The Martian nightside ionosphere has not been as well studied as the dayside ionosphere, due to measurement restrictions and its more chaotic nature compared to the dayside. This nature is a result of the primary energy source for ionization on the nightside: electron precipitation, while the dayside is dominated by more predictable photoionization. Electron precipitation has a complex dependence on many dynamic factors, including electron sources on the dayside and in the solar wind, the Martian magnetosphere and its interaction with the solar wind and Interplanetary Magnetic Field (IMF), neutral atmospheric abundance and extent, etc. This complexity has until now prevented the inclusion of nightside ionization in Mars Global Ionosphere‐Thermosphere Models (GITMs). We have developed an empirical model of ionization on the nightside for the most abundant species based on several years of data from the MAVEN spacecraft. This empirical model provides a realistic ionization source for input to GITMs, allowing more accurate modeling of the nightside ionosphere. Eventually this will enable a more complete characterization of the total global ionospheric response to the various parameters which can affect ion production. Here we present the empirical model as well as initial results of these improved nightside modeling efforts.

At JGR: Planets, the peer review process is critical to ensuring that the published articles are based on sound scientific principles, follow state‐of‐the‐art techniques while acknowledging relevant prior results, and present exciting discoveries or novel understanding of the fundamental processes that affect solar system objects. JGR: Planets covers a broad range of topics addressing every aspect of geoscience with the only requirement that the work addresses planetary processes. The wide breadth of topics published is reflected by our editorial team composed in 2024 of associate editors Adrian Brown, Jun Cui, Joel Davis, Leigh Fletcher, Sierra Ferguson, Yang Liu, Ananya Mallik, Germán Martínez, Anna Mittelholz, Molly McCanta, Katarina Miljkovic, Naomi Murdoch, Ryan Park, Arianna Piccialli, Laura Schaefer, Mariek Schmidt, Yasuhito Sekine, Kelsi Singer, Michael Sori, Norihiko Sugimoto, Jamey Szalay, David Trang, and Zhiyong Xiao in addition to the editors who authored this note. We rely on the expertise of the community to vet the articles submitted to the journal. In 2024, JGR: Planets benefited from 1,269 reviews provided by 816 unique volunteer referees. We also received help from organizers and guest editors working on eight active special collections. To these volunteers: We are truly grateful that you chose to dedicate your time and energy to evaluate manuscripts and to advise us on the suitability of each manuscript for JGR: Planets, often suggesting ways to improve the papers. We know that all our volunteers juggle many duties, both professional and personal. On behalf of the entire editorial board of JGR: Planets, we express our heartfelt gratitude to the many scientists who support this journal. Thank you! You are performing a valued service to this journal and to the community.