Journal of Geophysical Research: Planets最新文献

{"title":"Experimental Constraints on the Formation of Niningerite and Oldhamite Under Highly Reducing Conditions: Implications for Sulfide Formation in EH3 Chondrites","authors":"N. Imae","doi":"10.1029/2026JE009763","DOIUrl":"https://doi.org/10.1029/2026JE009763","url":null,"abstract":"<p>Enstatite chondrites record highly reducing conditions in the early solar nebula, yet the origin of their abundant sulfides remains unclear. Niningerite (MgS) and oldhamite (CaS) are ubiquitous in EH3 enstatite chondrites and distinguish them from other chondrite groups. To investigate sulfide formation, we conducted sulfidation experiments under ultra-reducing conditions using evacuated silica-glass tubes to reproduce extremely low oxygen pressure environments. Experiments at 1,200–1,420°C and IW−5 to −6 with pyrrhotite–troilite buffers examined reactions of Mg- and Ca-bearing silicates with sulfur-rich gas. Niningerite formed from forsterite–enstatite, and oldhamite from diopside, producing granular niningerite surrounding olivine and enstatite and granular oldhamite associated with diopside, coexisting with cristobalite and enstatite. Mg–Fe compositions of synthetic niningerite are included in those in EH3 chondrites. In the experiments, niningerite and oldhamite did not form within the coexisting Fe-S reservoir, whereas natural EH3 meteorites show enrichment of these sulfides in metal-sulfide nodules, a key discrepancy with natural EH3 textures. This suggests that the precursors of chondrules and metal nodules—aggregates of chondrules and metal nodules—underwent melting and segregation events, during which niningerite and oldhamite preferentially partitioned into the metal nodules. These multi-stage high-temperature processes provide new constraints on the physicochemical environment of sulfide formation in the inner solar nebula.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 8","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026JE009763","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148753131","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Currents in the Martian Ionosphere: Cases Without Strong Crustal Magnetic Fields","authors":"JunFeng Qin,&nbsp;Shannon Curry,&nbsp;Wenyi Sun,&nbsp;Matthew Fillingim,&nbsp;Robert Lillis,&nbsp;Yingjuan Ma,&nbsp;Yaxue Dong,&nbsp;Robin Ramstad,&nbsp;Shaosui Xu,&nbsp;Dave Mitchell","doi":"10.1029/2026JE009825","DOIUrl":"https://doi.org/10.1029/2026JE009825","url":null,"abstract":"<p>The Martian ionosphere hosts complex current systems driven both by solar wind interactions and neutral wind dynamo processes. While the global patterns of these current systems have been statistically examined, their detailed structures and orientations remain poorly constrained. Using magnetic field observations from NASA's Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft during the Deep Dip 2 campaign, we resolve the horizontal components of dayside ionospheric currents over regions without strong Crustal Magnetic Fields (CMF). The currents are most prominent between 130 and 150 km altitude, with peak magnitudes of ∼1 μA/m², and are oriented counterclockwise from, and roughly perpendicular to, the draped Interplanetary Magnetic Field in the horizontal plane when viewed from above. Theoretically calculated neutral wind-driven dynamo currents show significant discrepancies from the derived currents, likely reflecting uncertainties in neutral winds and conductivities. In contrast, simulated magnetohydrodynamic (MHD) ionospheric currents, which are purely solar wind-induced in the model, share similar features with the derived currents. We conclude that, for the four cases examined here, which were sampled in near-subsolar regions with weak CMF, the derived ionospheric currents are more consistent with a solar wind-induced origin, whereas neutral wind-driven dynamo currents may play only a minor role under these conditions.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 8","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026JE009825","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148753009","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Role of Magmatic Styles in Planetary Thermal Evolution Models","authors":"C. Herrera,&nbsp;A.-C. Plesa,&nbsp;J. Maia,&nbsp;D. Breuer","doi":"10.1029/2025JE009635","DOIUrl":"https://doi.org/10.1029/2025JE009635","url":null,"abstract":"<p>Previous studies that investigated the effects of magmatism on the interior dynamics, in particular for Earth-sized planets, suggest that magmatism leads to more efficient mantle cooling. However, the extent to which different magmatic styles influence the thermal evolution of planets, and in particular smaller rocky bodies, has not yet been systematically investigated. Using geodynamic models, we compare the evolution of Mercury-, Mars-, the Moon-, and Venus-like bodies under “fully intrusive” and “fully extrusive” magmatism. For all planets, fully intrusive cases result in hotter and thinner lithospheres and, at the same time, colder deep mantles and core-mantle boundaries compared to fully extrusive cases. During planetary evolution, intrusive models generate more melt and at shallower depths than extrusive models, thereby potentially leading to different melt compositions. While the global average temperature of the entire silicate interior is lower on Venus in the intrusive scenario compared to the extrusive scenario, the opposite is true for smaller bodies. This can be explained not only by their smaller size and lower temperatures, which allow for less melt production than on Venus, but also by their lithospheric regimes with lower mobility due to colder lithospheric temperatures. For large planets such as Venus, when an intrusive magmatism dominates, which promotes lithospheric recycling, cold recycled material leads to higher cooling efficiency than in the extrusive case. The release of latent heat due to the crystallization of intruded melt can further amplify lithospheric recycling for large bodies, while for smaller planets this generally leads to slower cooling.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 8","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JE009635","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148753262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Vertical Retention of Water Ice in Lunar Regolith Under Vacuum Conditions","authors":"Juping Gu,&nbsp;Yu Xu,&nbsp;Shanzhi Lyu,&nbsp;Qinggong Wang","doi":"10.1029/2026JE009862","DOIUrl":"https://doi.org/10.1029/2026JE009862","url":null,"abstract":"<p>The presence of water ice in permanently shadowed regions (PSRs) of lunar poles has been widely confirmed by remote sensing. However, its vertical retention within the regolith remains controversial due to the lack of in situ measurements. In this work, we build a small-scale vacuum-cryogenic experimental platform and study the vertical retention pattern of water ice in lunar regolith. A simulated heat flux is applied beneath a thick lunar soil layer under the vacuum-cryogenic conditions. The transient concentration of water vapor released into the vacuum chamber is monitored, and the final vertical distribution of water content in the lunar regolith after a cryogenic cycle is demonstrated. The results show that water ice at the surface of lunar regolith is prone to release into the vacuum, while below a certain depth beneath the surface, water ice is driven by heat flux from the bottom and migrates upward. Then, water ice accumulates in a middle layer where the concentration is independent of the magnitude of the heat flux applied to the same sample. The initial water content in the lunar regolith simulants has a limited influence on the thermodynamics pattern of water retention. The present results give important implications for the retention of water ice in PSRs on the moon: the heat input from the lunar interior drives water ice to migrate upward, and then water ice is retained in the middle layer at the maximum abundance, since this layer provides balanced temperature and local pressure to preserve the water ice.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 8","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148753059","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reconstructing Europa's Atmosphere From \u0000 \u0000 \u0000 \u0000 H\u0000 2\u0000 +\u0000 \u0000 \u0000 ${mathbf{H}}_{mathbf{2}}^{+}$\u0000 Pickup Ions Detected During the Juno PJ45 Flyby","authors":"Shane R. Carberry Mogan,&nbsp;Andrew R. Poppe,&nbsp;Lucas Liuzzo,&nbsp;Jamey R. Szalay,&nbsp;Sean P. Ellis,&nbsp;Robert E. Johnson,&nbsp;Lorenz Roth","doi":"10.1029/2026JE009724","DOIUrl":"https://doi.org/10.1029/2026JE009724","url":null,"abstract":"&lt;p&gt;We use a suite of single-species (&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;H&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{H}}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;) and multispecies (&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;H&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;mo&gt;+&lt;/mo&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;mo&gt;+&lt;/mo&gt;\u0000 &lt;mi&gt;H&lt;/mi&gt;\u0000 &lt;mo&gt;+&lt;/mo&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{H}}_{2}+{mathrm{O}}_{2}+mathrm{H}+mathrm{O}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;) Direct Simulation Monte Carlo models of Europa's atmosphere to interpret the &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msubsup&gt;\u0000 &lt;mi&gt;H&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;mo&gt;+&lt;/mo&gt;\u0000 &lt;/msubsup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{H}}_{2}^{+}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; pickup ions detected by &lt;i&gt;Juno&lt;/i&gt; at distances beyond &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $2$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; Europa radii &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mfenced&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;R&lt;/mi&gt;\u0000 &lt;mi&gt;E&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mfenced&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $left({R}_{E}right)$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; during the Perijove 45 flyby. The observations require contributions from both Europa's &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;H&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{H}}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; atmosphere and a background &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msubsup&gt;\u0000 &lt;mi&gt;H&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;mo&gt;+&lt;/mo&gt;\u0000 &lt;/msubsup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{H}}_{2}^{+}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; torus; the latter has local densities ranging","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 8","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026JE009724","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148752737","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Minerals in Iron and Titanium Skeletal Textures in Nakhlites MIL 090030, MIL 090136, MIL 090032, and MIL 03346: Comparative Analysis With Terrestrial Analogues From Canary Islands, Spain","authors":"Leire Coloma,&nbsp;Fernando Alberquilla,&nbsp;Julene Aramendia,&nbsp;Gorka Arana,&nbsp;Ed Cloutis,&nbsp;Juan Manuel Madariaga","doi":"10.1029/2026JE009954","DOIUrl":"https://doi.org/10.1029/2026JE009954","url":null,"abstract":"<p>The presence of minor minerals is a key factor distinguishing meteorite types, as they provide valuable insights into the formation processes, surface conditions, and evolutionary history of their parent bodies. In Martian nakhlites, one of the most distinctive minor phases is iron-titanium oxides forming characteristic skeletal textures. However, their mineralogical nature remains debated, with most studies identifying them as titanomagnetite, whereas others suggest ilmenite skeletal textures. This study uses Raman imaging to investigate the mineralogical distribution of these skeletal textures. Additionally, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) was used to assess titanium concentration gradients from the exterior to the core of the structures. Chemometric methods were applied to differentiate and represent the mineralogical distribution. Furthermore, similar skeletal textures observed in terrestrial analogs from the Timanfaya and Maciot volcanoes (Lanzarote, Canary Islands, Spain) were analyzed using Raman imaging to evaluate potential similarities or differences in composition and formation processes with those found in the paired meteorites studied. The results show that the skeletal textures in the MIL nakhlites consist of ilmenite surrounded by titanomagnetite and magnetite. In contrast, in the analogs, two types of skeletal textures were identified: some composed of ilmenite and others of magnetite. These findings indicate that skeletal oxide textures in Martian and terrestrial samples from two field sites formed through distinct processes and constitute sensitive recorders of the evolution of mafic magmatic systems. These differences reflect restricted redox conditions and limited subsolidus re-equilibration in the MIL nakhlites, versus oxidation and faster cooling histories in the terrestrial analogs.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 8","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026JE009954","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148752876","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Fluid-Mediated Alteration Process on the Howardite Parent Asteroid Recorded by Pyroxene Decomposition to Fe–Ti–Cr Oxides and Amorphous Silica","authors":"Lilin Huang,&nbsp;Yanxue Wu,&nbsp;Riqiang Wen,&nbsp;Chunwen Huang,&nbsp;Chunmei Li,&nbsp;Jiangmin Ma","doi":"10.1029/2026JE010002","DOIUrl":"https://doi.org/10.1029/2026JE010002","url":null,"abstract":"<p>In this study, we report amorphous silica dendrites in three eucritic pyroxene grains from a howardite meteorite NWA 14701. These textures exhibit enhanced metasomatic features characterized by irregular or rounded amorphous silica containing numerous nanoscale ilmenite and chromian ulvöspinel inclusions distributed along both sides of fractures to form dendritic networks in the host pyroxene. These dendritic networks manifest as a discontinuous series of discrete, equant-shaped silica masses that project as embayments into the walls of the fractures. We propose that the formation mechanism of these amorphous silica dendrites was related to fluid-mediated alteration processes, as recorded by pyroxene decomposition to Fe–Ti–Cr oxides and amorphous silica along fractures. Such fluid preferentially leached and removed highly mobile cations (e.g., Mg, Ca, and Fe). Concomitantly, high field-strength elements (Cr and Ti) with extremely low mobility became passively enriched in situ due to their limited transportability within the fluid phase, subsequently crystallizing as ilmenite and chromian ulvöspinel at nanoscale dimensions. Meanwhile, the Si-O framework of the original host pyroxene, depleted in most interstitial cations, was preserved as a chemically inert amorphous silica framework. Our work suggests that the amorphous silica dendrites represent an unique type of secondary alteration texture on the HED parent asteroid that was previously undocumented, and they may also occur on other airless, differentiated planetary bodies.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 8","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148752431","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"IR-Raman Study on Hexahydrite Amorphization Under Vacuum and Low Temperatures","authors":"S. De Angelis,&nbsp;F. Furnari,&nbsp;M. Ferrari,&nbsp;E. La Francesca,&nbsp;C. Carli,&nbsp;G. Piccioni,&nbsp;S. Rubino,&nbsp;S. Stefani,&nbsp;F. Tosi","doi":"10.1029/2026JE009723","DOIUrl":"https://doi.org/10.1029/2026JE009723","url":null,"abstract":"<p>Hexahydrite (MgSO₄·6H₂O) is among the possible candidates of the hydrated salts composing the “non-icy” materials on the surface of Europa. However, given the conditions of extreme vacuum characterizing the surfaces of icy and other airless Solar System bodies, a crucial aspect is to determine the conditions of stability of such hydrated salts in a wide range of pressures from ambient to high vacuum. The effect of varying temperatures in conjunction with variable vacuum is another important aspect to be considered. Studying the stability field of such compounds is crucial to establish the conditions of their presence on icy moons. In this work, we conducted an infrared (1–12 μm) and Raman spectral study on hexahydrite samples from ambient pressure to high vacuum, at ambient and low temperatures. We observe two main effects occurring upon lowering the pressure at which the sample is exposed, that is (a) de-hydration of the sample and consequent (b) loss of crystallinity and increase of structural disorder of the material. While the de-hydration is clear from the notable modification of H₂O absorption bands in the near-infrared, the effect of loss of crystallinity is observable in the mid-IR spectral region and also confirmed by Raman analyses. The transition is marked by the progressive loss of fine structure in the 1.5 and 2 μm hydration bands and by the collapse of the ∼9 μm Reststrahlen peak. Our measurements provide important laboratory constraints concerning the stability conditions of such hydrated materials that should provide aid in interpretation of mission data.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 8","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148752545","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydrocode Simulation of Lonar Impact Event: Insights Into Brittle Deformation and Formation of Simple Craters in Basalt","authors":"Gourab Dey,&nbsp;Rajit Das,&nbsp;Amar Agarwal,&nbsp;Jakob Wilk","doi":"10.1029/2026JE009739","DOIUrl":"https://doi.org/10.1029/2026JE009739","url":null,"abstract":"<p>The Lonar crater is one of the few well-preserved impact craters on Earth and provides an important analog for impact processes in basaltic targets. We model the Lonar impact event using iSALE-2D simulations incorporating ANEOS basalt–dunite equations of state, rock strength, and resolution tests to determine the transient crater dimensions, shock pressure, strain distribution, and fracture formation, bridging numerical simulations with field observations. The best-fit model produces a transient cavity ∼1,415 m in diameter and ∼530 m in depth at ∼5 s after impact, evolving into a final crater ∼1,900 m in diameter. Peak shock pressures of ∼10 GPa and temperatures of ∼1000 K occur at the crater floor, while pressures of 2–3 GPa occur at the crater wall. The simulation tracks the progressive formation of near-surface fractures followed by radial and concentric fractures, accompanied by zones of high plastic strain near the crater floor. By linking the modeled deformation with field-documented fracture geometries, this study provides new constraints on the mechanical and thermal evolution of Lonar-scale impact craters in basaltic targets. Modeled pressure conditions at the crater wall agree with the field occurrence of a shatter cone. Comparison with empirical scaling relations and resolution tests demonstrates that the crater dimensions, shock field, and fracture architecture are robust and converge at resolutions of CPPR ≥ 20. These results refine constraints on the formation conditions of the Lonar crater and provide a modeling framework for interpreting impact cratering in basaltic terrains on Earth and other planetary bodies.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 8","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148752546","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Topographic Relaxation of Tegid Crater: Implications for Processes on Europa's Ice Shell","authors":"M. L. Caussi,&nbsp;A. J. Dombard,&nbsp;Jeffrey M. Moore,&nbsp;Oliver L. White,&nbsp;Paul M. Schenk","doi":"10.1029/2025JE009390","DOIUrl":"https://doi.org/10.1029/2025JE009390","url":null,"abstract":"<p>Jupiter's moon Europa stands out for its potential to harbor life beneath an icy shell that probably overlies a global ocean, yet the shell's thickness and thermal state remain poorly constrained. Impact craters offer a window into Europa's interior because their shapes and post-impact evolution reflect subsurface mechanical properties and thermal gradients. Tegid crater, spanning roughly 30 km in diameter, features a uniquely flattened dome in its center. To explore how this morphology arose, we used finite element simulations that incorporate remnant impact heat, to assess the influence of post-impact viscoelastic relaxation on the final morphology of Tegid. Our results indicate that, for a high heat flux of 60 mW m⁻², relaxation is pronounced but does not fully account for the dome's height or unusually flattened appearance. For heat fluxes of 40 mW m⁻², relaxation is not pronounced and does not sufficiently explain Tegid's topographic height. These findings suggest that additional mechanisms might be involved that account for Tegid's observed topography. By integrating crater morphology studies with thermal and mechanical modeling, we can gain critical insights into the thickness and rheology of Europa's ice shell, which has implications for habitability.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 8","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148752430","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}