Journal of Geophysical Research: Planets最新文献

{"title":"Thermomagnetization of a Basaltic Lunar Regolith Simulant Driven by Fe Redistribution and Magnetic Phase Formation","authors":"Chunyu Peng,&nbsp;Xianze Ao,&nbsp;Wengan Sun,&nbsp;Shuyi Chen,&nbsp;Yunfei Xu,&nbsp;Hanchen Xu,&nbsp;Yuan Zhao,&nbsp;Honglun Yang,&nbsp;Biao Xie,&nbsp;Mingqi Sun,&nbsp;Gang Pei","doi":"10.1029/2026JE010010","DOIUrl":"https://doi.org/10.1029/2026JE010010","url":null,"abstract":"<p>The magnetic properties of lunar regolith are controlled by the abundance, valence state, grain size, and mineralogical occurrence of Fe-bearing phases. However, how weakly magnetic Fe²⁺ hosted in silicates and glassy components responds to thermal processing requires further study. Here, we investigate the temperature-dependent magnetic and mineralogical evolution of a basaltic lunar regolith simulant during controlled heating under low oxygen partial pressure. Vibrating sample magnetometry shows that the mass-specific magnetization measured at 20 kOe increases from 0.551 emu g⁻¹ for the control sample to 0.703 emu g⁻¹ after heating at 800°C, corresponding to a 27.5% increase, but decreases markedly at higher temperatures. Mössbauer spectroscopy reveals that the control sample is dominated by Fe²⁺-bearing components, whereas heating at 800°C produces metallic Fe and a magnetically ordered ferric component. X-ray diffraction and transmission electron microscopy further indicate the formation of a magnetite-like Fe-rich oxide phase. These results suggest that at approximately 800°C heating promotes Fe redistribution from olivine- and glass-related environments into metallic Fe, magnetite-like oxide, and pyroxene-like hosts. At higher temperature, these magnetic phases are no longer retained, and Fe is redistributed back into predominantly Fe²⁺-bearing environments. This study provides a plausible mechanistic interpretation based on Fe redistribution and magnetic-phase formation in basaltic lunar regolith simulants, with implications for the magnetic evolution and potential beneficiation of lunar surface materials.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 9","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148994208","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":"Tracking Deep Mantle Melting on Mars Using Phobos Tides","authors":"A. Guinard,&nbsp;A. Fienga,&nbsp;A. Mémin,&nbsp;D. Antonangeli","doi":"10.1029/2026JE009726","DOIUrl":"https://doi.org/10.1029/2026JE009726","url":null,"abstract":"<p>We study the deep internal structure and rheological state of Mars by analyzing its response to tidal forces exerted by Phobos and by introducing a melt fraction in the mantle layers. Motivated by recent seismic evidence for a basal molten layer near the base of the Martian mantle, we explore the distribution of melt within the mantle and its influence on the tidal response. Assuming a 3-layers mantle structure, tidal deformations alone provide a radially dependent melt fraction profile, with partial melting concentrated in the deepest layer. Adding thermal constraints from recent solidus and liquidus determinations refines these limits, confirming that only the deepest part of the mantle might exhibit significant melting. The inferred densities for the mantle and core align with previous studies and point toward iron-rich mantle layers and a core enriched in light elements. The excess density of the deepest layer favors iron enrichment rather than hydration. Viscosity reduction profiles suggest a transition from solid to partially molten behavior above the core-mantle boundary, consistent with the presence of a thin basal molten layer enriched in iron and radiogenic elements. However, the rheological parameters <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>α</mi>\u0000 </mrow>\u0000 <annotation> $alpha $</annotation>\u0000 </semantics></math> and <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>β</mi>\u0000 </mrow>\u0000 <annotation> $beta $</annotation>\u0000 </semantics></math> deviate from laboratory estimates for terrestrial materials, suggesting that the anelastic behavior of the Martian mantle may differ from terrestrial analogs. This highlights the need for experimental studies on iron-rich, melt-bearing compositions representative of Mars.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 9","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026JE009726","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148994587","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":"Thermal Conductivity of Lunar Simulant With Varying Water-Ice Saturation and Morphology","authors":"Yi Dong,&nbsp;Lin Lv,&nbsp;Pengzhi Pan,&nbsp;Liang Guo,&nbsp;Chao Zhang,&nbsp;Hejuan Liu","doi":"10.1029/2026JE009900","DOIUrl":"https://doi.org/10.1029/2026JE009900","url":null,"abstract":"<p>Water ice in lunar polar regolith is both a scientific target and a potential resource for sustained exploration, but its abundance cannot be inferred reliably unless its physical morphology is also constrained. Here we measure the thermal conductivity of a lunar regolith simulant under low-temperature and low-pressure conditions relevant to the lunar polar environment, with systematic variations in dry density, ambient pressure, temperature, ice saturation, and pore-ice morphology. Two contrasting specimen-preparation routes were used to generate ice-cemented (IC) and inter-mixed fabrics. Low-field nuclear magnetic resonance measurements and soil-freezing characteristic analysis show that unfrozen water is negligible under the thermal conductivity test conditions, so the observed response can be interpreted primarily in terms of solid ice content and ice morphology. The results show that the thermal conductivity of the dry simulant is governed jointly by density, pressure, and temperature through changing contributions from particle-contact conduction, pore-gas conduction, and radiative transfer. For ice-bearing specimens, thermal conductivity increases with ice saturation in both fabrics, but the conductivity-saturation trajectories differ fundamentally because the pore ice is distributed differently. Inter-mixed specimens, in which ice occurs mainly as discrete pore-filling particles, show a gradual increase close to lower-bound composite predictions, whereas IC specimens, in which ice bridges and cements particle contacts, show a much faster sigmoidal increase with saturation. These results demonstrate that thermal conductivity is not simply a proxy for ice abundance, but a joint indicator of ice content and pore-ice morphology, with direct implications for interpreting future thermophysical measurements in the lunar south polar region.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 9","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148943375","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":"Variation of Venusian Gravity Wave Absolute Momentum Fluxes and Drag as Retrieved From the Akatsuki Mission","authors":"Erdal Yiğit,&nbsp;Emilia Sloan","doi":"10.1029/2026JE009719","DOIUrl":"https://doi.org/10.1029/2026JE009719","url":null,"abstract":"&lt;p&gt;Using temperature retrievals from Akatsuki radio occultation measurements, we characterize gravity wave activity as a function of vertical wavenumber and altitude. For the first time, we estimate the absolute horizontal momentum fluxes and the magnitude of the gravity wave drag (i.e., wave acceleration), assuming a horizontal wavelength of 300 km. Our retrievals quantify the potential effects of these waves in the Venusian middle atmosphere between 40 and 95 km. Observed temperature perturbations, which are indicative of atmospheric gravity wave activity, reach amplitudes of approximately &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;±&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $pm $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;10K, and significant momentum flux (10–30 &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mi&gt;m&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{m}}^{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mi&gt;s&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{s}}^{-2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;) and wave drag (0.003–0.03 m &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mi&gt;s&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{s}}^{-2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;) are detected across all analyzed profiles. The inferred wave drag represents a lower bound on the total gravity wave-induced drag in the Venusian atmosphere. Momentum flux tends to increase exponentially with altitude below approximately 50–60 km, then peaks and attenuates at higher altitudes. Wave drag becomes prominent where momentum flux begins to decrease, which is a consequence of wave dissipation. Both quantities exhibit multiple altitude-localized maxima, which is consistent with upward wave propagation followed by dissipation at different altitudes for different vertical wavelengths. Damping due to gravity wave nonlinear interactions is likely to play the major role in limiting the growth of wave amplitudes and fluxes with height. These features are observed across a range of latitudes and local times. Overall, the results provide observational constraints on gravity wave momentum transport and dissipation in the Venu","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 9","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026JE009719","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148943264","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":"Ferric Chloride: The Venusian Unknown UV Absorber?","authors":"Joanna V. Egan,&nbsp;Wuhu Feng,&nbsp;Alexander D. James,&nbsp;James Manners,&nbsp;Daniel R. Marsh,&nbsp;Sébastien Lebonnois,&nbsp;Franck Lefèvre,&nbsp;Aurélien Stolzenbach,&nbsp;John M. C. Plane","doi":"10.1029/2025JE009634","DOIUrl":"https://doi.org/10.1029/2025JE009634","url":null,"abstract":"<p>Near-ultraviolet imaging of the planet Venus reveals inhomogeneous absorption features in the otherwise bright clouds. This absorption has been studied for nearly 100 years, but identification of the near-UV absorber remains one of the largest open questions in Venusian research. Based on a multiple scattering radiative transfer model, the observed absorption between 300 and 600 nm can be produced by 1.0–1.2 wt% ferric chloride (FeCl₃) in the mode 1 (∼0.2 μm radius) sulfuric acid cloud droplets—less than the in-cloud iron mass loading measured during the Venera-12 mission. We present a novel chemical network within a global chemistry-climate model, which provides the required source of FeCl₃ in the upper cloud region from the reaction of Fe-containing molecules, produced by the ablation of cosmic dust particles, with atmospheric HCl. A residence lifetime of ∼3,000 years is required to provide sufficient optical absorption from a purely meteoric source of FeCl₃.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 9","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JE009634","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148943265","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 Shared Magma Source for the Olivine-Rich Units in Jezero Crater, Mars","authors":"Shounak Dutta,&nbsp;Paul D. Asimow,&nbsp;Kenneth A. Farley,&nbsp;Arya Udry,&nbsp;Nicholas Randazzo,&nbsp;Kenneth H. Williford","doi":"10.1029/2026JE009746","DOIUrl":"https://doi.org/10.1029/2026JE009746","url":null,"abstract":"<p>The Margin Unit, explored by the Mars 2020 <i>Perseverance</i> rover in Jezero crater, is a distinct olivine-rich lithology whose origin has remained unresolved due to extensive alteration and lack of preserved primary textures. While hypotheses for its formation range from sedimentary to igneous, recent geochemical data allow for quantitative testing of these scenarios. To test the igneous hypothesis, we applied Markov Chain Monte Carlo simulations with MELTS thermodynamic modeling to assess whether the observed olivine and spinel compositions in the Margin Unit are consistent with igneous fractional crystallization. Our simulations reproduce the observed systematic increase in spinel TiO₂/Cr₂O₃ with decreasing olivine forsterite content, a pattern difficult to reconcile with sedimentary mixing processes, providing strong evidence for an igneous origin for the Margin Unit. Furthermore, continuing evolution of the same magma leads to coexisting olivine and clinopyroxene compositions that suggest a genetic link between the Margin Unit and the crater floor olivine-rich unit, Séítah, pointing toward the existence of an extensive igneous complex within Jezero crater. Modeled magma compositions for the Margin Unit are comparable to the parental melt compositions of the chassignite group of Martian meteorites, implying conditions necessary to produce chassignite-like melts were already established early in Noachian Mars.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 9","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148943110","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":"Numerical Simulations of the Central Peak to Peak Ring Transition of Complex Craters","authors":"Huacheng Li,&nbsp;Zongyu Yue","doi":"10.1029/2025JE009537","DOIUrl":"https://doi.org/10.1029/2025JE009537","url":null,"abstract":"&lt;p&gt;The block acoustic fluidization (AF) model has been widely used to simulate the collapse of complex impact craters. However, there is currently no consensus on the appropriate values of AF parameters in numerical modeling, and those used in previous studies fail to reproduce the observed central peak (CP) to peak ring (PR) transition diameter of lunar craters. In this study, we conduct 350 simulations using the hydrocode SALEc-2D with varying AF parameters to identify suitable values and analyze transient/final crater morphologies. Our simulations demonstrate that the morphology of final crater and CP/PR formation are highly sensitive to the AF parameters. Comparison with observed craters on the Moon shows that all tested AF parameter sets tend to overestimate the CP or PR diameter. Nevertheless, two groups of block AF parameter combinations are able reproduce the observed CP-PR transition diameter and the final crater depth-diameter relation: one with &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;γ&lt;/mi&gt;\u0000 &lt;mi&gt;β&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;mo&gt;=&lt;/mo&gt;\u0000 &lt;mn&gt;200&lt;/mn&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;mn&gt;300&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${gamma }_{beta }=200-300$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, &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;γ&lt;/mi&gt;\u0000 &lt;mi&gt;η&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;mo&gt;=&lt;/mo&gt;\u0000 &lt;mn&gt;0.03&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${gamma }_{eta }=0.03$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, and another with &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;γ&lt;/mi&gt;\u0000 &lt;mi&gt;β&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;mo&gt;=&lt;/mo&gt;\u0000 &lt;mn&gt;200&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${gamma }_{beta }=200$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, &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;γ&lt;/mi&gt;\u0000 &lt;mi&gt;η&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;mo&gt;=&lt;/mo&gt;\u0000 &lt;mn&gt;0.00375&lt;/mn&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;mn&gt;0.0075&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${gamma }_{eta }=0.00375-0.0075$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;. Although AF parameters do influence the transient crater size, in appropriate AF parameters, the transient crater diameters are consistent with scaling laws derived from small-scale experimental cratering. Furthermore, our simulations reveal the quantitative relationship between transient and final crater diameters in complex craters. In contrast to previous observationally based scaling relationships, which likely represen","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 9","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148942926","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":"Anomalous Dawn-Side O+ Density Enhancement in the Martian Ionosphere: MAVEN Observations and Photochemical Modeling","authors":"V. Leelavathi,&nbsp;Yutian Cao,&nbsp;Jun Cui,&nbsp;Yanxing Liu,&nbsp;N. V. Rao,&nbsp;Jing Wang,&nbsp;Tielong Zhang","doi":"10.1029/2026JE009855","DOIUrl":"https://doi.org/10.1029/2026JE009855","url":null,"abstract":"<p>The dominant ions in the dayside Martian ionosphere are O₂⁺, O⁺, and CO₂⁺, with NO⁺ becoming increasingly important on the nightside. Generally, ion densities are higher during the daytime than at nighttime and are typically enhanced on the dusk-side relative to the dawn-side. This behavior is primarily attributed to strong dayside photoionization, followed by continuous plasma depletion via recombination and day-to-night transport as the ionosphere rotates into darkness. In this study, observations from the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft reveal a unique feature during Martian Year (MY) 37. During this period, a pronounced enhancement in O⁺ density is observed on the dawn-side compared to the dusk-side, a behavior not seen in O₂⁺ and CO₂⁺ ions. Further analysis reveals that the O/CO₂ density ratio is significantly elevated, indicating a concurrent reduction in CO₂ density and an increase in atomic oxygen. Photochemical model calculations demonstrate that although O⁺ production rate on the dawn-side is ∼0.60 times the dayside value, its chemical loss frequency is approximately four times smaller. This reduced loss frequency substantially increases the chemical lifetime of O⁺, allowing ions to accumulate despite weaker production. The enhanced atomic oxygen abundance is likely driven by increased EUV-induced photodissociation of CO₂ on the dayside, producing CO and O, followed by the transport of O atoms toward the midnight and dawn sectors through global thermospheric circulation. The enhanced O abundance and together with reduced CO₂ availability, substantially limits CO₂-driven O⁺ loss. This mechanism explains the anomalous dawn-side O⁺ enhancement in the Martian ionosphere.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 9","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148943113","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":"Neutron Diffraction Evidence for Stress-Induced Melting of Ice During Deformation of D2O-Ice Ih—Fluorite Mixtures","authors":"Ceri A. Middleton,&nbsp;A. Dominic Fortes,&nbsp;Peter M. Grindrod,&nbsp;Shu Yan Zhang,&nbsp;Stephen J. Covey-Crump,&nbsp;Peter R. Sammonds,&nbsp;Ian G. Wood,&nbsp;David P. Dobson,&nbsp;Lidunka Vočadlo,&nbsp;Simon A. Hunt","doi":"10.1029/2026JE009877","DOIUrl":"https://doi.org/10.1029/2026JE009877","url":null,"abstract":"<p>Water ice is an important rock-forming mineral, both on the Earth and on various extraterrestrial bodies. Naturally occurring ice is often “dirty”–an intimate mixture with harder mineral grains, which can have significant effects on the bulk properties of the aggregate. We have used neutron powder diffraction, with in situ triaxial deformation, to characterize laboratory analogs of such “dirty” ices, isolating the strain partitioning in polyphase mixtures of ice and a “rock” analog (fluorite). Bounds on the expected elastic behavior of the mixtures have been calculated as a function of the volume fraction and material properties of the two phases, under iso-strain (Voigt) and iso-stress (Reuss) conditions and also using narrower Hashin-Shtrikman bounds. Under certain experimental conditions the observed behavior data does not fit within these theoretical bounds: at low volume fraction and low strains, fluorite measurements show unexpected expansion, against the applied load. We conclude that under some conditions, increased stresses at the tips of sharp mineral particles, combined with the negative pressure-melting curve of water ice, lead to localized melting. The presence of liquid water in “dirty” ice may have important implications for the rheology of both terrestrial and planetary ices.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 9","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026JE009877","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148943111","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":"Formation and Alteration of Magnesite Nodules From Kunwarara, Queensland, Australia, as an Analog to Mg-Carbonate Formation on Mars","authors":"E. L. Cardarelli,&nbsp;T. M. Present,&nbsp;P. M. Vasconcelos,&nbsp;L. C. Kah,&nbsp;C. Swindle,&nbsp;S. Bhattacharjee,&nbsp;K. Farley","doi":"10.1029/2026JE009660","DOIUrl":"https://doi.org/10.1029/2026JE009660","url":null,"abstract":"<p>Magnesite (MgCO₃) is a magnesium (Mg) carbonate mineral that records the aqueous environmental conditions of its formation. On Earth, magnesite forms in metamorphic, diagenetic or pedogenic environments, and distinguishing between these environments is critical for understanding the fluid chemistry during magnesite precipitation. Mg carbonates have been observed across the Nili Fossae region on Mars and in Jezero crater by orbital spectroscopy as well as in situ by the Perseverance rover. Rover acquired core samples with Mg carbonates may provide constraints on the chemical conditions of the ancient aqueous environments of Jezero crater, and may also be an important target for the preservation of potential biosignatures. This work explores magnesite phases found in Vertisols of the Kunwarara Mine, Australia, as a potential analog environment for magnesite on Mars. We document the principal microtextures, mineralogical context, and elemental compositions. We investigate the processes involved in the formation and diagenesis of magnesite nodules and a magnecrete. Kunwarara hosted magnesite shows complex textural relationships at the outcrop scale, and these relationships extend down to the nanoscale in samples that were collected along a depth profile. By characterizing textural and chemical variations in magnesite at different scales, this work reveals a continuum between diagenetic and pedogenic magnesites. It illustrates that diagenetic reactions produce magnesite from ascending Mg²⁺-rich groundwater interacting with detrital phases; groundwater interaction with descending meteoric solutions result in the conversion of magnesite into authigenic dolomite. Overall, this work shows how the superposition of textures and elemental compositions permits reconstruction of pedogenic processes leading to magnesite authigenesis.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 9","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026JE009660","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148993949","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}