Journal of Geophysical Research: Planets最新文献

{"title":"Planetary Rotation Effects on Ionospheric Electrodynamics With Closed-Field, Magnetospherically Unforced Polar Caps: Earth-Parameterized Simulations With Implications for Jupiter and Saturn","authors":"Junjie Chen,&nbsp;Jiuhou Lei,&nbsp;Peter A. Delamere,&nbsp;Binzheng Zhang","doi":"10.1029/2026JE010060","DOIUrl":"https://doi.org/10.1029/2026JE010060","url":null,"abstract":"<p>Ionospheric electrodynamics are classically governed by magnetic topology, with solar wind driving two-cell convection in open polar regions and neutral wind dynamo prevailing at closed lower latitudes. However, it remains unclear whether this paradigm applies to fast-rotating planets or Earth's state with extremely weak upstream conditions, where polar regions become largely closed. Global Earth-based simulations under closed-field, magnetospherically unforced polar cap conditions predict that the neutral wind dynamo generates a one-cell convection pattern in polar regions, a fundamental departure from the magnetospherically driven two-cell structure. The convection direction is primarily controlled by the pressure gradient from neutral temperature distributions and the Coriolis force, forming counterclockwise flow around high-latitude cold regions and clockwise around low-latitude warm regions in the Northern Hemisphere. Furthermore, faster planetary rotation suppresses dynamo efficiency through Coriolis-induced wind deceleration. These results establish a theoretical baseline for planetary atmospheric ion-neutral coupling without imposed magnetospheric forcing.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 9","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149146751","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":"Beyond Hydrogen: Simultaneous Depth Profiling of Water and Rock-Forming Elements in the Martian Shallow Subsurface via Combined Active Neutron and Prompt Gamma-Ray Spectroscopy","authors":"Sang Woo Kim,&nbsp;Kyeong Ja Kim","doi":"10.1029/2026JE009892","DOIUrl":"https://doi.org/10.1029/2026JE009892","url":null,"abstract":"&lt;p&gt;The Dynamic Albedo of Neutrons (DAN) instrument on the Curiosity rover has mapped subsurface hydrogen along an extensively analyzed 27-km segment of its traverse in Gale Crater, revealing water-equivalent hydrogen (WEH) of 1–6 wt%. Neutron die-away measurements alone, however, cannot determine whether this hydrogen resides in adsorbed water, hydrated minerals, or ice. Here we use Geant4 Monte Carlo simulations (&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;msup&gt;\u0000 &lt;mn&gt;0&lt;/mn&gt;\u0000 &lt;mn&gt;8&lt;/mn&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $1{0}^{8}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; source neutrons per configuration) to quantify what a pulsed neutron generator with time-resolved prompt gamma-ray neutron activation analysis (PGNAA) adds to neutron-only measurements, for eight representative Martian regolith compositions under idealized detection. The model reproduces the established first-order sensitivity of the epithermal die-away constant to WEH (&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;τ&lt;/mi&gt;\u0000 &lt;mtext&gt;epi&lt;/mtext&gt;\u0000 &lt;/msub&gt;\u0000 &lt;mo&gt;=&lt;/mo&gt;\u0000 &lt;mn&gt;57&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${tau }_{text{epi}}=57$&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;mn&gt;77&lt;/mn&gt;\u0000 &lt;mspace&gt;&lt;/mspace&gt;\u0000 &lt;mi&gt;μ&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $77hspace*{.5em}mu $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;s for WEH &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;mn&gt;15&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${=}15$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;–1 wt%; power-law &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;R&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msup&gt;\u0000 &lt;mo&gt;=&lt;/mo&gt;\u0000 &lt;mn&gt;0.87&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${R}^{2}=0.87$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;)—an internal benchmark. The central experiment holds WEH fixed at 3 wt% across six compositionally distinct host endmembers: &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;τ&lt;/mi&gt;\u0000 &lt;mtext&gt;epi&lt;/mtext&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${tau }_{text{epi}}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; compresses to 61.4–67.0 µs, whereas simultaneously measured PGNAA ratios (Fe/Cl, apparent Si/Ca, Fe/H) provide complementary elemental constraints: for every host pair, at least one of the three ratios gives","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 9","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149146563","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":"Interaction of Trace Species and Three-Dimensional Circulation in Titan's Middle Atmosphere","authors":"Nicholas A. Lombardo,&nbsp;Juan M. Lora","doi":"10.1029/2026JE009948","DOIUrl":"https://doi.org/10.1029/2026JE009948","url":null,"abstract":"<p>The atmosphere of Titan, Saturn's largest moon, is home to a suite of hydrocarbons and nitriles that are primarily produced high in the atmosphere. These trace molecules are distributed away from their high altitude sources by Titan's atmospheric circulation, resulting in a seasonality in their stratospheric abundance. In this paper, we simulate the distribution of trace molecules in Titan's middle atmosphere using the Titan Atmospheric Model, a three-dimensional General Circulation Model. Using an observationally constrained, fixed abundance at the model top (500 km), the simulated molecules are advected throughout the atmosphere and subjected to a pressure-dependent lifetime informed by published photochemical models. We find that enrichment in the high winter latitudes is initiated by downward transport by the meridional overturning circulation, with a pressure-dependent impact from transient eddies in both the horizontal and vertical directions that act to mix molecules down-gradient. We confirm that molecular tongues equatorward of the polar vortex are enabled by three-dimensional horizontal mixing processes, with the most notable tongues in simulated <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>C</mi>\u0000 <mn>2</mn>\u0000 </msub>\u0000 <msub>\u0000 <mi>H</mi>\u0000 <mn>6</mn>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${mathrm{C}}_{2}{mathrm{H}}_{6}$</annotation>\u0000 </semantics></math>, <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>C</mi>\u0000 <mn>2</mn>\u0000 </msub>\u0000 <msub>\u0000 <mi>H</mi>\u0000 <mn>4</mn>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${mathrm{C}}_{2}{mathrm{H}}_{4}$</annotation>\u0000 </semantics></math>, and HCN; due to its shorter chemical lifetime, <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mtext>HC</mtext>\u0000 <mn>3</mn>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${text{HC}}_{3}$</annotation>\u0000 </semantics></math>N does not exhibit a substantial tongue. Finally, we quantify the contributions of adiabatic descent, longwave radiative cooling, and enrichment from the vertical convergence of air to identify the drivers of ice cloud production. We find that, contrary to the prevailing paradigm, the dominant driver of ice cloud production is (im)balance between radiative cooling and adiabatic warming, with the enrichment from downward transport of molecules being several orders of magnitude less important.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 9","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149047841","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":"Radar Fog in SHARAD Observations of the Martian South Polar Layered Deposits as a Result of Dust-Rich Layers","authors":"G. Brighi,&nbsp;D. M. Schroeder,&nbsp;M. Zannoni,&nbsp;P. Tortora","doi":"10.1029/2025JE009518","DOIUrl":"https://doi.org/10.1029/2025JE009518","url":null,"abstract":"<p>The polar caps of Mars, primarily composed of water ice with minor fractions of Martian dust, serve as a record of the planet's past dynamics. Distinct dust-rich subsurface layers, observed in exposed outcrops of both the north and south polar layered deposits (NPLD and SPLD), have been detected by the orbital sounder SHAllow RADar (SHARAD) as sharp, bright, parallel reflectors. Some of the radargrams from high-latitude regions of the SPLD also include a pervasive elevated radar background either filling the spaces between layers or obscuring them entirely, usually referred to as “fog.” This phenomenon is typically attributed to off-nadir surface roughness or volume scattering based primarily on fog's appearance in radargrams. While a few studies have investigated its radar properties, none has used them to conclusively explain its origin. In this work, we measure fog backscattering and its decay with depth from a few SHARAD tracks and compare these to the signatures of plausible subsurface interfaces. While volume scattering is too weak to explain fog, specular reflections from dusty layers, when sufficiently thin or low in dust content, can account for fog's radar properties. This suggests that fog regions of the SPLD may host dust layers with lower reflectivity and more densely packed compared to the brighter reflectors detected in the NPLD.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 9","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149048136","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":"Oxygen-Deficient Magnetite in Chang’e-6 Sample as Evidence for Impact Induced Deoxygenation of the Moon","authors":"Shengdong Chen,&nbsp;Xiaoju Lin,&nbsp;Haiyang Xian,&nbsp;Jianxi Zhu,&nbsp;Yiping Yang,&nbsp;Jiaxin Xi,&nbsp;Shan Li,&nbsp;Akira Tsuchiyama,&nbsp;Yanqiang Zhang,&nbsp;Yi-Gang Xu,&nbsp;Hongping He","doi":"10.1029/2026JE009777","DOIUrl":"https://doi.org/10.1029/2026JE009777","url":null,"abstract":"<p>The Moon’s highly reduced nature contrasts with recent findings of ferric iron (Fe³⁺)-bearing phases, suggesting an active redox cycle on the Moon. While solar wind proton reduction and impact-vaporization oxygen loss from minerals are proposed drivers for lunar reduction, direct nanometer-scale evidence for impact-driven deoxygenation has been lacking. Here we report the discovery of oxygen-deficient magnetite within impact melt glass in Chang’e-6 lunar farside samples from the South Pole-Aitken basin. This subhedral magnetite grain (Length 2.5 μm; width 1.5 μm.) exhibits a non-stoichiometric composition and crystal chemical formula [(Fe²⁺_1.158(7)Mg_0.070(5))_∑1.228(Fe³⁺_1.534(9)Cr³⁺_0.137(14)Al_0.101(8))_∑1.772]_∑3.000(O_3.886□_0.114)_∑4.000, confirming significant oxygen vacancies (□). Magnetite heating experiments (1000°C, in Ar atmosphere) replicated these features, demonstrating thermal deoxygenation generates oxygen vacancies through O₂ evolution and concurrent Fe³⁺ reduction. Our findings provide the first mineral structural evidence that post-shock heating drives deoxygenation in oxygen-bearing minerals, establishing impact-induced oxygen removal as a fundamental mechanism making the localized lunar surface chemically reduced.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 9","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149146604","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":"Surface Change Detection on Venus: An Inter-Mission Comparison Framework Between Magellan and Future Radar Images","authors":"Yao Gao,&nbsp;Gerard Gallardo i Peres,&nbsp;Shubham Awasthi,&nbsp;Nikol Davidova,&nbsp;Richard Ghail,&nbsp;Philippa J. Mason","doi":"10.1029/2026JE009994","DOIUrl":"https://doi.org/10.1029/2026JE009994","url":null,"abstract":"<p>Detecting surface changes on Venus by comparing Magellan synthetic aperture radar (SAR) data with future high-resolution data from Envision and VERITAS will be essential for constraining present-day volcanism and characterizing planetary surface processes. However, such inter-mission SAR change detection requires resampling images to comparable pixel spacing, which results in image pairs with different equivalent numbers of looks (ENLs) and this invalidates classical statistical models that assume the two images are identically distributed. To address this issue, we propose an unsupervised change detection method for SAR image pairs with different ENLs, termed GB2KI. This method models the ratio image with the generalized beta prime distribution (GB2) and incorporates it into the minimum-error thresholding framework. An entropy-weighted maximum likelihood estimation method is introduced for robust parameter estimation when the changed class occupies only a small fraction of the scene. Additionally, a multiscale post-processing technique is developed to suppress isolated false detections in the final change map. Simulations using Magellan Cycle 1 and Cycle 3 images of a volcanic plain on Venus, with synthetic lava-flow changes varying in intensity, extent, and location, show that GB2KI improves overall detection accuracy and reduces false alarms. Further validation is performed using two Earth analog data sets from the 2014–2015 Holuhraun lava flow in Iceland, including Sentinel-1 images from different imaging modes (1-year interval) and Radarsat-1/Sentinel-1 images (15-year interval). Experimental results indicate that GB2KI accurately identifies lava-flow changes in both cases, supporting inter-mission comparisons between Magellan and future Venus SAR missions.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"131 9","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026JE009994","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149047971","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":"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}