Journal of Geophysical Research: Planets最新文献

{"title":"The Sporadic Fluvial Regime of Pliva Vallis, the Outlet Valley of Jezero Crater Lake, Mars","authors":"J. Villette,&nbsp;N. Mangold,&nbsp;E. S. Kite,&nbsp;S. J. Conway,&nbsp;L. Le Deit","doi":"10.1029/2024JE008862","DOIUrl":"https://doi.org/10.1029/2024JE008862","url":null,"abstract":"<p>In situ and orbital observations have suggested that Jezero crater (field site for the Mars 2020 Perseverance rover) once hosted a paleolake fed by two inlet valleys. An outlet valley, Pliva Vallis, is present on the eastern rim of the crater and raises the question of whether the lake system operated as an open basin or as a closed basin system with one or more overflow events. To tackle this uncertainty, we present a detailed morphological study of Pliva Vallis, using digital elevation models and imagery. The atypical morphology of the valley, including reincised fluvial layered deposits, a perched valley, and bedrock incision terraces, led us to interpret that Pliva Vallis was formed by discontinuous and episodic flows rather than from a steady outlet river. These observations allowed us to infer at least four main breach episodes and propose a new scenario for the evolution of the lake system over time. We give a minimum estimate of the duration of these overflow events using a 0-D model, simulating a valley formation by breach erosion and lake overflow. Modeling results suggest that each flood event causing a part of the incision of the outlet valley would not have lasted for more than a few weeks, and some may have lasted only a few days. These time scales are consistent with our morphological interpretation that the outlet valley was carved by discontinuous and temporary flows. In this scenario, Jezero lake was predominantly a closed basin, spilling over episodically in at least four breach events.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 5","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JE008862","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144091670","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":"Compositional and Morphological Variations of Effusive Lava Flows and Explosive Pyroclastic Deposits at the Caldera-Forming Gardner Shield Volcano on the Moon","authors":"Henal V. Bhatt,&nbsp;Timothy D. Glotch,&nbsp;Edgard G. Rivera-Valentín,&nbsp;Hunter Vannier,&nbsp;Heather M. Meyer","doi":"10.1029/2024JE008692","DOIUrl":"https://doi.org/10.1029/2024JE008692","url":null,"abstract":"<p>We identified a ∼31 km diameter caldera with a well-developed ring fault and ring dike structure at the Gardner shield volcano. Using Chandrayaan-1 Moon Mineralogy Mapper (M³) and Lunar Reconnaissance Orbiter (LRO) Diviner data, we investigated 15 effusive flow units and an explosive unit. Spectral analysis revealed compositional similarities between effusive and explosive eruptions, indicating a single sourced magmatic eruption. Detailed hyperspectral and multispectral analyses (visible, near-infrared, thermal infrared, and radar) indicate the presence of explosive pyroclastic material in the central part of the shield. We identified key morphological structures at the Gardner shield, including three major faults, the caldera's ring fault and ring dike structure, subsidence and resurgence crustal blocks, a graben, a parasitic cone, and extended lineaments beyond the previous work. Our analysis indicates that the well-developed Gardner caldera exhibits lower subsidence compared to Earth's calderas, likely due to the Moon's lower gravity and lower crustal density. These surficial structures preserve the evidence of subsurface magmatic chamber dynamics, making the Gardner shield a unique location for understanding the thermophysical evolution of a central vent shield regime on the Moon. We describe six evolutionary stages, evidenced by multiple volcano-tectonic structures, two distinct eruption styles, and the shield's relationship with the subsurface magmatic chamber, revealing a thermophysical evolution of a central-vent polygenetic shield volcano on the Moon, following a formation mechanism similar to those observed in the shield volcanoes on Earth and Mars.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 5","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144091668","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":"Impacts of Dry Deposition Processes With Resolved Dust Particle Sizes on Simulating the Martian Dust","authors":"Lulu Li,&nbsp;Chun Zhao,&nbsp;Claire E. Newman,&nbsp;Yongxuan Zhao,&nbsp;Jiawang Feng,&nbsp;Tao Li,&nbsp;Chengyun Yang,&nbsp;Yingxi Yue","doi":"10.1029/2024JE008616","DOIUrl":"https://doi.org/10.1029/2024JE008616","url":null,"abstract":"<p>Mars, characterized as a “desert” planet with little water vapor, primarily relies on dry deposition for dust removal. Although these processes include gravitational sedimentation, turbulent transfer, Brownian diffusion, impaction, interception, and rebound, most current models consider only gravitational sedimentation. To have a more comprehensive understanding of the effects of Martian dust removal processes, a physics-based scheme of dry deposition processes with resolved dust particle sizes is implemented in the Mars Weather Research and Forecasting (MarsWRF) model. Results show that the size-resolved dry deposition scheme significantly increases the dry deposition velocity, with the maximum difference (over 0.024 m/s) occurring at 0.884 μm size bin. This enhanced removal efficiency leads to an increase of 0.4 μm in the effective radius of airborne dust throughout the year and a reduction of approximately 0.09 in dust opacity, particularly in the northern high latitudes during autumn and winter, compared to the simulation that only considers a size-resolved gravitational sedimentation scheme. The overestimation of low-level atmospheric temperature in the mid-to-low latitudes, excluding near-surface regions between <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>20</mn>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <annotation> $20mathit{{}^{circ}}$</annotation>\u0000 </semantics></math> and <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>60</mn>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <annotation> $60mathit{{}^{circ}}$</annotation>\u0000 </semantics></math>N, during <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>L</mi>\u0000 <mi>s</mi>\u0000 </msub>\u0000 <mo>=</mo>\u0000 <mrow>\u0000 <mrow>\u0000 <mn>230</mn>\u0000 <mo>−</mo>\u0000 <mn>250</mn>\u0000 </mrow>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 </mrow>\u0000 <annotation> ${L}_{s}=230-250mathit{{}^{circ}}$</annotation>\u0000 </semantics></math> (considered as peak-dust phase) is partially corrected, with a correction of up to 1 K compared to the single-particle size simulation and up to 5 K compared to the size-resolved sedimentation-only simulation, bringing it closer to MCS observations. Additionally, the size-resolved dry deposition simulation reduces the condensation rate of atmospheric CO₂ and the thickness of the northern CO₂ ice cap, aligning better with Viking Lander observations during northern winter and spring than the size-resolved sedimentation-only simulation.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 5","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144091669","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":"The Chang’E-6 Landing Region: Geologic Context, Mare Basalt, and Regolith Properties","authors":"Bojun Jia,&nbsp;Wenzhe Fa,&nbsp;Mingwei Zhang","doi":"10.1029/2025JE009018","DOIUrl":"https://doi.org/10.1029/2025JE009018","url":null,"abstract":"<p>Chang’E-6 (CE-6) is the first lunar farside sample-return mission. It landed in an Eratosthenian mare basalt unit within the South Pole-Aitken basin (SPA) and returned 1,935.3 g samples. These returned samples can address a wide range of fundamental questions about the Moon, including the nature of farside volcanism and mantle, the stratigraphy and evolution of the SPA terrain, the impact flux, chronology, and space weathering process of the lunar farside. This study investigates the geological context, mare basalt, and regolith properties of the CE-6 landing region using multi-source remote sensing observations. The size and spatial distributions of the penetrating craters and buried craters reveal that the thickness of the surface Eratosthenian basalt in most regions ranges from <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>30–60 m, and a layer of Imbrian basalts with a thickness of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>90–120 m lies beneath. Morphology and rock population of small fresh craters within a 3 km radius of the landing site indicate a 2–10 m thick regolith layer with a median thickness of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>3 m. Combined analysis of infrared and radar observations suggests a finer regolith at the landing site, with fewer meter-scale rocks but more centimeter- to decimeter-scale rocks compared with Chang’E-5 landing site. The surface features in the mare unit suggest that the regolith at the landing site may contain exotic ejecta primarily from Chaffee S, Vavilov, Lovell, and White craters, potentially including SPA melt and mantle materials. These findings improve the understanding of volcanic activity and regolith evolution at the landing site, and further provide foundations for subsequent laboratory analysis of the returned samples.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 5","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144074471","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":"A Simulation Study of Martian Airglow Emission Response to the X8.2 Solar Flare on 10 September 2017","authors":"Zerui Liu,&nbsp;Jiuhou Lei,&nbsp;Maodong Yan,&nbsp;Tong Dang","doi":"10.1029/2024JE008878","DOIUrl":"https://doi.org/10.1029/2024JE008878","url":null,"abstract":"&lt;p&gt;During the solar flare, the planetary upper atmosphere and ionosphere are rapidly impacted, and the airglow emission intensity can be significantly enhanced. Previous studies have been carried out on the variation of Martian airglow emissions using the Imaging Ultraviolet Spectrograph instrument aboard the Mars Atmosphere Volatile EvolutioN mission. However, the underlying mechanisms responsible for Martian emission intensity during solar flare events remain to be addressed. In this study, we explore the variation of the emission intensity caused by the X8.2 solar flare on 10 September 2017, using photoelectron transport model, focusing on two typical emission spectra—&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msubsup&gt;\u0000 &lt;mtext&gt;CO&lt;/mtext&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; ${text{CO}}_{2}^{+}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; Ultraviolet doublet (UVD) and &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mtext&gt;CO&lt;/mtext&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $text{CO}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; Cameron band. We show the comparison of the simulated and observed emission intensity and find that the variation trend with altitude of simulated limb intensity is in agreement with the observation. In both the simulated and observed results, a sub-peak in the limb intensity around 100 km is observed, attributed to the photoelectron impact process. Additionally, the photoelectron impact process responds more strongly to the solar flare than the photon impact process, and leads to a sharper sub-peak at the peak flare period. Furthermore, the photon impact process, causing the different response of &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msubsup&gt;\u0000 &lt;mtext&gt;CO&lt;/mtext&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;mo&gt;+&lt;/mo&gt;\u0000 &lt;/msubsup&gt;\u0000 &lt;mfenced&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mi&gt;B&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msup&gt;\u0000 &lt;msubsup&gt;\u0000 &lt;mi&gt;Σ&lt;/mi&gt;\u0000 &lt;mi&gt;u&lt;/mi&gt;\u0000 &lt;mo&gt;+&lt;/mo&gt;\u0000 &lt;/msubsup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/mfenced&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${text{CO}}_{2}^{+}left({mathrm{B}}^{2}{{Sigma }}_{mathrm{u}}^{+}right)$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; and &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mtext&gt;CO&lt;/mtext&gt;\u0000 &lt;mfenced&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mi&gt;a&lt;/mi&gt;\u0000 &lt;mn&gt;3&lt;/mn&gt;\u0000 &lt;/msup&gt;\u0000 ","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 5","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144074545","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":"Paleo-Scours Within the Layered Sulfate-Bearing Unit at Gale Crater, Mars: Evidence for Intense Wind Erosion","authors":"Amelie L. Roberts,&nbsp;Sanjeev Gupta,&nbsp;Steven G. Banham,&nbsp;Aster Cowart,&nbsp;Lauren A. Edgar,&nbsp;William Rapin,&nbsp;William E. Dietrich,&nbsp;Joel M. Davis,&nbsp;Edwin S. Kite,&nbsp;Gwénaël Caravaca,&nbsp;Claire A. Mondro,&nbsp;Patrick J. Gasda,&nbsp;Jeffrey R. Johnson,&nbsp;Stéphane Le Mouélic,&nbsp;Deirdra M. Fey,&nbsp;Alexander B. Bryk,&nbsp;Gerhard Paar,&nbsp;Emma R. A. Harris,&nbsp;Abigail Fraeman,&nbsp;Ashwin R. Vasavada","doi":"10.1029/2024JE008680","DOIUrl":"https://doi.org/10.1029/2024JE008680","url":null,"abstract":"<p>The surface of modern Mars is largely shaped by wind, but the influence of past wind activity is less well constrained. Sedimentary rocks exposed in the lower foothills of Aeolis Mons, the central mound within Gale crater, record a transition from predominantly lacustrine deposition in the Murray formation to aeolian deposition in the Mirador formation. Here, we report a series of enigmatic decameter-wide, concave-up scour-and-fill structures within the Mirador formation and discuss their formation mechanisms. Using panoramic images of stratigraphy exposed in cliff faces acquired by the <i>Curiosity</i> rover, we map the extent, distribution and orientation of the scour-and-fill structures and document the sedimentary facies within and surrounding these structures. The scours are grouped into two classes: (A) scours with a simple, symmetric morphology and light-toned, draping infill; and (B) scours with lateral pinching and dark-toned infill. We find that the scour-enclosing environment is composed of planar, even-in-thickness laminations with a pin-stripe pattern which we interpret as wind-ripple strata formed within an aeolian sandsheet environment. Class B contains cm-scale cross-bedding and a wing-shaped feature making this scour-and-fill structure consistent with fluvial processes. We interpret scour fill of class A as an aeolian infill due to similarities with the surrounding sandsheet strata. The broad morphologies and distribution of class A are also consistent with the geometry of blowout structures formed by localized, enhanced wind deflation. These paleo-blowout structures occur clustered within the same stratigraphic interval, which may imply that they record an interval of intensified wind activity at Gale crater.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 5","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JE008680","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143944808","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 Link Between Subsurface Rheology and Ejecta Mobility: The Case of Small New Impacts on Mars","authors":"A. J. Sokolowska,&nbsp;G. S. Collins,&nbsp;I. J. Daubar,&nbsp;M. Jutzi","doi":"10.1029/2024JE008561","DOIUrl":"https://doi.org/10.1029/2024JE008561","url":null,"abstract":"<p>The dynamics of crater ejecta are sensitive to the material properties of the target, much like the crater size and morphology. We isolate and quantify the effect of target properties on the ejecta mobility (EM) - the maximum radial extent of ejecta scaled by the crater radius. We compile geologically motivated subsurface structures based on data gathered by orbiters and landers. Those structures arise from varying properties of materials in single layers (strength, composition, porosity); the thickness of top regolith cover; and the sequence and thicknesses of 3–4 stacked layers. We realize 2D simulations with the iSALE shock physics code which result in a 50 m diameter crater (an analog of new craters formed in the period of spacecraft observation). We find that varied subsurface rheologies result in EM numbers with a wide range of values between 7 and 19. Some subsurface models can result in a similar EM, and some have distinct EMs, which shows potential for using this quantity as a new diagnostic of target properties. We also show that ejecta dynamics are sensitive not only to the material in the excavation zone but also at much greater depths than commonly assumed (at least 1–2 crater radii). EM also depends on both material properties and layering: the impedance contrast governs the nature of wave propagation, while the layer depth controls the timing of the shock wave reflection. Detailed studies of EM thus have promise for unveiling shallow subsurface rheologies on many Solar System bodies in the future.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 5","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JE008561","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143944479","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":"Differences in Rock Magnetic Properties From Heterogeneous Weathering of the LL7 Chondrite Northwest Africa 12780","authors":"Haijun Li,&nbsp;Huapei Wang","doi":"10.1029/2024JE008768","DOIUrl":"https://doi.org/10.1029/2024JE008768","url":null,"abstract":"<p>Meteorites preserve valuable remanent magnetization from the early solar system. However, the residence on the Earth's surface often leads to the formation of iron oxides, which can alter or obliterate the primary remanence and complicate the paleomagnetic data interpretation. The weathering degree varies significantly depending on residence time, location, climate, and the chemical composition of the meteorite. Additionally, individual meteorites can exhibit varying oxidation degrees within a single stone due to partial burial in soil. This study examines the LL7 chondrite Northwest Africa 12780, revealing heterogeneous weathering across different parts of the meteorite. While one part shows extensive metal oxidation, another remains unoxidized. Although most oxidized subsamples contain paramagnetic iron oxides, maghemite is observed in some oxidized subsamples. Our findings highlight the presence of heterogeneous weathering in meteorites, which leads to the formation of various iron oxides, including maghemite, potentially acquiring chemical remanent magnetization and overprinting primary remanence. This also indicates that certain subsamples may retain their primary remanence even in weathered meteorites. However, systematic investigations are necessary to eliminate the influence of ferromagnetic iron oxides.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 5","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143939527","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":"Micro X-Ray Diffraction Observations and Calibration of Experimentally Shocked Plagioclase Feldspars: Comparison With Raman Spectroscopic Observations","authors":"Fengke Cao,&nbsp;Roberta L. Flemming,&nbsp;Matthew R. M. Izawa,&nbsp;Steven J. Jaret,&nbsp;Jeffrey R. Johnson","doi":"10.1029/2024JE008574","DOIUrl":"https://doi.org/10.1029/2024JE008574","url":null,"abstract":"<p>Plagioclase feldspar is a ubiquitous mineral found in planetary bodies such as Earth, Moon, Mars, large igneous asteroids such as Vesta, numerous achondrites, and every class of chondritic meteorite. Because all solid planetary bodies are potentially subject to hypervelocity impacts, understanding the shock response of plagioclase enables a better understanding of the geological histories of planetary bodies. This study investigates the response of andesine and bytownite to high-pressure shock waves using micro-XRD and Raman. Fourteen andesine and 11 bytownite samples, which had been previously shocked to peak pressures of 0–56 GPa, were examined. Micro-XRD revealed characteristic signatures of shock damage, including weakened diffraction intensities and heightened background signal, reflecting structural collapse under high pressures. Andesine-bearing rock showed the onset of amorphization at 28.4–29.6 GPa, progressing to complete amorphization at 47.5–50 GPa. Bytownite-bearing rock displayed a similar trend but with higher pressure thresholds: partial amorphization occurred at 25.5–27.0 GPa, and complete amorphization at 38.2–49 GPa. To quantify the degree of shock experienced by plagioclase minerals, we measured the Full Width at Half Maximum (FWHMχ) of Debye rings (from 2D XRD images) for samples across different shock levels. We established linear regression models between ΣFWHMχ and peak shock pressure for both andesine (0–28.4 GPa) and bytownite (0–25.5 GPa) using data from samples that remained crystalline. The model is particularly effective for low shock levels, while Raman is more effective at higher shock pressures. These quantitative relationships provide a valuable tool for assessing the shock history recorded in plagioclase minerals.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 5","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143939533","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":"Formation of Pancake Domes on Venus as Viscous Flows Over an Elastic Lithosphere","authors":"M. E. Borrelli,&nbsp;C. Michaut,&nbsp;J. G. O'Rourke","doi":"10.1029/2024JE008571","DOIUrl":"https://doi.org/10.1029/2024JE008571","url":null,"abstract":"<p>Venus' steep-sided domes are circular volcanoes ∼10s of km wide and ∼1 km tall, which are known for their characteristic flat tops and steep sides. However, their composition remains mysterious. These “pancake” domes are likely formed by a high-viscosity lava, and other studies have predicted a range of compositions, from rhyolite to basalt. In this study, we build on previous work modeling pancake domes as spreading viscous gravity currents. However, previous models of dome formation assumed that they form over a rigid lithosphere. We previously found signatures of lithospheric flexure at 14 out of 75 pancake domes and therefore built a new model of dome formation over a bending elastic lithosphere. We found that flexure during formation can influence the shape of the resulting pancake dome. Our results also support the idea that pancake domes continue to spread for a long time after their emplacement. In comparing our model to the topography of a real pancake dome (Narina Tholus), we find a range of high, though variable, lava viscosities. Our range of lava viscosities is related to the size of the observed dome, and our results for a large dome agree with those of other studies. We test different lava densities and find that a lava density of ∼2,400–2,700 kg/m³ best reproduces the flexural signatures observed at Narina Tholus. Low-density lava (∼1,500 kg/m³) does not reproduce the flexural signatures, implying that dome-forming lava is not highly vesiculated.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 5","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JE008571","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143930224","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}