Journal of Geophysical Research: Planets最新文献

{"title":"Morphological and Structural Characterization of Shortening Landforms on Mars","authors":"Leta R. McCullough,&nbsp;Kelsey T. Crane,&nbsp;Stephan R. Loveless,&nbsp;Christian Klimczak","doi":"10.1029/2023JE008196","DOIUrl":"https://doi.org/10.1029/2023JE008196","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <p>The lithosphere of Mars accommodates horizontal shortening through folding and faulting, producing landforms described as wrinkle ridges or lobate scarps. Despite this nomenclature, we lack a deep understanding of the drivers of morphological differences observed between landform types. This study aims to develop a quantitative model for shortening landform classification based on surface morphology, subsurface architecture, and strain accommodation, facilitating interpretations of where and how lithospheric stresses are recorded. We developed this model by mapping 100 shortening landforms in a Geographic Information System, recording 12 unique geomorphic parameters such as length and asymmetry, and estimating the strain of each landform. We conducted a Discriminant Function Analysis (DFA) using surface morphometrics. This DFA produced a predictive linear function for categorizing wrinkle ridges and lobate scarps and for quantifying which landforms were exemplars within those categories. The three most influential variables on the surface morphometry DFA were the maximum width, forelimb slope, and back limb length. We then modeled the subsurface structural geology of 50 landforms using MOVE Structural Geology Modeling Software and conducted a second DFA based on subsurface metrics. DFA was most influenced by the dip and depth of the lower ramp base. When both surface morphology and subsurface geometry are input into single DFA, wrinkle ridges and lobate scarps can be distinguished quantitatively 96% of the time. Our results also show that lobate scarps accommodate more strain and imply that studies should consider landform type when interpreting local, regional, and global geological stress histories.</p>\u0000 </section>\u0000 </div>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"129 10","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023JE008196","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142449208","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":"Preservation Potentials of Siderite in Low-Temperature Brines Relevant to Mars","authors":"Bohao Chen,&nbsp;Xiao-Wen Yu,&nbsp;Yu-Yan Sara Zhao,&nbsp;Di-Sheng Zhou,&nbsp;Shuai-Yi Qu,&nbsp;Jiannan Zhao,&nbsp;Chao Qi,&nbsp;Xiongyao Li,&nbsp;Jianzhong Liu","doi":"10.1029/2023JE008250","DOIUrl":"https://doi.org/10.1029/2023JE008250","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <p>The scarce carbonate record on the Martian surface is one of the fundamental unsolved issues for paleoclimate and environmental evolution. Whether carbonates first formed and then dissolved due to a transition in global environments or whether Mg–Fe carbonates never extensively formed due to geochemical kinetics thresholds remains unknown. In this study, we experimentally examined the preservation potential of siderite in Mars-relevant fluids, including ultrapure water, H₂O₂, NaClO₄, NaClO₃, NaCl, Na₂SO₄, NaHCO₃, and Na₂SiO₃ solutions, at 277 K. The effects of the water/rock ratio at WR10 and WR100 on dissolution rates were also investigated. We found that siderite dissolution and subsequent oxidation and hydrolysis of leached Fe did not substantially acidify the solutions. The siderite dissolved relatively rapidly in the chloride and chlorate solutions and slowly in the silica or bicarbonate solutions. In a circum-neutral to slightly alkaline aqueous environment with oxidative species, the mobility of leached Fe was limited, leading to the formation of goethite or lepidocrocite, which clustered on the siderite surface. The longest lifetime of 1-mm siderite grains was found in the Na₂SiO₃ solution at WR100, which was estimated to range from 198 ka to 198 Ma. Water-limited, silica-rich, and oxidative aqueous environments benefit siderite preservation on the Martian surface. Our results support that the lack of voluminous siderite on Mars may be primarily due to the inhibition of its formation rather than alteration and dissolution after its presence, consistent with the recent detection of Mg–Fe carbonate at Gale Crater and Jezero Crater.</p>\u0000 </section>\u0000 </div>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"129 10","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142447645","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":"Geostratigraphic Mapping of the Intrusive Valentine Domes on the Moon","authors":"Javier Eduardo Suárez-Valencia,&nbsp;Angelo Pio Rossi","doi":"10.1029/2024JE008423","DOIUrl":"https://doi.org/10.1029/2024JE008423","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <p>Lunar intrusive igneous domes have not been the center of much research in the past due to their rare occurrence on the lunar surface, and the difficulty in locating them. Most of the known structures were discovered using images with low illumination angles, including data from the Lunar Orbiter, telescopic images, and photos taken during the Apollo Missions. These intrusive domes are characterized by an oval shape and low slopes. We analyzed one of these systems, the Valentine domes, located near the rim of the western Serenitatis basin, with modern techniques and data sets from the Lunar Reconnaissance Orbiter (LRO) and Chandrayaan-1 missions. We created a geostratigraphic map of the area, combining geomorphological and spectral classifications. The aspect map (direction of the slope) proved to be the most suitable product to locate and delimit these structures; using it, we identified a new dome southeast of the principal body, suggesting that the intrusive system is larger than previously thought. It was found that the three domes can be classified as laccoliths, and that several derived structures such as rilles, dykes, and secondary domes represent different stages of intrusive activity in the area. Based on crater counting analysis, we determined that the intrusive activity began after 2.98 ± 0.15 Ga and lasted at least until 1.88 ± 0.5 Ga ago.</p>\u0000 </section>\u0000 </div>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"129 10","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JE008423","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142447774","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":"Dust Dynamics in Gale Crater Observed Using the Line-Of-Sight Extinction Through 3,663 Sols of the Mars Science Laboratory Mission","authors":"G. Bischof,&nbsp;S. D. Guzewich,&nbsp;J. E. Moores,&nbsp;M. T. Lemmon,&nbsp;J. M. Battalio,&nbsp;C. W. Hayes,&nbsp;A. C. Innanen,&nbsp;C. L. Smith","doi":"10.1029/2024JE008349","DOIUrl":"https://doi.org/10.1029/2024JE008349","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <p>The Curiosity Rover has been exploring the Gale Crater using the on-board Navigation Camera to monitor the line-of-sight (LOS) dust extinction within the crater. Previous studies of the line-of-sight extinction have shown an annual trend where a minimum in extinction occurs around L_s = 100° and a maximum occurs around L_s = 300°. However, past studies have been constrained to images acquired only between 10:00 and 14:00 local time, limiting our understanding of the variation of dust extinction in Gale Crater throughout the day. Here, using a method that corrects for variable lighting geometry, we reanalyze the line-of-sight images captured throughout the mission to include images acquired in the early morning and late afternoon. Additionally, we update the line-of-sight record to include over 1,000 additional sols of the mission through sol 3,663, which updates our record of extinction in Gale to the end of Mars Year 36—a period of almost 5.5 Mars Years. Using images taken throughout the sol, we examine the diurnal trend in dust extinction, where a maximum is seen around solar noon. This diurnal trend is observed throughout the year, with a larger diurnal variation observed during the southern summer. Additionally, the geographic homogeneity in dust loading is quantified, with higher dust loading observed in the western portion of the line-of-sight images, corresponding with the north-western portion of the crater rim. These observations suggest that dust lifting from the surface and vertical mixing are factors in the diurnal, seasonal, and geographic dynamics observed in the extinctions.</p>\u0000 </section>\u0000 </div>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"129 10","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JE008349","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142447776","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":"Sub-Milankovitch Signals in the Northern Polar Layered Deposits of Mars","authors":"J. P. Sotzen,&nbsp;K. W. Lewis","doi":"10.1029/2024JE008543","DOIUrl":"https://doi.org/10.1029/2024JE008543","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <p>Our understanding of the paleoclimate of Mars and the dominant forcing functions that drive large-scale changes largely remains a mystery. However, the Martian Polar Layered Deposits (PLD) offer a promising avenue for unraveling the planet's recent paleoclimate history. Despite recent progress to detect a climate signal in the PLD, definitive evidence of a correlation between the stratigraphic record and Mars' recent orbital history remains elusive. We utilized new and updated techniques, including high-resolution stratigraphic reconstruction from High Resolution Imagine Science Experiment stereo imagery and digital terrain models, combined with a technique of variable dip correction to account for three dimensional bedding orientations. Signal processing methods, such as wavelet and Fourier analysis, were applied to perform detailed time-series analysis. These analyses revealed a quasi-periodic signal indicative of fine bedding at a scale of approximately 2 m. Based on previously proposed deposition rates, these fine layers appear to correspond to timescales centering around 4,000 years. This suggests that the meter-scale layers may not be the result of orbital forcing and hint at an unknown sub-Milankovitch climate forcing mechanism. We discuss potential exogenic causal mechanisms, such as cyclic variations in solar activity, and endogenic factors, including large-scale changes in dust distribution. Understanding the formation processes of these fine layers may significantly enhance our knowledge of Martian climate history and its driving forces.</p>\u0000 </section>\u0000 </div>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"129 10","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142447539","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 Synchronous Moon as a Possible Cause of Mars' Initial Triaxiality","authors":"Michael Efroimsky","doi":"10.1029/2023JE008277","DOIUrl":"https://doi.org/10.1029/2023JE008277","url":null,"abstract":"<p>The paper addresses the possibility of a young Mars having had a massive moon, which synchronized the rotation of Mars, and gave Mars an initial asymmetric triaxiality to be later boosted by geological processes. It turns out that a moon of less than a third of the lunar mass was capable of producing a sufficient initial triaxiality. The asymmetry of the initial tidal shape of the equator depends on timing: the initial asymmetry is much stronger if the synchronous moon shows up already at the magma-ocean stage. From the moment of synchronization of Mars' rotation with the moon's orbital motion, and until the moon was eliminated (as one possibility, by an impact in the beginning of the Late Heavy Bombardment), the moon was sustaining an early value of Mars' rotation rate.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"129 10","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142447538","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":"Mg Exosphere of Mercury Observed by PHEBUS Onboard BepiColombo During Its Second and Third Swing-Bys","authors":"Y. Suzuki,&nbsp;E. Quémerais,&nbsp;J.-Y. Chaufray,&nbsp;R. Robidel,&nbsp;G. Murakami,&nbsp;F. Leblanc,&nbsp;K. Yoshioka,&nbsp;I. Yoshikawa,&nbsp;O. Korablev","doi":"10.1029/2024JE008524","DOIUrl":"https://doi.org/10.1029/2024JE008524","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <p>Mercury's exosphere is an important target for understanding the dynamics of coupled systems in space environments, tenuous planetary atmospheres, and planetary surfaces. Magnesium (Mg) is especially crucial for establishing methods for estimating the surface chemical composition distribution through observations of the exosphere because its distribution in the exosphere and on the surface is strongly correlated. However, owing to its low radiance, the Hermean Mg exosphere has only been detected by the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) onboard the Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) spacecraft. Thus, we have few observation data for areas other than low latitude regions in addition to few detection cases of short-term or sporadic fluctuations, resulting in a poor understanding of ejection and transportation mechanisms of the Mg exosphere. In this study, we analyzed the distribution of the Hermean Mg exosphere by the Probing of Hermean Exosphere by Ultraviolet Spectroscopy (PHEBUS) onboard the Mercury Planetary Orbiter of the BepiColombo mission during its second and third Mercury swing-bys (MSBs). First, we constructed a calibration method including background subtraction and calibration using stellar observations. Mg light curves at two true anomaly angles were obtained, which were in agreement with the Chamberlain model and a three-dimensional numerical calculation. Comparing the Mg and calcium (Ca) radiances obtained by PHEBUS during the MSBs, the exospheric Mg atoms have a lower energy than the exospheric Ca atoms. This is consistent with the lower energy necessary for producing the Mg atoms produced by molecular photodissociation than for Ca atoms.</p>\u0000 </section>\u0000 </div>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"129 10","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JE008524","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443442","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":"Surface Variability Mapping and Roughness Analysis of the Moon Using a Coarse-Graining Decomposition","authors":"Siyu Xue,&nbsp;Benjamin A. Storer,&nbsp;Rachel C. Glade,&nbsp;Hussein Aluie","doi":"10.1029/2024JE008484","DOIUrl":"https://doi.org/10.1029/2024JE008484","url":null,"abstract":"<p>The lunar surface contains a wide variety of topographic shapes and features, each with different distributions and scales, and any analysis technique to objectively measure roughness must respect these qualities. Coarse-graining is a naturally scale-dependent filtering technique that preserves scale-dependent symmetries and produces coarse elevation maps that gradually erase the smaller features from the original topography. In this study of the lunar surface, we present two surface variability metrics obtained from coarse-graining lunar topography: fine elevation and coarse curvature. Both metrics are isotropic, deterministic, slope-independent, and coordinate-agnostic. Fine (detrended) elevation is acquired by subtracting the coarse elevation from the original topography and contains features that are smaller than the coarse-graining length-scale. Coarse curvature is the Laplacian of coarsened topography, and naturally quantifies the curvature at any scale and indicates whether a location is elevated or depressed relative to its neighborhood at that scale. We find that highlands and maria have distinct roughness characteristics at all length-scales. Our topographic spectra reveal four scale-breaks that mark characteristic shifts in surface roughness: 100, 300, 1,000, and 4,000 km. Comparing fine elevation distributions between maria and highlands, we show that maria fine elevation is biased toward smaller-magnitude elevations and that the maria–highland discrepancies are more pronounced at larger length-scales. We also provide local examples of selected regions to demonstrate that these metrics can successfully distinguish geological features of different length-scales.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"129 10","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142435372","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":"Revealing the Local Time Structure of the Alfvén Radius and Travel Times in Jupiter's Magnetosphere","authors":"A. Jenkins,&nbsp;L. C. Ray,&nbsp;T. Fell,&nbsp;S. V. Badman,&nbsp;C. T. S. Lorch","doi":"10.1029/2024JE008414","DOIUrl":"https://doi.org/10.1029/2024JE008414","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <p>Jovian magnetospheric plasma is coupled to the ionosphere through Alfvén waves. Alfvén waves enable the transport of angular momentum and energy between the planet and magnetospheric plasma, a process that ultimately generates Jupiter's bright auroral emissions. However, past the Alfvén radius, the location where the radial velocity is greater than the Alfvén velocity, magnetospheric plasma is decoupled from the planet. Alfvén waves launched by magnetospheric plasma do not reach the ionosphere, angular momentum cannot be transported from the planet, and auroral emissions should diminish. Knowledge of Jupiter's Alfvén radius location is critical for interpreting drivers of auroral emissions, in situ data, and applications of numerical models. Previous studies that determined the location of the Alfvén radius assumed an azimuthally symmetric magnetosphere and local-time independent magnetic field. Here, we employ a statistical description of the magnetic field that includes local time effects. We find a minimum Alfvén radius of 30 <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>R</mi>\u0000 <mi>J</mi>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${mathrm{R}}_{J}$</annotation>\u0000 </semantics></math> (Jupiter radii) at 6 LT, with plasma decoupled from the planet in the post-dusk through dawn sector. Furthermore, no Alfvén radius exists within 60 <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>R</mi>\u0000 <mi>J</mi>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${mathrm{R}}_{J}$</annotation>\u0000 </semantics></math> between 8 and 20 LT. At distances greater than 50 <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>R</mi>\u0000 <mi>J</mi>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${mathrm{R}}_{J}$</annotation>\u0000 </semantics></math>, the Alfvén travel time is such that magnetospheric plasma moves substantially in the magnetosphere before angular momentum can be efficiently transferred from the atmosphere. Therefore, the angular momentum supplied may no longer be sufficient for the local conditions. Our results highlight the importance of local time considerations and offer new interpretations for local time dependent auroral features, such as the polar collar.</p>\u0000 </section>\u0000 </div>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"129 10","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JE008414","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142435579","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":"Lunar Low-Titanium Magmatism During Ancient Expansion Inferred From Ejecta Originating From Linear Gravity Anomalies","authors":"G. Nishiyama,&nbsp;T. Morota,&nbsp;N. Namiki,&nbsp;K. Inoue,&nbsp;S. Sugita","doi":"10.1029/2023JE008034","DOIUrl":"https://doi.org/10.1029/2023JE008034","url":null,"abstract":"<p>Linear gravity anomalies (LGAs) on the Moon have been interpreted as ancient magmatic intrusions formed during the lunar expansion. The composition of such ancient subsurface intrusions may offer hints for the lunar thermodynamic state in the initial stage of lunar history. To pose a first compositional constraint on magmatism related to lunar expansion, this study analyzed the spectrum and gravity around craters on LGAs, such as Rowland, Roche, and Edison craters. Using reflectance spectra around the craters, we first surveyed non-mare basaltic exposures. To test the LGA excavation scenario as a possible origin of the discovered exposures, we then compared the Gravity Recovery and Interior Laboratory data and post-cratering gravity simulation with the iSALE shock physics code. Our spectral analysis reveals no basaltic exposure around the Rowland crater. Further, the observed termination of LGA at the crater rim contradicts the gravity simulation, which assumes that LGA predates the Rowland crater. These results suggest that LGA formation might postdate the Rowland formation and that lunar expansion lasted even after the Nectarian age. On the other hand, we found that both Roche and Edison craters possess basaltic exposures in their peripheries. Because the gravity reduction inside Roche crater can be reproduced in our simulation, the discovered basaltic exposures are possibly LGA materials ejected from these craters. The composition of those exposures shows that the LGA intrusions at the two locations are composed of low-titanium magma, indicating that ancient magma during the expansion did not contain ilmenite-rich melt, perhaps resulting from the low-ilmenite content of the ancient upper mantle.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"129 10","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023JE008034","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142430016","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}