Journal of Geophysical Research: Planets最新文献

{"title":"Microwave Emissivity Variations Across Ovda Regio, Venus","authors":"Indujaa Ganesh,&nbsp;Martha S. Gilmore","doi":"10.1029/2024JE008563","DOIUrl":"https://doi.org/10.1029/2024JE008563","url":null,"abstract":"<p>The surface composition of highland tesserae on Venus critically constrains the geologic and climate history of the planet. We examine one such highland, Ovda Regio, which contains tessera terrain as well as a rare festoon-type volcano, both of which have unknown compositions. Observations of declining surface microwave emission with increasing elevation at Ovda Regio has been attributed to the presence of ferroelectric minerals that undergo a sharp dielectric transition at high elevations. However, there is significant spatial variability in this elevation-dependent emissivity trend. We find that emissivity is lower in the interior of Ovda Regio than in the margins at similar elevations, indicating higher concentrations of ferroelectric minerals in the interior. The lowest emissivity values are associated with the festoon flow and neighboring surfaces, including a morphological unit that drapes over underlying tessera. We hypothesize that the festoon flow eruption produced reactive gasses and tephra that contributed to rapid weathering and formation of abundant ferroelectrics. Modeling the elevation-dependent emissivity behavior demonstrates the presence of ferroelectric minerals with a diffuse, rather than sharp, transition in dielectric properties consistent with relaxor ferroelectrics. These findings indicate that spatial non-uniformity in Ovda Regio's microwave emission is governed by surface modification processes, with the festoon flow eruption leading to the formation of high amounts of ferroelectric minerals. Similar resurfacing processes that occur on other highlands likely regulate regional rates of surface-atmosphere interactions and directly impact present-day surface composition.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 3","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JE008563","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143595209","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":"Depositional Environment of the Amapari Marker Band: Rising Water Levels Formed Kilometer-Scale Lake in Gale Crater, Mars","authors":"Claire A. Mondro,&nbsp;J. Grotzinger,&nbsp;C. M. Fedo,&nbsp;M. P. Lamb,&nbsp;S. Gupta,&nbsp;W. E. Dietrich,&nbsp;S. Banham,&nbsp;C. Weitz,&nbsp;P. Gasda,&nbsp;D. Rubin,&nbsp;A. Cowart,&nbsp;K. Lewis,&nbsp;A. Roberts,&nbsp;A. B. Bryk,&nbsp;R. M. E. Williams,&nbsp;W. Rapin,&nbsp;C. Seeger,&nbsp;E. Kite,&nbsp;J. M. Davis,&nbsp;G. Caravaca,&nbsp;J. Schieber,&nbsp;A. R. Vasavada","doi":"10.1029/2024JE008606","DOIUrl":"https://doi.org/10.1029/2024JE008606","url":null,"abstract":"<p>The Amapari Marker Band (AMB) is a layer within the Mount Sharp stratigraphy that has been mapped around the Gale crater in orbital images and was recently investigated up close by the Curiosity rover. Symmetric wave ripple marks within the AMB indicate a lacustrine depositional environment in the area investigated along the Curiosity traverse. The wavelength and morphology of the ripples constrain the water depth to a few meters or less. The lateral continuity of the ripple unit defines a minimum extent of the lake during ripple formation. The stratigraphy of the AMB is consistent with an environment of increasing water depth during sedimentation and the lateral correlation of the AMB stratigraphy suggests a transgressive depositional system building upon an eroded surface. The location of the AMB within the surrounding aeolian stratigraphy, coupled with the progression of depositional environments through the Mirador formation, records a pattern of a rising water table relative to sedimentation rates. The potential regional extent of the lacustrine environment, based on orbital mapping of the AMB's variable elevation, spans at minimum 2.0 km of the lateral AMB deposit in the area around Marker Band Valley and may have extended up to 14 km to the west across the northern Gale crater.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 3","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143595210","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":"Remote Determination of Martian Chloride Salt Abundances","authors":"Eashan Das,&nbsp;Timothy D. Glotch,&nbsp;Christopher S. Edwards,&nbsp;Cheng Ye,&nbsp;Ralph E. Milliken,&nbsp;A. Deanne Rogers,&nbsp;Lars Ehm,&nbsp;Kristen Norberg","doi":"10.1029/2024JE008541","DOIUrl":"https://doi.org/10.1029/2024JE008541","url":null,"abstract":"<p>Chloride salt-bearing deposits are widely distributed across the southern highlands of Mars. Because chloride salts are highly water-soluble, these deposits may be representative of the last significant period of stable liquid water at the Martian surface. Therefore, these deposits are key to understanding the fate and evolution of surface waters on Mars. However, little consensus exists about the formation conditions of these deposits, and their origins remain enigmatic. This is due in part because remote spectroscopic detection and quantification of many anhydrous chlorides is hampered by a lack of easily discernible diagnostic absorption features. To address this issue, we present a novel Hapke radiative transfer model-based method to estimate hydration states and salt abundances of Martian chloride salt-bearing deposits using visible/near-infrared (VNIR) reflectance spectra. VNIR laboratory spectra are used to derive water abundances of analog chloride-bearing materials, establishing an experimental basis for application of these methods to Mars. These methods are then applied to orbital Compact Reconnaissance Imaging Spectrometer for Mars data to create maps of the hydration state and modeled salt abundance of chloride-bearing deposits. When overlain onto high resolution 3D digital terrain models, these methods produce the highest resolution site-specific salt abundance maps currently available, enhancing our understanding of chloride deposit geologic context. As an example, deposits in the Terra Sirenum region are observed to have higher estimated salt abundances than previously recognized, exhibiting spatial variations in both abundance and surface morphology.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 3","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JE008541","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143581665","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":"Spatially Resolved Visible Wavelength Spectroscopy of the Galilean Moons With VLT/MUSE","authors":"Oliver R. T. King,&nbsp;Leigh N. Fletcher,&nbsp;Fraser Clarke,&nbsp;Andrea Hidalgo","doi":"10.1029/2024JE008511","DOIUrl":"https://doi.org/10.1029/2024JE008511","url":null,"abstract":"<p>We present observations of all four Galilean satellites using spatially resolved visible wavelength (475–935 nm) spectroscopic observations with the ground-based VLT/MUSE + AOF facility in 2019. A range of features in the observed reflectance spectra were compared to laboratory measured spectra, and mapped to understand the spatial distributions (at <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>300 km spatial resolution) of different compositional species on the moons' surfaces, providing near-global context for future observations. The <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>485 nm spectral slope on Io is consistent with the presence sulfur materials such as <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>S</mi>\u0000 <mn>8</mn>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${mathrm{S}}_{8}$</annotation>\u0000 </semantics></math>, with stronger slopes on the trailing hemisphere and at high latitudes. Io's 560 nm absorption band is strongest at high latitudes, and shows an enhancement in the Pele plume deposit, consistent with the presence of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>S</mi>\u0000 <mn>4</mn>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${mathrm{S}}_{4}$</annotation>\u0000 </semantics></math>. The similar 530 nm absorption band on Europa is constrained to the trailing hemisphere, and also appears consistent with sulfur materials. On Ganymede, a proxy for the 577.3 nm molecular oxygen absorption was found to be strongest at low-mid latitudes, particularly around the trailing hemisphere, with a potential slight southward bias. This distribution appears consistent with the hypothesis that Ganymede's closed magnetic field line region allows stable bubbles of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>O</mi>\u0000 <mn>2</mn>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${mathrm{O}}_{2}$</annotation>\u0000 </semantics></math> to exist in Ganymede's surface ice.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 3","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JE008511","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143581664","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":"Global Distribution and Geological Features of Ilmenite-Rich Sites on the Lunar Surface","authors":"Satoru Yamamoto,&nbsp;Moe Matsuoka,&nbsp;Hiroshi Nagaoka,&nbsp;Makiko Ohtake,&nbsp;Ayame Ikeda","doi":"10.1029/2024JE008663","DOIUrl":"https://doi.org/10.1029/2024JE008663","url":null,"abstract":"<p>We studied the global distribution and geological features of lunar surface sites whose spectra indicate an ilmenite-rich composition. Hyperspectral data obtained by the Kaguya Spectral Profiler were used for data mining to identify diagnostic features of a 1- and 2-<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>μ</mi>\u0000 </mrow>\u0000 <annotation> ${upmu }$</annotation>\u0000 </semantics></math>m spectral reflectance of ilmenite, revealing the global distribution of sites showing ilmenite-rich spectra. The results show that regions with ilmenite-rich spectra are concentrated at the margins of impact basins on the lunar nearside, whereas no such regions are identified in the Feldspathic Highland Terrain or the South Pole-Aitken basin. Using multiband images and a digital terrain model obtained by the Kaguya Multiband Imager and Terrain Camera, we examined the geological features of each site showing ilmenite-rich spectra and found that most of the sites are distributed on pyroclastic deposits overlying highland materials. Spectra interpreted as glass-rich material are prevalent in and around areas having ilmenite-rich spectra. However, sites showing ilmenite-rich spectra do not correspond to mare regions with <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mtext>TiO</mtext>\u0000 <mn>2</mn>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${text{TiO}}_{2}$</annotation>\u0000 </semantics></math>-rich basalts. These results may indicate that the concentration of ilmenite in pyroclastic deposits is high enough to exhibit diagnostic features of 1- and 2-<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>μ</mi>\u0000 </mrow>\u0000 <annotation> ${upmu }$</annotation>\u0000 </semantics></math>m spectral reflectance of ilmenite, whereas the concentration in mare regions with <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mtext>TiO</mtext>\u0000 <mn>2</mn>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${text{TiO}}_{2}$</annotation>\u0000 </semantics></math>-rich basalt is not. Since pyroclastic deposits are expected to be extensive, deep unconsolidated deposits of relatively block-free debris, resulting in high processing efficiency in the hydrogen reduction processes, our data may be useful for developing an efficient exploration strategy for ilmenite as a lunar resource.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 3","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143581663","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":"Probing the Viscosity of Venus's Mantle From Dynamic Topography at Baltis Vallis","authors":"Nathan J. McGregor,&nbsp;Francis Nimmo,&nbsp;Cedric Gillmann,&nbsp;Gregor J. Golabek,&nbsp;Alain M. Plattner,&nbsp;Jack W. Conrad","doi":"10.1029/2024JE008581","DOIUrl":"https://doi.org/10.1029/2024JE008581","url":null,"abstract":"<p>The Baltis Vallis channel on Venus preserves a record of long-wavelength deformation generated by a convecting mantle, providing a unique window into the planet's geodynamics. Notably, the observed topography along the channel is not downhill, suggesting complex interactions between surface processes and mantle dynamics. We statistically compare the observed dynamic topography of Baltis Vallis with dynamic topographies generated by a suite of stagnant-lid mantle convection models to constrain Venus' interior dynamics. Baltis Vallis's relatively young age (likely <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>&lt;</mo>\u0000 </mrow>\u0000 <annotation> ${&lt; } $</annotation>\u0000 </semantics></math>250 Myr) and low root-mean-square relief of 217 m indicate vigorous convection in Venus's mantle, with a Rayleigh number <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>&gt;</mo>\u0000 </mrow>\u0000 <annotation> ${ &gt;} $</annotation>\u0000 </semantics></math>4 <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>×</mo>\u0000 </mrow>\u0000 <annotation> ${times} $</annotation>\u0000 </semantics></math> <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msup>\u0000 <mn>10</mn>\u0000 <mn>8</mn>\u0000 </msup>\u0000 </mrow>\u0000 <annotation> ${10}^{8}$</annotation>\u0000 </semantics></math>, implying a mantle viscosity 1–2 orders of magnitude lower than Earth's. This difference may result from either a water-rich, less-degassed interior or a higher-temperature mantle beneath an insulating lid. Additionally, our simulations suggest that melt advection may dominate heat transport on Venus, potentially leading to non-linear temperature profiles in the crust. Upcoming missions such as <i>VERITAS</i> and <i>EnVision</i> will deliver higher-resolution gravity and topographic data, providing further constraints on Venus's present-day internal dynamics and the origin of Baltis Vallis.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 3","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143571270","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 Timing and Origin of Lobate Ejecta Forms at Craters in Mercury's South Polar Region","authors":"A. R. Lennox,&nbsp;A. J. Blance,&nbsp;D. A. Rothery,&nbsp;J. Wright,&nbsp;M. Balme,&nbsp;S. J. Conway","doi":"10.1029/2024JE008713","DOIUrl":"https://doi.org/10.1029/2024JE008713","url":null,"abstract":"<p>We present six newly identified examples of lobate ejecta in Mercury's south polar quadrangle (H15), providing the first evidence of syn-impact formation through our observation of perched impact melt at Nairne and Magritte craters. This finding challenges the idea that lobate forms could have developed post-impact via mass wasting or landslide processes, suggesting instead that many, if not all, lobate ejecta deposits formed contemporaneously with the impact event. We present detailed morphostratigraphic maps of two exemplary case studies: Nairne and Magritte, for which we used shadow measurements to better constrain the morphology of their lobes. Many examples globally, including Nairne, have been formed by deposition of the lobe material into a topographically lower antecedent crater. While we confirm that topography plays a significant role in the formation of lobate ejecta, it cannot be the sole factor, as similar impacts onto pre-existing craters do not always produce these features and not all lobate ejecta exhibit evidence for a topographic control. Our study also highlights the frequent association between lobate ejecta and characteristics of oblique impacts. Considering analogous features at Mars and the Moon in particular, lobate ejecta on Mercury is likely the result of either fluidized or dry granular flows, with minimal delay between impact and emplacement. Our findings suggest that lobate ejecta are more widespread on Mercury than previously recognized, and future studies and missions, such as a comprehensive global survey with higher resolution data from BepiColombo, will continue to constrain their formation mechanisms and prevalence.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 3","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JE008713","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143571246","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":"Crack Development Inside and Around Lunar Lava Tubes","authors":"E. A. Williams,&nbsp;L. G. J. Montési","doi":"10.1029/2024JE008553","DOIUrl":"https://doi.org/10.1029/2024JE008553","url":null,"abstract":"<p>Evidence shows that lava tubes on the Moon, which constitute intriguing targets for exploration and long-term habitation, could be much larger than terrestrial tubes. However, existing observation strategies cannot confidently constrain the exact dimensions of lunar tubes in anticipation of in situ exploration. We produced and analyzed numerical models of the elastic gravity-induced deformation field around lunar lava tubes to determine where failure may occur on their internal surfaces and how the lunar surface above them may deform. This analysis suggests ways to determine tube dimensions from lunar surface morphological observations. The models predict extensive failure on the tube floors and roofs, leaving relatively small sections of pristine floor near the tube walls even if the tube itself may not collapse. The most extensive type of internal failure, tensile floor failure, depends on the tube shape. Additionally, the lunar surface around lava tubes develops cracks and subtle topographic bulges running parallel to the tube axis at distances proportional to the tube width. If observed, these could be used to determine the tube's width remotely. We examined several lunar sinuous rilles using orbital data to search for the surface features we expect near tubes. Linear cracks consistent with the presence of lava tubes are present on the possible extensions of three rilles: Rimae Mairan, Sharp, and Marius. Other locations did not show similar features, possibly because of the resolution of available data, tube depths, or surface degradation. However, surface or low-altitude observations would be more sensitive to the expected structures.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 3","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JE008553","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143571247","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":"Electron Densities in Jupiter's Upper Ionosphere Inferred From Juno Plasma Wave Observations","authors":"W. S. Kurth,&nbsp;J. B. Faden,&nbsp;J. H. Waite,&nbsp;A. H. Sulaiman,&nbsp;S. S. Elliott,&nbsp;G. B. Hospodarsky,&nbsp;J. E. P. Connerney,&nbsp;J. A. Kammer,&nbsp;T. Greathouse,&nbsp;P. Valek,&nbsp;F. Allegrini,&nbsp;F. Bagenal,&nbsp;T. Stallard,&nbsp;L. Moore,&nbsp;D. A. Coffin,&nbsp;O. Agiwal,&nbsp;P. Withers,&nbsp;S. J. Bolton","doi":"10.1029/2024JE008845","DOIUrl":"https://doi.org/10.1029/2024JE008845","url":null,"abstract":"&lt;p&gt;Juno's highly eccentric polar orbit takes it to perijove distances of &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; ${sim} $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;1.06 &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;R&lt;/mi&gt;\u0000 &lt;mi&gt;J&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{R}}_{J}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; on each orbit. For the first perijove, this occurred just north of the jovigraphic equator, but has precessed north by about a degree per orbit over the mission. Minimum altitudes vary from &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; ${sim} $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;3,200–8,000 km through the mission. The Waves instrument observes a number of plasma wave modes in and near the non-auroral ionosphere that provide information on the local electron number density, including electron plasma oscillations that occur at the electron plasma frequency &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;f&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;p&lt;/mi&gt;\u0000 &lt;mi&gt;e&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${f}_{pe}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; and whistler-mode hiss which has an upper frequency limit of &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;f&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;p&lt;/mi&gt;\u0000 &lt;mi&gt;e&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${f}_{pe}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; in Jupiter's strongly magnetized inner magnetosphere. The electron plasma frequency provides the electron number density. We present electron densities in the topside ionosphere, similar to Earth's F2 layer, from the &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; ${sim} $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;59 perijoves analyzed to date. Peak densities range from &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; ${sim} $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;100 to 80,000 &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 ","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 3","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JE008845","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143564919","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":"Dynamo Models With a Mercury-Like Magnetic Offset Dipole","authors":"P. Kolhey,&nbsp;D. Heyner,&nbsp;J. Wicht,&nbsp;T. Gastine,&nbsp;K.-H. Glassmeier,&nbsp;F. Plaschke","doi":"10.1029/2024JE008660","DOIUrl":"https://doi.org/10.1029/2024JE008660","url":null,"abstract":"<p>Mercury has a global magnetic field that is unique in our solar system. It is dominated by a weak axial dipole and a substantial axial quadrupole contribution. The field has a dipole tilt which is smaller than one degree and an offset of the magnetic equator toward north by about 20% of the planetary radius. The only dynamo model that succeeds in continuously reproducing these features without having to rely on an unrealistic heat-flux pattern through the core-mantle boundary is a double-diffusive model by Takahashi et al. (2019), https://doi.org/10.1038/s41467-018-08213-7, where thermal effects cause a thick, stably stratified layer in the outer parts of the core. In this study we further show the sensitivity of this model to the choice of parameters. In the explored parameter set, the model yields solutions which are unrealistic for Mercury when convection becomes vigorous. We present a new single-diffusive model, that captures Mercury's field characteristics during long periods that are interrupted by dipole field reversals causing the magnetic equator to switch between the northern and southern hemisphere. The Mercury-like solutions are stable over a broader range of parameters. An important ingredient for the success is the fact that dynamo action sets in with the equatorially symmetric magnetic field family.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 3","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JE008660","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143564920","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}