Journal of Geophysical Research: Planets最新文献

{"title":"Observed Latitudinal, Longitudinal and Temporal Variability of Io's Atmosphere Simulated by a Purely Sublimation Driven Atmosphere","authors":"A.-C. Dott, J. Saur, S. Schlegel, D. F. Strobel, K. de Kleer, I. de Pater","doi":"10.1029/2024JE008869","DOIUrl":"https://doi.org/10.1029/2024JE008869","url":null,"abstract":"<p>How much of Io's <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mtext>SO</mtext>\u0000 <mn>2</mn>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${text{SO}}_{2}$</annotation>\u0000 </semantics></math> atmosphere is driven by volcanic outgassing or sublimation of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mtext>SO</mtext>\u0000 <mn>2</mn>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${text{SO}}_{2}$</annotation>\u0000 </semantics></math> surface frost is a question with a considerable history. We develop a time dependent surface temperature model including thermal inertia and the exact celestial geometry to model the radiation driven global structure and temporal evolution of Io's atmosphere. We show that many observations can be explained by assuming a purely sublimation driven atmosphere. We find that a thermal diffusivity <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>α</mi>\u0000 <mo>=</mo>\u0000 <mn>2.41</mn>\u0000 <mo>×</mo>\u0000 <mn>1</mn>\u0000 <msup>\u0000 <mn>0</mn>\u0000 <mrow>\u0000 <mo>−</mo>\u0000 <mn>7</mn>\u0000 </mrow>\u0000 </msup>\u0000 </mrow>\u0000 <annotation> $alpha =2.41times 1{0}^{-7}$</annotation>\u0000 </semantics></math> <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msup>\u0000 <mi>m</mi>\u0000 <mn>2</mn>\u0000 </msup>\u0000 <msup>\u0000 <mi>s</mi>\u0000 <mrow>\u0000 <mo>−</mo>\u0000 <mn>1</mn>\u0000 </mrow>\u0000 </msup>\u0000 </mrow>\u0000 <annotation> ${mathrm{m}}^{2}{mathrm{s}}^{-1}$</annotation>\u0000 </semantics></math> yields an averaged atmospheric <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mtext>SO</mtext>\u0000 <mn>2</mn>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${text{SO}}_{2}$</annotation>\u0000 </semantics></math> column density decreasing by more than one order of magnitude from the equator to the poles in accordance with the observed spatial variations of Io's column densities. Our model produces a strong day-night-asymmetry with modeled column density variations of almost two orders of magnitude at the equator as well as a sub-anti-Jovian hemis","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 7","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JE008869","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144564126","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":"Investigating the Extent of Bladed Terrain on Pluto via Photometric Surface Roughness","authors":"I. Mishra, R. Dhingra, B. J. Buratti, B. Seignovert, O. L. White","doi":"10.1029/2024JE008554","DOIUrl":"https://doi.org/10.1029/2024JE008554","url":null,"abstract":"<p>NASA's New Horizons spacecraft discovered fields of sub-parallel sets of steep ridges situated in the high-altitude, low-latitude regions in Pluto's encounter hemisphere called “bladed terrain.” Thought to be formed due to sublimational erosion of methane ice, bladed terrain represents an active response of Pluto's landscape to current and past climates. The observation of a strong methane signature within the low latitudes of Pluto's non-encounter hemisphere points to the possibility that this terrain type is also present there. To test this hypothesis, in the absence of high resolution images of Pluto's non-encounter hemisphere, we employ photometric analysis of the methane rich regions. We specifically focus on determining the macroscopic surface roughness in selected images, whose photometric-effect can be apparent even in low-resolution images. We employ the “crater-roughness” photometric model of Buratti and Veverka (1985, https://doi.org/10.1016/0019-1035(85)90094-6), which assumes that the surface is covered with parabolic depressions defined by a depth-to-radius ratio parameter <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>q</mi>\u0000 </mrow>\u0000 <annotation> $q$</annotation>\u0000 </semantics></math> (higher <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>q</mi>\u0000 </mrow>\u0000 <annotation> $q$</annotation>\u0000 </semantics></math> values correspond to rougher surfaces). Despite the high uncertainty in the retrieved roughness values from our analysis, we can safely conclude that the hypothesized bladed terrain region on the non-encounter hemisphere of Pluto is very rough (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>q</mi>\u0000 <mo>=</mo>\u0000 <mn>0.4</mn>\u0000 <msubsup>\u0000 <mn>7</mn>\u0000 <mrow>\u0000 <mo>−</mo>\u0000 <mn>0.11</mn>\u0000 </mrow>\u0000 <mrow>\u0000 <mo>+</mo>\u0000 <mn>0.10</mn>\u0000 </mrow>\u0000 </msubsup>\u0000 </mrow>\u0000 <annotation> $q=0.4{7}_{-0.11}^{+0.10}$</annotation>\u0000 </semantics></math>, 2<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>σ</mi>\u0000 </mrow>\u0000 <annotation> $sigma $</annotation>\u0000 </semantics></math>), with the median roughness more than twice that of other broad regions of Pluto studied in this work, including the encounter-hemisphere bladed terrain region (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>q</mi>\u0000 <mo>=</mo>\u0000 <mn>0.2</mn>\u0000 <msubsup>\u0000 <mn>1</mn>\u0000 <mrow>\u0000 ","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 7","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144558183","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":"Survey of Cold Plasma Blobs in Jupiter's Magnetosphere: Evidence for Centrifugal Instabilities","authors":"Jian-zhao Wang,&nbsp;Fran Bagenal,&nbsp;Robert J. Wilson,&nbsp;Peter A. Delamere,&nbsp;Robert W. Ebert,&nbsp;Philip W. Valek,&nbsp;Frederic Allegrini,&nbsp;Jamey R. Szalay","doi":"10.1029/2025JE009021","DOIUrl":"https://doi.org/10.1029/2025JE009021","url":null,"abstract":"<p>In Jupiter's magnetosphere, plasma originating from Io's escaping atmosphere is radially transported outward via two modes of centrifugally driven dynamics. In flux tube interchange events from the Rayleigh–Taylor instability, the cold and dense flux tube moves outward, while hot and depleted flux tubes are injected inwards. In the ballooning mode of the firehose instability, the flux tube breaks off with bursts of plasma blobs. Both modes suggest outward transport of cold, dense plasma blobs. In this study, we survey the cold blobs, analyzing 147 events based on thermal plasma measurements from the Juno/JADE-I instrument. The cold blobs are identified by searching time-of-flight spectra for very narrow signatures in the energy distributions. Plasma parameters determined by forward modeling reveal two types of cold blob events. The first type of event, occurring outside 25 R_<i>J</i>, exhibits high density and fast radial velocity accompanied by magnetic nulls and mainly occurs on the dawnside, suggesting an origin from the ballooning mode. The second type of event, occurring within 35 R_<i>J</i>, shows simultaneous outward moving cold, dense plasma with inward moving hot, tenuous plasma with no dependence on local time, indicating flux tube interchange. Based on statistics between 15 R_<i>J</i> and 30 R_<i>J</i>, the mass transport rate of the cold blobs is estimated to be about 100 kg/s, which is insufficient to account for the plasma production rate at Io.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 7","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144550876","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":"Sodium and Potassium Linewidths as an Atmospheric Escape Diagnostic at Mercury","authors":"P. Lierle,&nbsp;C. Schmidt","doi":"10.1029/2025JE008975","DOIUrl":"https://doi.org/10.1029/2025JE008975","url":null,"abstract":"<p>The spatial distribution and linewidth of Mercury's sodium and potassium exospheres were observed using a combination of long-slit and high-resolution point spectroscopy. Effective temperatures were estimated from emission line profiles by forward modeling their Doppler broadening. These serve as an energy metric for collisionless gas that is inherently nonthermal. The Na gas at low and mid-latitudes ranges from 1,200 to 1,300 K along the noon meridian, in agreement with MESSENGER scale heights, increasing by ∼200 K at the poles and terminator. This increase is attributed to the loss of low energy atoms to the surface during photon-driven transport antisunward. An escaping potassium tail was measured for the first time, observed out to 10.4 R_M with Na/K ∼95 at 5.8 R_M. Emission linewidths increase sharply between the dayside and escaping tail, with Na growing from about 1,200 to 7,500 K, and K from 750 to 8,500 K by the time the gas reaches 4.3 R_M downtail. Na D line profiles down the exotail also evolve from Gaussian to boxcar in shape. Both characteristics are interpreted as filtering of the nascent velocity distribution function, where low energy atoms on gravitationally bound trajectories are removed from the gas population, while high energy escaping atoms are retained. Na linewidths become invariant past 3.5 R_M, placing this altitude as the ballistic apex of bound trajectories. In this way, Mercury's emissions prototype a novel technique toward a broader understanding of atmospheric escape, using emission line morphology to probe the transition between bound and escaping gas.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 7","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144537195","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":"Cooling History and Evolution Dynamics of Green Glass Beads During Lunar Fire-Fountain Eruptions: Insights From Na, K and Cu Distributions","authors":"Xue Su,&nbsp;Youxue Zhang,&nbsp;Yang Liu,&nbsp;Robert M. Holder","doi":"10.1029/2025JE009027","DOIUrl":"https://doi.org/10.1029/2025JE009027","url":null,"abstract":"<p>Volcanic glass beads on the Moon have traditionally been thought to only record volatile loss during pyroclastic eruptions. However, recent discoveries have shown that lunar orange glass beads, representing primitive high-Ti basalts, experienced both outgassing and in-gassing of volatile elements such as Na, K, Cu, and S. In this work, we examine lunar green glass beads from samples 15421 and 15366, representing primitive very-low-Ti basalts, for the distribution of Na, K and Cu using EMP analyses and LA-ICP-MS mapping. It is found that all studied lunar green beads show increased Na, K and Cu concentrations near the bead surfaces, indicative of in-gassing. A quantitative model was developed to simulate the concentration evolution of Na and Cu in individual green glass beads during eruption and cooling. The presence of similar in-gassing diffusion profiles of volatile elements in beads from different eruptions indicates a common behavior of lunar volcanic gas. In addition to volatile in-gassing, LA-ICP-MS mapping of Na and K in one green bead from sample 15366 shows features suggesting collision of melt droplets during the fire-fountain eruption, revealing more details in the dynamic aspects of lunar fire-fountain eruptions. Compared to orange glass beads, the varying boundary conditions of green glass beads during formation may suggest that their eruption plume evolved and dissipated more rapidly, potentially linked to changes in the global lunar atmosphere.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 7","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JE009027","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144551251","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":"Perpendicular-Parallel Asymmetry of Venus Bow Shock Under Different Parker Spiral Angles","authors":"Nihan Chen,&nbsp;Haoyu Lu,&nbsp;Jinbin Cao,&nbsp;Shibang Li,&nbsp;Mingyu Wu,&nbsp;Yihui Song,&nbsp;Jianxuan Wang,&nbsp;Jianing Zhao,&nbsp;Yuchen Cao","doi":"10.1029/2024JE008829","DOIUrl":"https://doi.org/10.1029/2024JE008829","url":null,"abstract":"<p>Several typical asymmetries in the Venusian bow shock (BS) location, including the magnetic north-south asymmetry, the pole-equator asymmetry, and the perpendicular-parallel asymmetry, have been proven to be controlled or affected by the interplanetary magnetic field orientation. The physical reasons behind the perpendicular-parallel shock asymmetry remain inadequately explained. The effects of ion-scale dynamics have not been adequately addressed in both previous observational data and numerical simulations. Using global multifluid simulations, we demonstrate that the electric field strength differs significantly between the two types of BS, resulting in their asymmetric positions relative to the planet. The quasi-perpendicular BS generates a stronger Hall electric field, which decelerates the solar wind at a greater distance from Venus. In contrast, the weaker electric field at the quasi-parallel BS only effectively slows down the solar wind closer to the planet, leading to further compression of the induced magnetosphere and an enhanced ambipolar electric field due to increased electron pressure gradients. The differential energy transfer from the solar wind at the two BS types contributes to the asymmetry in plasma flow and magnetic field accumulation downstream. These findings provide new insights into the plasma dynamics around unmagnetized planets and highlight the role of electric field structure in shaping the induced magnetosphere of Venus.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 7","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144515130","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 Influence of Interior Structure and Thermal State on Impact Melt Generation Upon Large Impacts Onto Terrestrial Planets","authors":"Lukas Manske,&nbsp;Thomas Ruedas,&nbsp;Ana-Catalina Plesa,&nbsp;Philipp Baumeister,&nbsp;Nicola Tosi,&nbsp;Natalia Artemieva,&nbsp;Kai Wünnemann","doi":"10.1029/2024JE008481","DOIUrl":"https://doi.org/10.1029/2024JE008481","url":null,"abstract":"<p>We investigate the melt production of planetary impacts as a function of planet size (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mrow>\u0000 <mi>R</mi>\u0000 <mo>/</mo>\u0000 <msub>\u0000 <mi>R</mi>\u0000 <mtext>Earth</mtext>\u0000 </msub>\u0000 </mrow>\u0000 </mrow>\u0000 <annotation> $R/{R}_{text{Earth}}$</annotation>\u0000 </semantics></math> = 0.1–1.5), impactor size (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mrow>\u0000 <mi>L</mi>\u0000 </mrow>\u0000 </mrow>\u0000 <annotation> $L$</annotation>\u0000 </semantics></math> = 1–1,000 km), and core size ratio (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mrow>\u0000 <msub>\u0000 <mi>R</mi>\u0000 <mtext>core</mtext>\u0000 </msub>\u0000 <mo>/</mo>\u0000 <mi>R</mi>\u0000 </mrow>\u0000 </mrow>\u0000 <annotation> ${R}_{text{core}}/R$</annotation>\u0000 </semantics></math> = 0.2–0.8) using a combination of parameterized convection models and fully dynamical 2D impact simulations. To this end, we introduce a new method to determine impact-induced melt volumes which we normalize by the impactor volume for better comparability. We find that this normalized melt production, or melting efficiency, is enhanced for large planets when struck by smaller impactors, while for small planets, melting efficiency is elevated when impacted by larger impactors. This diverging behavior can be explained by the thickness of the planets' thermal boundary layer and the shapes of their thermal and lithostatic pressure profiles. We also find that melting efficiency maxima are usually highest on Earth-size planets. We show that the melting efficiency is only affected by core size ratio for large cores and older planets, where melt production is decreased significantly compared to smaller core size ratios. Projecting the lunar impactor flux on the generic planets, we find that Moon-sized planets produce the most melt throughout their evolution, relative to planet volume. Contrary to previous scaling laws, our method accounts for melt production by decompression or plastic work in addition to shock melting. We find that traditional scaling laws underestimate melt production on length scales where variations in the target planets' lithology, temperature, and lithostatic pressure become significant. We propose empirical formulas to predict melt generation as a function of radial structure and thermal age.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 7","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JE008481","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144482293","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":"Sulfur Dioxide Distribution at the Venusian Cloud-Top Retrieved From Akatsuki UV Images","authors":"T. Iwanaka,&nbsp;T. Imamura,&nbsp;S. Aoki,&nbsp;E. Marcq,&nbsp;H. Sagawa,&nbsp;A. Stolzenbach,&nbsp;Y. J. Lee,&nbsp;A. Yamazaki","doi":"10.1029/2024JE008775","DOIUrl":"https://doi.org/10.1029/2024JE008775","url":null,"abstract":"&lt;p&gt;&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;S&lt;/mi&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $mathrm{S}{mathrm{O}}_{mathrm{2}}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; and the unidentified UV absorber are major absorbers in the near-ultraviolet region in the Venusian atmosphere and influence the climate system. We developed a method to retrieve &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;S&lt;/mi&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $mathrm{S}{mathrm{O}}_{mathrm{2}}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; and the imaginary part of the refractive index &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;n&lt;/mi&gt;\u0000 &lt;mi&gt;i&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${n}_{mathrm{i}}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, a proxy for the unidentified absorber, from 15,002 pairs of 283 and &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;365&lt;/mn&gt;\u0000 &lt;mspace&gt;&lt;/mspace&gt;\u0000 &lt;mi&gt;n&lt;/mi&gt;\u0000 &lt;mi&gt;m&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $365,mathrm{n}mathrm{m}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; images taken by the Ultraviolet imager (UVI) onboard Akatsuki. We obtained the distributions of &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;S&lt;/mi&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $mathrm{S}{mathrm{O}}_{mathrm{2}}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; and the unidentified absorber with high spatial resolution every 2 hours for about 6.5 years. We analyzed the local time and latitudinal distributions of &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;S&lt;/mi&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $mathrm{S}{mathrm{O}}_{mathrm{2}}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; and the unidentified absorber. The &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;S&lt;/mi&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $mathrm{S}{mathrm{O}}_{mathrm{2}}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; mixing ratio at the cloud top around &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 7","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144482093","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 Meter-Scale Roughness of Asteroid (101955) Bennu From the OSIRIS-REx Laser Altimeter","authors":"F. M. Rossmann,&nbsp;C. L. Johnson,&nbsp;E. B. Bierhaus","doi":"10.1029/2024JE008799","DOIUrl":"https://doi.org/10.1029/2024JE008799","url":null,"abstract":"<p>Asteroid (101955) Bennu is a near-Earth, potentially hazardous, rubble pile asteroid, and was the primary target of the NASA OSIRIS-REx mission. The surface is dominated by the expression of boulders and has been heavily modified by impact cratering. Here, we analyze surface roughness, calculated using data from the OSIRIS-REx Laser Altimeter, to investigate spatial variations in boulders and finer-grained material across Bennu globally. Surface roughness is a statistical measure of change in surface height over a given baseline (horizontal spatial scale) and can be used to gain insight into the geologic processes that form and modify the surface over different scales. We calculate surface roughness at baselines of 0.20–20 m using the root-mean-square (RMS) deviation. We find that Bennu's surface roughness is self-affine over length scales between 0.2 m and <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>1.0 m, and between <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>1.0 and 20.0 m. We also find that surface roughness varies spatially and is dominated by the local size-frequency distribution of boulders. At the longest baselines, roughness is produced by the prominent equatorial ridge and the topographic relief of Bennu's largest boulders. At baselines between 0.20 and 2.0 m, the interiors of craters with diameters less than <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>25 m tend to be smooth compared with larger craters and the average background, supporting the presence of a finer-grained subsurface layer. Our results extend previous LiDAR-based asteroid roughness studies of (25143) Itokawa and (433) Eros to baselines more than 10 times shorter, and to an asteroid with different spectral class.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 6","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JE008799","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144339373","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":"Evolution of Convective Stresses in Stagnant-Lid Planets","authors":"C. Grigné","doi":"10.1029/2024JE008817","DOIUrl":"https://doi.org/10.1029/2024JE008817","url":null,"abstract":"<p>Stresses generated by convection in the mantle of rocky planets depend on the convective velocity and on the viscosity of the layer. When planets cool down, their convective motion slows down and the heat transfer becomes less efficient. The evolution of convective stresses as a function of this declining convective vigor has been described in contradictory ways, with either a decrease or an increase of stresses over time being invoked to explain some change of tectonic style when a planet cools down. In this study, 2-D Cartesian numerical simulations for a bottom-heated Newtonian fluid and scaling laws are used to show that, with a strongly temperature-dependent viscosity, convective stresses always increase, even if moderately, when the system gets colder. The stagnant-lid regime of convection for statistical steady-state is studied. The thickness of the stagnant lid and the viscous stress at its base are analyzed as a function of the temperature at the base of the model. Additional simulations with transient cooling are conducted and also exhibit an increase of convective stresses over time. The tectonic style of a planet (stagnant-lid mode or plate tectonics) is generally thought to be controlled by a fixed yield strength, with a transition from one mode to the other when the convective stresses cross this fixed limit. In this study, the evolution of convective stresses does not point to a clear temperature limit that would trigger a change of regime, and thermal evolution alone is not sufficient to explain transitions between tectonic styles.</p>","PeriodicalId":16101,"journal":{"name":"Journal of Geophysical Research: Planets","volume":"130 6","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JE008817","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144315331","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}