Icarus最新文献

{"title":"Not enough H2O2 to warm early Mars","authors":"Maxime Maurice ,&nbsp;François Forget ,&nbsp;Franck Lefèvre ,&nbsp;Aurélien Stolzenbach ,&nbsp;A. Yassin Jaziri ,&nbsp;Ashwin S. Braude ,&nbsp;Martin Turbet ,&nbsp;Ehouarn Millour ,&nbsp;Yangcheng Luo","doi":"10.1016/j.icarus.2025.116914","DOIUrl":"10.1016/j.icarus.2025.116914","url":null,"abstract":"<div><div>There exists strong geomorphological, sedimentary and mineralogical evidence that Mars had an active surface hydrological cycle during the Noachian period, about 3.8 Gyr ago (Ga). However, how surface temperatures compatible with perennial liquid water could be sustained in spite of a Sun that only had 75% of its present-day brightness has remained elusive, leading to the faint young Sun paradox for Mars. Recently, the greenhouse effect of hydrogen peroxide (H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>O<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>) has been proposed as a solution by Ito et al. (2020). Radiative transfer models have shown that a few ppmv of H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>O<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> in a 1 or 2 bar CO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> atmosphere could solve the faint young Sun paradox on early Mars. In a warm and wet CO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> atmosphere, H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>O<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> is produced by photochemistry and contributes to the stability of the CO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> atmosphere along with the HO<span><math><msub><mrow></mrow><mrow><mi>x</mi></mrow></msub></math></span> (H, OH and HO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>) catalytic cycles. Nevertheless, a thorough assessment of the viability of such a high H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>O<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> abundance is still lacking. Using 1D and 3D climate models coupled with a C–H–O photochemistry solver, we show that in the most favorable case for H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>O<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> to build up, its steady-state abundance is several orders of magnitude short from its required abundance of <span><math><mrow><mo>∼</mo><mn>1</mn></mrow></math></span> ppmv to have a significant radiative effect. Furthermore, we also show that a transient warming episode associated with massive H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>O<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> release cannot exceed 10 Martian years. We therefore rule out H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>O<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> as a warming agent for early Mars.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"448 ","pages":"Article 116914"},"PeriodicalIF":3.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145882242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On the stability limits for moons orbiting planets: A numerical investigation","authors":"G.O. Barbosa ,&nbsp;T. Santana ,&nbsp;O.C. Winter","doi":"10.1016/j.icarus.2025.116924","DOIUrl":"10.1016/j.icarus.2025.116924","url":null,"abstract":"<div><div>We investigate the long-term dynamical stability of moons orbiting planets by performing high-resolution <span><math><mi>N</mi></math></span>-body simulations across five planet-to-star mass ratios (<span><math><mrow><mi>μ</mi><mo>=</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span> to <span><math><mrow><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>−</mo><mn>5</mn></mrow></msup></mrow></math></span>). Moons are modeled as massless test particles and their orbits are initialized at pericenter, where stellar perturbations are minimized. This setup yields upper-envelope estimates of the outermost stable semimajor axis (<span><math><msub><mrow><mi>a</mi></mrow><mrow><mi>E</mi></mrow></msub></math></span>) under optimally phased initial conditions, which we systematically map as a function of eccentricity. We derive empirical fits for <span><math><mrow><msub><mrow><mi>a</mi></mrow><mrow><mi>E</mi></mrow></msub><mrow><mo>(</mo><mi>e</mi><mo>)</mo></mrow></mrow></math></span> in each <span><math><mi>μ</mi></math></span> regime and observe that the stable region contracts with increasing eccentricity and decreasing planetary mass. For larger values of <span><math><mi>μ</mi></math></span>, we identify a detached island of stability at intermediate eccentricities (<span><math><mrow><mn>0</mn><mo>.</mo><mn>2</mn><mo>≲</mo><mi>e</mi><mo>≲</mo><mn>0</mn><mo>.</mo><mn>7</mn></mrow></math></span>), which we show to be associated with the evection resonance; additional integrations confirm libration of the resonant angle. We examine the sensitivity of <span><math><msub><mrow><mi>a</mi></mrow><mrow><mi>E</mi></mrow></msub></math></span> to the initial satellite–star mean-anomaly offset (<span><math><mrow><mi>Δ</mi><mi>M</mi></mrow></math></span>) and find that orbital phase can modulate the critical stability threshold by <span><math><mrow><mo>≲</mo><mn>10</mn><mtext>%</mtext></mrow></math></span>. Our updated stability criteria therefore consist of: (i) new empirical fits for the critical semimajor axis as a function of eccentricity, (ii) its systematic dependence on the planet-to-star mass ratio, and (iii) the role of the evection resonance and orbital phase in extending stability beyond classical limits. These results provide a refined framework for assessing exomoon survivability across diverse planetary systems. The empirical relations presented in this work can be directly employed to constrain the parameter space in observational searches for exomoons.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"448 ","pages":"Article 116924"},"PeriodicalIF":3.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145882261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Meteor luminous efficiencies from simultaneous multi-frequency radar and high-resolution optical observations","authors":"Logan Dewsnap ,&nbsp;Margaret Campbell-Brown","doi":"10.1016/j.icarus.2025.116926","DOIUrl":"10.1016/j.icarus.2025.116926","url":null,"abstract":"<div><div>We examine the effects of assumptions in the calculation of electron line density of radar meteors on the value of luminous efficiency calculated using simultaneous radar and optical observations. We combine high-resolution optical measurements from the Canadian Automated Meteor Observatory (CAMO) with multi-frequency radar echoes from the Canadian Meteor Orbit Radar (CMOR). Previous work relating <span><math><mi>β</mi></math></span> and <span><math><mi>τ</mi></math></span> has been limited to single-frequency radar observations, which requires additional modeling assumptions such as the initial trail radius (Weryk and Brown, 2013). In this work, we require model fits to all three frequencies at which CMOR operates, which provides better constraints which reduce the need for these assumptions, at the cost of significantly shrinking the pool of suitable data. Between 2017–2022, 299 candidates for three-frequency CMOR simultaneously observed by CAMO were identified, of which 1% were suitable for fitting. Although the fittable data set was too small to determine statistical trends, all events showed lower luminous efficiencies than those that would be found through single-frequency modeling. This emphasizes the need for better models of scattering from meteor trails in these studies.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"448 ","pages":"Article 116926"},"PeriodicalIF":3.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145922784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Monte-Carlo radiative transfer model to simulate thermal infrared emission spectra from planetary surfaces: Mineralogical mixtures and thermal gradients","authors":"C. Pilorget ,&nbsp;C. Ye ,&nbsp;C.S. Edwards","doi":"10.1016/j.icarus.2026.116936","DOIUrl":"10.1016/j.icarus.2026.116936","url":null,"abstract":"<div><div>Thermal IR spectroscopy has been widely used in the exploration of the Solar System to characterize the mineralogical composition of planetary surfaces. Beyond the identification of the different compounds, estimating their abundances presents significant challenges, hence the usual application of simplified models that generally assume linear mixtures for example. These approaches, relatively easy to use, might however lead to important biases. Here we present a novel model based on a Monte-Carlo approach to compute the radiative transfer within a granular medium where the grains are resolved. A critical aspect of our model is that it can more directly accept data acquired from lab experiments to simulate various types of mixtures (linear, intimate, layered) in a realistic manner. Variable thermal profiles can also be simulated in the sample. Such a model can be used to better constrain the abundances of mineral compounds in natural planetary surfaces. We present some first applications, in particular estimating potential biases when neglecting multiple scattering in the models. We also evaluate the effect of porosity and thermal gradients in a few limited cases to prove the feasibility for future applications.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"448 ","pages":"Article 116936"},"PeriodicalIF":3.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145922785","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Upper limits of CH4 and OCS in the Martian atmosphere from NOMAD/TGO solar occultation: A study of vertical averaging and systematic uncertainties","authors":"M. Escudero-Jiménez ,&nbsp;M.A. López-Valverde ,&nbsp;J. Peralta ,&nbsp;T. Moya ,&nbsp;A. Belmonte ,&nbsp;A. Brines ,&nbsp;I. Thomas ,&nbsp;G. Villanueva ,&nbsp;G. Liuzzi ,&nbsp;E. Knutsen ,&nbsp;S. Viscardy ,&nbsp;F. González-Galindo ,&nbsp;A. Modak ,&nbsp;B. Funke ,&nbsp;J.J. López-Moreno ,&nbsp;J. Rodríguez ,&nbsp;R. Sanz ,&nbsp;F. Daerden ,&nbsp;L. Trompet ,&nbsp;A.S.J. Khayat ,&nbsp;A.C. Vandaele","doi":"10.1016/j.icarus.2025.116923","DOIUrl":"10.1016/j.icarus.2025.116923","url":null,"abstract":"<div><div>Here we update the search for two trace species of high interest in the Martian atmosphere, methane (CH<span><math><msub><mrow></mrow><mrow><mn>4</mn></mrow></msub></math></span>) and carbonyl sulfide (OCS), using solar occultation (SO) measurements from the NOMAD spectrometer on board the Trace Gas Orbiter (TGO). Neither species has been detected in previous analyses of TGO’s dedicated SO instruments, ACS and NOMAD. Our approach focused on NOMAD-SO data, assessing in detail the calibration uncertainties to quantify systematic error components, and investigating if vertical averaging of spectra to reduce random noise would enhance the signal-to-noise ratio (SNR). The latter step required careful data cleaning with precise radiative transfer modeling and should improve upon earlier searches that analyzed spectra individually.</div><div>We examined 19,330 NOMAD SO spectra targeting CH<span><math><msub><mrow></mrow><mrow><mn>4</mn></mrow></msub></math></span> and OCS, from diffraction orders 134 and 129, corresponding to 76 and 142 vertical scans, respectively. These scans span a wide range of latitudes and seasons over three Martian years (April 2018 to November 2022, MY34-MY36). No CH<span><math><msub><mrow></mrow><mrow><mn>4</mn></mrow></msub></math></span> or OCS absorption features were detected and our composite vertical profiles (5–50 km tangent altitude) yielded stringent upper limits. For methane, the 1-<span><math><mi>σ</mi></math></span> upper limits typically lie around 0.5 ppbv, reaching 0.2 ppbv at some altitudes and locations. Our methane limits were primarily constrained by systematic uncertainties, particularly the residual baseline shape, and are therefore relatively higher than those previously reported in Knutsen et al. (2021), who processed the spectra differently to remove this effect. For OCS, our composite profiles indicate concentrations below 5 ppbv at low altitudes and below 2 ppbv in some cases, also at the 1-<span><math><mi>σ</mi></math></span> significance level.</div><div>Further improvements will require additional calibration refinements, ideally through better characterization of instrument behavior under thermal variations. As a practical step, narrowing the analyzed spectral intervals can reduce continuum uncertainties, provided contaminating features are absent. For methane features in diffraction order 134, such narrowing lowers uncertainties by a factor of three, getting closer to the most stringent limits previously reported (Knutsen et al., 2021).</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"448 ","pages":"Article 116923"},"PeriodicalIF":3.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145922783","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Identification and characterization of the topside bulge of the Venusian ionosphere","authors":"Satyandra M. Sharma ,&nbsp;Varun Sheel ,&nbsp;Martin Pätzold","doi":"10.1016/j.icarus.2025.116920","DOIUrl":"10.1016/j.icarus.2025.116920","url":null,"abstract":"<div><div>Venus, in the absence of an intrinsic magnetic field, undergoes a direct interaction between its ionosphere and the solar wind. Previous missions, including <em>Mariner</em>, <em>Venera</em>, and the <em>Pioneer Venus Orbiter</em> (<em>PVO</em>), reported a recurring localized increase in electron density, often termed a ”bulge,” at altitudes between 160 and 200 km. This study investigates this topside bulge using over 200 dayside electron density profiles derived from the <em>Venus Radio Science experiment (VeRa)</em> onboard the <em>Venus Express (VEX)</em>. We employ an automated, gradient-based classification algorithm to provide a quantitative and reproducible method for identifying and categorizing the bulge morphology into three types. Type 1 profiles exhibit a distinct secondary peak above the main V2 layer. Type 2 profiles display a shoulder-like feature near the bulge altitude. Type 3 bulges are not visually apparent but can be identified through residuals obtained after subtracting a Chapman layer fit to the V2 peak. The bulge is detected in over 80% of the analyzed profiles, with a higher occurrence during periods of low solar activity and at lower solar zenith angles (<span><math><mrow><mi>S</mi><mi>Z</mi><mi>A</mi><mi>s</mi></mrow></math></span>). Type 1 morphologies are only observed at low latitudes (within <span><math><mo>±</mo></math></span>40°N). The peak altitude of the bulge negatively correlates with <span><math><mrow><mi>S</mi><mi>Z</mi><mi>A</mi></mrow></math></span>, suggesting that thermospheric cooling toward the terminator significantly influences the bulge altitude. The occurrence patterns and morphological characteristics indicate that the bulge is likely influenced by external drivers, such as solar wind interaction, rather than being solely a result of local photochemical processes.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"448 ","pages":"Article 116920"},"PeriodicalIF":3.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145839436","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"From lunar terrain to learned representations: A comparative study of crater extraction","authors":"Ersa Wei ,&nbsp;Xiangmei Liu ,&nbsp;Minxuan Gao ,&nbsp;Feng Zhang ,&nbsp;Pingping Lu ,&nbsp;Yanan Dang ,&nbsp;Jiahan Wang ,&nbsp;Tao Wu ,&nbsp;Jiaqi Chen","doi":"10.1016/j.icarus.2025.116909","DOIUrl":"10.1016/j.icarus.2025.116909","url":null,"abstract":"<div><div>Lunar craters are crucial for understanding the Moon’s evolutionary history and mission planning. However, their vast quantity and extensive distribution make establishing a reliable database through manual counting extremely challenging. To improve crater extraction efficiency, this study proposes and evaluates optimized traditional morphological methods and novel deep learning models within the 60°S-60°N latitude range. For traditional methods, we developed a morphological feature extraction algorithm that integrates highlight-shadow region detection with edge features from multi-source data (DOM and DEM). Compared to single detection benchmarks, this fusion strategy significantly enhances performance, improving recall and precision by 13.42% and 28.91% respectively. In deep learning, we propose Bottleneck Residual U-Net (BRU-Net) and Spatial Attention Bottleneck Residual U-Net (SA-BRU-Net) based on the U-Net architecture. These models were trained on cropped and transformed lunar DEM data and combined with template matching algorithms. Their overall performance surpasses the baseline U-Net model. The study further demonstrates that model extraction effectiveness can be progressively improved through dataset optimization, network depth increase, and extended training duration. To enable fair quantitative evaluation of both technical approaches, the study designed comparative extraction experiments using the same DEM dataset. The SA-BRU-Net model successfully extracted 171,136 craters, while the traditional algorithm identified only 31,760 from the same data source. This advantage was particularly evident in detecting small craters with degraded morphology and blurred features (accounting for 80.20% of total extractions), confirming the generational advantage of deep learning models in pattern recognition and generalization capability. This result identified approximately seven times more craters than the combined Head and Povilaitis catalogs, potentially supplementing existing manual crater inventories.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"447 ","pages":"Article 116909"},"PeriodicalIF":3.0,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145797668","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Considerations on the process of target selection for the Comet Interceptor mission","authors":"C. Snodgrass ,&nbsp;E. Mazzotta Epifani ,&nbsp;C. Tubiana ,&nbsp;J.P. Sánchez ,&nbsp;N. Biver ,&nbsp;L. Inno ,&nbsp;M.M. Knight ,&nbsp;P. Lacerda ,&nbsp;J. De Keyser ,&nbsp;A. Donaldson ,&nbsp;N.J.T. Edberg ,&nbsp;M. Galand ,&nbsp;A. Guilbert-Lepoutre ,&nbsp;P. Henri ,&nbsp;S. Kasahara ,&nbsp;H. Kawakita ,&nbsp;R. Kokotanekova ,&nbsp;M. Kueppers ,&nbsp;M. Micheli ,&nbsp;M. Pajusalu ,&nbsp;E. Jehin","doi":"10.1016/j.icarus.2025.116887","DOIUrl":"10.1016/j.icarus.2025.116887","url":null,"abstract":"<div><div>Comet Interceptor is an ESA science mission with payload contributions from ESA Member States and with an international participation by JAXA. It is the first mission that is being designed, built, and potentially launched <em>before</em> its target is known. This approach will enable the spacecraft to perform the first mission to a Long Period Comet from the Oort Cloud, as these comets have fleeting visits to the inner Solar System lasting only months to years from first discovery, too short for the usual process of mission development to be followed. In this paper we describe a number of factors that need to be considered in selecting a target for the mission, including scientific, orbital, spacecraft and instrument constraints, and discussion of different prioritisation strategies. We find that, in the case where we have a choice of targets, our decisions will mostly be driven by orbital information, which we will have relatively early on, with information on the activity level of the comet an important but secondary consideration. As cometary activity levels are notoriously hard to predict based on early observations alone, this prioritisation / decision approach based more on orbits gives us confidence that a good comet that is compatible with the spacecraft constraints will be selectable with sufficient warning time to allow the mission to intercept it.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"447 ","pages":"Article 116887"},"PeriodicalIF":3.0,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145692534","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Information content analysis of venus clouds and haze based on polarization bands of the SPICAV IR and Venspec-H instruments","authors":"Yiqi Li ,&nbsp;Xiaobing Sun ,&nbsp;Xiao Liu ,&nbsp;Honglian Huang ,&nbsp;Xiaobing Zheng ,&nbsp;Yichen Wei ,&nbsp;Yizhe Fan ,&nbsp;Shun Yao","doi":"10.1016/j.icarus.2025.116905","DOIUrl":"10.1016/j.icarus.2025.116905","url":null,"abstract":"<div><div>Using the <span>PyMieDAP</span> radiative-transfer model, we constructed a multi-layer representation of Venus clouds and haze and designed multiple observing scenarios to quantify the sensitivity of intensity and polarization measurements to aerosol parameters as a function of altitude, wavelength, and phase angle. Intensity observations are more sensitive to variations in lower-cloud microphysical parameters (<span><math><msubsup><mrow><mi>r</mi></mrow><mrow><mi>g</mi></mrow><mrow><mn>3</mn></mrow></msubsup></math></span>, <span><math><msubsup><mrow><mi>σ</mi></mrow><mrow><mi>g</mi></mrow><mrow><mn>3</mn></mrow></msubsup></math></span>), whereas polarization at small phase angles (<span><math><mrow><mi>α</mi><mo>≈</mo><mn>15</mn><mo>°</mo></mrow></math></span>) is dominated by single scattering and is therefore more sensitive to upper-cloud parameters. Introducing a joint-observation mode increases the degrees of freedom for signal (DFS) by about 3; further adding potential <span>Venspec-H</span> near-infrared bands yields an additional <span><math><mrow><mo>∼</mo><mn>0</mn><mo>.</mo><mn>6</mn></mrow></math></span> DFS. The optimal observing geometry depends on phase angle: upper-cloud parameters are best constrained at <span><math><mrow><mi>α</mi><mo>&gt;</mo><mn>140</mn><mo>°</mo></mrow></math></span>; lower-cloud parameters and the real refractive index (<span><math><msub><mrow><mi>n</mi></mrow><mrow><mi>r</mi></mrow></msub></math></span>) at <span><math><mrow><mi>α</mi><mo>&lt;</mo><mn>20</mn><mo>°</mo></mrow></math></span>. The upper-cloud number density (<span><math><msubsup><mrow><mi>V</mi></mrow><mrow><mn>0</mn></mrow><mrow><mn>2</mn></mrow></msubsup></math></span>) is best retrieved near <span><math><mrow><mi>α</mi><mo>≈</mo><mn>80</mn><mo>°</mo></mrow></math></span>. For future instrument design, appropriate aerosol-window bands should be selected across 650 nm–<span><math><mrow><mn>2</mn><mo>.</mo><mn>5</mn><mspace></mspace><mi>μ</mi><mi>m</mi></mrow></math></span>; under the joint-observation mode, we recommend polarization accuracy <span><math><mrow><mo>≤</mo><mn>0</mn><mo>.</mo><mn>002</mn></mrow></math></span> and intensity (radiance) accuracy <span><math><mrow><mo>≤</mo><mn>3</mn><mtext>%</mtext></mrow></math></span> to optimize retrieval accuracy.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"447 ","pages":"Article 116905"},"PeriodicalIF":3.0,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145748591","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The moon's formation time recorded in lunar mare basalts","authors":"Mu-Han Yang ,&nbsp;Qian W.L. Zhang ,&nbsp;Richard W. Carlson ,&nbsp;Bi-Wen Wang ,&nbsp;Dongjian Ouyang ,&nbsp;Qiu-Li Li","doi":"10.1016/j.icarus.2025.116889","DOIUrl":"10.1016/j.icarus.2025.116889","url":null,"abstract":"<div><div>The Moon's formation time is a key factor for understanding the early evolution of the Earth-Moon system. The lunar magma ocean (LMO) model explains how cumulate mafic materials crystallizing from the LMO form the source of mare basalts (SMB). The SMB with an equilibrated Sm–Nd system is considered to share an identical initial Pb isotope signature (Pb_SMB). Because Pb is volatile while U is refractory, Pb_SMB can provide constraints for the timing of volatile depletion, most likely dating the time of Moon formation by a giant impact. The Pb_SMB is a link between the initial Pb composition of lunar mare basalts and the Moon's early evolution via a two-stage Pb evolution model that provides a simplified but informative framework. Using four mare basalts with well-constrained ages and initial Pb isotopic compositions, we estimate the Moon's formation time at <span><math><msubsup><mn>4516</mn><mrow><mo>−</mo><mn>18</mn></mrow><mrow><mo>+</mo><mn>21</mn></mrow></msubsup></math></span> Ma and the SMB formation time at <span><math><msubsup><mn>4377</mn><mrow><mo>−</mo><mn>27</mn></mrow><mrow><mo>+</mo><mn>57</mn></mrow></msubsup></math></span> Ma, which we regard as the preferred solution within the statistical framework of the model. Our modelling strategy also facilitates the dating of mare basalt fragments lacking Zr-bearing minerals using the initial Pb isotopic compositions constrained by U-poor minerals.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"447 ","pages":"Article 116889"},"PeriodicalIF":3.0,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145692533","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}