Icarus最新文献

{"title":"Evaluating an embryo origin for detached TNOs within full Kuiper belt formation models","authors":"Nathan A. Kaib ,&nbsp;Chadwick A. Trujillo ,&nbsp;Scott S. Sheppard","doi":"10.1016/j.icarus.2025.116733","DOIUrl":"10.1016/j.icarus.2025.116733","url":null,"abstract":"<div><div>With perihelia well beyond Neptune, but semimajor axes and eccentricities indicative of substantial perturbation, the origins of detached trans-Neptunian objects (TNOs) remain a dynamical puzzle. In particular, detached TNOs with orbital inclinations below <span><math><mo>∼</mo></math></span>25° are not easily generated from any known mechanism currently in the modern solar system. One notable hypothesis for the origins of detached TNOs is that a <span><math><mo>∼</mo></math></span>Mars- to Earth-mass planetary embryo detached the perihelia of these objects from Neptune during the process of Kuiper belt formation before the embryo itself was ejected. We numerically model this scenario via simulations of Kuiper belt formation from a primordial planetesimal belt that is dispersed through the migration of the giant planets. In addition to <span><math><mo>∼</mo></math></span> 10⁵ Kuiper belt objects, each of our simulations contains a hypothetical population of embryos in the primordial belt. We find that our embryos are unlikely to reach the high-perihelion, large semimajor axis orbit necessary to efficiently detach TNO perihelia from Neptune’s influence. Moreover, embryos will typically take at least 100 Myrs to reach these unlikely orbits, at which point most of the primordial belt will have already been ejected by the planets, limiting the available population that can be detached. Finally, the TNOs that our embryos do detach consistently have a semimajor axis distribution that is more biased toward small values than observed detached TNOs have. Thus, we conclude that planetary embryos in the primordial Kuiper belt are not likely to have been the primary mechanism for the origin of detached TNOs.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"442 ","pages":"Article 116733"},"PeriodicalIF":2.5,"publicationDate":"2025-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144703637","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":"Adaptive isoline interval optimization for precise contour segmentation and instance-level detection of Martian impact craters","authors":"Dong Chen ,&nbsp;Fan Hu ,&nbsp;Jiaming Na ,&nbsp;Zhenxin Zhang ,&nbsp;Zhen Cao ,&nbsp;Liqiang Zhang ,&nbsp;Zhizhong Kang ,&nbsp;Jiju Poovvancheri ,&nbsp;Norbert Pfeifer","doi":"10.1016/j.icarus.2025.116722","DOIUrl":"10.1016/j.icarus.2025.116722","url":null,"abstract":"<div><div>This study presents an adaptive method for optimizing isoline intervals for semantic segmentation and object detection of Martian impact crater contours based on Mars HRSC DEM data. The method uses an isoline interval division technique to improve the discernibility of terrain boundary features. This enhancement enables effective tracking and detection of closed contours of impact craters within the detection box. An energy function is designed for precise crater contouring, and a Bayesian optimization algorithm is applied to adaptively adjust contour intervals and optimize the contours. To address inaccuracies in the detection box, the paper proposes a progressively iterative correction method for refining impact crater target boxes. This method adjusts the width and height of the target box during iterations to make the bounding box tighten and fully enclose the impact crater. The position and size of the detection box are automatically optimized, thereby improving its accuracy. A pre-trained Segment Anything Model (SAM) is used to segment the morphological structures of the impact crater. Experimental results show that, for Martian impact craters larger than 3 km in the study area using Mars HRSC DEM data, the contouring accuracy achieved an mIoU of 69.75% and an mF1-Score of 80.51%. This substantially outperforms the performance of traditional watershed and depression filling contouring methods. The correction method improves the mIoU accuracy of bounding boxes within the study area by 7.49% for the YOLOv8 object detection network and 15.28% for the Robbins crater catalog database. The resulting high-precise crater contours, bounding boxes, and internal morphological features provide valuable inputs for deep space exploration and planetary science. The source code is available at <span><span>https://github.com/shincccc/CraterContourSeg</span><svg><path></path></svg></span>.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"441 ","pages":"Article 116722"},"PeriodicalIF":2.5,"publicationDate":"2025-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144653206","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":"Regolith properties and Stokes vector radar polarimetry models for the moon","authors":"Bruce A. Campbell","doi":"10.1016/j.icarus.2025.116738","DOIUrl":"10.1016/j.icarus.2025.116738","url":null,"abstract":"<div><div>Earth-based and orbital radar systems collect images of the Moon in a polarimetric format that allows derivation of the Stokes vector, which represents the echo power and relative phase of signals in two orthogonal polarizations. Backscattering analyses for geologic studies often use two observable parameters, such as the opposite-sense circular echo power with the circular polarization ratio (CPR or μ_c), or the three components from a decomposition model such as the <em>m</em>-χ approach. The <em>m</em>-χ model provides a composite of power values assumed to correlate with the properties of “polarized” single-bounce and double-bounce reflections, and a random or “unpolarized” component. This model can be written equivalently in terms of <em>m</em> (degree of polarization) and the circular polarization ratio, and there is a similar correlation between the <em>m</em>-χ components and the CPR in data for the lunar maria (and superposed craters) at 12.6-cm and 70-cm wavelengths. These correlations suggest that the fully polarized mare echo is primarily produced by scattering from subsurface rocks, with an approximately constant degree of linear polarization of 30–40 % at the two wavelengths. Most of the surface echo is unpolarized until roughness becomes extreme in areas like crater ejecta or impact melt where the CPR is &gt;1. Because of the substantial subsurface component, the <em>m</em>-χ model cannot uniquely separate single-bounce and double-bounce surface returns, consistent with similar ambiguities in interpreting the CPR. Understanding these general properties of lunar regolith scattering can be used to highlight areas with anomalous enhancements and suggests new directions for modeling of radio-frequency scattering by regolith surfaces, particles, and rocks. Future work can produce Stokes-vector values from existing Earth-based data, and these products can provide a larger wavelength and incidence angle range to complement images from orbital radar systems.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"441 ","pages":"Article 116738"},"PeriodicalIF":2.5,"publicationDate":"2025-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144672269","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":"Book review: “Planetary Geology: An Introduction”","authors":"Johannes M. Meusburger","doi":"10.1016/j.icarus.2025.116735","DOIUrl":"10.1016/j.icarus.2025.116735","url":null,"abstract":"","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"443 ","pages":"Article 116735"},"PeriodicalIF":3.0,"publicationDate":"2025-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145099874","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":"Angular momentum drain: Despinning embedded planetesimals","authors":"Stephen Li,&nbsp;Maggie Ju,&nbsp;A.C. Quillen,&nbsp;Adam E. Rubinstein","doi":"10.1016/j.icarus.2025.116723","DOIUrl":"10.1016/j.icarus.2025.116723","url":null,"abstract":"<div><div>Young and forming planetesimals experience impacts from particles present in a protostellar disk. Using crater scaling laws, we integrate ejecta distributions for oblique impacts. For impacts at 10 to 65 m/s, expected for impacts associated with a disk wind, we estimate the erosion rate and torque exerted on the planetesimal. We find that the mechanism for angular momentum drain proposed by Dobrovolskis and Burns (1984) for asteroids could operate in the low velocity regime of a disk wind. We find that angular momentum drain via impacts operates in the gravitational focusing regime. The angular momentum transfer is most effective when the wind speed is high, the projectile density is high compared to the bulk planetesimal density, and the planetesimal is sufficiently weak that cratering is in the gravity regime. We find that angular momentum drain due to impacts within a pebble cloud may, in those specific conditions, facilitate collapse of single planetesimals.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"441 ","pages":"Article 116723"},"PeriodicalIF":2.5,"publicationDate":"2025-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144631977","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":"Dynamical origin of Theia, the last giant impactor on Earth","authors":"Duarte Branco ,&nbsp;Pedro Machado ,&nbsp;Sean N. Raymond","doi":"10.1016/j.icarus.2025.116724","DOIUrl":"10.1016/j.icarus.2025.116724","url":null,"abstract":"<div><div>Cosmochemical studies have proposed that Earth accreted roughly 5%–10% of its mass from carbonaceous (CC) material, with a large fraction delivered late via its final impactor, Theia (the Moon-forming impactor). Here, we evaluate this idea using dynamical simulations of terrestrial planet formation, starting from a standard setup with a population of planetary embryos and planetesimals laid out in a ring centered between Venus and Earth’s orbits, and also including a population of CC planetesimals and planetary embryos scattered inward by Jupiter. We find that this scenario can match a large number of constraints, including (i) the terrestrial planets’ masses and orbits; (ii) the CC mass fraction of Earth; (iii) the much lower CC mass fraction of Mars, as long as Mars only accreted CC planetesimals (but no CC embryos); (iv) the timing of the last giant (Moon-forming) impact; and (v) a late accretion phase dominated by non-carbonaceous (NC) bodies. For this scenario to work, the total mass in scattered CC objects must have been <span><math><mrow><mo>∼</mo><mn>0</mn><mo>.</mo><mn>2</mn><mo>−</mo><mn>0</mn><mo>.</mo><mn>3</mn><msub><mrow><mi>M</mi></mrow><mrow><mo>⊕</mo></mrow></msub></mrow></math></span>, with an embryo-to-planetesimal mass ratio of at least 8, and CC embryos in the <span><math><mrow><mo>∼</mo><mn>0</mn><mo>.</mo><mn>01</mn><mo>−</mo><mn>0</mn><mo>.</mo><mn>05</mn><msub><mrow><mi>M</mi></mrow><mrow><mo>⊕</mo></mrow></msub></mrow></math></span> mass range. In that case, our simulations show there are roughly 50-50 odds of Earth’s last giant impactor (Theia) having been a carbonaceous object — either a pure CC embryo or an NC embryo that previously accreted a CC embryo. Our simulations thus provide dynamical validation of cosmochemical studies.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"441 ","pages":"Article 116724"},"PeriodicalIF":2.5,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144611682","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":"Experimental and theoretical porosity determination for ices of astrophysical interest: CH4, C2H4, C2H6, CH3OH, N2, NH3, CO, and CO2","authors":"C. Millán,&nbsp;R. Luna,&nbsp;M. Domingo,&nbsp;M.Á. Satorre,&nbsp;C. Santonja","doi":"10.1016/j.icarus.2025.116710","DOIUrl":"10.1016/j.icarus.2025.116710","url":null,"abstract":"<div><div>In a previous work of this group, the effective medium approximations (EMAs), mainly Lorentz-Lorenz, Maxwell-Garnett, and Bruggeman models, were experimentally tested for the case of CO₂ for determination of porosity. The present work extends the porosity calculation for a set of astrophysical relevant molecules from their experimental density and refractive index. Important discrepancies between theoretical and experimental values are not detected except in case of CO₂, already reported. In addition, the porosity acquired by this set of molecules becomes quite clear.</div><div>The theoretical values of porosity predicted by EMAs models show similar trends for all the molecules subject of our study. Porosity vs. temperature behavior allows us to group molecules in two sets, and each molecule displays characteristics of its own possibly caused by phase changes.</div><div>A given set of molecules no longer appears to exhibit density variation in the temperature range from the accretion to desorption one, and as a consequence porosity remains unchanged, which does not mean an absolute lack of porosity. All the molecules show a temperature range in which the porosity is constant (plateau). In this work, a relation between the desorption energy and the temperature at which the porosity vs temperature shows a plateau is obtained. This could be explained as a possible consequence of desorption and diffusion energy dependence. On this basis, it can be speculated the existence of a limit temperature for this set of molecules, upon which, the porosity stops evolving and becomes constant.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"441 ","pages":"Article 116710"},"PeriodicalIF":2.5,"publicationDate":"2025-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144631976","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":"Physical properties of subsurface water ice deposits in Mars’s Mid-Latitudes from the shallow radar","authors":"Yuval Steinberg ,&nbsp;Isaac B. Smith ,&nbsp;Oded Aharonson","doi":"10.1016/j.icarus.2025.116716","DOIUrl":"10.1016/j.icarus.2025.116716","url":null,"abstract":"<div><div>Understanding Mars’s water budget and distribution is crucial for evaluating its habitability and studying its evolution and past climate. Evidence for past and present glaciation includes geomorphological features: polar ice caps and subsurface ice. Among the most compelling evidence are Viscous Flow Features (VFFs), which suggest the presence of water ice due to surface patterns similar to Earth’s rock glaciers and debris-covered glaciers. These features, including Lobate Debris Aprons (LDAs), are found in the mid-latitudes (30° and 50°) of both hemispheres.</div><div>This study focuses on the composition of LDAs, which are large, ice-rich deposits found on slopes of massifs. Two hypotheses for their formation propose either low water ice content (30%) (“rock glaciers”) or near-pure water ice under a debris layer (“debris-covered glaciers”). Using SHARAD (SHAllow RADar) data, we calculate two key parameters – dielectric constant (<span><math><msup><mrow><mi>ϵ</mi></mrow><mrow><mo>′</mo></mrow></msup></math></span>) and loss tangent (<span><math><mrow><mo>tan</mo><mi>δ</mi></mrow></math></span>) – to better understand the purity and composition of these deposits. Previous studies suggest LDAs consist of nearly pure water ice. Our work increases global coverage across the northern and southern hemispheres, examining five sites with enhanced data coverage and incorporating both <span><math><msup><mrow><mi>ϵ</mi></mrow><mrow><mo>′</mo></mrow></msup></math></span> and <span><math><mrow><mo>tan</mo><mi>δ</mi></mrow></math></span> to improve the analysis.</div><div>Our results indicate that LDAs are most likely part of a global population of features composed of <span><math><mo>&gt;</mo></math></span>80% water ice, supporting the debris-covered glacier hypothesis. The results also point to the consistency of the debris cover across the globally distributed sites. This finding suggests that these features formed under similar climatic conditions, such as might occur under a specific orbital configuration. The high purity of the ice in LDAs has significant implications for understanding Mars’s past climate and for future exploration, as LDAs represent accessible reservoirs of water ice at mid-latitudes. Additionally, our findings highlight the need for future radar-based studies to incorporate the calculation of the loss tangent, as this can alleviate the sensitivity to the topography of the LDA base inherent in <span><math><msup><mrow><mi>ϵ</mi></mrow><mrow><mo>′</mo></mrow></msup></math></span>.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"441 ","pages":"Article 116716"},"PeriodicalIF":2.5,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144604571","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 impact of whistler mode waves on Jupiter's auroral intensity distribution","authors":"Arvind K. Tripathi ,&nbsp;Rajendra P. Singhal ,&nbsp;Ashish K. Mishra","doi":"10.1016/j.icarus.2025.116731","DOIUrl":"10.1016/j.icarus.2025.116731","url":null,"abstract":"<div><div>The diffuse aurora at Jupiter has been studied, and the intensities of its ultraviolet diffuse auroral emissions have been measured. Electrons trapped on closed magnetic field lines are diffused into the atmospheric loss cone through resonant interactions with whistler-mode waves. Observational data collected by the Juno orbiter have been utilized in this study. The precipitation flux of diffused particles into the atmospheric loss-cone has been calculated for five distinct L-shells <em>L</em> = 10, 12, 15, 18, and 20. Additionally, the volume excitation and ionization rates in Jupiter's atmosphere have been determined using the Analytical Yield Spectrum (AYS) approach for electron energy degradation. The calculations have been performed for H Lyman-α from atomic H excitation, H Lyman-α from dissociative excitation of molecular H₂, and the Lyman and Werner bands from H₂ excitation. The height-integrated volume excitation rates yield the intensities of H Lyman-α, Lyman, and Werner bands. At two L-shells, <em>L</em> = 10 and (<em>L</em> = 20), the calculated diffuse auroral intensities for various cases—H Lyman-α, Lyman, and Werner bands—are found to be 97 kR (12 kR), 490 kR (63 kR), and 520 kR (67 kR), respectively. The intensities obtained in this study are approximately 4 to 20 times higher than those estimated in a previous study involving electron cyclotron harmonic (ECH) waves. The electron density in Jupiter's atmosphere has been calculated, with the peak density reaching 2.3 × 10⁷ cm⁻³ at an altitude of 600 km. In contrast, a previous study involving ECH waves found the peak density to be 1 × 10⁷ cm⁻³. Outcomes are discussed.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"441 ","pages":"Article 116731"},"PeriodicalIF":2.5,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144614281","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":"Exploring the impact of wind-driven saltation on methane in the atmosphere of Mars","authors":"Mikkel Bregnhøj ,&nbsp;Svend J. Knak Jensen ,&nbsp;Jan Thøgersen ,&nbsp;Kai Finster","doi":"10.1016/j.icarus.2025.116734","DOIUrl":"10.1016/j.icarus.2025.116734","url":null,"abstract":"<div><div>The presence or absence of methane in the atmosphere of Mars has been a matter of intense investigations and debate for decades. Current theories and observations require some as-yet unidentified mechanism that can remove methane from the lower martian atmosphere on a timescale of a few weeks or less.</div><div>In this work, we experimentally tested if methane sequestration by wind-driven saltation of martian surface minerals can explain the observations. Triboelectric charging of sand particles during the frequent martian dust storms could potentially provide the energy needed to chemically sequester methane and thereby act as a sink for methane on Mars. We performed laboratory experiments with basaltic martian mineral analog sand from Gufunes, Iceland, which was abraded by tumbling end-over-end in a container made from a monolithic block of the same mineral. In this way, wind-driven saltation was simulated in an all-basalt environment with minimal interference from wall-effects.</div><div>The results show that methane is not affected during more than 100 terrestrial days of simulated saltation in the all-basalt environment. This stands in contrast to similar experiments using quartz or glass simulation containers. Furthermore, methane remains unaffected by saltation in the presence of excess amounts of Mars-relevant oxidants, such as oxygen and perchlorate salt, which again contrasts to experiments performed in glass containers. However, methane is oxidized to carbon dioxide in the presence of reactive hypochlorite salt. Our results are discussed in the context of recent reports on the chemistry of oxychlorine species on Mars, and they highlight the need to account for wall-effects in experimental simulations of wind-driven saltation in planetary environments.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"441 ","pages":"Article 116734"},"PeriodicalIF":2.5,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144597406","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}