Pub Date : 2025-12-19DOI: 10.1016/j.icarus.2025.116918
R.J. Wilson
This paper investigates ion plasma properties in the jovian middle magnetosphere utilizing two Juno JADE-I datasets, and two different techniques. Proton properties are found using the SPECIES proton dataset and numerical moments. Simultaneous forward modeling of the TOF and SPECIES data is used to extract plasma parameters from 4 heavy ion species of sulfur and oxygen ions (S, S, O and a ion species representing both S and O). These four ion species share a bulk velocity but have independent density and isotropic temperatures. The proton moments provide an isotropic temperature, and velocities that are consistent with that of the heavies. Data from Juno’s Prime Mission are analyzed, showing that most data is sub-corotational, with occasional intervals of super-corotation or anti-corotation flows. The relative abundances of the five ions are investigated, and while the ion species dominates throughout all radial distances, protons density can be the second largest abundance, and equivalent to the minor heavy ions at larger distances, suggesting their influence had been previously underestimated.
{"title":"Jupiter’s middle magnetosphere as observed by Juno JADE-I","authors":"R.J. Wilson","doi":"10.1016/j.icarus.2025.116918","DOIUrl":"10.1016/j.icarus.2025.116918","url":null,"abstract":"<div><div>This paper investigates ion plasma properties in the jovian middle magnetosphere utilizing two Juno JADE-I datasets, and two different techniques. Proton properties are found using the SPECIES proton dataset and numerical moments. Simultaneous forward modeling of the TOF and SPECIES data is used to extract plasma parameters from 4 heavy ion species of sulfur and oxygen ions (S<span><math><msup><mrow></mrow><mrow><mo>+</mo></mrow></msup></math></span>, S<span><math><msup><mrow></mrow><mrow><mo>+</mo><mo>+</mo><mo>+</mo></mrow></msup></math></span>, O<span><math><msup><mrow></mrow><mrow><mo>+</mo><mo>+</mo></mrow></msup></math></span> and a <span><math><mrow><mi>m</mi><mo>/</mo><mi>q</mi><mo>=</mo><mn>16</mn></mrow></math></span> <span><math><mrow><mi>a</mi><mi>m</mi><mi>u</mi><mo>/</mo><mi>q</mi></mrow></math></span> ion species representing both S<span><math><msup><mrow></mrow><mrow><mo>+</mo><mo>+</mo></mrow></msup></math></span> and O<span><math><msup><mrow></mrow><mrow><mo>+</mo></mrow></msup></math></span>). These four ion species share a bulk velocity but have independent density and isotropic temperatures. The proton moments provide an isotropic temperature, and velocities that are consistent with that of the heavies. Data from Juno’s Prime Mission are analyzed, showing that most data is sub-corotational, with occasional intervals of super-corotation or anti-corotation flows. The relative abundances of the five ions are investigated, and while the <span><math><mrow><mi>m</mi><mo>/</mo><mi>q</mi><mo>=</mo><mn>16</mn></mrow></math></span> <span><math><mrow><mi>a</mi><mi>m</mi><mi>u</mi><mo>/</mo><mi>q</mi></mrow></math></span> ion species dominates throughout all radial distances, protons density can be the second largest abundance, and equivalent to the minor heavy ions at larger distances, suggesting their influence had been previously underestimated.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"447 ","pages":"Article 116918"},"PeriodicalIF":3.0,"publicationDate":"2025-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145837351","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}
Pub Date : 2025-12-19DOI: 10.1016/j.icarus.2025.116914
Maxime Maurice , François Forget , Franck Lefèvre , Aurélien Stolzenbach , A. Yassin Jaziri , Ashwin S. Braude , Martin Turbet , Ehouarn Millour , Yangcheng Luo
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 (HO) has been proposed as a solution by Ito et al. (2020). Radiative transfer models have shown that a few ppmv of HO in a 1 or 2 bar CO atmosphere could solve the faint young Sun paradox on early Mars. In a warm and wet CO atmosphere, HO is produced by photochemistry and contributes to the stability of the CO atmosphere along with the HO (H, OH and HO) catalytic cycles. Nevertheless, a thorough assessment of the viability of such a high HO 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 HO to build up, its steady-state abundance is several orders of magnitude short from its required abundance of ppmv to have a significant radiative effect. Furthermore, we also show that a transient warming episode associated with massive HO release cannot exceed 10 Martian years. We therefore rule out HO as a warming agent for early Mars.
有强有力的地形学、沉积学和矿物学证据表明，火星在3.8 Gyr ago (Ga) Noachian时期有一个活跃的地表水循环。然而，在太阳亮度只有现在的75%的情况下，火星表面的温度如何能与常年存在的液态水保持一致，这仍然是一个难以捉摸的问题，这导致了火星年轻太阳微弱的悖论。最近，Ito等人（2020）提出了过氧化氢（H2O2）的温室效应作为解决方案。辐射传输模型表明，在1或2巴的二氧化碳大气中，几ppmv的H2O2可以解决早期火星上微弱的年轻太阳悖论。在温暖潮湿的CO2大气中，H2O2通过光化学反应产生，并与HOx （H， OH和HO2）催化循环一起有助于CO2大气的稳定性。然而，对如此高的H2O2丰度的生存能力的全面评估仍然缺乏。利用1D和3D气候模型加上C-H-O光化学解算器，我们发现，在H2O2最有利的情况下，其稳态丰度比产生显著辐射效应所需的丰度（~ 1 ppmv）短几个数量级。此外，我们还表明，与大量H2O2释放相关的短暂变暖事件不会超过10个火星年。因此，我们排除了H2O2作为早期火星变暖剂的可能性。
{"title":"Not enough H2O2 to warm early Mars","authors":"Maxime Maurice , François Forget , Franck Lefèvre , Aurélien Stolzenbach , A. Yassin Jaziri , Ashwin S. Braude , Martin Turbet , Ehouarn Millour , 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":"2025-12-19","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}
Pub Date : 2025-12-16DOI: 10.1016/j.icarus.2025.116913
Aster G. Taylor , Fred C. Adams , Nuria Calvet
During their formative stages, giant planets are fed by infalling material sourced from the background circumstellar disk. Due to conservation of angular momentum, the incoming gas and dust collects into a circumplanetary disk that processes the material before it reaches the central planet itself. This work investigates the complex vertical structure of these circumplanetary disks and calculates their radiative signatures. A self-consistent numerical model of the temperature and density structure of the circumplanetary environment reveals that circumplanetary disks are thick and hot, with aspect ratios and temperatures approaching that of the central planet. The disk geometry has a significant impact on the radiative signatures, allowing future observations to determine critical system parameters. The resulting disks are gravitationally stable and viscosity is sufficient to drive the necessary disk accretion. However, sufficiently rapid mass accretion can trigger a thermal instability, which sets an upper limit on the mass accretion rate. This paper shows how the radiative signatures depend on the properties of the planetary system and discuss how the system parameters can be constrained by future observations.
{"title":"The two-dimensional structure of circumplanetary disks and their radiative signatures","authors":"Aster G. Taylor , Fred C. Adams , Nuria Calvet","doi":"10.1016/j.icarus.2025.116913","DOIUrl":"10.1016/j.icarus.2025.116913","url":null,"abstract":"<div><div>During their formative stages, giant planets are fed by infalling material sourced from the background circumstellar disk. Due to conservation of angular momentum, the incoming gas and dust collects into a circumplanetary disk that processes the material before it reaches the central planet itself. This work investigates the complex vertical structure of these circumplanetary disks and calculates their radiative signatures. A self-consistent numerical model of the temperature and density structure of the circumplanetary environment reveals that circumplanetary disks are thick and hot, with aspect ratios <span><math><mrow><mi>H</mi><mo>/</mo><mi>R</mi><mo>∼</mo><mn>0</mn><mo>.</mo><mn>1</mn><mo>−</mo><mn>0</mn><mo>.</mo><mn>25</mn></mrow></math></span> and temperatures approaching that of the central planet. The disk geometry has a significant impact on the radiative signatures, allowing future observations to determine critical system parameters. The resulting disks are gravitationally stable and viscosity is sufficient to drive the necessary disk accretion. However, sufficiently rapid mass accretion can trigger a thermal instability, which sets an upper limit on the mass accretion rate. This paper shows how the radiative signatures depend on the properties of the planetary system and discuss how the system parameters can be constrained by future observations.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"447 ","pages":"Article 116913"},"PeriodicalIF":3.0,"publicationDate":"2025-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145797665","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}
Pub Date : 2025-12-13DOI: 10.1016/j.icarus.2025.116909
Ersa Wei , Xiangmei Liu , Minxuan Gao , Feng Zhang , Pingping Lu , Yanan Dang , Jiahan Wang , Tao Wu , Jiaqi Chen
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.
{"title":"From lunar terrain to learned representations: A comparative study of crater extraction","authors":"Ersa Wei , Xiangmei Liu , Minxuan Gao , Feng Zhang , Pingping Lu , Yanan Dang , Jiahan Wang , Tao Wu , 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":"2025-12-13","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}
Pub Date : 2025-12-13DOI: 10.1016/j.icarus.2025.116908
Alicia Neesemann , Stephan van Gasselt , Christian Riedel
This study examines the effects of crater-size frequency data collections and modeling parameters to better understand their influence on model ages for Cerealia Facula on Ceres. Key factors in this investigation include (a) analyst-dependent data collection, (b) slope discrepancies between measured distributions and modeled production functions, and (c) choice of chronology models. The foundational cartographic product for this work is a novel controlled high-resolution image mosaic built from data of NASA’s Dawn Framing Camera in XMO7 orbit. Our study returns crater-based absolute model ages for Cerealia Facula using the Lunar-derived chronology model (4.23 ± 0.36 Ma) and the Asteroid-flux-derived chronology model (0.43 ± 0.04 to 39.53 ± 3.26 Ma). Results show that model ages derived from small-area measurements are highly sensitive to (1) data collection bias and variability, particularly for craters smaller than 50 m, (2) the chosen distribution diameter range for age modeling, and (3) the chronology model, which can shift ages by a factor of up to 10. For complex regions like Cerealia Facula, using larger craters across wider areas offers more robust results. This investigation highlights the importance of high-resolution datasets for improving CSFD reliability and emphasizes the need for consistency in data collection and model selection. To provide additional geological context, an IHS pan-sharpened RGB orthomosaic was generated from XMO7 clear-filter data combined with LAMO-based RGB data, covering both Cerealia Facula and Vinalia Faculae at a ground sample distance of 8.5 m. The corresponding mosaics have been uploaded at the Zenodo (https://zenodo.org/records/17615401) data repository and are permanently accessible.
{"title":"Revisiting the crater-based age of Cerealia Facula: High-resolution XMO7 data, measurement uncertainties, and chronological frameworks","authors":"Alicia Neesemann , Stephan van Gasselt , Christian Riedel","doi":"10.1016/j.icarus.2025.116908","DOIUrl":"10.1016/j.icarus.2025.116908","url":null,"abstract":"<div><div>This study examines the effects of crater-size frequency data collections and modeling parameters to better understand their influence on model ages for Cerealia Facula on Ceres. Key factors in this investigation include (a) analyst-dependent data collection, (b) slope discrepancies between measured distributions and modeled production functions, and (c) choice of chronology models. The foundational cartographic product for this work is a novel controlled high-resolution image mosaic built from data of NASA’s Dawn Framing Camera in XMO7 orbit. Our study returns crater-based absolute model ages for Cerealia Facula using the Lunar-derived chronology model (4.23 ± 0.36 Ma) and the Asteroid-flux-derived chronology model (0.43 ± 0.04 to 39.53 ± 3.26 Ma). Results show that model ages derived from small-area measurements are highly sensitive to (1) data collection bias and variability, particularly for craters smaller than 50 m, (2) the chosen distribution diameter range for age modeling, and (3) the chronology model, which can shift ages by a factor of up to 10. For complex regions like Cerealia Facula, using larger craters across wider areas offers more robust results. This investigation highlights the importance of high-resolution datasets for improving CSFD reliability and emphasizes the need for consistency in data collection and model selection. To provide additional geological context, an IHS pan-sharpened RGB orthomosaic was generated from XMO7 clear-filter data combined with LAMO-based RGB data, covering both Cerealia Facula and Vinalia Faculae at a ground sample distance of 8.5 m. The corresponding mosaics have been uploaded at the Zenodo (<span><span>https://zenodo.org/records/17615401</span><svg><path></path></svg></span>) data repository and are permanently accessible.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"447 ","pages":"Article 116908"},"PeriodicalIF":3.0,"publicationDate":"2025-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145837352","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}
Pub Date : 2025-12-13DOI: 10.1016/j.icarus.2025.116917
Alain S.J. Khayat, Michael D. Smith, Scott D. Guzewich
Surface-atmosphere interactions play a major role in shaping the north polar layered deposits (NPLD) on Mars, the major source of atmospheric water during northern spring and summer seasons. Extensive work has been undertaken to study and understand polar processes and their evolutionary patterns. High-resolution water vapor retrievals provide context into these polar processes, in particular with respect to the sublimation of surface ice and the volatile transport across the NPLD. We here report the first high-spatial resolution (∼ 160 m) retrievals of water vapor over the north polar region, including the NPLD, and extending between MY 28, Ls = 113° (September 29, 2006) and MY 31, Ls = 115° (May 21, 2012). We have processed 1.7 million near-infrared spectra from hyperspectral observations returned by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) aboard the Mars Reconnaissance Orbiter (MRO) to provide the column-integrated water vapor abundance (pr-μm), after improving our radiative transfer model to accommodate the presence of surface ice. Our findings demonstrate that water vapor can accumulate significantly at the bottom of polar troughs, acting as a catalyst for trough cloud formation. We further identify scenarios where elevated water vapor levels correlate with surface ice rather than topography, and conversely, situations where combined sloped terrain and surface ice did not yield significant water vapor increases. These critical water vapor results would help understand the formation of trough clouds, a direct observation of the ice migration processes in the NPLD, hence the evolution of the north polar cap.
地表-大气相互作用在形成火星上的北极层状沉积物（NPLD）中起着重要作用，这是火星北部春季和夏季大气水的主要来源。已经进行了大量的工作来研究和了解极地过程及其演化模式。高分辨率的水汽检索提供了这些极地过程的背景，特别是关于表面冰的升华和通过NPLD的挥发性运输。在此，我们报告了包括NPLD在内的北极地区首次高空间分辨率（~ 160 m）的水汽检索，并在MY 28， Ls = 113°（2006年9月29日）和MY 31， Ls = 115°（2012年5月21日）之间扩展。我们对火星勘测轨道器（MRO）上的火星紧凑侦察成像光谱仪（CRISM）传回的高光谱观测数据中的170万张近红外光谱进行了处理，以提供柱集成的水蒸气丰度（pr-μm），并改进了我们的辐射传输模型，以适应表面冰的存在。我们的研究结果表明，水蒸气可以在极地槽底部大量积累，作为槽云形成的催化剂。我们进一步确定了水汽水平升高与表面冰而不是地形相关的情况，相反，斜坡地形和表面冰结合的情况不会产生显著的水汽增加。这些临界水蒸气的结果将有助于了解槽云的形成，直接观察NPLD的冰迁移过程，从而了解北极帽的演变。
{"title":"Tracking the non-uniformity in atmospheric water vapor over the north polar layered deposits on Mars using high-resolution observations by MRO/CRISM","authors":"Alain S.J. Khayat, Michael D. Smith, Scott D. Guzewich","doi":"10.1016/j.icarus.2025.116917","DOIUrl":"10.1016/j.icarus.2025.116917","url":null,"abstract":"<div><div>Surface-atmosphere interactions play a major role in shaping the north polar layered deposits (NPLD) on Mars, the major source of atmospheric water during northern spring and summer seasons. Extensive work has been undertaken to study and understand polar processes and their evolutionary patterns. High-resolution water vapor retrievals provide context into these polar processes, in particular with respect to the sublimation of surface ice and the volatile transport across the NPLD. We here report the first high-spatial resolution (∼ 160 m) retrievals of water vapor over the north polar region, including the NPLD, and extending between MY 28, L<sub>s</sub> = 113° (September 29, 2006) and MY 31, L<sub>s</sub> = 115° (May 21, 2012). We have processed 1.7 million near-infrared spectra from hyperspectral observations returned by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) aboard the Mars Reconnaissance Orbiter (MRO) to provide the column-integrated water vapor abundance (pr-μm), after improving our radiative transfer model to accommodate the presence of surface ice. Our findings demonstrate that water vapor can accumulate significantly at the bottom of polar troughs, acting as a catalyst for trough cloud formation. We further identify scenarios where elevated water vapor levels correlate with surface ice rather than topography, and conversely, situations where combined sloped terrain and surface ice did not yield significant water vapor increases. These critical water vapor results would help understand the formation of trough clouds, a direct observation of the ice migration processes in the NPLD, hence the evolution of the north polar cap.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"447 ","pages":"Article 116917"},"PeriodicalIF":3.0,"publicationDate":"2025-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145797655","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}
JAXA's Hayabusa2 spacecraft executed several low-altitude (down to <25 m) operations during its proximity maneuvers on asteroid Ryugu. Analysis of images acquired during the ascent (i.e., soon after thruster gas injection) revealed that many surface boulders were in motion on Ryugu. While previous studies documented boulder movement resulting from physical contact, such as the Hayabusa2 touchdowns and NASA's OSIRIS-REx sampling operations, this study uniquely confirms movement induced by remote disturbance through thruster gas. Boulder movement was analyzed using a series of Optical Navigation Camera (ONC) images taken during the DO-S01 operation, where the greatest number of boulders displayed movement over an extended period among the low-altitude descents by Hayabusa2. 74 moving boulders were identified, and the largest one was approximately 40 cm in diameter. The maximum velocity was 1.7 cm/s. The momentum imparted to the rock from the thruster injection pressure exceeded the observed momentum, suggesting that the boulder motion was induced directly by thruster gas, and subsequent friction with the surface decelerated the boulders. Notably, the observations revealed sustained boulder motion lasting more than 10 min, during which the trajectories of some boulders changed, suggesting multiple bouncing on the asteroid surfaces. This observation implies a significant restitution coefficient for boulder motion on microgravity asteroids, allowing for multiple bouncing. However, shadow measurements indicate minimal or zero leap height. This indicates that a mode of motion akin to rolling on the surface should not be ruled out either. Comparison between moving and stationary boulders showed that the numbers of the moving boulders relative to the stational is lower for smaller size. This suggests that the inertia of larger boulders, making them harder to stop, has stronger effect than the ease of acceleration in smaller boulders. These findings on the characteristics of motion are pivotal for predicting the dynamical response of surface materials after physical disturbances on asteroids. This understanding is crucial for deciphering the mode of surface renewal in near-Earth asteroids and for planning expected proximity observations of near-Earth objects (e.g., OSIRIS-APEX and RAMSES missions).
{"title":"Boulder motions on asteroid Ryugu induced by thruster gas disturbance by Hayabusa2","authors":"Naoya Sakatani , Shingo Kameda , Kosuke Kitsunai , Hiroshi Kikuchi , Shota Kikuchi , Yuto Takei , Yuya Mimasu , Osamu Mori , Toru Kouyama , Tomokatsu Morota , Eri Tatsumi , Yuichiro Cho , Manabu Yamada , Yasuhiro Yokota , Moe Matsuoka , Chikatoshi Honda , Hidehiko Suzuki , Masahiko Hayakawa , Kazuo Yoshioka , Kazunori Ogawa , Seiji Sugita","doi":"10.1016/j.icarus.2025.116916","DOIUrl":"10.1016/j.icarus.2025.116916","url":null,"abstract":"<div><div>JAXA's Hayabusa2 spacecraft executed several low-altitude (down to <25 m) operations during its proximity maneuvers on asteroid Ryugu. Analysis of images acquired during the ascent (i.e., soon after thruster gas injection) revealed that many surface boulders were in motion on Ryugu. While previous studies documented boulder movement resulting from physical contact, such as the Hayabusa2 touchdowns and NASA's OSIRIS-REx sampling operations, this study uniquely confirms movement induced by remote disturbance through thruster gas. Boulder movement was analyzed using a series of Optical Navigation Camera (ONC) images taken during the DO-S01 operation, where the greatest number of boulders displayed movement over an extended period among the low-altitude descents by Hayabusa2. 74 moving boulders were identified, and the largest one was approximately 40 cm in diameter. The maximum velocity was 1.7 cm/s. The momentum imparted to the rock from the thruster injection pressure exceeded the observed momentum, suggesting that the boulder motion was induced directly by thruster gas, and subsequent friction with the surface decelerated the boulders. Notably, the observations revealed sustained boulder motion lasting more than 10 min, during which the trajectories of some boulders changed, suggesting multiple bouncing on the asteroid surfaces. This observation implies a significant restitution coefficient for boulder motion on microgravity asteroids, allowing for multiple bouncing. However, shadow measurements indicate minimal or zero leap height. This indicates that a mode of motion akin to rolling on the surface should not be ruled out either. Comparison between moving and stationary boulders showed that the numbers of the moving boulders relative to the stational is lower for smaller size. This suggests that the inertia of larger boulders, making them harder to stop, has stronger effect than the ease of acceleration in smaller boulders. These findings on the characteristics of motion are pivotal for predicting the dynamical response of surface materials after physical disturbances on asteroids. This understanding is crucial for deciphering the mode of surface renewal in near-Earth asteroids and for planning expected proximity observations of near-Earth objects (e.g., OSIRIS-APEX and RAMSES missions).</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"448 ","pages":"Article 116916"},"PeriodicalIF":3.0,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145882260","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}
Pub Date : 2025-12-12DOI: 10.1016/j.icarus.2025.116915
Rahil Makadia , Steven R. Chesley , Davide Farnocchia , Brent W. Barbee , Siegfried Eggl
We introduce a new method for selecting kinetic impactor target sites on near-Earth asteroids. Most asteroids that possess a significant impact risk with Earth admit multiple impacting trajectories. Uncontrolled deflection of such asteroids might dismiss the immediate impact risk but can also push the asteroid into a ‘keyhole’, which would lead to a future impact. Our method maps potential outcomes of a kinetic impactor mission to the surface of the asteroid, allowing us to identify the optimal target site and rotation phase that minimizes the risk of pushing the asteroid off the Earth and into a keyhole. In this work, we illustrate this process using the keyholes for asteroid (101955) Bennu. We map the Bennu keyholes onto shape models of various asteroids to demonstrate the influence of shapes on the deflection outcomes. By computing the per-facet impact probability for different shapes, we can assess the dependence of the optimal target site on the asteroid’s shape and spin state. Our results indicate that an optimal kinetic impact mission must take the spin state and shape of the target asteroid into account to minimize post-deflection impact risk. We also assess the effect of varying the targeting uncertainty of the kinetic impactor spacecraft in anticipation of future improvements. This work provides a framework for selecting optimal timing and target locations for kinetic impact missions at near-Earth asteroids, which can be used by mission designers to inform future asteroid impact hazard mitigation efforts.
{"title":"Keyhole-aware target site selection for kinetic impact missions to near-Earth asteroids","authors":"Rahil Makadia , Steven R. Chesley , Davide Farnocchia , Brent W. Barbee , Siegfried Eggl","doi":"10.1016/j.icarus.2025.116915","DOIUrl":"10.1016/j.icarus.2025.116915","url":null,"abstract":"<div><div>We introduce a new method for selecting kinetic impactor target sites on near-Earth asteroids. Most asteroids that possess a significant impact risk with Earth admit multiple impacting trajectories. Uncontrolled deflection of such asteroids might dismiss the immediate impact risk but can also push the asteroid into a ‘keyhole’, which would lead to a future impact. Our method maps potential outcomes of a kinetic impactor mission to the surface of the asteroid, allowing us to identify the optimal target site and rotation phase that minimizes the risk of pushing the asteroid off the Earth and into a keyhole. In this work, we illustrate this process using the keyholes for asteroid (101955) Bennu. We map the Bennu keyholes onto shape models of various asteroids to demonstrate the influence of shapes on the deflection outcomes. By computing the per-facet impact probability for different shapes, we can assess the dependence of the optimal target site on the asteroid’s shape and spin state. Our results indicate that an optimal kinetic impact mission must take the spin state and shape of the target asteroid into account to minimize post-deflection impact risk. We also assess the effect of varying the targeting uncertainty of the kinetic impactor spacecraft in anticipation of future improvements. This work provides a framework for selecting optimal timing and target locations for kinetic impact missions at near-Earth asteroids, which can be used by mission designers to inform future asteroid impact hazard mitigation efforts.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"447 ","pages":"Article 116915"},"PeriodicalIF":3.0,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145797666","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}
Pub Date : 2025-12-11DOI: 10.1016/j.icarus.2025.116912
Jayesh Pabari , M. Roshni
During summer in Mars' southern hemisphere, dust devils/storms routinely sweep across the surface, lofting massive quantities of dust that drastically lower the atmosphere's electrical conductivity. In this study, we investigate a dust devil triggered under either low-dust or high-dust conditions, which is set by a prior dust activity, and show outcomes of its electrification by varying atmospheric conductivity in existing models. By tracking how the electric field evolves and comparing it to Mars' breakdown threshold, we determined a narrow range of conductivity from [1–9.6] × 10−13 S/m, as the condition where near surface lightning becomes feasible. We also examined conductivity profiles spanning few Martian years, confirming that these low-conductivity conditions indeed recur on Mars.
By analyzing time-domain evolution of electric field in Martian dust devils, we derived the discharge current characteristics based on allowable streamer speeds on Mars. The current provided the three moments in the three-component analysis, viz. current moment, charge moment and radiation moment, to estimate electromagnetic radiation's frequency spectrum. The electrical discharge launches extremely low frequency waves in surface-ionosphere cavity, potentially exciting Schumann Resonances on Mars. We further compute the resonator's quality factor and signal attenuation under different dust conditions. Our findings highlight that dust-driven electrical discharges on Mars could be strong enough to generate detectable Extremely Low Frequency signals. The work could be useful to plan observations of lightning or Schumann Resonance, the most promising detection related to electrical activity on the Red Planet, by a future mission.
{"title":"Electrification in Martian dust devils: Possibility and implications","authors":"Jayesh Pabari , M. Roshni","doi":"10.1016/j.icarus.2025.116912","DOIUrl":"10.1016/j.icarus.2025.116912","url":null,"abstract":"<div><div>During summer in Mars' southern hemisphere, dust devils/storms routinely sweep across the surface, lofting massive quantities of dust that drastically lower the atmosphere's electrical conductivity. In this study, we investigate a dust devil triggered under either low-dust or high-dust conditions, which is set by a prior dust activity, and show outcomes of its electrification by varying atmospheric conductivity in existing models. By tracking how the electric field evolves and comparing it to Mars' breakdown threshold, we determined a narrow range of conductivity from [1–9.6] × 10<sup>−13</sup> S/m, as the condition where near surface lightning becomes feasible. We also examined conductivity profiles spanning few Martian years, confirming that these low-conductivity conditions indeed recur on Mars.</div><div>By analyzing time-domain evolution of electric field in Martian dust devils, we derived the discharge current characteristics based on allowable streamer speeds on Mars. The current provided the three moments in the three-component analysis, viz. current moment, charge moment and radiation moment, to estimate electromagnetic radiation's frequency spectrum. The electrical discharge launches extremely low frequency waves in surface-ionosphere cavity, potentially exciting Schumann Resonances on Mars. We further compute the resonator's quality factor and signal attenuation under different dust conditions. Our findings highlight that dust-driven electrical discharges on Mars could be strong enough to generate detectable Extremely Low Frequency signals. The work could be useful to plan observations of lightning or Schumann Resonance, the most promising detection related to electrical activity on the Red Planet, by a future mission.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"447 ","pages":"Article 116912"},"PeriodicalIF":3.0,"publicationDate":"2025-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145797664","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}
Pub Date : 2025-12-10DOI: 10.1016/j.icarus.2025.116910
Sean N. Raymond , Nathan A. Kaib
An instability among the giant planets’ orbits can match many aspects of the Solar System’s current orbital architecture. We explore the possibility that this dynamical instability was triggered by the close passage of a star or substellar object during the Sun’s embedded cluster phase. We run N-body simulations starting with the giant planets in a resonant chain and an outer planetesimal disk, with a wide-enough planet-disk separation to preserve the planets’ orbital stability for Myr. We subject the system to a single flyby, testing a wide range in flyby mass, velocity and closest approach distance. We find a variety of outcomes, from flybys that over-excite the system (or strip the planets entirely) to flybys too weak to perturb the planets at all. An intermediate range of flybys triggers a dynamical instability that matches the present-day Solar System. Successful simulations – that match the giant planets’ orbits without over-exciting the cold classical Kuiper belt – are characterized by the flyby of a substellar object () passing within 20 au of the Sun. We performed Monte Carlo simulations of the Sun’s birth cluster phase, parameterized by the product of the stellar density and the cluster lifetime . The balance between under- and over-excitation of the young Solar System is at Myr pc−3, in a range consistent with previous work. We find a probability of 1% that the Solar System’s dynamical instability was triggered by a substellar flyby. The probability increases to 5% if the occurrence rate of free-floating planets and low-mass brown dwarfs is modestly higher than predicted by standard stellar initial mass functions.
{"title":"Was the Solar System’s dynamical instability triggered by a (sub)stellar flyby?","authors":"Sean N. Raymond , Nathan A. Kaib","doi":"10.1016/j.icarus.2025.116910","DOIUrl":"10.1016/j.icarus.2025.116910","url":null,"abstract":"<div><div>An instability among the giant planets’ orbits can match many aspects of the Solar System’s current orbital architecture. We explore the possibility that this dynamical instability was triggered by the close passage of a star or substellar object during the Sun’s embedded cluster phase. We run N-body simulations starting with the giant planets in a resonant chain and an outer planetesimal disk, with a wide-enough planet-disk separation to preserve the planets’ orbital stability for <span><math><mrow><mo>></mo><mn>100</mn></mrow></math></span> Myr. We subject the system to a single flyby, testing a wide range in flyby mass, velocity and closest approach distance. We find a variety of outcomes, from flybys that over-excite the system (or strip the planets entirely) to flybys too weak to perturb the planets at all. An intermediate range of flybys triggers a dynamical instability that matches the present-day Solar System. Successful simulations – that match the giant planets’ orbits without over-exciting the cold classical Kuiper belt – are characterized by the flyby of a substellar object (<span><math><mrow><mn>3</mn><mo>−</mo><mn>30</mn><msub><mrow><mi>M</mi></mrow><mrow><mi>Jup</mi></mrow></msub></mrow></math></span>) passing within 20 au of the Sun. We performed Monte Carlo simulations of the Sun’s birth cluster phase, parameterized by the product of the stellar density <span><math><mi>η</mi></math></span> and the cluster lifetime <span><math><mi>T</mi></math></span>. The balance between under- and over-excitation of the young Solar System is at <span><math><mrow><mi>η</mi><mi>T</mi><mo>≈</mo><mn>5</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>4</mn></mrow></msup></mrow></math></span> Myr pc<sup>−3</sup>, in a range consistent with previous work. We find a probability of <span><math><mo>∼</mo></math></span>1% that the Solar System’s dynamical instability was triggered by a substellar flyby. The probability increases to <span><math><mo>∼</mo></math></span>5% if the occurrence rate of free-floating planets and low-mass brown dwarfs is modestly higher than predicted by standard stellar initial mass functions.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"447 ","pages":"Article 116910"},"PeriodicalIF":3.0,"publicationDate":"2025-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145748592","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}
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