Icarus最新文献

{"title":"Further reverberations of the 1983 impact with Saturn’s C ring","authors":"Richard G. French , Philip D. Nicholson , Matthew M. Hedman , Heikki Salo , Essam A. Marouf , Colleen A. McGhee-French , Nicole Rappaport , Joshua Colwell , Richard Jerousek , Victor M. Afigbo , Sophia Flury , Jolene Fong , Ryan Maguire , Glen Steranka , Matthew S. Tiscareno","doi":"10.1016/j.icarus.2025.116463","DOIUrl":"10.1016/j.icarus.2025.116463","url":null,"abstract":"<div><div>A pattern of <span><math><mo>∼</mo></math></span>1 km wavelength ripples exhibiting a periodic beating pattern in Saturn’s inner C ring (74,500–77,765 km) was detected in low-inclination <em>Cassini</em> Radio Science Subsystem (RSS) occultation observations made in 2010 (Marouf et al., 2011). Initially interpreted as analogous to the <span><math><mo>∼</mo></math></span>30 km wavelength vertical corrugations with <span><math><mrow><mi>m</mi><mo>=</mo><mn>1</mn></mrow></math></span> discovered in the C and D rings in near-equinox Cassini Imaging Science Subsystem (ISS) images by Hedman et al. (2007, 2011), the shorter wavelength of these features suggested that they had evolved from a pair of impacts several centuries ago. However, important inconsistencies with this model prevented a secure identification of their origin. A comprehensive search has revealed additional detections of this pattern in <em>Cassini</em> RSS, Visual and Infrared Mapping Spectrometer (VIMS) and Ultraviolet Imaging Spectrograph (UVIS) occultations observed between 2008 and 2017 that show a significant decrease in the wavelength of the ripples over time, suggesting a much more recent origin than centuries ago. We identify the conspicuous beat pattern visible in the ripple structure as the interference of <span><math><mrow><mi>m</mi><mo>=</mo><mn>0</mn></mrow></math></span> and <span><math><mrow><mi>m</mi><mo>=</mo><mn>2</mn></mrow></math></span> vertical modes of similar amplitudes but slightly different frequencies, evolving over time and winding up at a rate governed by the mean motion of ring particles, rather than by the much slower node rate that is applicable to the <span><math><mrow><mi>m</mi><mo>=</mo><mn>1</mn></mrow></math></span> corrugations. From empirical fits to the observed time-dependent wavelengths of the two modes and power spectral analysis of individual optical depth profiles, we demonstrate that the short-wavelength vertical corrugations originated from the same event that produced the longer-wavelength <span><math><mrow><mi>m</mi><mo>=</mo><mn>1</mn></mrow></math></span> periodic structure in the rings. We infer an impact date of UTC 1983 Sep 19.25 ± 5.5 d, taking into account a plausibly small contribution of ring self-gravity to the windup rates of the corrugations. No convincing signatures of counterpart <span><math><mrow><mi>m</mi><mo>=</mo><mn>0</mn></mrow></math></span> or <span><math><mrow><mi>m</mi><mo>=</mo><mn>2</mn></mrow></math></span> radial modes, or of vertical modes with <span><math><mrow><mi>m</mi><mo>≥</mo><mn>3</mn></mrow></math></span>, are present in the occultation data, and no evidence of ripple structure is detectable beyond an orbital radius of 77,765 km. The measured amplitudes <span><math><msubsup><mrow><mi>A</mi></mrow><mrow><mi>z</mi></mrow><mrow><mn>0</mn></mrow></msubsup></math></span> and <span><math><msubsup><mrow><mi>A</mi></mrow><mrow><mi>z</mi></mrow><mrow><mn>2</mn></mrow></msubsup></math></span> of the ","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"431 ","pages":"Article 116463"},"PeriodicalIF":2.5,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143348990","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":"Corrigendum to “Discovery of a highly shocked alkali suite clast in the Chang'e-5 lunar soils” [Icarus 429 (2025) 116448]","authors":"Mengfan Qiu , Sen Hu , Huicun He , Zongyu Yue , Hejiu Hui , Jialong Hao , Ruiying Li , Sheng Gou , Lixin Gu , Xu Tang , Jinhua Li , Wei Yang , Hengci Tian , Chi Zhang , Di Zhang , Qian Mao , Lihui Jia , Xiaoguang Li , Yi Chen , Shitou Wu , Fuyuan Wu","doi":"10.1016/j.icarus.2025.116486","DOIUrl":"10.1016/j.icarus.2025.116486","url":null,"abstract":"","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"430 ","pages":"Article 116486"},"PeriodicalIF":2.5,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143148046","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":"Planetary surface dating from crater size–frequency distribution measurements: Interpretation of small-area and low number counts","authors":"Greg Michael ,&nbsp;Jianzhong Liu","doi":"10.1016/j.icarus.2025.116489","DOIUrl":"10.1016/j.icarus.2025.116489","url":null,"abstract":"<div><div>Recent interest in the crater-dating of smaller and younger features of planetary surfaces has provoked questions about how far the method's validity extends. This work addresses the problem theoretically over a range of measurement scenarios, predicting the consequent statistical measurement uncertainty, and suggesting it should be the first criterion to determine usability. We map out the relationship between crater measurement area, observable crater diameters, measured age uncertainty, and the actual age of surface structures. Constraints on the range of possible measured ages arising from particular combinations of counting area and observable crater diameter are presented in a generalised form, with the intent to provide a reference for the choice and suitability for measurements of surfaces from different epochs.</div><div>Additionally, several perhaps non-obvious aspects of evaluation of the chronology model, namely, the influence of the limits of the considered crater diameter interval, of varying the counting area at fixed crater density, of varying the counting area perimeter for a buffered count of a linear feature, and the logarithmic behaviour of the time-resolving ability of the method are described and demonstrated, likewise with the intent to support well-informed choices for actual crater-dating measurements.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"431 ","pages":"Article 116489"},"PeriodicalIF":2.5,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143373001","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Decoupling the influence of solar cycle and seasons on Mars’ dayside ionosphere: Insights from MAVEN observations during the declining phase of solar cycle 24","authors":"Vrinda Mukundan ,&nbsp;Paul Withers ,&nbsp;Smitha V. Thampi ,&nbsp;Anil Bhardwaj","doi":"10.1016/j.icarus.2025.116470","DOIUrl":"10.1016/j.icarus.2025.116470","url":null,"abstract":"<div><div>The Mars ionosphere, highly sensitive to solar activity and seasonal changes, exhibited noticeable variation in plasma density during the declining phase of solar cycle 24. This study aims to differentiate the impact of solar activity and changes in Sun–Mars distance (seasons) by comparing ionospheric density measurements from MAVEN NGIMS and LPW instruments during 2015–2018 period. We also investigated whether the ionosphere on opposite hemispheres show symmetry during equinoxes. In each case, we quantified the contribution of atmospheric contraction to observed variability by analyzing densities at fixed pressure levels.</div><div>Our finding suggests that a shift in solar activity from medium to low results in a plasma density decrease of up to 40%, with an additional 5–20% attributed by atmospheric contraction. A 90° phase change in solar longitude showed insignificant plasma density variation when the 10% effect from atmospheric expansion is accounted. However, transition from perihelion to aphelion position results in atmospheric contraction that contribute up to 50% of observed variability, along with <span><math><mo>∼</mo></math></span>35% decrease due to reduction in solar radiation. Under similar solar activity and equinox conditions, ionospheric densities are symmetric in opposite hemispheres, when data from regions with strong crustal magnetic fields are excluded.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"431 ","pages":"Article 116470"},"PeriodicalIF":2.5,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143193412","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":"Illumination and regolith temperature for China's candidate lunar landing sites with multiple scattering considerations","authors":"Zhen Zhong ,&nbsp;Zhen Yang ,&nbsp;Bin Liu ,&nbsp;Jianguo Yan ,&nbsp;Jia Wang ,&nbsp;Lidan Zhang","doi":"10.1016/j.icarus.2025.116488","DOIUrl":"10.1016/j.icarus.2025.116488","url":null,"abstract":"<div><div>Following the Chang'e-6 mission, China is planning a lunar landing and sampling mission at the Moon's South Pole, with a focus on volatile components such as water ice. To support future missions, this study combines orbital images with elevation data to reconstruct a three-dimensional (3D) model of the candidate landing region, producing a 1-m resolution digital elevation model (DEM). The DEM is then utilized to analyze the illumination conditions of the candidate landing site. A finite volume method is applied to solve the 1-dimensional (1D) heat conduction equation for the regolith, accounting for non-uniform density. Based on the high-resolution DEM and illumination data, we estimate the lunar regolith temperature at the candidate site. The main findings are as follows: (1) The high-resolution DEM accurately captures terrain details, and the simulated illumination closely matches observed image, validating the DEM and demonstrating the reliability of the illumination model for temperature simulations. (2) The candidate landing area, due to its elevation, receives sufficient illumination, enabling effective solar radiation throughout the lunar day. (3) Direct solar radiation is the primary heat source, with minor contributions from scattered solar and infrared radiation. Earth's reflected solar and longwave radiation have the least impact on the regolith temperature. (4) Surface temperatures fluctuate with short-term illumination cycles, while deeper layers (depth ≥ 0.18 m) remain more thermally stable. (5) Some regions at a depth of 0.18 m maintain temperatures below 112 K, indicating potential sites for volatile components sampling. These locations have been identified and mapped for future landing missions. This study provides insights for lunar landing site selection and regolith thermal analysis, offering essential data for future missions.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"430 ","pages":"Article 116488"},"PeriodicalIF":2.5,"publicationDate":"2025-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143284268","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":"Atmospheric escape explains diverse surface compositions of Pluto vs Sedna","authors":"Amelia Bettati ,&nbsp;Jonathan Lunine","doi":"10.1016/j.icarus.2025.116482","DOIUrl":"10.1016/j.icarus.2025.116482","url":null,"abstract":"<div><div>Kuiper Belt Objects are thought to be remnants of early solar system materials, which have retained volatiles such as CH₄ and C₂H₆. Spectroscopic data from various sources reveals that while Pluto retains CH₄ and C₂H₆, Sedna shows a lack of CH₄ but an abundance of C₂H₆ (Emery et al. 2024). We hypothesized that CH₄, while stable on Pluto, is able to escape from less massive Sedna sufficiently rapidly to be depleted over the age of the solar system, while C₂H₆ has been retained due to its larger molecular mass.</div><div>Utilizing models for Jeans escape and hydrodynamic escape, as appropriate for a given mass of object and of escaping species, we analyzed the stability and escape rates of CH₄ and C₂H₆ on both Pluto and Sedna. We explored a wide range of masses of Sedna, ranging from ½ to ⅒ the mass of Pluto, and three different abundances of CH₄ and C₂H₆ using measured values from Comet 67-P, and Enceladus, and an upper limit assuming clathrate hydrate.</div><div>We find that CH₄ remains stable on Pluto, but escapes from Sedna due to its lower mass, whereas C₂H₆ remains stable when using both 100 % and 10 % outgassing rates. This result is in agreement with the observed spectra and leads to a tighter mass constraint for Sedna. Our model also explains the observed absence of methane on another KBO, Gonggong.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"430 ","pages":"Article 116482"},"PeriodicalIF":2.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143284267","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The variability of the topside ionospheres of Venus and Mars as seen by recent radio science observations","authors":"Kerstin Peter ,&nbsp;Martin Pätzold ,&nbsp;Paul Withers ,&nbsp;Robin Ramstad ,&nbsp;Edward Thiemann ,&nbsp;Markus Fränz ,&nbsp;Silvia Tellmann ,&nbsp;Bernd Häusler ,&nbsp;Yoshifumi Futaana ,&nbsp;Mats Holmström","doi":"10.1016/j.icarus.2025.116469","DOIUrl":"10.1016/j.icarus.2025.116469","url":null,"abstract":"<div><div>This study combines the observations of the Venus Express Venus Radio science experiment (VeRa), Mars Express Mars Radio Science experiment (MaRS), and MAVEN Radio Occultation Science Experiment (ROSE) at Venus and Mars with proxies for environmental parameters, insolation and solar wind characteristics to compare the effects of individual drivers on the variability of the topside ionospheres of both planets.</div><div>The average extent and variability of the ionospheric topside of both planets decrease with increasing solar wind dynamic pressure. On Venus, the average altitude and variability of the ionospheric topside increase with rising solar EUV irradiation. On Mars, the extent of the ionospheric topside on the northern hemisphere under very low solar wind conditions is similarly affected by solar EUV, while the southern hemisphere is influenced by the presence of strong crustal magnetic fields and heliocentric distance. The relationship between the ionosphere on the southern hemisphere and heliocentric distance indicates that increased solar irradiation and atmospheric dust affect the extent of the ionospheric topside during southern summer.</div><div>A wide variety of ionospheric topside features, including traditional ionopause gradients, are observed in low noise level and near-vertical electron density profiles on the ionospheric dayside of both planets. All topside structures observed in the Venus ionosphere during the VEX mission are also seen at Mars. This suggests that despite the influence of unique drivers on each planet's ionosphere, the overall interaction of Mars with the solar wind shows many similarities to that of Venus during a weak solar cycle.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"432 ","pages":"Article 116469"},"PeriodicalIF":2.5,"publicationDate":"2025-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143429604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Pediment formation and subsequent erosion in Gale crater: Clues to the climate history of Mars","authors":"A.B. Bryk ,&nbsp;W.E. Dietrich ,&nbsp;K.A. Bennett ,&nbsp;V.K. Fox ,&nbsp;C.M. Fedo ,&nbsp;M.P. Lamb ,&nbsp;E.S. Kite ,&nbsp;L.M. Thompson ,&nbsp;S.G. Banham ,&nbsp;J. Schieber ,&nbsp;J.A. Grant ,&nbsp;A.R. Vasavada ,&nbsp;A.A. Fraeman ,&nbsp;L.A. Edgar ,&nbsp;P.J. Gasda ,&nbsp;R.C. Wiens ,&nbsp;J.P. Grotzinger ,&nbsp;K. Stack-Morgan ,&nbsp;R.E. Arvidson ,&nbsp;O. Gasnault ,&nbsp;M.C. Malin","doi":"10.1016/j.icarus.2024.116445","DOIUrl":"10.1016/j.icarus.2024.116445","url":null,"abstract":"<div><div>Evidence of paleo-rivers, fans, deltas, lakes, and channel networks across Mars has prompted much debate about what climate conditions would permit the formation of these surface water derived features. Pediments, gently sloping erosional surfaces of low relief developed in bedrock, have also been identified on Mars. On Earth, these erosional landforms, often thought to be created by overland flow and shallow channelized runoff, are typically capped by fluvial sediments, and thus in exceptionally arid regions, pediments are interpreted to record past wet periods. Here we document the Greenheugh pediment in Gale crater, exploiting the observational capability of the Curiosity rover. The absence of a fluvial cap suggests that the pediment was likely cut by wind erosion, not fluvial processes. The pediment was then buried by an aeolian deposit (Stimson sandstone) that mantled the lower footslopes of Aeolis Mons (informally known as Mt. Sharp). This burial terminated active wind erosion, preserving the pediment surface (as an angular unconformity). Groundwater was present prior-to, during, and shortly after Stimson deposition, perhaps contributing to lithification and certainly to early diagenesis. Post lithification, wind erosion first cut canyons in the northern most footslopes (north of Vera Rubin ridge). Unlithified gravels were deposited in these canyons, likely due to runoff from Mt. Sharp. Boulder-rich fluvial and debris flow deposits built a &gt; 70 m thick sequence (Gediz Vallis ridge) on the southern Greenheugh pediment. Continued wind erosion left elevated patches of gravel on the northern footslopes, and exposure age dating shows that erosion essentially ceased before 1 Ga (but possibly much earlier). Erosion to the south led to emergence of Vera Rubin ridge, retreat of the Greenheugh pediment, and the formation of Glen Torridon valley. Hence, this footslope environment of Mt. Sharp records climate-driven periods of wind erosion, aeolian deposition (and groundwater activity), surface runoff and sediment deposition, followed by further significant wind erosion that declined to present very slow rates. This likely occurred during the late Hesperian and possibly into the Amazonian.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"430 ","pages":"Article 116445"},"PeriodicalIF":2.5,"publicationDate":"2025-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143148014","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Low thermal inertia of (162173) Ryugu a result of horizontal cracks in boulders","authors":"Maximilian Hamm ,&nbsp;Moritz Strauß ,&nbsp;Matthias Grott ,&nbsp;Jörg Knollenberg ,&nbsp;Robert Luther ,&nbsp;Jens Biele ,&nbsp;Hiroki Senshu","doi":"10.1016/j.icarus.2025.116484","DOIUrl":"10.1016/j.icarus.2025.116484","url":null,"abstract":"<div><div>Observations of the diurnal variations of the surface temperature of asteroid (162173) Ryugu from orbit and on the surface were performed by the Haybusa2 spacecraft and MASCOT lander. A low thermal inertia of the boulders on Ryugu was derived from these temperature variations and interpreted as the consequence of high porosity. Samples of Ryugu returned to Earth by Hayabusa2 showed higher thermal inertia when investigated by microscopic thermography. Here, we apply a simple thermal model, considering a horizontal fracture interrupting the heat flow into the surface, and investigate whether the low thermal inertia of Ryugu's boulders might be caused by fractures rather than high porosity. We find that the diurnal temperature variations on Ryugu observed by MARA can be partially explained by introducing a single horizontal crack at 9 mm depth below the surface observed by MARA.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"430 ","pages":"Article 116484"},"PeriodicalIF":2.5,"publicationDate":"2025-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143284359","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Viking biology experiments on Mars revisited","authors":"Christopher P. McKay,&nbsp;Richard C. Quinn,&nbsp;Carol R. Stoker","doi":"10.1016/j.icarus.2025.116466","DOIUrl":"10.1016/j.icarus.2025.116466","url":null,"abstract":"<div><div>The discovery of perchlorate on Mars by the Phoenix mission has provided a basis for explaining the results of the Viking Landers. Thermal decomposition of perchlorate in the ovens of the instrument can explain the lack of organics detected. Accumulation of hypochlorite in the soil from cosmic ray decomposition of perchlorate can explain the reactivity seen when nutrient solutions were added to the soil in the Viking Biology Experiments. A non-biological explanation for the Viking results does not preclude life on Mars.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"431 ","pages":"Article 116466"},"PeriodicalIF":2.5,"publicationDate":"2025-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143386431","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}