Icarus最新文献

{"title":"Impact-induced fayalite glass from Chang'e-5 regolith revealed by electron pair distribution function and ReaxFF molecular dynamics","authors":"Hongmei Yang ,&nbsp;Haiyang Xian ,&nbsp;Jianxi Zhu ,&nbsp;Xiao Wu ,&nbsp;Shan Li ,&nbsp;Xiaoju Lin ,&nbsp;Jiaxin Xi ,&nbsp;Yiping Yang ,&nbsp;Hongping He","doi":"10.1016/j.icarus.2025.116643","DOIUrl":"10.1016/j.icarus.2025.116643","url":null,"abstract":"<div><div>Impacts play a vital role in lunar formation and evolution. The mineral phase transformations induced by impacts are crucial for understanding the impact processes, such as the amorphization of olivine. In this study, we investigated the formation mechanism of fayalite glass in Chang'e-5 breccia using the electron pair distribution function and molecular dynamics simulations. The results show that fayalite glass formed during pressure release, with temperatures ranging from 3200 to 3400 K before fayalite melt quenching and a residual pressure of around 1 GPa. By integrating micro-regional analyses, the results suggest that impact-induced particle fragmentation creates shear surfaces, where particle friction generates enough heat to cause local melting of fayalite, followed by rapid quenching to produce the glass. This study provides a microscopic perspective on the formation mechanism of impact glass, enhancing our understanding of the impact processes in the solar system.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"438 ","pages":"Article 116643"},"PeriodicalIF":2.5,"publicationDate":"2025-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143947442","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":"Water production rates from SOHO/SWAN observations of Comets C/2017 K2 (PanSTARRS) and C/2022 E3 (ZTF)","authors":"M.R. Combi ,&nbsp;T. Mäkinen ,&nbsp;J.-L. Bertaux ,&nbsp;E. Quémerais ,&nbsp;S. Ferron","doi":"10.1016/j.icarus.2025.116645","DOIUrl":"10.1016/j.icarus.2025.116645","url":null,"abstract":"<div><div>In 2022 and 2023 the hydrogen comae of two long period comets, C/2017 K2 (PanSTARRS) and C/2022 E3 (ZTF), were observed with the Solar Wind ANisotropies (SWAN) all-sky hydrogen Lyman-alpha camera on the SOlar and Heliosphere Observer (SOHO) satellite. SWAN obtains nearly daily full-sky images of the hydrogen Lyman-alpha distribution of the interstellar hydrogen as it passes through the solar system yielding information about the solar wind and solar ultraviolet fluxes that eat away at it by ionization and charge exchange. The hydrogen comae of comets, when of sufficient brightness, are also observed. Water production rates have been calculated over time for each of these comets, covering about 6 months mostly of the post-perihelion period of C/2017 K2 (PanSTARRS) and about 3 months around perihelion of C/2022 E3 (ZTF).</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"438 ","pages":"Article 116645"},"PeriodicalIF":2.5,"publicationDate":"2025-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143942602","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":"Evolution of granular salty ice analogs for Europa: Sublimation and irradiation","authors":"Rafael Ottersberg ,&nbsp;Antoine Pommerol ,&nbsp;Linus Leo Stöckli ,&nbsp;Lorenzo Obersnel ,&nbsp;André Galli ,&nbsp;Axel Murk ,&nbsp;Peter Wurz ,&nbsp;Nicolas Thomas","doi":"10.1016/j.icarus.2025.116590","DOIUrl":"10.1016/j.icarus.2025.116590","url":null,"abstract":"<div><div>We study the evolution of the Vis–NIR reflectance spectrum of salty granular ice analog samples in a simulation chamber under conditions relevant to the surface of Europa. A novel application and custom calibration of a thermopile sensor enabled the measurement of the surface temperature of the samples in far infrared emission. This allows the kinetics of the observed changes to be scaled to equivalent timescales on Europa. We observed significant changes in the depth and shape of the broad water absorption bands for all samples on timescales of a few thousand years of equatorial conditions on Europa. This effect should be taken into account if quantitative predictions about bulk composition are made based on remote-sensing data. A narrow absorption feature attributed to hydrohalite formed during the sublimation of the sodium chloride sample. We used near-infrared spectroscopy in an irradiation chamber to assess the stability of this narrow feature under electron irradiation. We find that the radiation environment present on Europa dehydrates the hydrohalite on short timescales. Therefore, we expect hydrohalite not to be present on the surface, unless erupted very recently (<span><math><mrow><mo>&lt;</mo><mn>10</mn></mrow></math></span> yr) or located in thermal anomalies (<span><math><mo>&gt;</mo></math></span> 145 K). Thus, a detection of hydrohalite would clearly indicate recent activity.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"439 ","pages":"Article 116590"},"PeriodicalIF":2.5,"publicationDate":"2025-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144083874","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":"Effects of the interior conductivity on Mercury's field-aligned currents","authors":"Z. Shi ,&nbsp;S. Fatemi ,&nbsp;Z.J. Rong ,&nbsp;F. He ,&nbsp;Y. Wei","doi":"10.1016/j.icarus.2025.116633","DOIUrl":"10.1016/j.icarus.2025.116633","url":null,"abstract":"<div><div>Mercury lacks an (significant) ionosphere, leading to the hypothesis that its large-scale field-aligned currents (FACs) are instead closed through its highly conductive core. Mercury's interior is usually characterized by a two-layer model: a resistive outer layer (the crust and mantle) and a conductive inner layer (the iron-rich core). While this model is widely used, the effects of Mercury's conductivity and core on FACs have not been extensively explored. Therefore, we conducted analytical calculations combined with hybrid-kinetic simulations to study these effects. We found that the total currents of FACs are enhanced by ∼2 times when a conducting core is included, and the current density is directly proportional to the outer layer's conductivity. Combining our analysis with previous observations, the conductivity of the outer layer is estimated to be ∼<span><math><mn>5.4</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>7</mn></mrow></msup><mo>−</mo><mn>1.1</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>6</mn></mrow></msup><mspace></mspace><mi>S</mi><mo>/</mo><mi>m</mi></math></span>. Our study suggests that future observations of Mercury's FACs will better constrain Mercury's conductivity profile.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"438 ","pages":"Article 116633"},"PeriodicalIF":2.5,"publicationDate":"2025-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143947440","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":"Volcanic gas plumes’ effect on the spectrum of Venus","authors":"J.A. Dias ,&nbsp;P. Machado ,&nbsp;S. Robert ,&nbsp;J. Erwin ,&nbsp;M. Lefèvre ,&nbsp;C.F. Wilson ,&nbsp;D. Quirino ,&nbsp;J.C. Duarte","doi":"10.1016/j.icarus.2025.116589","DOIUrl":"10.1016/j.icarus.2025.116589","url":null,"abstract":"<div><div>Venus is home to thousands of volcanoes, with a wide range of volumes and sizes. Its surface is relatively young, with a temperature of approximately 735 K and an atmosphere of 92 bar. Past and possible ongoing volcanic outgassing is expected to provide a source to the sustenance of this massive atmosphere, dominated by CO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> and SO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>. The lower atmosphere can be investigated in the near-infrared transparency windows on the nightside, such as the <span><math><mrow><mn>2</mn><mo>.</mo><mn>3</mn><mspace></mspace><mi>μ</mi><mi>m</mi></mrow></math></span> thermal emission window, which provides a chance of detection of species with volcanic origin, such as water vapor.</div><div>The Planetary Spectrum Generator was used to simulate the nightside <span><math><mrow><mn>2</mn><mo>.</mo><mn>3</mn><mspace></mspace><mi>μ</mi><mi>m</mi></mrow></math></span> thermal emission window of Venus. We simulated the effect of a volcanic gas plume rising to a ceiling altitude, for species such as H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>O, CO, OCS, HF and SO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>. The sensitivity of the radiance spectrum at different wavelengths was explored as an attempt to qualitatively access detection for future measurements of both ground-based and space-instrumentation.</div><div>We conclude from our qualitative analysis that for the H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>O, CO and OCS plumes simulated there is potential to achieve a detection in the future, given a minimum required signal-to-noise ratio of 50. For SO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> and HF plumes, a higher signal-to-noise ratio would be needed.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"438 ","pages":"Article 116589"},"PeriodicalIF":2.5,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143906462","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":"Accreted volatiles influence low-temperature rock equilibria on Europa","authors":"Nisha K. Ramkissoon,&nbsp;Mark G. Fox-Powell,&nbsp;Lewis Sym,&nbsp;Martin D. Suttle,&nbsp;Alvaro Del Moral,&nbsp;Victoria K. Pearson","doi":"10.1016/j.icarus.2025.116631","DOIUrl":"10.1016/j.icarus.2025.116631","url":null,"abstract":"<div><div>The subsurface ocean of Europa has been identified as a high-priority target in the search for habitable environments beyond Earth. Determining the chemical composition of Europa's ocean, a result of water-rock interaction in Europa's interior, is essential to understanding the moon's geological history and whether it can support life. In this study, we used a thermochemical computer modelling code (CHIM-XPT) to explore the range of potential ocean compositions that could result from water-rock interactions at the ocean-silicate interface immediately following the formation of the ocean. We modelled a range of plausible silicate starting materials (based on CV, L and LL chondritic material) and endmember accreted ice compositions (pure H₂O vs. cometary) that could have contributed to the volatile inventory of Europa. These models assume a water/layer of its current size and do not incorporate compositional changes resulting from further processes (e.g., ice sheet formation) or additional sources of material (e.g., micrometeorite impacts). Our results show that the initial composition of volatiles had a stronger influence on the resulting ocean composition than the initial composition of the silicate, which produced variation in secondary mineral assemblages and differences in ocean chemistry that could be detectable by future missions. In particular, the absence of Fe-oxides in secondary mineral assemblages for cometary melt systems indicates limited Fe-oxidation_, which could impact the generation of H₂. We also show that, under all modelled scenarios, water-rock interactions would release redox elements into the ocean, albeit at varying concentrations, supporting proposals that Europa's ocean could be a habitable environment. Significantly, the ocean composition derived from water-rock reactions involving initial fluids with a cometary melt composition had relatively higher concentrations of Mg (by one to five orders of magnitude) and lower concentrations of Fe (by more than two orders of magnitude, except at W/Rs of 3–10) compared to those involving pure H₂O initial fluids. This difference in Fe and Mg concentration found between the pure H₂O and cometary melt systems could potentially be used as a diagnostic tool to identify the source material for Europa's volatile inventory.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"438 ","pages":"Article 116631"},"PeriodicalIF":2.5,"publicationDate":"2025-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143936897","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":"Spectro-photometry of Phobos simulants II. Effects of porosity and texture","authors":"Antonin Wargnier ,&nbsp;Olivier Poch ,&nbsp;Giovanni Poggiali ,&nbsp;Thomas Gautier ,&nbsp;Alain Doressoundiram ,&nbsp;Pierre Beck ,&nbsp;Tomoki Nakamura ,&nbsp;Hideaki Miyamoto ,&nbsp;Shingo Kameda ,&nbsp;Nathalie Ruscassier ,&nbsp;Arnaud Buch ,&nbsp;Pedro H. Hasselmann ,&nbsp;Robin Sultana ,&nbsp;Eric Quirico ,&nbsp;Sonia Fornasier ,&nbsp;Maria Antonietta Barucci","doi":"10.1016/j.icarus.2025.116611","DOIUrl":"10.1016/j.icarus.2025.116611","url":null,"abstract":"<div><div>Surface porosity and texture has been found to be an important property for small bodies. Some asteroids and comets can exhibit an extremely high surface porosity in the first millimeter layer. This layer may be produced by various processes and maintained by the lack of an atmosphere. However, the influence of porosity on the spectro-photometric properties of small body surfaces is not yet fully understood.</div><div>In this study, we looked into the effect of the texture on the spectro-photometric properties of Phobos regolith spectroscopic simulants. Macro- and micro-porosity were created by mixing the simulants with ultra-pure water, producing ice-dust particles, and then sublimating the water. The sublimation of the water ice enabled the production of porous and rough powdered simulants with significant micro- and macro-porosity associated with macro-roughness. The reflectance spectroscopic properties in the visible and near-infrared (0.5–4.2 <span><math><mrow><mi>μ</mi><mi>m</mi></mrow></math></span>) demonstrate a brightening of the porous samples in comparison to the compact ones. One simulant exhibits a bluing of the spectral slope after increasing porosity, which is likely linked to the presence of expandable phyllosilicates. In the mid-infrared range, a contrast increase of the 10 <span><math><mrow><mi>μ</mi><mi>m</mi></mrow></math></span> emissivity-related plateau due to silicates is observed. This spectral feature is typically observed as a 10 <span><math><mrow><mi>μ</mi><mi>m</mi></mrow></math></span> emissivity plateau on some asteroids, making the mid-infrared region important for assessing mineralogy and surface texture.</div><div>Photometry reveals a modification of the phase reddening behavior between the compact powder and the sublimation residue for both simulants. However, the observed behavior is different between the simulants, suggesting that the phase reddening may be dependent on the composition of the simulants. The phase curves of the sublimation residues exhibit a higher contribution of forward scattering. The derivation of the Hapke parameters indicates an increase in roughness for the porous sample, but no significant modification of the opposition effect. The modifications of the spectrophotometric properties observed in this experiment are definitely due to the textural changes obtained after sublimation, which depend on the initial composition of the simulants.</div><div>This study aims to provide new insights into the understanding of porosity by using two Phobos simulants in the context of the upcoming JAXA/Martian Moons eXploration mission. We suggest that the Phobos blue unit may be due to the presence of a highly porous layer, rather than only to space-weathering processes, as often postulated.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"438 ","pages":"Article 116611"},"PeriodicalIF":2.5,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143917797","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":"Impacts of mesoscale meteorology on the evolution of fluvial features in Lyot crater, Mars","authors":"Lori-Ann Foley,&nbsp;Stephen Lewis,&nbsp;Matt Balme,&nbsp;James Holmes","doi":"10.1016/j.icarus.2025.116603","DOIUrl":"10.1016/j.icarus.2025.116603","url":null,"abstract":"<div><div>Identifying possible fluvial activity during the past and near present on Mars is a key area of martian research, as the occurrence of stable surface water can be an indicator of potentially habitable locations which are of astrobiological interest. Lyot crater is an early Amazonian-aged impact crater in the northern lowlands of Mars. It has a microenvironment due to the low elevation of its interior, where fluvial features and ice-rich landforms have been identified today. We modelled the mesoscale atmospheric conditions in Lyot over the past 20 million years, as Mars’s orbital parameters changed, to identify periods in time and space where conditions were suitable for stable surface water. As well as investigating surface temperature and pressure, an assessment was also made of the impact of relative humidity and evaporation on stable surface water, and the effect of solar insolation and shadowing on the longevity of ice-rich meltwater source materials. At lower obliquities the modelled atmospheric states identify conditions when stable surface water could flow in the summer over much of the crater for a few hours per sol. At higher obliquities modelled conditions suitable for stable water were restricted to the lowest elevation areas of the crater interior. These are areas where the longest channels have been identified and are also areas where standing bodies of water may have formed as these long channels drained into topographic lows. The conditions suitable for supporting stable liquid water at the surface only occurred in the model for short periods of time, hence, an assessment was also made as to the possible behaviour of surface water during the longer intervals when conditions were not suitable. During these times surface water would have boiled or frozen, although if the depth of surface water was sufficiently deep, then a layer of ice on the surface of the water could have protected the liquid water underneath. It would then flow again when conditions were suitable and the ice cover melted or if conditions remained unsuitable the covered water feature would stagnate and disappear over time. This research supports the conclusion drawn from geomorphological analysis that stable surface water occurred in specific locations such as Lyot crater in the recent past on Mars.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"438 ","pages":"Article 116603"},"PeriodicalIF":2.5,"publicationDate":"2025-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143917796","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 steady state population of Earth’s minimoons of lunar provenance","authors":"Robert Jedicke ,&nbsp;Elisa Maria Alessi ,&nbsp;Naja Wiedner ,&nbsp;Mehul Ghosal ,&nbsp;Edward B. Bierhaus ,&nbsp;Mikael Granvik","doi":"10.1016/j.icarus.2025.116587","DOIUrl":"10.1016/j.icarus.2025.116587","url":null,"abstract":"&lt;div&gt;&lt;div&gt;This work examines the plausibility of a lunar origin of natural objects that have a negative total energy with respect to the geocenter, &lt;em&gt;i.e.&lt;/em&gt; &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;E&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;potential＋ kinetic energy&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, while they are within 3 Earth Hill radii (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;), a population that we will refer to as ‘bound’. They are a super-set of the informally named population of ‘minimoons’ which require that the object make at least one orbit around Earth in a synodic frame rotating with Earth and that its geocentric distance be &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; at some point while &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;E&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. Bounded objects are also a dynamical subset of the population of Earth’s co-orbital population, objects in a 1:1 mean motion resonance with Earth or, less specifically, on Earth-like orbits. Only two minimoons have been discovered to date, 2006&lt;!--&gt; &lt;!--&gt;RH&lt;sub&gt;120&lt;/sub&gt; and 2020&lt;!--&gt; &lt;!--&gt;CD&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, while 2024&lt;!--&gt; &lt;!--&gt;PT&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;5&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and 2022&lt;!--&gt; &lt;!--&gt;NX&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; meet our condition for ’bound’. The likely source region of co-orbital objects is either the MB of asteroids, lunar ejecta, or a combination of both. Earlier works found that dynamical evolution of asteroids from the MB could explain the observed minimoon population, but spectra of 2020&lt;!--&gt; &lt;!--&gt;CD&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and 2024&lt;!--&gt; &lt;!--&gt;PT&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;5&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and Earth co-orbital (469219)&lt;!--&gt; &lt;!--&gt;Kamo‘oalewa are more consistent with lunar basalts than any MB asteroid spectra, suggesting that the ejection and subsequent evolution of material from the Moon’s surface contributes to the minimoon and, more generally, Earth’s co-orbital population. This work numerically calculates the steady-state size-frequency distribution of the bound population given our current understanding of the lunar impact rate, the energy of the impactors, crater-scaling relations, and the relationship between the ejecta mass and speed. We numerically integrate the trajectory of lunar ejecta and calculate the statistics of ‘prompt’ bounding that take place immediately after ejection, and ‘delayed’ bounding that occurs after the objects have spent time on heliocentric orbits. A sub-set of the delayed bound population composes the minimoon population. We find that lunar ejecta can account for the observed population of bound o","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"438 ","pages":"Article 116587"},"PeriodicalIF":2.5,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143908132","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":"Recent boulder falls on the Moon","authors":"S. Vijayan ,&nbsp;K.S. Sharini ,&nbsp;K.B. Kimi ,&nbsp;S. Tuhi ,&nbsp;Harish ,&nbsp;Rishav Sahoo ,&nbsp;T.R. Watters ,&nbsp;Anil Bhardwaj","doi":"10.1016/j.icarus.2025.116627","DOIUrl":"10.1016/j.icarus.2025.116627","url":null,"abstract":"<div><div>Lunar boulder fall tracks indicate recent surface activity, however, to date there has been no systematic attempt to identify recent fall locations and it remains elusive that how recent the falls actually are. Our study mapped the recent boulder falls located within ±40° latitude, identified by the presence of boulder bounce-induced ejecta along the tracks referred to as Boulder Fall Ejecta (BFE). Our comprehensive survey revealed 245 tracks with ∼373 km total length, which are clearly distinguishable from classical boulder tracks, which lack such ejecta. We found 46 % of BFE tracks are located on the Mare and 54 % in Highland regions, suggesting relatively more falls in the Mare region, as there are fewer steep slopes here. We report that ∼62 % of our mapped locations host multiple BFE tracks, which indicates more boulder falls within those regions. Placing the BFE tracks with their contextual region revealed the first geomorphic evidence for impact ejected/triggered boulder falls. We find that fresh craters hosting the BFE tracks are a few 100 Ka old, meaning that the BFE tracks are even more recent. We observed BFE tracks adjacent to the Lee-Lincoln scarp at the Apollo17 site and a few other locations neighboring to Apollo seismic epicenters/wrinkle ridge/lobate scarps, which we hypothesize as potential hotspots. We infer from the spatial distribution of these BFE tracks that various triggers have played a role in causing the recent falls. With these newly found BFE tracks, the Moon joins Earth and Mars, with records of recent boulder falls driven by multiple sources suggesting a sporadically active Moon. Such regions could be potential landing sites for future missions to understand the recent surface/subsurface activity on the Moon.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"438 ","pages":"Article 116627"},"PeriodicalIF":2.5,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143908148","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}