Icarus最新文献

{"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":"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}

{"title":"Mie theory-based light scattering analysis of entrained grains in Io's Tvashtar plume observed during new horizons' 2007 flyby","authors":"A.O. Adeloye ,&nbsp;L.M. Trafton ,&nbsp;D.B. Goldstein ,&nbsp;P.L. Varghese ,&nbsp;A. Mahieux","doi":"10.1016/j.icarus.2025.116628","DOIUrl":"10.1016/j.icarus.2025.116628","url":null,"abstract":"<div><div>Io, the most volcanically active body in the Solar System, frequently produces large-scale plumes capable of reaching hundreds of kilometers in height. During the 2007 New Horizons (NH) flyby, the Tvashtar Catena region exhibited a ∼ 350 km high “Pele-type” plume whose canopy radiance in scattered sunlight increased unexpectedly by an order of magnitude over 3–4 days. This radiance surge occurred as the solar phase angle between the Sun, Io, and NH rose from ∼40° to 150°, suggesting that observational geometry could play a key role; earlier investigations found that changes in basic volcanic vent parameters, such as stagnation temperature and vent area, did not fully explain this irregular brightness increase (Adeloye et al., 2025).</div><div>In this study, we utilize Mie theory to characterize light scattering and integrate multiple lines of analysis to identify the primary factors influencing Tvashtar's plume radiance. We employ Direct Simulation Monte Carlo (DSMC) modeling to simulate SO₂ gas dynamics and entrained basaltic grains, assuming a log-normal grain size distribution. Additionally, we examine multiple factors that could potentially contribute to the observed phenomena, including variations in the NH observation geometry, the scattering properties of individual and ensembles of grains, and vent parameters such as mass flow rate and grain mass loading.</div><div>Our results indicate that no single factor can fully account for the irregular brightness surge. Instead, a combination of observational geometry effects, the optical scattering behavior of the grains in the plume, and changes in grain mass loading are required to reproduce the observed radiance profile and its changes. Although our methodology assumes continuous, steady-state ejection over tens of minutes and does not explicitly model condensation, sublimation, or episodic grain injection at the vent, the integrated approach presented here offers a novel perspective on plume dynamics at Io. These findings not only enhance the interpretation of the NH Tvashtar observations but also provide a framework for future investigations of Io's volcanic plumes and potential exploration missions.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"438 ","pages":"Article 116628"},"PeriodicalIF":2.5,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143899379","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":"Implications of a highly convective lunar magma ocean: Insights from phase equilibria modeling","authors":"K.A. Cone ,&nbsp;S.M. Elardo ,&nbsp;F.J. Spera ,&nbsp;W.A. Bohrson ,&nbsp;R.M. Palin","doi":"10.1016/j.icarus.2025.116629","DOIUrl":"10.1016/j.icarus.2025.116629","url":null,"abstract":"<div><div>The Moon's internal structure was largely defined within the first 200 million years following the initial Moon-forming impact. During this period, the lunar magma ocean (LMO) lost most of its heat through early vigorous convection, crystallizing and forming an initial cumulate stratigraphy through, potentially, robust equilibrium crystallization followed by fractional crystallization once the LMO became sufficiently viscous. This rheological transition is estimated to have occurred at 50 % to 60 % LMO solidification, and although the petrological effects of the regime switch have been frequently investigated at the lower value, such effects at the upper limit have not been formally examined until now. Given this scenario, we present two new internally consistent, high-resolution models that simulate the solidification of a deep LMO of Earth-like bulk silicate composition at both rheological transition values, focusing on the petrological characteristics of the evolving mantle and crust. The results suggest that increasing the volume of early suspended solids from the oft-examined 50 % to 60 % may lead to non-trivial differences. The appearance of minor mantle garnet without the need to invoke a refractory-element enriched bulk silicate Moon composition, a bulk mantle relatively richer in orthopyroxene than olivine, a lower density upper mantle, and a thinner crust are shown to change systematically between the two models, favoring prolonged early crystal suspension. In addition, we show that late-stage, silica-enriched melts may not have sufficient density to permit plagioclase to continue building a floatation crust and that plagioclase likely sinks or stagnates. As the ability of a lunar magma ocean to suspend crystals is directly tied to the Moon's early thermal state, the degree of early LMO convection – and the immediate Solar System environment that drives it – require as much consideration in LMO models as more well-investigated parameters such as bulk silicate Moon composition and initial magma ocean depth.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"438 ","pages":"Article 116629"},"PeriodicalIF":2.5,"publicationDate":"2025-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143908133","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":"Lunar impact ejecta flux on the Earth","authors":"Jose Daniel Castro-Cisneros ,&nbsp;Renu Malhotra ,&nbsp;Aaron J. Rosengren","doi":"10.1016/j.icarus.2025.116606","DOIUrl":"10.1016/j.icarus.2025.116606","url":null,"abstract":"<div><div>The transfer of material between planetary bodies due to impact events is important for understanding planetary evolution, meteoroid impact fluxes, the formation of near-Earth objects (NEOs), and even the provenance of volatile and organic materials at Earth. This study investigates the dynamics and fate of lunar ejecta reaching Earth. We employ the high-accuracy IAS15 integrator within the REBOUND package to track for 100,000 years the trajectories of 6,000 test particles launched from various lunar latitudes and longitudes. Our model incorporates a realistic velocity distribution for ejecta fragments (tens of meters in size), derived from large lunar cratering events. Our results show that 22.6% of lunar ejecta collide with Earth, following a power-law <span><math><mrow><mi>C</mi><mrow><mo>(</mo><mi>t</mi><mo>)</mo></mrow><mo>∝</mo><msup><mrow><mi>t</mi></mrow><mrow><mn>0</mn><mo>.</mo><mn>315</mn></mrow></msup></mrow></math></span>, with half of the impacts occurring within <span><math><mo>∼</mo></math></span>10,000 years. We also confirm that impact events on the Moon’s trailing hemisphere serve as a dominant source of Earth-bound ejecta, consistent with previous studies. Additionally, a small fraction of ejecta remains transiently in near-Earth space, providing evidence that lunar ejecta may contribute to the NEO population. This aligns with recent discoveries of Earth co-orbitals such as Kamoóalewa (469219, 2016 HO3) and 2024 PT5, both exhibiting spectral properties consistent with lunar material. These findings enhance our understanding of the lunar ejecta flux to Earth, providing insights into the spatial and temporal patterns of this flux and its broader influence on the near-Earth environment.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"438 ","pages":"Article 116606"},"PeriodicalIF":2.5,"publicationDate":"2025-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143902229","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":"New astrometric positions of Neptune and Triton in 2020–2024","authors":"D. Yan ,&nbsp;R.C. Qiao ,&nbsp;H.Y. Zhang ,&nbsp;Y. Yu","doi":"10.1016/j.icarus.2025.116625","DOIUrl":"10.1016/j.icarus.2025.116625","url":null,"abstract":"<div><div>A total of 3836 astrometric positions of Neptune and its largest irregular satellite Triton were obtained in the period 2020–2024 by the 1.0 m telescopes at Yunnan Astronomical Observatory. Based on Gaia DR3 catalogue and the six-parameter plate model, 1918 new positions of Neptune and 1918 new positions of Triton were collected. For the observations of Neptune, with the comparison of DE441, the mean residuals are 30 mas and − 27 mas in right ascension and declination, the standard deviation of residuals are 28 mas and 33 mas in right ascension and declination. For the observations of Triton, with the comparison of the theoretical positions derived from <span><span>Jacobson (2009)</span></span> satellite orbit model and DE441, the mean residuals are 7 mas and − 14 mas in right ascension and declination, the standard deviation of residuals are 29 mas and 31 mas in right ascension and declination. Moreover, we also compared three recent orbit models of triton as well as three different planetary ephemerides of Neptune. These comparisons show that the differences among all the three planetary ephemerides are obvious.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"437 ","pages":"Article 116625"},"PeriodicalIF":2.5,"publicationDate":"2025-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143886219","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":"Preservation and detection of carotenoid pigments of Deinococcus radiodurans on mineral substrates under UV irradiation","authors":"Tamires Gallo ,&nbsp;Fabio Rodrigues ,&nbsp;Evelyn A.M. Sanchez ,&nbsp;Fabio S. de Vicente ,&nbsp;Veronica C. Teixeira ,&nbsp;Evandro P. Silva ,&nbsp;Marcia Rizzuto ,&nbsp;Gabriel S. Teofilo-Guedes ,&nbsp;Douglas Galante","doi":"10.1016/j.icarus.2025.116624","DOIUrl":"10.1016/j.icarus.2025.116624","url":null,"abstract":"<div><div>Biosignatures (or biomarkers), such as carotenoids, derived from microorganisms serve as valuable indicators of past or present life within the geological record on planetary surfaces. This study investigates the resistance and preservation of carotenoid pigments from the poly-extremophilic bacterium <em>Deinococcus radiodurans</em> across various mineral substrates using Raman spectroscopy and diffuse reflectance in the UV–Vis range. Pigment-substrate mixtures were exposed to simulated conditions mimicking the surface of Mars, a UV-rich terrestrial environment, and space conditions at the Toroidal Grating Monochromator beamline of the Brazilian Synchrotron Light Laboratory. Our findings reveal that the topmost layers of the substrate act as protective shields against radiation, preserving biomolecules located a few hundred micrometers below the surface in all three simulated environments. This integrated approach offers a promising analysis protocol for an in situ search for molecular fossils on diverse planetary surfaces, eliminating the need for extensive sample preparation.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"438 ","pages":"Article 116624"},"PeriodicalIF":2.5,"publicationDate":"2025-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143902429","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}