Icarus最新文献

{"title":"The fall of asteroid 2024 XA1 and the location of possible meteorites","authors":"Francesco Gianotto ,&nbsp;Albino Carbognani ,&nbsp;Marco Fenucci ,&nbsp;Maxime Devogèle ,&nbsp;Pablo Ramirez-Moreta ,&nbsp;Marco Micheli ,&nbsp;Raffaele Salerno ,&nbsp;Toni Santana-Ros ,&nbsp;Juan Luis Cano ,&nbsp;Luca Conversi ,&nbsp;Charlie Drury ,&nbsp;Laura Faggioli ,&nbsp;Dora Föhring ,&nbsp;Reiner Kresken ,&nbsp;Selina Machnitzky ,&nbsp;Richard Moissl ,&nbsp;Francisco Ocaña ,&nbsp;Dario Oliviero ,&nbsp;Eduardo Alonso-Peleato ,&nbsp;Margherita Revellino ,&nbsp;Regina Rudawska","doi":"10.1016/j.icarus.2025.116511","DOIUrl":"10.1016/j.icarus.2025.116511","url":null,"abstract":"<div><div>Asteroid 2024 XA<span><math><msub><mrow></mrow><mrow><mn>1</mn></mrow></msub></math></span> was discovered on 3 December 2024 at 05:54 UTC by the Bok telescope in Kitt Peak, Arizona, and impacted Earth about 10 h later over a remote area of the Sakha Republic (Russia). The estimated size of the object was about one meter, and the atmospheric entry produced a bright fireball that was captured by a webcam and several eyewitnesses. The first impact alert was issued at 07:50 UTC by the Meerkat Asteroid Guard of the European Space Agency, which triggered subsequent follow-up observations that confirmed both the object to be real and the occurrence of the impact with Earth. Here we present the operations and results from the NEO Coordination Centre (NEOCC) upon the impact event. Because the entry likely dropped meteorites on the ground, we also estimate the possible strewn fields for future meteorite search campaigns.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"433 ","pages":"Article 116511"},"PeriodicalIF":2.5,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143480436","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":"Time scales for Co-orbital Cycles of Venus Trojans Asteroids","authors":"V. Carruba ,&nbsp;S. Di Ruzza ,&nbsp;G. Caritá ,&nbsp;S. Aljbaae ,&nbsp;R.C. Domingos ,&nbsp;M. Huaman ,&nbsp;R.A.N. Araujo ,&nbsp;D.C. Mourão ,&nbsp;A.A. Alves ,&nbsp;E.M.D.S. Delfino ,&nbsp;V.R. Silva","doi":"10.1016/j.icarus.2025.116508","DOIUrl":"10.1016/j.icarus.2025.116508","url":null,"abstract":"<div><div>Co-orbital asteroids are asteroids locked in a 1:1 mean-motion resonance with a planet. The mechanism of capture of these objects into their current resonant configuration can shed light on the origin and evolution of asteroids and the whole Solar System. Terrestrial planets’ co-orbital configurations include retrograde satellite orbits (RS), tadpole orbits (T) around the Lagrangian equilibrium points L4 or L5, and horseshoe orbits around both L4 and L5 (H). At high eccentricity or inclination, co-orbital configurations may include compounds of T and RS (T-RS, T-RS-T), H and RS (H-RS) orbits, or transitions between distinct co-orbital modes. These instantaneous configurations may change into one another in short time scales, and Venus Trojans may alternate between several of these configurations before being lost to a passing orbit. We define the time between long periods of staying in a passing orbit as a co-orbital cycle. Here, we use digital filtering of the resonant arguments and rolling averages, a calculation used to analyze data points by creating averages of different subsets of the full data set, of the number of close encounters with Venus of a large population of clones of the currently known co-orbitals of Venus to estimate the times of permanence in one or several cycles. The typical duration of a single cycle is <span><math><mrow><mn>12000</mn><mo>±</mo><mn>6000</mn></mrow></math></span> yrs. Some asteroids may experience two or more cycles before finally escaping co-orbital status, remaining in circulating orbits in between cycles. We call these orbital configurations “dormant orbit”. Six of the Venus’ Trojan may become Potentially Hazardous Asteroid (PHA) with Earth in a few thousand of years, and three asteroids, 2020 SB, 524522, and 2020 CL1, have a severe risk of collision.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"433 ","pages":"Article 116508"},"PeriodicalIF":2.5,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143465242","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":"Reassessing the origin and evolution of Ecliptic Comets in the Planet-9 Scenario","authors":"Rafael Ribeiro de Sousa ,&nbsp;Andre Izidoro ,&nbsp;Alessandro Morbidelli ,&nbsp;David Nesvorny ,&nbsp;Othon Cabo Winter","doi":"10.1016/j.icarus.2025.116472","DOIUrl":"10.1016/j.icarus.2025.116472","url":null,"abstract":"&lt;div&gt;&lt;div&gt;A group of newly observed extreme trans-Neptunian objects show an unexpected level of orbital confinement, characterized by an approximate alignment of the orbital angular momentum vectors and apsidal lines. It has been proposed that a yet undiscovered giant planet (named &lt;em&gt;Planet-9&lt;/em&gt;,) exists in the outer parts of the solar system and is causing this clustering. Initial studies suggested that Planet-9 could be as massive as 15&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;⊕&lt;/mo&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;. In this mass range, however, this planet tends to strongly interact with scattered disk objects (SDOS; &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;50&lt;/mn&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mn&gt;1000&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; au) and influence the dynamics and the orbits of a population of short period comets known as ecliptic comets. The outcome of this interaction is a population of ecliptic comets with orbital inclinations broadly inconsistent with observations. In this work, we model the formation and long-term dynamical evolution of trans-Neptunian object populations and Oort cloud during the solar system dynamical instability phase considering a revised set of mass and orbital parameters for Planet-9. In our simulation, Planet-9, is assumed to have a mass of &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;m&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;9&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;∼&lt;/mo&gt;&lt;mn&gt;7&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;5&lt;/mn&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;⊕&lt;/mo&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, a moderately inclined orbit with &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;9&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;∼&lt;/mo&gt;&lt;mn&gt;20&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; deg, semi-major axis &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;9&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;∼&lt;/mo&gt;&lt;mn&gt;600&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; au, and orbital eccentricity of &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;mn&gt;9&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;∼&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. Our results show that a relatively less massive Planet-9 is broadly consistent with the inclination distribution of trans-Neptunian objects and the observed number of ecliptic comets (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;D&lt;/mi&gt;&lt;mo&gt;&gt;&lt;/mo&gt;&lt;mn&gt;10&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; km) in the solar system. Furthermore, our results indicate that under the influence of Planet-9, distant Kuiper belt objects with &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;40&lt;/mn&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mi&gt;q&lt;/mi&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mn&gt;100&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mi&gt;au&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;200&lt;/mn&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mn&gt;500&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mi&gt;au&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; that are significantly inclined, are more likely to be apsidally aligned with the planet rather than anti-aligned, with an anti-aligned-to-aligned population ratio of approximately 0.5-0.7. Objects within this semi-major axis and perihelion range and with orbital inclinations lower than &lt;span&gt;&lt;math&gt;&lt;mo&gt;≲&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt; 20 deg (comparable to that assumed for Planet-9), however, exhibit significan","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"433 ","pages":"Article 116472"},"PeriodicalIF":2.5,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143465170","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":"Analysis of pit craters on asteroids and small bodies: Predictions about the regolith layer and internal structure","authors":"Miguel de Luis ,&nbsp;Laura M. Parro","doi":"10.1016/j.icarus.2025.116514","DOIUrl":"10.1016/j.icarus.2025.116514","url":null,"abstract":"<div><div>In this work, we investigate and compare potential features called pit craters on the surfaces of (951) Gaspra, (243) Ida, (433) Eros, and the Martian moon, Phobos. Pit craters are typically arranges as chains on the surface and appear to be formed by the drainage of overlying loose material into internal voids promoted by fractures, assessing a piece of direct information about the approximate thickness of the regolith layer, and the internal configuration of each small body. Methodologically, we analyzed images taken by Galileo, NEAR Shoemaker, and other Martian rendezvous missions and mapped these geological morphologies across their surfaces. We analyzed pit sizes using Analysis of Variance and looked for correlations in terms of their different intrinsic physical properties. The pit sizes range between 0.034 and 0.971 km and their estimated regolith layers between 100 and 300 m thick for the four bodies. We demonstrated a strong correlation between the mean diameter of these depressions and the density of the body, making possible a linear model to predict the size of pit craters on small bodies to be visited in future missions, such as Deimos or asteroid (16) Psyche. We also proposed an internal fracturing index for these small bodies that shows a strong correlation with each mean body density. The data provided by future missions for different pitted small objects will allow us to validate or reject these models and predictions.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"433 ","pages":"Article 116514"},"PeriodicalIF":2.5,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143474341","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":"Predominance of porphyritic textures in chondrules due to density sorting of precursor materials? Constraints from melting experiments","authors":"Scott A. Whattam","doi":"10.1016/j.icarus.2025.116510","DOIUrl":"10.1016/j.icarus.2025.116510","url":null,"abstract":"<div><div>Although chondrule textures are diverse, the absolute number of texture types is relatively small essentially encompassing cryptocrystalline (glassy) to microcrystalline (radial pyroxene), barred, granular, metallic and porphyritic/micro-porphyritic varieties; and the vast majority (∼70–90 %) of all textures are a variety of porphyritic (e.g., porphyritic olivine,). Textural diversity has been attributed to the influence of many variables, e.g., bulk composition, duration of heating, cooling rate and size of precursor phases. Here, I show experimentally that when charges are heated initially at 1550 °C that differences in the bulk compositions have an enormous effect on ultimate texture. I construct several bulk compositions by mixing varied quantities of olivine with plagioclase and pyroxene. When synthetic chondrule materials are heated below their liquidus (maximum 1718 °C), the predominant texture is porphyritic if olivine (liquidus of ∼1844 °C) is abundant. If more easily fusible dust (En + An liquidus of 1429 °C) is abundant, barred and glassy chondrule textures result. Assuming amoeboid olivine aggregates (AOA) are possible precursors, I also replaced olivine by synthetic (pre-sintered) granoblastic olivine aggregates (GOA) and isothermally produced PO chondrule analogs when ‘AOA’ (with En + An) mixtures have Ol: En + An ratios of 99:01 to 30:70, but glass-rich analogs at mixtures with ratios of 20:80 and 10:90. If charges are subsequently cooled at 1000 °C/h to 100 °C/h after an isothermal dwell of 1 h at 1550 °C, PO analogs prevail at ratios of Ol:En + An of 30:70 and (presumably, based on isothermal experiments) higher, barred olivine (BO)-like analogs occur at ratios of 20:80; elongated skeletal hopper olivine (EHO) ensues at ratios of 10:90. Models of chondrule formation have not explained the propensity of PO textures but these experiments suggest simply that the predominance of PO chondrules is largely a function of the abundance of Mg in the chondrule precursors and that the ratio of olivine to dust was high in chondrule precursors. Stratification of chondrule precursors may have occurred before chondrule formation, resulting in a greater volume of denser olivine in the central region and greater volume of less dense, fusible An+En in the periphery. Results are compatible with large chondrule-forming regions with a great variety of chondrules being formed in the same event(s) at the same temperature.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"432 ","pages":"Article 116510"},"PeriodicalIF":2.5,"publicationDate":"2025-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143438047","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 phase- and color-ratio techniques as applied to Dawn images of the dwarf planet Ceres and asteroid (4) Vesta","authors":"Ivan G. Slyusarev ,&nbsp;Valeria V. Rychahova ,&nbsp;Vadym G. Kaydash ,&nbsp;Irina N. Belskaya ,&nbsp;Yuriy G. Shkuratov ,&nbsp;Vasilij G. Shevchenko","doi":"10.1016/j.icarus.2025.116507","DOIUrl":"10.1016/j.icarus.2025.116507","url":null,"abstract":"<div><div>Identification of regolith structure anomalies on atmosphereless Solar System bodies is important as an indicator of the surface changes. With the phase ratio method, we are able to map phase curve slopes and distinguish the areas with different regolith optical roughness. These areas are caused by topographic slope processes, formation of new craters and the possible effects of endogenous processes. Global mapping of asteroid (4) Vesta and the dwarf planet Ceres from two orbits High Altitude Mapping Orbit (HAMO) and Low Altitude Mapping Orbit (LAMO) provide the necessary data for applying the phase-ratio technique to these bodies. Using multispectral images from the Dawn Framing Camera (FC) for the dwarf planet Ceres and the asteroid (4) Vesta, phase-ratio and color-ratio methods were applied for selected areas on surfaces of Vesta (Laelia, Laeta, Aricia, Vibidia) and Ceres (Ahuna Mons, craters Occator, Oxo, Xevioso). The phase-ratio method gives us a good tool for both bodies, Ceres and Vesta, to detect changes in regolith structure associated with mass movement due to slope processes on crater walls and hillsides, as well as with ejecta from the youngest craters.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"432 ","pages":"Article 116507"},"PeriodicalIF":2.5,"publicationDate":"2025-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143445720","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":"A case for young igneous volcanism in the Terra Sirenum region, Mars","authors":"Shreekumari Patel ,&nbsp;Harish ,&nbsp;S. Vijayan ,&nbsp;M.R. El-Maarry","doi":"10.1016/j.icarus.2025.116512","DOIUrl":"10.1016/j.icarus.2025.116512","url":null,"abstract":"<div><div>In this study, we concentrate on an large field of 73 cones situated on the floor of an unnamed crater centered at 27.6°S, 156.9°W. This crater has been subjected to detailed investigations by at least three different scientific teams, each supporting various hypotheses like sedimentary and igneous volcanism regarding the cones origins. The cone field is circumferentially distributed around a triad of primary fractures, which have instigated the formation of the graben structure within the crater. The crater floor exhibits a variety of geomorphological and stratigraphic units, suggesting that the crater has undergone a complex history of different episodes of geological events, including volcanism, tectonic activity and potential fluvial processes. Cones display one of two broad morphologies: domical cones and pitted cones. The morphometric analysis of the W_CR/W_CO in relation to the Cone width of pitted cones aligns with the trends observed in both terrestrial and Martian scoria cones. However, the morphometric measurements of domical cones deviate from the discernible trends typically seen in igneous volcanic structures, sedimentary formations on Earth, and Martian edifices. The cumulative Size-Frequency Distribution (CSFD) analysis indicates the formation of the cone field in the crater occurred between ∼1.26 Ga and ∼1 Ga, corresponding to the Mid-Amazonian epoch. Spectral analysis of the crater floor units indicates the presence of kaolinite, along with low-calcium and high-calcium pyroxene minerals, which could potentially be a marker of volcanic as well as aqueous activities. However, the spectral signature of high-calcium pyroxene in the cone-field bearing crater unit suggests a recent igneous volcanic origin. This study highlights the complex geological history of the unnamed crater, with spectral and morphometric analyses suggesting a likely igneous volcanic origin for the cones amidst evidence of tectonic and aqueous activity.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"432 ","pages":"Article 116512"},"PeriodicalIF":2.5,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143429606","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 mystery of the missing mantle problem and insights from spectroscopy","authors":"B.G. Rider-Stokes ,&nbsp;S.L. Jackson ,&nbsp;T.H. Burbine ,&nbsp;R.C. Greenwood ,&nbsp;E.M. MacLennan ,&nbsp;L.F. White ,&nbsp;S.S. Russell ,&nbsp;M. Anand ,&nbsp;M.M. Grady","doi":"10.1016/j.icarus.2025.116506","DOIUrl":"10.1016/j.icarus.2025.116506","url":null,"abstract":"<div><div>Differentiation of planetesimals results in the segregation of materials, with the densest materials sinking, producing a metallic core, while the lighter fraction, rises, fabricating a crust. While there are multiple examples of planetary crusts (e.g., V-type asteroids) and metallic cores (e.g., M-type asteroids), there appears to be a scarcity of mantle-like materials in both the asteroid (e.g., A-type asteroids) and meteorite record. This lack of olivine-dominated material has been dubbed ‘The Missing Mantle Problem’. Here we measure the reflectance spectra of four olivine-rich meteorites expected to originate from the mantle of differing planetesimals. Following the Bus-DeMeo taxonomy, NWA 12264 and Chassigny can be classified as Sa-types, while NWA 8535 and NWA 15717 are classified as Q-types. This result implies that mantle-like materials are not restricted to A-type asteroids as previously expected. This study provides a significant step toward the resolution of the apparent shortage of olivine-rich material in the early Solar System.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"432 ","pages":"Article 116506"},"PeriodicalIF":2.5,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143421071","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":"Multi-instrument sounding of a Jovian thunderstorm from Juno","authors":"Shawn R. Brueshaber ,&nbsp;Zhimeng Zhang ,&nbsp;John H. Rogers ,&nbsp;Gerald Eichstädt ,&nbsp;Glenn S. Orton ,&nbsp;Davide Grassi ,&nbsp;Leigh N. Fletcher ,&nbsp;Cheng Li ,&nbsp;Shinji Mizumoto ,&nbsp;Alessandro Mura ,&nbsp;Fabiano Oyafuso ,&nbsp;Ramanakumar Sankar ,&nbsp;Michael H. Wong ,&nbsp;Candice J. Hansen ,&nbsp;Steven Levin ,&nbsp;Scott Bolton","doi":"10.1016/j.icarus.2025.116465","DOIUrl":"10.1016/j.icarus.2025.116465","url":null,"abstract":"<div><div>Thunderstorms play a significant role in transporting heat from the deep interior to space on giant planets. We present observations of a 3,400-km wide thunderstorm complex in Jupiter’s North Equatorial Belt (NEB) during the 38th periapse of the Juno spacecraft on 29 Nov. 2021. Data were acquired by the Microwave Radiometer (MWR), the visible light JunoCam instrument, the Jovian InfraRed Auroral Mapper (JIRAM), and from supporting Earth-based imaging. This was the first time Juno was able to observe a thunderstorm at suitably low emission angles with multiple instruments at close range (<span><math><mo>∼</mo></math></span>5,690 km), making it the most comprehensive close-up assessment of a Jovian thunderstorm to date. Lightning detection confirmed the Storm’s vigorous convective nature. MWR brightness temperatures indicate this Storm appears to be wholly contained within the weather layer, i.e., no deeper than the expected base of the H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>O cloud, and not as a result of any detected deep-seated upwelling beneath the H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>O cloud base. Earth-based observations tracked it over its <span><math><mo>∼</mo></math></span> 2-week lifespan, providing evidence that mesoscale-to-synoptic-scale forcing mechanisms were involved in sustaining it, including the intriguing possibility of a humidity front (‘dryline’), a sharp gradient in the vapor abundance, promoting lift along a concentrated region.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"432 ","pages":"Article 116465"},"PeriodicalIF":2.5,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143420863","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":"Synthesized microstructures and reflectance spectra of solids in the ice Ih–MgCl2•12H2O system: Implications for Europa","authors":"Thomas B. Czernik ,&nbsp;Kevin Robertson ,&nbsp;Cameron Meyers ,&nbsp;Christine McCarthy ,&nbsp;Greg Hirth ,&nbsp;Reid F. Cooper","doi":"10.1016/j.icarus.2025.116481","DOIUrl":"10.1016/j.icarus.2025.116481","url":null,"abstract":"<div><div>The existence of hydrated MgCl₂ on Europa's surface has been suggested by remote sensing spectrometry, but this interpretation is limited by the low signal-to-noise ratio of the data and a lack of relevant laboratory-derived spectra within spectral libraries. Furthermore, the compaction state of Europa's surface remains poorly constrained, yet there is a lack of laboratory-measured spectra for dense specimens that are necessary to understand endmember behavior of a dense surface. We acquired vis-near-infrared reflectance spectra at wavelengths from 0.35 to 2.5 μm for synthetic specimens in the ice Ih–MgCl₂•12H₂O system. Reflectance spectra were measured for dense water-ice aggregates with different grain sizes and were used to assess the influence of density on spectral signature. In general, large-grained aggregates exhibited decreased albedo, broadening of absorption bands, and decreased absorption band depth. Additionally, reflectance spectra of powdered MgCl₂•12H₂O were measured as a function of particle size and were observed to contain spectral features distinct from other hydration states (MgCl₂•nH₂O, <em>n</em> = 1,2,4,6,8). Particle size dependency observed in the spectra of powdered MgCl₂•12H₂O mirrored grain size dependent trends observed in the spectra of dense water-ice aggregates. We also measured the spectra of eutectic (20.6 wt% MgCl₂) and porphyritic hypoeutectic (7.7 and 16.4 wt% MgCl₂) dense ice Ih–MgCl₂•12H₂O aggregates. We argue that the microstructures of synthesized eutectic and hypoeutectic aggregates are suitable to represent texture likely existent in Europa's shell and are appropriate for use in mechanical testing where texture needs to be carefully considered.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"432 ","pages":"Article 116481"},"PeriodicalIF":2.5,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143445874","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}