Icarus最新文献

{"title":"Degasing of Phobos in a giant impact scenario: Implications for the MMX sample return mission","authors":"Sébastien Charnoz,&nbsp;Angela Limare,&nbsp;Eva De Araujo Pereira,&nbsp;Razvan Caracas,&nbsp;Frédéric Moynier","doi":"10.1016/j.icarus.2025.116462","DOIUrl":"10.1016/j.icarus.2025.116462","url":null,"abstract":"<div><div>The MMX mission, led by JAXA, is a sample return mission whose primary goal is to test whether the Martian moons, Phobos and Deimos, were formed during a giant impact or were captured. One of the main observations to test these scenarios will be whether Phobos and Deimos have lost volatile elements. If Phobos formed in a giant impact, simulations show that the impact was much less energetic than the Moon-forming impact, with peak temperatures as low as 2000 K. We present here a quantification of the volatile loss in anticipation of the MMX mission, assuming that Phobos’ building blocks were made of bulk silicate Mars material. We investigate the cooling of Phobos in two end-member scenarios : a convective case (relevant for an initially fully molten proto-Phobos) and a conductive case (relevant for an assemblage of 10 m building blocks). A homogeneous evaporation model is used for the convective case, and a diffusion-limited evaporation model is used for the conductive case. In both cases, we find that the cooling time is about 1–10 years in the absence of external heating sources (but the Sun). This leaves little time for evaporation: the most volatile elements, Na and K, may be depleted by 10% for the case of a fully molten and convective proto-Phobos. If Phobos is rather an assemblage of 10 m building blocks that cool conductively, the loss of Na and K would be limited to the first 10 cm below the blocks’ surface (by about 4%) representing about 0.1% loss in averaged bulk composition.</div><div>If external sources of heating were present (such as a hot radiating Mars or a hot surrounding disk), and the body was kept at T <span><math><mo>&gt;</mo></math></span> 1400K (our assumed rheological transition temperature) for more than 10 years, a larger loss of Na and K is found. If degassing lasted more than 100 years with exterior temperature <span><math><mo>&gt;</mo></math></span> 1400K, then all Na and K may have been lost for the convective case, and more than 50% for the conductive case. Furthermore, a significant fraction of the refractory elements may also have been lost in both cases. K abundance will be measured from space by the MEGANE instrument onboard the MMX mission. If low K content is measured by the MEGANE instrument, this would favor the giant impact formation scenario and would imply either a long cooling time of the proto-Phobos (<span><math><mo>≥</mo></math></span>100 years), or degassing prior to the assembling of the proto-Phobos. If MEGANE does not measure K depletion, this could mean either that Phobos was not formed in a giant impact, or that it formed in a giant impact but experienced a short cooling time (<span><math><mo>&lt;</mo></math></span>10 years). In that case, laboratory analysis of the returned sample will be crucial in deciphering the origin of Phobos by focusing on various volatile elements and constraining their isotopic ratios.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"434 ","pages":"Article 116462"},"PeriodicalIF":2.5,"publicationDate":"2025-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143601005","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 3D thermophysical model for binary asteroid systems: Application to the BYORP effect on (175706) 1996 FG3","authors":"Kya C. Sorli ,&nbsp;Paul O. Hayne ,&nbsp;Rachel H. Cueva ,&nbsp;Chloe J. Long ,&nbsp;Jay W. McMahon ,&nbsp;Daniel J. Scheeres","doi":"10.1016/j.icarus.2025.116527","DOIUrl":"10.1016/j.icarus.2025.116527","url":null,"abstract":"<div><div>Binary asteroids originate from a wide range of evolutionary pathways, and are the targets of several previous and upcoming spacecraft missions. Differential heating and radiation on asymmetric asteroids can cause measurable changes in their rotation rates and spin axes, collectively known as the Yarkovsky–O’Keefe–Radzievskii–Paddack (YORP) effect. In binary systems, such radiation-driven torques can cause changes to the mutual asteroid orbits, termed the binary YORP or BYORP effect. To study how binary asteroid shapes and thermophysical properties affect surface temperatures and BYORP, we developed a new 3D thermophysical model. This model can be applied to binary asteroid systems, solitary asteroids, and other airless bodies with complex topography. The model balances direct insolation, 1D conduction, visible light reflection, and mutual heating through scattered infrared radiation. Using 3D ray tracing, we include eclipses, shadowing from horizons and topography, as well as the mutual radiation exchange between the primary and secondary asteroids. Using this model, we perform global temperature modeling of the binary asteroid (175706) 1996 FG3, a target of the Janus mission. At perihelion, we find that the 1996 FG3 system experiences temperatures between <span><math><mo>∼</mo></math></span>100 and 475 K. We also find that eclipses and thermal inertia can alter surface temperatures on the secondary by up to 14%, with a mean difference due to radiation from the primary of just over 1%. These radiative effects decrease with higher thermal inertia. We also present a model for calculating the BYORP effect using the results of the binary thermophysical model. This model compares well to analytical approximations of the BYORP coefficient <span><math><mi>B</mi></math></span>, and suggests that thermal effects such as eclipses and thermal inertia can reduce torque in the 1996 FG3 system and alter the BYORP coefficient <span><math><mi>B</mi></math></span> by up to several percent. Though small, these second-order effects may produce significant dynamical changes. For 1996 FG3, eclipses alter <span><math><mi>B</mi></math></span> by approximately 7%, resulting in a lower torque on the secondary. In the absence of tidal effects, this change would reduce the contraction of the semimajor axis by about 20 meters over 10,000 years. Mutual radiation from the primary also causes a small nonzero change to <span><math><mi>B</mi></math></span>, although of an order of magnitude smaller. Our findings suggest that thermal effects can alter temperatures and BYORP calculations sufficiently that they should be included when modeling binaries, and the relative importance of each effect is predicted to vary with the properties of the system being studied.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"434 ","pages":"Article 116527"},"PeriodicalIF":2.5,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143578091","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":"Disintegration and separation of the bilobate-shaped meteoric fragment during hypersonic atmospheric entry","authors":"Ziwen Li ,&nbsp;Yong Yu ,&nbsp;Xiangyuan Zeng ,&nbsp;Haoyu Li ,&nbsp;Tongge Wen ,&nbsp;Xiaoran Yan","doi":"10.1016/j.icarus.2025.116537","DOIUrl":"10.1016/j.icarus.2025.116537","url":null,"abstract":"<div><div>A novel method for simulating the disintegration of bilobate-shaped meteoric fragments is presented, which integrates aerodynamic interactions, rotational dynamics, structural strength, and ablation into the analysis. A disintegration criterion is proposed in this method, based on a comparison between the mechanism strength of the sintered bond and the required contact force to maintain the integrity of the bilobate shape. The disintegration of fragment 109 from the Morávka meteoroid, which deviates from the Weibull-like scaling law, is explained physically by applying this approach. Predictive numerical simulations are conducted by varying the initial attitudes, geometries, strengths, and angular velocities of the bilobate-shaped fragments. During atmospheric entry, variations in attitude, landing positions, and residual masses are analyzed as indicators of characteristics in the dynamical evolution.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"433 ","pages":"Article 116537"},"PeriodicalIF":2.5,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143578558","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 GCM study of synoptic-scale vortices in the lower cloud layer on Venus","authors":"Masataka Imai ,&nbsp;Masahiro Takagi ,&nbsp;Hiroki Ando ,&nbsp;Hideo Sagawa","doi":"10.1016/j.icarus.2025.116523","DOIUrl":"10.1016/j.icarus.2025.116523","url":null,"abstract":"<div><div>A synoptic-scale vortex was observed as a spiral cloud feature in mid-latitudes of the nightside northern hemisphere of the Venusian atmosphere by the 2-μm camera (IR2) onboard the Venus Climate Orbiter, Akatsuki. Using a general circulation model (GCM), we reproduced vortices consistent with the observation. The result shows that the cyclonic vortex with a longitudinal scale of ∼5000 km develops in mid-latitudes at ∼60 km altitude within the middle cloud layer, accompanied by upward (downward) winds on the downstream (upstream) side of the zonal-mean zonal wind. The spiral cloud feature could be formed by the meridional and vertical winds associated with the vortex. The linear stability analysis suggests that the synoptic-scale vortices, with an <em>e</em>-folding time of 4.3 days, could be generated by barotropic instability due to the meridional shear of the mid-latitude jet, which is consistent with the present GCM result. The vortices and mid-latitude jets develop and decay alternately in both hemispheres because the growing and decaying vortices in the southern and northern (northern and southern) hemispheres induce the northward (southward) angular momentum transport across the equator and enhance the mid-latitude jet in the northern (southern) hemisphere, which generates a new vortex by barotropic instability in the northern (southern) hemisphere.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"433 ","pages":"Article 116523"},"PeriodicalIF":2.5,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143548640","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 effect of out-of-equilibrium outgassing on the cooling of planetary magma oceans","authors":"Arthur Walbecq,&nbsp;Henri Samuel,&nbsp;Angela Limare","doi":"10.1016/j.icarus.2025.116513","DOIUrl":"10.1016/j.icarus.2025.116513","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Rocky planet mantles likely experienced at least one global magma ocean stage. These magma oceans cooled and solidified rapidly, setting the conditions under which rocky planet mantles evolved in the long-term. Upon magma ocean solidification, vigorous convective motions are commonly thought to efficiently outgas dissolved volatiles, progressively forming a secondary atmosphere. Through the atmospheric blanketing effect, exsolved volatiles can then significantly slow down the solidification of magma oceans, which can alter the final thermo-chemical state of the mantles and their long-term evolution. While the efficient outgassing is a common hypothesis in magma ocean evolution models, the outgassing efficiency may be limited by the fact that fluid parcels containing dissolved volatiles need to reach small pressures corresponding to shallow exsolution depths, &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;exsol&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, allowing bubbles to form and volatiles to be outgassed. A recent numerical study (Salvador and Samuel, 2023) revealed that small exsolution depths can delay exsolution of volatiles beyond the solidification time of the mantle, in the case of a magma ocean of constant extent and for a constant exsolution depth.&lt;/div&gt;&lt;div&gt;Here, we extended this work by performing computational fluid dynamics and analog experiments at various Rayleigh and Prandtl numbers, which govern convective motions. We derived for the first time a general law that describes the flux of exsolved volatiles for a magma ocean of evolving thickness, &lt;span&gt;&lt;math&gt;&lt;mi&gt;D&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;, and exsolution depth, &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;exsol&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;. For sufficiently high Reynolds numbers, in a magma ocean, convecting with velocities &lt;span&gt;&lt;math&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;, the time evolution of the fraction of exsolved volatiles &lt;span&gt;&lt;math&gt;&lt;mi&gt;χ&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; obeys a first order differential equation &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;χ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;̇&lt;/mo&gt;&lt;/mrow&gt;&lt;/mover&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;C&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;b&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;exsol&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mi&gt;χ&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;D&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, with &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;C&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;b&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;6&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;6&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;.&lt;/div&gt;&lt;div&gt;We implemented this parameterized flux into a coupled magma ocean–atmosphere evolution model to more realistically assess the effect of convective motions on the formation of secondary atmospheres, along with their mantle evolution.&lt;/div&gt;&lt;div&gt;We found that for a broad range of parameters (&lt;em&gt;e.g.&lt;/em&gt;, high rotation rates, large planetary masses, or relatively low initial volatile contents) inefficient outgassing can lead to a ","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"434 ","pages":"Article 116513"},"PeriodicalIF":2.5,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143570573","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":"Secondary craters reveal differences in neighboring geologic units: An example on Mars","authors":"Jack W. Conrad ,&nbsp;Caleb I. Fassett","doi":"10.1016/j.icarus.2025.116529","DOIUrl":"10.1016/j.icarus.2025.116529","url":null,"abstract":"<div><div>Secondary craters, formed from ejecta during impact events, complicate surface age estimation, as they violate key assumptions required for age inference from crater counts. However, the nearly common formation conditions of nearly co-located secondaries make them potentially useful for inferring target properties. We present a technique to estimate surface property differences between bordering geologic units using secondary crater characteristics. This process is straightforward if secondary crater clusters sourced from a known primary crater cross a geologic border and can be properly surveyed. We demonstrate the technique at the geologic contact between Amazonis Planitia, a volcanic plain, and the Olympus Mons aureole, a landslide deposit, on Mars. We located a secondary crater cluster sourced from the primary crater, Tooting, which impacted ∼165 km to the southwest in Amazonis Planitia. The Tooting-sourced secondary craters in Amazonis Planitia are ∼1.43 times larger than the craters found just across the geologic border in the Olympus Mons aureole. The smaller craters in the aureole suggest the aureole is either stronger and/or more porous. Based on the geology of those units, we prefer an explanation that attributes the difference to increased porosity; if so, the mean porosity in the aureole is &gt;43 %. The technique we employ here can be applied to any solid surface in the solar system with young impact craters relative to the target surfaces and clear geologic contacts where the contact transition is shorter than the width of the secondary crater cluster. We encourage others to use this technique opportunistically when contact-crossing secondary clusters are discovered in their geologic analysis.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"433 ","pages":"Article 116529"},"PeriodicalIF":2.5,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143526943","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 origin of the high-TiO2 region near the Manilius and Hyginus craters within Mare Vaporum on the Moon","authors":"Eung Seok Yi ,&nbsp;Kyeong Ja Kim ,&nbsp;Christian Wöhler ,&nbsp;Alexey A. Berezhnoy ,&nbsp;Marcel Hess ,&nbsp;Megha Bhatt","doi":"10.1016/j.icarus.2025.116495","DOIUrl":"10.1016/j.icarus.2025.116495","url":null,"abstract":"<div><div>Finding and utilizing the resources of the Moon is becoming more important with the prospect of human outposts on our planets satellite. When selecting a landing site, ilmenite, the main carrier of TiO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> on the Moon, is a key target due to its potential for oxygen extraction and because ilmenite traps <span><math><msup><mrow></mrow><mrow><mn>3</mn></mrow></msup></math></span>He most effectively among the lunar minerals. The large dark mantle deposit in Mare Vaporum is one of the TiO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> richest areas on the Moon. Furthermore, dark haloed impact craters around Manilius crater within the Mare Vaporum region are surrounded by ejecta material with increased TiO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> abundance, making the larger region an important target for further scrutiny. In this work, we study this region to (1) assess the distribution of potential resources, (2) determine the formation mechanisms and (3) evaluate the suitability for establishing a human outpost. We use spectral parameters in the near-infrared wavelength range to determine the abundances of the major elements as well as glasses. Dark mantle deposits show higher glass and TiO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> abundances, while the surface surrounding the dark haloed impact craters only show increased TiO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>. From a resource perspective, dark mantle deposits are of special interest because <span><math><msup><mrow></mrow><mrow><mn>3</mn></mrow></msup></math></span>He bubbles form in the glasses, which require less energy to be extracted. Additionally, we use polarimetric observations to infer the relative grain sizes of the study area. It shows that the regolith of the region of interest is more coarsely grained, which in turn is characteristic for fresher or glassy material. Finally, digital elevation models show that the dark mantle deposit is characterized by steeper slopes compared to the terrain surrounding the dark haloed impact craters, which makes it challenging to land directly in the dark mantle deposit. After formation of the dark mantle deposits, ejecta and residue lead to a degradation of the north-western part of the dark mantle deposit, contributing to the U-shape observed today. The Rima Hyginus and Hyginus crater were formed by volcanic processes.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"433 ","pages":"Article 116495"},"PeriodicalIF":2.5,"publicationDate":"2025-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143519217","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":"An analogue study of impact craters on Titan: Implications for Titan's surface age","authors":"J. Shah ,&nbsp;C.D. Neish ,&nbsp;S. Trozzo","doi":"10.1016/j.icarus.2025.116536","DOIUrl":"10.1016/j.icarus.2025.116536","url":null,"abstract":"<div><div>Titan is the only planetary body in our solar system, besides Earth, that has stable liquids on its surface and a thick, nitrogen-rich atmosphere. NASA's Cassini mission detected an unusually low number of impact craters on Titan's surface, possibly due to degradation and burial by fluvial erosion and aeolian infilling. This is similar to the reduced number of craters seen on Earth, which is a result of both endogenic and exogenic processes, like erosion and weathering. Given these similarities, Earth serves as a strong analogue for studying the preservation of Titan's craters. There are 200 confirmed craters on Earth, of which 67 are buried and therefore unobservable from orbit. This study determines the percentage of the remaining exposed and resolvable terrestrial craters that can be identified in synthetic aperture radar data (SAR), in order to estimate the number of craters we may be missing in Cassini RADAR images of Titan. The results show that only ∼60 % of the non-buried terrestrial craters are distinctly visible in radar images; the remaining 40 % were not clearly identified by the authors. These findings were further validated through a crowd-sourcing exercise, where users attempted to identify craters in a smaller sample of radar images. If a similar number of craters are obscured on Titan, it suggests that 40 % of Titan's non-buried craters are not visible in the Cassini RADAR data set. Thus, the surface age of Titan could be ∼1.5-2× older (∼300 Ma – 2 Ga) than currently hypothesized (∼200 Ma – 1 Ga).</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"433 ","pages":"Article 116536"},"PeriodicalIF":2.5,"publicationDate":"2025-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143548641","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":"Tectonic patterns on Vesta and Ceres revealed by polygonal impact craters","authors":"Hiu Ching Jupiter Cheng ,&nbsp;Christian Klimczak","doi":"10.1016/j.icarus.2025.116528","DOIUrl":"10.1016/j.icarus.2025.116528","url":null,"abstract":"<div><div>Polygonal impact craters (PICs), impact craters with straight rims that form polygonal shapes in plan-view, form where pre-existing structures exist in the impact target rock. The straight rim segments of PICs and their preferred orientations are known to reveal hidden tectonic patterns that otherwise are invisible in spacecraft data. Vesta and Ceres are heavily cratered bodies that also experienced tectonics. We systematically mapped crater rims on Vesta and Ceres with crater diameters ≥ 10 and 20 km, respectively. We identified and extracted straight rim segments that maintain consistent orientations for at least 5 km to assess their segment lengths and orientations. The majority of mapped craters on Vesta and all craters on Ceres have at least one straight rim segment and thus are considered PICs. Analyses of straight rim segment orientations reveal multiple fracture sets that form complex but systematic regional and global patterns on both bodies. In particular, we detected an E–W trending fracture pattern in Vesta's north-polar region. Ceres predominantly shows NE–SW oriented fractures in the northern hemisphere and NW–SE oriented fractures in the southern hemisphere that are most pronounced at the poles. None of these patterns correlate with the orientations of large-scale troughs on Vesta and pit chains on Ceres or with large impact basins on Vesta, indicating that their origins are not directly linked. Their differing tectonic patterns indicate that different planetary processes controlled the formation of fractures responsible for the straight rim segments of the PICs. We compare our identified fracture patterns with predicted tectonic patterns caused by changes in spin rate, volume change, and true polar wander. However, predictions of tectonic patterns in the existing literature are not specific to, and thus not applicable to Vesta and Ceres, requiring more detailed modeling efforts and rock-mechanical reassessments to investigate the underlying processes that produced the fracture sets.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"433 ","pages":"Article 116528"},"PeriodicalIF":2.5,"publicationDate":"2025-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143519218","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 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}