Icarus最新文献

{"title":"A controlled mosaic of Moon Mineralogy Mapper (M3) reflectance data in the lunar polar regions for understanding the mineralogy and water of the Artemis exploration zone","authors":"Shuai Li ,&nbsp;Daniel P. Moriarty III ,&nbsp;Carle M. Pieters ,&nbsp;Rachel L. Klima ,&nbsp;Angela M. Dapremont","doi":"10.1016/j.icarus.2025.116668","DOIUrl":"10.1016/j.icarus.2025.116668","url":null,"abstract":"<div><div>This study presents high-resolution (140 m/pixel) controlled mosaics of Moon Mineralogy Mapper (M³) data in the lunar polar regions (80°–90° N/S), with a focus on assessing mineralogy and water content across the Artemis exploration zone. M³ extensively sampled the lunar polar regions, providing a high spatial resolution, hyperspectral imaging dataset that uniquely covers reflectance absorptions of major minerals and water on the lunar surface. We developed a methodology to preferentially use M³ image cubes acquired when the star tracker was operational to ensure accurate spatial registration of M³ pixels in our new mosaics. Integrated band depth (IBD) analyses were conducted to map distributions of hematite and other mineral species at the Artemis exploration zone. We also derived water contents at the Artemis sites from our new M³ mosaics. Our findings indicate that the Artemis exploration zone is largely dominated by mature regolith that is probably rich in plagioclase. Hematite is predominantly concentrated on east-facing slopes, likely due to enhanced oxidation from Earth wind oxygen interacting with the lunar regolith. Pyroxene-rich exposures are observed in three Artemis candidate landing regions and they are all associated with fresh impact craters. The water distribution is highly variable, with higher concentrations on pole-facing slopes and near permanently shadowed regions, likely controlled by low surface temperatures. High water contents are observed at hematite exposures, which reinforces that water may play a crucial role in hematite formation on the Moon. These results provide valuable insights for future lunar exploration, aiding in the selection of landing sites, planning of traverse routes, and informing in situ resource utilization (ISRU) for the Artemis missions.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"440 ","pages":"Article 116668"},"PeriodicalIF":2.5,"publicationDate":"2025-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144168857","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":"Spectral feature variations of low-iron olivine under intense pulse-laser irradiations","authors":"Zichen Wei ,&nbsp;Yan Zhuang ,&nbsp;Hao Zhang ,&nbsp;Pengfei Zhang ,&nbsp;Yang Li ,&nbsp;Menghua Zhu ,&nbsp;Te Jiang ,&nbsp;Ronghua Pang","doi":"10.1016/j.icarus.2025.116665","DOIUrl":"10.1016/j.icarus.2025.116665","url":null,"abstract":"<div><div>Space weathering processes, including micrometeoroid impact and solar wind irradiation typically redden, darken, and attenuate the fingerprint absorption features in the visible and near-infrared (VNIR) reflectance spectra of planetary surface materials. The so-called lunar style space weathering typically produces nanophase metallic iron (npFe⁰) and amorphous mineral layers. This paradigm has been known to be inadequate in describing the weathering processes on many other airless bodies and many open questions are waiting to be answered. For example, the greater flux of micrometeorite impacts or higher surface temperature on Mercury may produce larger npFe⁰ particles; the gardening effects on space weathering remain largely unknown; on asteroids such as Vesta, random regolith mixing and contamination by exogenic material from impacts are believed to be the dominant space weathering processes. To understand these and other questions in non-lunar style space weathering, we conducted pulsed laser irradiations on low-iron olivine grains in powders and pellets at various energy levels. By performing transmission electron microscope and reflectance spectroscopic measurements, we found that progressive irradiation caused continuous darkening. Meanwhile, the VNIR spectral slope changed from reddening to bluing after reaching a “saturation point”, and the absorption band depth transitioned from weakening to stabilization. At the same time, repeated irradiations led to limited growth of npFe⁰ particles in low-iron olivine. In all simulated irradiations, significant spectral alterations occurred in early stages, implying that fresh surfaces are more sensitive to space weathering. The rates of spectral modification of powder samples were found to be remarkably lower than those of the pellet samples. We also observed that exogenous metal contaminants could evaporate and condense into an opaque layer during simulated bombardments, obscuring the original spectral features of regolith.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"440 ","pages":"Article 116665"},"PeriodicalIF":2.5,"publicationDate":"2025-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144168856","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 structural failure in fast-spinning small bodies","authors":"Qian Pan ,&nbsp;Xiangyu Li ,&nbsp;Dong Qiao","doi":"10.1016/j.icarus.2025.116662","DOIUrl":"10.1016/j.icarus.2025.116662","url":null,"abstract":"<div><div>Small bodies exist widely in the solar system, and plenty of them belong to fast-spinning small bodies. The fast spin of a small body will lead to the principal stress perpendicular to the rotation axis as tensile stress, and the pull-down stress in the very fast spinner will dominate the internal structure of the small body, so the D<img>P yield criterion is no longer applicable. In this paper, considering the yield criterion of tensile stress, the formula of limit cohesion of elastic solid ellipsoid is derived, and the correctness of the formula is verified by comparing the analytical results with the finite element numerical results. The influence of self-gravitation on spinning small bodies is analyzed, and the parameters of the flatness and volume of small bodies are analyzed. This paper also calculates the limit cohesion of yield failure of real small bodies (469219) 2016 HO₃ and (29075) 1950 DA, and analyzes the structural failure modes of small bodies with different grain sizes. Compared to previous analyses of (29075) 1950 DA, this work proposes an alternative result under tensile stress yield criteria.</div><div>© 2024 xxxxxxxx. Hosting by Elsevier B.V. All rights reserved.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"440 ","pages":"Article 116662"},"PeriodicalIF":2.5,"publicationDate":"2025-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144168858","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 bulk composition and initial size of Mercury","authors":"Emily L. Fischer,&nbsp;Stephen W. Parman","doi":"10.1016/j.icarus.2025.116664","DOIUrl":"10.1016/j.icarus.2025.116664","url":null,"abstract":"<div><div>Enstatite chondrites are often used as models for the bulk composition of Mercury because they have similarly low oxygen fugacities. However, e-chondrites are too Si-rich to explain the observed composition of Mercury's lavas. Here we explore a model in which an initially enstatite chondrite-like Mercurian silicate magma ocean loses Si to the large Fe core during early differentiation. We define a Mercury Fractionation Line (MFL) based on average basaltic geochemical terrane compositions and assume Mercury's bulk silicate composition must fall along this line. We estimate that 26.5–36.7 ± 7.5 % (1σ) Si must be lost from an initial mantle to bring the e-chondrite compositions up to the MFL. Assuming that the Si is partitioned into the core, this implies a core Si content of 2.8–3.9 ± 0.8 wt% and an oxygen fugacity of IW–4.5 ± 1.0. We also show that a model where Mercury was initially ∼2 times larger is consistent with more reducing oxygen fugacities (IW–5.0 ± 1.0) and a higher core Si content (∼15 wt%). This estimated initial Mercury size is also consistent with predictions from dynamical simulations. We consider how Si partitioning into the core affects the δ³⁰Si composition of the mantle. Though uncertainties are large, we show that as the initial radius of Mercury increases, δ³⁰Si decreases, trending towards the δ³⁰Si composition of enstatite chondrites. Our calculations do not constrain the mechanism by which Mercury's mantle may have been lost. However, if they are correct, they imply that the mantle loss must have happened after core formation.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"439 ","pages":"Article 116664"},"PeriodicalIF":2.5,"publicationDate":"2025-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144167455","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 influence of spin–orbit resonances on the evolution of Mercury’s mantle and crust","authors":"Nicola Tosi ,&nbsp;Falko Schulz ,&nbsp;Michaela Walterová ,&nbsp;Sebastiano Padovan","doi":"10.1016/j.icarus.2025.116630","DOIUrl":"10.1016/j.icarus.2025.116630","url":null,"abstract":"<div><div>Mercury’s record of large impact basins and spin evolution models suggest that its present-day 3:2 spin–orbit resonance may not be primordial. It could have been established up to hundreds of millions of years after planet formation, possibly triggered by the impact that created the Caloris basin about 3.7 billion years ago. Before this, Mercury may have been in a synchronous rotation or a 2:1 resonance, which would have induced strong hemispheric surface temperature variations, influencing the thermal structure of the lithosphere and mantle.</div><div>Using 3D thermochemical mantle convection models, we simulate Mercury’s mantle evolution and volcanic crust formation over one billion years, incorporating surface temperature distributions from different spin–orbit resonances. We assess whether these variations can generate large-scale lateral differences in crustal thickness, as inferred from gravity, topography and surface composition data, and compare predicted radius changes due to mantle and core cooling with existing estimates from compressional tectonic features.</div><div>Crustal thickness, interior cooling rate, and radius change are primarily controlled by internal heat production, with models using intermediate to high heat production rates (characteristic of CI and EH chondrites) best matching observations. The mantle reference viscosity, low thermal conductivity attained at Mercury’s mantle conditions, and cooling due to melt extraction exert first-order controls on the timing of crust emplacement and its final extent. Regardless of surface temperature patterns, mantle convection is dominated by small, stable cells. While surface temperature variations influence the location of hot and cold regions at large scales, they do not alter the spatial scale of convection. Assuming vertical melt extraction, crustal thickness locally follows the convection pattern. The present-day 3:2 resonance does not induce significant large-scale variations in crustal thickness, but a past synchronous rotation could have produced hemispheric differences, with crust up to 10–15 km thicker on the dayside. Similarly, radial contraction is hemispherical, with the hot hemisphere contracting less and at a slower rate than the cold one as long as the resonance persists.</div><div>The surface record does not clearly support these hemispheric patterns. This suggests that past spin–orbit resonances may have been short lived, or that they may have affected Mercury’s interior more subtly than our models predict, or that subsequent geological processes erased or modified early large-scale asymmetries. Future high-resolution imaging and surface composition data from BepiColombo, particularly of Mercury’s poorly-mapped southern hemisphere, will be critical in testing this hypothesis and in refining the available constraints on the planet’s crustal evolution and tectonic history.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"439 ","pages":"Article 116630"},"PeriodicalIF":2.5,"publicationDate":"2025-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144130896","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":"Activity in quasi-Hilda objects: A photometric approach","authors":"E. García-Migani,&nbsp;R. Gil-Hutton,&nbsp;J. Correa-Otto","doi":"10.1016/j.icarus.2025.116634","DOIUrl":"10.1016/j.icarus.2025.116634","url":null,"abstract":"<div><div>We present the results of a search for quasi-Hilda objects that could be candidates for exhibiting cometary activity. To achieve this, observations of objects from the quasi-Hilda region in the MPCAT-OBS Observation Archive were examined. We then analyzed the observed brightness and compared it with the expected values, looking for discrepancies between the two (<span><math><msub><mrow><mi>Δ</mi></mrow><mrow><mi>m</mi><mi>a</mi><mi>g</mi></mrow></msub></math></span>). These deviations from their expected brightness could be the result of weak cometary-like activity that does not manifest as an observable coma and/or tail. The <span><math><msub><mrow><mi>Δ</mi></mrow><mrow><mi>m</mi><mi>a</mi><mi>g</mi></mrow></msub></math></span> values were analyzed and evaluated for objects in the quasi-Hilda region. We believe that the objects <span><math><mrow><mrow><mo>(</mo><mn>30512</mn><mo>)</mo></mrow><mspace></mspace><mn>2001</mn><mspace></mspace><mi>H</mi><msub><mrow><mi>O</mi></mrow><mrow><mn>8</mn></mrow></msub></mrow></math></span>, <span><math><mrow><mrow><mo>(</mo><mn>18916</mn><mo>)</mo></mrow><mspace></mspace><mn>2000</mn><mspace></mspace><mi>O</mi><msub><mrow><mi>G</mi></mrow><mrow><mn>44</mn></mrow></msub></mrow></math></span>, and <span><math><mrow><mn>2017</mn><mspace></mspace><mi>F</mi><msub><mrow><mi>U</mi></mrow><mrow><mn>158</mn></mrow></msub></mrow></math></span> are interesting candidates for searching for activity in the quasi-Hilda region. Additionally, some unnumbered objects are also noted as potentially interesting, although they have few observations.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"439 ","pages":"Article 116634"},"PeriodicalIF":2.5,"publicationDate":"2025-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144115670","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":"Global N-body simulation of gap edge structures created by perturbations from a small satellite embedded in Saturn’s rings II: The effect of satellite’s orbital eccentricity and inclination","authors":"Naoya Torii ,&nbsp;Shigeru Ida ,&nbsp;Eiichiro Kokubo ,&nbsp;Shugo Michikoshi","doi":"10.1016/j.icarus.2025.116608","DOIUrl":"10.1016/j.icarus.2025.116608","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Small satellites, Pan and Daphnis, are embedded in Saturn’s rings and opening a clear gap with satellite wakes at the gap edges. Furthermore, in the case of Daphnis, pronounced vertical wall structures casting shadows on the rings are also observed in the satellite wakes. In our previous paper (Torii, N., Ida, S., Kokubo, E., Michikoshi, S. [2024]. Icarus, 425, 116029), we found through global 3D N-body simulation that the ring particles’ lateral epicycle motions excited by an encounter with a satellite are converted to the vertical motions through oblique physical collisions between the particles at the wavefronts of satellite wakes. In order to highlight this dynamics, Torii et al., (2024) considered the circular (&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;s&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) and coplanar (&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;mi&gt;s&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) satellite orbit, where &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;e&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; are the satellite orbital eccentricity and inclination, respectively. However, Daphnis has non-negligible eccentricity and inclination. In this paper, we perform a global 3D N-body simulation with non-zero &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;e&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; or non-zero &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; of the satellite orbit to investigate how they affect the gap edge structures. We found that the effect of satellite eccentricity is important both in the satellite wakes and the vertical walls at the gap edges. The non-sinusoidal sawtooth-like satellite wakes and azimuthally more localized vertical walls observed by Cassini are simultaneously reproduced in the detailed structures and spatial scales. Both of them periodically vary due to the satellite excursions between the apocenter and the pericenter. The ring particles in outer (inner) rings that undergo closest encounters with the satellite near the apocenter (pericenter) are excited the most highly. Because the excited eccentricities of the ring particles are converted to the inclinations through physical collisions, the conversion is the most active for the particles that acquire the highest eccentricities, resulting in the azimuthally more localized vertical wall structures. The predicted height of the tallest vertical walls is &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;∼&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; times the satellite Hill radius in the case of the satellite eccentricity comparable to Daphnis when adopting Hill scaling, which is twice as much as the height obtained in the case of the circular satellite orbit and is quantitatively more consistent with the Cassini observation. The simulation with the inclined satellite orbit reveals th","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"439 ","pages":"Article 116608"},"PeriodicalIF":2.5,"publicationDate":"2025-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144116148","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 influence of passing field stars on the solar system’s dynamical future","authors":"Nathan A. Kaib ,&nbsp;Sean N. Raymond","doi":"10.1016/j.icarus.2025.116632","DOIUrl":"10.1016/j.icarus.2025.116632","url":null,"abstract":"<div><div>The long-term dynamical future of the Sun’s planets has been simulated and statistically analyzed in great detail, but most prior work considers the solar system as completely isolated, neglecting the potential influence of field star passages. To understand the dynamical significance of field star encounters, we simulate several thousand realizations of the modern solar system in the presence of passing field stars for 5 Gyrs. We find that the impulse gradient of the strongest stellar encounter largely determines the net dynamical effect of field stars. Because the expected strength of such an encounter is uncertain by multiple orders of magnitude, the possible significance of field stars can be large. Our simulations indicate that isolated models of the solar system can underestimate the degree of our giant planets’ future secular orbital changes by over an order of magnitude. In addition, our planets and Pluto are significantly less stable than previously thought. Field stars transform Pluto from a completely stable object over 5 Gyrs to one with a <span><math><mo>∼</mo></math></span>5% instability probability. Furthermore, field stars increase the odds of Mercury’s instability by <span><math><mo>∼</mo></math></span>50%–80%. We also find a <span><math><mo>∼</mo></math></span>0.3% chance that Mars will be lost through collision or ejection and a <span><math><mo>∼</mo></math></span>0.2% probability that Earth will be involved in a planetary collision or ejected. Compared to previously studied instabilities in isolated solar systems models, those induced by field stars are much more likely to involve the loss of multiple planets. In addition, they typically happen sooner in our solar system’s future, making field star passages the most likely cause of instability for the next 4–4.5 Gyrs.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"439 ","pages":"Article 116632"},"PeriodicalIF":2.5,"publicationDate":"2025-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144090205","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":"Landslide chronology on mars: A window into the past of Valles Marineris and martian slopes","authors":"Giovanni Battista Crosta,&nbsp;Fabio Vittorio De Blasio,&nbsp;Elena Valbuzzi,&nbsp;Alessandro Martinazzi","doi":"10.1016/j.icarus.2025.116653","DOIUrl":"10.1016/j.icarus.2025.116653","url":null,"abstract":"<div><div>Martian landslide deposits provide valuable insights into the planet's geomorphological evolution. Their degree of preservation is such that they can be recognized after billions of years. Therefore, a study of Martian landslides may reveal clues as to the surface and environmental conditions at the moment of collapse. In particular, determining their age is of great importance for reconstructing the geomorphological and structural evolution of the Martian surface. We conducted a comprehensive age dating analysis of 32 clusters, encompassing 102 landslides and 38 non-landslide units across various Martian regions. Most of the landslides dated in this work are considered here for the first time, while for several others we present an updating of their age, allowing for a validation of previous dating, and a broader geomorphological interpretation. Important factors affecting age determination such as landslide type, secondary craters, and resurfacing processes have been examined in detail to improve data quality and provide more robust conclusions. While very low frequency of slope collapse is observed between 3.2 and 2.4 Ga after a period of higher instability as confirmed by fluvial and glacial features, the overall trend of increasing frequency with time remains dominant. This is consistent with previous studies, and is now supported by a significantly larger dataset which modifies existing age determinations. This suggests the presence of a large number of ancient undetected landslides, buried beneath more recent deposits. This research provides new insights into the timing and frequency of mass wasting events on Mars, contributing to a better understanding of the planet's geomorphological evolution.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"439 ","pages":"Article 116653"},"PeriodicalIF":2.5,"publicationDate":"2025-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144139384","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":"Measurement of viscous erosion rate from plume surface interactions in low-pressure environments","authors":"B. Dotson,&nbsp;D. Britt,&nbsp;P. Metzger","doi":"10.1016/j.icarus.2025.116654","DOIUrl":"10.1016/j.icarus.2025.116654","url":null,"abstract":"<div><div>Experimental measurements of viscous erosion rate with regolith simulants were completed under vacuum conditions with a splitter plate, plume cratering setup and non-reacting flows. Using Lunar Highlands Simulant (LHS-1), Lunar Mare Simulant (LMS-1), LHS-1D (Dust) Simulants, this study examined the impacts of bulk density and mass flow rate on crater morphology and viscous erosion rate with ambient pressures between 2 and 760,000 mTorr. Results show that crater shape changes as a function of ambient pressure, owing to plume expansion under vacuum conditions, resulting in annular craters below 1000 mTorr. Erosion rate and ejecta streaking appears to be dependent on the Knudsen number (<em>Kn</em>) and increases with a decrease in ambient pressure. When compared to the continuum region (<em>Kn</em> ≤ 0.1), viscous erosion rate is higher in the free-molecular region (<em>Kn</em> ≥ 10), but the highest measured erosion rates were noted in the transition region (0.1 &lt; <em>Kn</em> &lt; 1) which best corresponds to Martian ambient conditions. A modified version of <span><span>Metzger's (2024a)</span></span> equation for volumetric erosion rate is presented using empirical fits for lunar mare and highlands regolith simulants, with limitations discussed. Measurements show that mass flow rate and bulk density can influence viscous erosion rate by 30 % under vacuum conditions, particularly in the free-molecular region. While cohesion clearly influences erosion rate, results suggest that plume dynamics, porosity, and surface roughness may also play an important role in rarified conditions such as on the Moon. To help protect personnel and equipment on future missions, models of plume surface interactions should incorporate these modified equations for viscous erosion.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"439 ","pages":"Article 116654"},"PeriodicalIF":2.5,"publicationDate":"2025-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144099387","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}