Icarus最新文献

{"title":"An integrated study of Rutherfurd crater: Composition, morphology, and chronology","authors":"D.D. Patel ,&nbsp;G.R. Osinski ,&nbsp;S.M. Patel","doi":"10.1016/j.icarus.2026.116971","DOIUrl":"10.1016/j.icarus.2026.116971","url":null,"abstract":"<div><div>The youngest era in the lunar geological timescale, the Copernican period, is estimated to have commenced approximately 1.1 billion years ago and is named after the prominent 95 km-diameter Copernicus crater. Copernican craters represent the youngest and best-preserved impact craters on the Moon. This study presents the first high-resolution geological and morphological map of the ∼48 km diameter Copernican-age Rutherfurd crater, produced through the integration of optical, radar, and hyperspectral datasets. Observations reveal significant asymmetry in the crater's structure, particularly in terms of slumping, terracing, and rim preservation, which we interpret as being due to the effects of pre-existing topography. Spectral analysis indicates the dominance of high-calcium pyroxene (HCP) within the central peak, rim, and isolated mounds, suggesting excavation of a buried HCP-rich plagioclase layer. Crater Size-Frequency Distribution (CSFD) analysis of the continuous ejecta blanket yields an age of ∼1-1.1 Ga, confirming Rutherfurd as the youngest crater in the Clavius crater arching chain. In contrast, CSFDs from the impact melt ponds yield anomalously younger apparent ages (∼200–510 Myr), likely reflecting statistical uncertainties arising from their limited surface area and the paucity of large craters, rather than true differences in formation age. Distinct asymmetries in ejecta distribution and secondary crater patterns are interpreted to reflect the oblique nature of the impact and interactions with local topographic variations. Ejecta morphology and secondary crater orientations suggest an oblique impact from the southeast to northwest at an angle of ∼20–30°. This study not only refines our understanding of Rutherfurd’s formation and evolution but also highlights its significance as a target for future lunar exploration, particularly due to its exposure of deeper crustal materials and proximity to regions with potential hydration signatures.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"449 ","pages":"Article 116971"},"PeriodicalIF":3.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074894","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":"Titan’s refractory core evolution: Implications for organics in its subsurface ocean","authors":"Kelly E. Miller ,&nbsp;Mohit Melwani Daswani ,&nbsp;Christophe Sotin ,&nbsp;Charles S. Cockell ,&nbsp;Catherine Neish ,&nbsp;Michael J. Malaska ,&nbsp;Kendra K. Farnsworth ,&nbsp;Conor A. Nixon ,&nbsp;Krista M. Soderlund ,&nbsp;Peter M. Higgins ,&nbsp;Antonin Affholder ,&nbsp;Rosaly M.C. Lopes","doi":"10.1016/j.icarus.2026.116961","DOIUrl":"10.1016/j.icarus.2026.116961","url":null,"abstract":"<div><div>As an organic-rich world with a subsurface ocean, Titan is an object of great astrobiological interest. However, geological signs of surface-subsurface exchange are limited, and Titan’s thick icy crust may significantly impede delivery of organic-rich surface materials to the subsurface ocean. Heating of accreted complex organic material in Titan’s interior may provide an additional source of organic molecules to serve as building blocks for life and/or chemical energy sources for ocean habitability. Here, we investigate the composition of Titan’s subsurface ocean with a focus on organic materials derived from the rocky interior. We develop organic-rich compositional models, and consider what effects heating of these organics may have on the total noble gas signature in Titan’s atmosphere. We compare this signature to existing constraints to provide a consistent framework for the abundance of organic material derived from the interior. Present day constraints generally allow contributions of both noble gas ices and Phase Q noble gases from heating of abundant organic material, but the Xe signature may be inconsistent with ices. We combine this compositional framework with a thermal profile for Titan’s interior that includes the thermophysical properties of organic material, and perform thermodynamic calculations for extraction of volatiles and formation of the hydrosphere. Our results suggest that formation of Titan’s massive hydrosphere requires a large initial ice mass, including a minimum ice/dust mass ratio of 1.4 for anhydrous cometary dust. Finally, we consider the composition and abundance of organic material produced by such processes and them to dissolved organic carbon in terrestrial oceans. We find that Titan’s accreted complex organic material may be a significant contributor to organic material in the subsurface ocean, producing organic abundances that are comparable to terrestrial oceans.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"449 ","pages":"Article 116961"},"PeriodicalIF":3.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074896","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":"Automated precision counting of very small lunar craters – A simulation study","authors":"Peter Howard Cadogan","doi":"10.1016/j.icarus.2026.116935","DOIUrl":"10.1016/j.icarus.2026.116935","url":null,"abstract":"&lt;div&gt;&lt;div&gt;An automated system for counting very small lunar craters has been applied to many locations on the Moon, including some on the far side and others at high latitudes. Many of these locations are on level mare terrain, but a few highland areas and the ejecta blankets and impact melts of several Copernican-age craters have been investigated.&lt;/div&gt;&lt;div&gt;Craters smaller than 50 m in diameter can be no more that a few hundred million years old, so are of little use for dating more ancient lunar features. However, in this size range, significant differences in crater densities exist across sites, implying that recent surface activity must have occurred. So a simulation model has been developed to investigate these processes further.&lt;/div&gt;&lt;div&gt;A 1 Ma crater production function has been developed, based of the size distribution of craters on the ejecta blanket of the young crater Giordano Bruno, assuming its age to be 10 Ma. This function is consistent with predictions based on the meteoroid flux at the surface of the Moon. Using a simple model for obliteration and topographic diffusion, the primary mechanisms by which small craters are thought to be erased and eroded, simulated distributions have been successfully matched to measured densities. The results indicate that several locations on the Moon must have been wholly or partially resurfaced within the last 100 Ma.&lt;/div&gt;&lt;div&gt;The simulation model has also been used to confirm published formation ages for Tycho, North Ray and Cone craters. Several other large young craters (including Necho, Dawes, Lalande, Tharp, Messier, Messier A, Euclides C, Furnerius A and Proclus) have been confidently dated, where necessary making adjustments for the predicted variation in meteoroid flux between the apex and antapex of the Moon's orbit around the Earth. Densities of small craters on a Tycho impact melt are much lower than those on its ejecta blanket. These craters last for much longer, enabling impact melts at older craters (such as King, Kepler and Aristarchus) to be estimated more precisely than was possible from their ejecta blankets.&lt;/div&gt;&lt;div&gt;Simulation results confirm that erosion and obliteration are the primary factors responsible for crater destruction, but blanketing by ejecta from larger impacts and seismic shaking have clearly been effective at some sites. Seismic shaking during the excavation of km-sized craters may erase nearby small craters prior to ejecta blanket deposition. Self-secondaries are visibly different from primaries and are typically found closer to crater rims. There is no obvious need to invoke self-secondaries to explain high crater densities at the smallest sizes.&lt;/div&gt;&lt;div&gt;At many sites, crater densities have clearly reached equilibrium. This enables lifetimes of craters smaller than 30 m in diameter to be determined, the results being consistent with published values. Equilibrium densities can vary significantly between sites, presumably due to the different regolith pro","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"449 ","pages":"Article 116935"},"PeriodicalIF":3.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146035828","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":"Upper estimate of possible sizes of Venusian lava tubes from the perspective of structural stability","authors":"M. Chwała ,&nbsp;G. Komatsu ,&nbsp;P. D'Incecco","doi":"10.1016/j.icarus.2026.116946","DOIUrl":"10.1016/j.icarus.2026.116946","url":null,"abstract":"<div><div>In this study, we estimate the theoretical upper bounds of Venusian lava tube dimensions by performing parametric numerical analyses under two scenarios of rock-mass strength. Using Finite Element Limit Analysis (FELA) with both lower- and upper-bound estimates of the limit load, we determine the maximum possible widths of lava tubes for given heights and roof thicknesses. This approach provides a range of plausible dimensions for structurally stable Venusian lava tubes. Our results suggest that lava tubes with widths of a few hundred meters may remain stable, and these dimensions are consistent with observed Venusian channel sizes. The study also indicates that future missions with higher-resolution imaging and geophysical investigation capacities should be able to detect possible surface expressions of lava tubes, such as pit chains, skylights, subsurface voids and gravity anomalies to further support their existence.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"449 ","pages":"Article 116946"},"PeriodicalIF":3.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146035955","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":"CO2 condensation and sublimation on a range of substrates under simulated mars conditions","authors":"L.E. Mc Keown ,&nbsp;S. Diniega ,&nbsp;M.J. Poston ,&nbsp;G. Portyankina ,&nbsp;C.J. Hansen ,&nbsp;K.-M. Aye ,&nbsp;I. Mishra ,&nbsp;E. Carey ,&nbsp;J.E.C. Scully ,&nbsp;S. Piqueux ,&nbsp;M. Choukroun","doi":"10.1016/j.icarus.2026.116938","DOIUrl":"10.1016/j.icarus.2026.116938","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The winter/springtime CO&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; condensation and sublimation cycle is recognized as a cardinal agent of present-day surface change on Mars, and was likely also instrumental in modifying the surface during the recent past. The Kieffer Model postulates that slab ice condenses in winter and sublimates in spring, causing pressurized CO&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; gas beneath the ice to rush to the surface, forming a ‘zoo’ of features ranging from seasonal plumes, dark fans and spots and the mysterious ‘spiders’ or araneiforms surrounding the Martian south pole. However, the lack of terrestrial analogs or empirical observations of this conceptual process hamper our understanding of how the Martian surface is modified in this way today. In Mc Keown et al. (2024), we presented experiments that simulated all three main stages of the Kieffer model on a &lt;span&gt;&lt;math&gt;&lt;mo&gt;∼&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt;1 cm layer of Mars Mojave (regolith) Simulant (MMS) &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mn&gt;150&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mi&gt;μ&lt;/mi&gt;&lt;mi&gt;m&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;: (i) CO&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; condensation, (ii) sublimation of CO&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; ice, and plume, spot and halo formation and (iii) the resultant formation of ‘cracked’ spiders, where interstitial pore ice is sublimated and cracks, preserving patterns in the surrounding regolith. In this paper, we present experiments where CO&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; condenses on different discrete grain size ranges of regolith: &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mn&gt;53&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mi&gt;μ&lt;/mi&gt;&lt;mi&gt;m&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, 75–150&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mi&gt;μ&lt;/mi&gt;&lt;mi&gt;m&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, and 180–500 &lt;!--&gt; &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;μ&lt;/mi&gt;&lt;mi&gt;m&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, for both ‘dry’ regolith and a water-mixed ‘permafrost’ simulant, and on glass beads 250–355&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mi&gt;μ&lt;/mi&gt;&lt;mi&gt;m&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, but forms and sublimates in different ways. We find that CO&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; diffuses deeper and across a greater area within the regolith pore spaces for finer grain sizes, and the top ice layer grows inward from the sample edges for coarser grains, resulting in finer grains being more prone to ‘cracked’ spider morphologies than coarser grains. Condensation of CO&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; appears to be affected by thermal properties and circularity of the grains, with rate of ice accumulation on the surface slower on the surface of glass beads and final patterns of ice on the surface differing in appearance from the MMS simulant. Water ice within the pore spaces of the regolith encourages the growth","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"449 ","pages":"Article 116938"},"PeriodicalIF":3.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146035984","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 of organic molecules in silica and sepiolite clay under UV radiation","authors":"Simon Gouzy ,&nbsp;Fabien Stalport ,&nbsp;Benjamin Rondeau ,&nbsp;Vassilissa Vinogradoff ,&nbsp;Elisabeth Lapp ,&nbsp;Florian Massuyeau ,&nbsp;Maxime Pineau ,&nbsp;Rachel Gonthier ,&nbsp;Hervé Cottin ,&nbsp;John Carter","doi":"10.1016/j.icarus.2026.116937","DOIUrl":"10.1016/j.icarus.2026.116937","url":null,"abstract":"<div><div>On Earth, alteration minerals, such as clays and amorphous silica, have proved to be able to preserve organic molecules linked to life over geological timescales. These minerals are also widespread on the Martian surface and have been shown to be associated with organic molecules by the rovers. However, continuous bombardment by radiation of the surface, including UV, raises questions about the alteration state of the organic molecules and, consequently, the preservation capacity of the mineral phases that host them. To investigate this, we experimentally exposed natural organo-mineral complexes to UV radiation, comprising four mineral matrices (opal, chalcedony, sepiolite and silicified sepiolite) naturally coloured in pink by chromophoric polycyclic aromatic hydrocarbons known to be photodegradable. We monitored the evolution of the intensity of the pink colour through UV–visible spectroscopy as a proxy of the degradation of the organic molecules. Results show that all the mineral matrices possess a distinct preservation capacity of their pink colour for which opal and silicified sepiolite (channels filled with amorphous silica) proved to be the most effective. Moreover, our results tend to indicate that less than an equivalent of 100 years of UV-exposure at the surface of Mars are sufficient to drastically alter the organic molecules, even embedded in a mineral matrix. We infer that to maximize the chances of detecting the best-preserved organic molecules on the surface of Mars, priority should be given to silica-rich alteration phases and silicification events as key astrobiological targets.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"449 ","pages":"Article 116937"},"PeriodicalIF":3.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146035948","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":"Reflectance spectroscopy (200-4200 nm) of the red-sloped C2 carbonaceous chondrites MET 00432, Tagish Lake, Tarda, and WIS 91600 (“CT” grouplet)","authors":"Edward A. Cloutis ,&nbsp;Devin L. Schrader ,&nbsp;Daniel M. Applin ,&nbsp;Tomoki Nakamura ,&nbsp;Timothy D. Glotch ,&nbsp;Takahiro Hiroi ,&nbsp;Moe Matsuoka ,&nbsp;Michael E. Zolensky ,&nbsp;Joshua P. Emery ,&nbsp;Kristi M. Peters","doi":"10.1016/j.icarus.2026.116952","DOIUrl":"10.1016/j.icarus.2026.116952","url":null,"abstract":"<div><div>Four carbonaceous chondrite (CC) meteorites – MET 00432, Tagish Lake, Tarda, and WIS 91600 - have been proposed to be members of a CC grouplet, hereafter termed the Carbonaceous Tagish Lake Grouplet (CTG). We investigated their possible affinities via a spectral reflectance-focused study of them, as chips and variously sized powders. We also considered possible spectrum-altering effects of space weathering and composition of the organic component on such red-sloped spectra. Ultraviolet-region spectra (200-400 nm) exhibit absorption features attributable to unspecific Fe²⁺-O and/or Fe³⁺-O charge transfers, possibly due to Fe-rich phyllosilicates. Both albedo and spectral slope vary as a function of grain size. The 0.35-2.50 μm interval is characterized by dark, variably red-sloped spectra with low albedos in the visible region (&lt;6% reflectance at 0.550 μm). Spectral slopes are redder for powders than slabs or chips. CTG spectra also exhibit shallow (&lt;4% deep) absorption bands attributable to known components, such as magnetite and phyllosilicates, particularly in the 1 μm region. Spectral analysis of an extensive suite of phyllosilicate+opaque mixtures suggests that only a subset of CTG opaque components can cause darkening and overall red spectral slopes, in particular low H/C ratio carbonaceous compounds. Other opaque components, such as iron sulfides, magnetite and other carbonaceous materials, some of which are red-sloped when pure, cause spectral bluing or only slight spectral reddening. Albedo and spectral slopes and shapes are affected by physical properties, such as grain size, as well as the types, compositions, abundances, dispersion, and grain sizes of opaque components. At longer wavelengths (to 14 μm), CTG spectra exhibit a number of absorption features that can be related to their silicate, carbonate, and organic components. A prominent absorption feature is present in the 2.7-3.1 μm region attributable to phyllosilicates ± H₂O, some of which is likely attributable to terrestrial alteration. Petrological, mineralogical, and isotopic information provide support for these meteorites having strong affinities to each other and comprising a grouplet. Additional CTG meteorites may lurk among the many tens of CCs that have been incompletely characterized.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"449 ","pages":"Article 116952"},"PeriodicalIF":3.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074885","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":"Primitive asteroids in the main belt, Cybele, and Hilda populations from Gaia DR3","authors":"N. El-Bez-Sebastien ,&nbsp;S. Fornasier ,&nbsp;A. Seurat ,&nbsp;A. Wargnier","doi":"10.1016/j.icarus.2026.116950","DOIUrl":"10.1016/j.icarus.2026.116950","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Primitive asteroids include C-, P-, and D-classes, known to be dark and having spectra mostly featureless. They differ in the spectral slope, which ranges from moderate values for C-types, and progressively increases in P- and D-types, the latter being the reddest. While C- and P-types are commonly observed in the asteroid main belt, D-types are commonly found further from the Sun, in the Cybele, Hilda, and Jupiter Trojans regions, and very few are reported in the main belt. This study aims at characterizing the abundance of primordial and red asteroids, belonging to the P-, D-, and Z-classes in the Mahlke et al. (2022) taxonomy, in the 2-5.2 AU region using the third data release by the Gaia mission (DR3) spectral catalog, which includes more than 60000 spectrophotometric data of asteroids. We have applied the following methodology to identify primordial asteroids in the catalog: (1) selection of objects with signal to noise ratio (SNR) greater than 20; 2) albedo value less than 12%; (3) chi-squared fit to automatically identify potential D-, Z-, and P-types using Bus-DeMeo and Mahlke taxonomy; (4) visual inspection of every spectrum to confirm the taxonomic classification.&lt;/div&gt;&lt;div&gt;Referring to Mahlke taxonomy, we have found 318 new D-types across the main belt, as well as 124 Z-types, which is a considerable increase from previous studies (Mahlke et al., 2022 and DeMeo et al., 2014; Humes et al., 2024b; Gartrelle et al., 2021b), and is in agreement with theoretical estimations (DeMeo et al., 2014; Vokrouhlický et al., 2016). We look for correlations among physical and orbital parameters, and we computed the spectral slope in the visible range (0.55 – &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;81&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mi&gt;μ&lt;/mi&gt;&lt;mi&gt;m&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;). We also have identified 265 P-types in the main belt. For the Cybele and Hilda asteroids, we characterize the taxonomic class of all the bodies with SNR higher than 20 in the Gaia catalog, for a total sample of 193 and 180 asteroids, respectively.&lt;/div&gt;&lt;div&gt;For D- and Z-types in the main belt, we have found a correlation between size and semimajor axis, meaning that the D-types closer to the Sun are smaller and also brighter, which could uncover their implantation processes, such as collisions or Yarkovsky effect. No families dominated by D- or Z-types have been identified so far. These red asteroids were likely formed further from the Sun and implanted during the giant planets’ migrations.&lt;/div&gt;&lt;div&gt;For both the Cybele and Hilda, we found a bimodal spectral slope distribution as already reported in the literature. These groups are dominated by P- and D-types. Furthermore, for both populations, despite not being the most abundant group, P-types show a larger range of diameters and include the biggest bodies, hinting at a more robust material.&lt;/div&gt;&lt;div&gt;We have identified 42 D- and 18 Z-asteroids having orbits with high inclination and eccentricity, and Tisserand parameter lower ","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"449 ","pages":"Article 116950"},"PeriodicalIF":3.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146075348","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":"SynthGen: A gravity field simulator for planetary interior modelling","authors":"Edoardo Santero Mormile ,&nbsp;Giuseppe Mitri","doi":"10.1016/j.icarus.2026.116960","DOIUrl":"10.1016/j.icarus.2026.116960","url":null,"abstract":"<div><div>Determining the internal structure of planetary bodies from gravitational observations is a key challenge in planetary geophysics. Traditional gravity inversion methods suffer from non-uniqueness due to trade-offs between mass distribution and depth, limiting their ability to resolve internal layering. We present <em>SynthGen</em>, a forward-modelling code developed to simulate the gravitational response of planetary bodies using parametric, multi-layer interior models without any a priori assumption, like the hydrostatic equilibrium. <em>SynthGen</em> calculates gravitational potential, Free-Air, and Bouguer anomalies through spherical harmonic expansions, leveraging the <em>SHTools</em> library (Wieczorek and Meschede, 2018). It accommodates a wide variety of internal configurations, including homogeneous layers with user-defined densities, thicknesses, and topographic geometries of internal interfaces, such as spherical, ellipsoidal, random, or Bouguer anomaly-derived interfaces. The code can be used both predictively and diagnostically: about the latter, <em>SynthGen</em> performs parameter-space exploration constrained by total mass, moment of inertia, and shape, identifying best-fit interior models by minimising the misfit between observed and synthetic gravity fields using combined statistical metrics. We apply <em>SynthGen</em> to Mercury, using the HgM009 gravity model derived from MESSENGER data (Genova et al., 2023), and recover crustal thickness and core parameters consistent with recent independent geophysical estimates. In predictive mode, <em>SynthGen</em> generates synthetic gravity fields for planetary bodies where gravity data are not available or are still limited in resolution, such as Ganymede. These simulations can support the planning and optimisation of space missions. By integrating physical constraints, statistical validation, and flexibility in model design, <em>SynthGen</em> offers a robust platform for planetary interior studies, constraining interior structures from gravity measurements across a broad range of Solar System bodies.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"449 ","pages":"Article 116960"},"PeriodicalIF":3.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146035949","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":"Duration of high temperature-pressure conditions in impact-induced plumes on the Moon","authors":"Xiaoying Liu ,&nbsp;Chi Zhang ,&nbsp;Zongyu Yue,&nbsp;Lixin Gu,&nbsp;Jing Li,&nbsp;Heng-Ci Tian,&nbsp;Sen Hu,&nbsp;Yangting Lin","doi":"10.1016/j.icarus.2026.116969","DOIUrl":"10.1016/j.icarus.2026.116969","url":null,"abstract":"<div><div>Meteorite impact is a key process on the Moon, having profoundly reshaped the lunar surface, modified the physical properties of lunar regolith, and transported water and other volatiles on the surface. However, the temperature-pressure conditions of impact-induced plumes and their duration were poorly constrained. Here, we report the first discovery of immiscibility a FeNi-P-S bead from Chang'e-5 lunar soils, which consists of abundant spherules of metallic FeNi and sulfide both evenly dispersed in phosphide-rich matrix. The observed texture and compositions are consistent with quenching of an FeNi-P-S melt droplet, generated during an iron meteorite impact. The initial droplet was homogeneous and formed at &gt;1800 °C and &gt; 11–16 GPa within the impact plume, based on high-pressure experiments of the Fe-P-S system. As the plume expanding, FeNi spherules emerged from the droplet at 11–16 GPa, estimated by P partitioning between the metal and P-S-rich melt. Subsequent separation of the P-S-rich melt into immiscible sulfide-rich spherules and phosphide-rich mesostasis occurred at 1 bar–3 GPa and 1000–1100 °C. The duration of the pressure declining from &gt;11–16 GPa to 1 bar–3 GPa was estimated to be 0.5–1 s, combining the impact plume expansion model with the cooling rate inferred from the metallic bead. This study demonstrates that high-pressure conditions of impact plumes can be retained for second timescales, which is critical for chemical reactions and water and other volatile migration on the Moon's surface.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"449 ","pages":"Article 116969"},"PeriodicalIF":3.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074463","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}