Pub Date : 2025-10-08DOI: 10.1016/j.icarus.2025.116844
B.G. Rider-Stokes , A.Y.C. Wong , T.H. Burbine , E. MacLennan , R.C. Greenwood , S.L. Jackson , M. Anand , L.F. White , M.M. Grady
Ungrouped achondrites with affinities to Howardite-Eucrite-Diogenite (HED) meteorites offer critical insights into the diversity of differentiated bodies in the inner Solar System. They can help address the longstanding discrepancy between V-type asteroids related to the asteroid (4) Vesta and those that show similar characteristics but lack a dynamical relationship. In this study, we present new spectral, mineralogical, and oxygen isotopic analyses of two ungrouped achondritic meteorites. Al Bir Lahlou 001 exhibits strong compositional and spectral similarities to typical V-type asteroids, while Wan Zawatin 001 shows unexpected affinities to S-type asteroids. These findings suggest a more complex evolutionary history for differentiated asteroids than previously recognized and support the existence of multiple asteroidal bodies with HED-like characteristics. Our results highlight the importance of continued investigation into ungrouped achondrites to better understand the formation, distribution, and evolution of differentiated material beyond the Vesta family.
{"title":"The Noritic mineralogy of V- and S-type objects and the links with asteroid (4) Vesta","authors":"B.G. Rider-Stokes , A.Y.C. Wong , T.H. Burbine , E. MacLennan , R.C. Greenwood , S.L. Jackson , M. Anand , L.F. White , M.M. Grady","doi":"10.1016/j.icarus.2025.116844","DOIUrl":"10.1016/j.icarus.2025.116844","url":null,"abstract":"<div><div>Ungrouped achondrites with affinities to Howardite-Eucrite-Diogenite (HED) meteorites offer critical insights into the diversity of differentiated bodies in the inner Solar System. They can help address the longstanding discrepancy between V-type asteroids related to the asteroid (4) Vesta and those that show similar characteristics but lack a dynamical relationship. In this study, we present new spectral, mineralogical, and oxygen isotopic analyses of two ungrouped achondritic meteorites. Al Bir Lahlou 001 exhibits strong compositional and spectral similarities to typical V-type asteroids, while Wan Zawatin 001 shows unexpected affinities to S-type asteroids. These findings suggest a more complex evolutionary history for differentiated asteroids than previously recognized and support the existence of multiple asteroidal bodies with HED-like characteristics. Our results highlight the importance of continued investigation into ungrouped achondrites to better understand the formation, distribution, and evolution of differentiated material beyond the Vesta family.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"445 ","pages":"Article 116844"},"PeriodicalIF":3.0,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145321772","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}
Pub Date : 2025-10-06DOI: 10.1016/j.icarus.2025.116841
A. Emran
Europa's surface composition and physical characteristics are commonly constrained using spectral deconvolution through linear mixture (LM) modeling and radiative transfer–based (RT) intimate mixture modeling. Here, I compared the results of these two spectral modeling— LM versus RT— against laboratory spectra of water (H2O) ice and sulfuric acid octahydrate (SAO; H2SO4·8H2O) mixtures measured at near-infrared wavelengths (∼1.2–2.5 μm) with grain sizes of 90–106 μm (Hayes and Li, 2025). The modeled abundances indicate that the RT more closely reproduces the laboratory abundances, with deviations within ±5 % for both H2O ice and H2SO4·8H2O with ∼100 μm grains. In contrast, the LM shows slightly larger discrepancies, typically ranging from ±5–15 % from the true abundances. Interestingly, both LM and RT tend to consistently overestimate the abundance of H2SO4·8H2O and underestimate H2O ice across all mixtures. Nonetheless, when H2SO4·8H2O either dominates (>80 % as observed on Europa's trailing hemisphere; Carlson et al., 2005) or is present only in trace amounts (∼10 % on areas in Europa's leading hemisphere; Dalton et al., 2013; Ligier et al., 2016), both the LM and RT render acceptable results within ±10 % uncertainty. Thus, spectral modeling using the RT is preferred for constraining the surface composition across Europa, although the LM remains viable in specific compositional regimes.
{"title":"Spectral mixture modeling with laboratory near-infrared data I: Insights into compositional analysis of Europa","authors":"A. Emran","doi":"10.1016/j.icarus.2025.116841","DOIUrl":"10.1016/j.icarus.2025.116841","url":null,"abstract":"<div><div>Europa's surface composition and physical characteristics are commonly constrained using spectral deconvolution through linear mixture (LM) modeling and radiative transfer–based (RT) intimate mixture modeling. Here, I compared the results of these two spectral modeling— LM versus RT— against laboratory spectra of water (H<sub>2</sub>O) ice and sulfuric acid octahydrate (SAO; H<sub>2</sub>SO<sub>4</sub>·8H<sub>2</sub>O) mixtures measured at near-infrared wavelengths (∼1.2–2.5 μm) with grain sizes of 90–106 μm (<span><span>Hayes and Li, 2025</span></span>). The modeled abundances indicate that the RT more closely reproduces the laboratory abundances, with deviations within ±5 % for both H<sub>2</sub>O ice and H<sub>2</sub>SO<sub>4</sub>·8H<sub>2</sub>O with ∼100 μm grains. In contrast, the LM shows slightly larger discrepancies, typically ranging from ±5–15 % from the true abundances. Interestingly, both LM and RT tend to consistently overestimate the abundance of H<sub>2</sub>SO<sub>4</sub>·8H<sub>2</sub>O and underestimate H<sub>2</sub>O ice across all mixtures. Nonetheless, when H<sub>2</sub>SO<sub>4</sub>·8H<sub>2</sub>O either dominates (>80 % as observed on Europa's trailing hemisphere; <span><span>Carlson et al., 2005</span></span>) or is present only in trace amounts (∼10 % on areas in Europa's leading hemisphere; <span><span>Dalton et al., 2013</span></span>; <span><span>Ligier et al., 2016</span></span>), both the LM and RT render acceptable results within ±10 % uncertainty. Thus, spectral modeling using the RT is preferred for constraining the surface composition across Europa, although the LM remains viable in specific compositional regimes.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"444 ","pages":"Article 116841"},"PeriodicalIF":3.0,"publicationDate":"2025-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145268262","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}
Pub Date : 2025-10-06DOI: 10.1016/j.icarus.2025.116838
V.D. Gusev, E.D. Kuznetsov
A search for pairs of trans-Neptunian objects in close orbits with semi-major axes greater than 30 AU has been conducted. The proximity of the orbital pairs was determined using Kholshevnikov metrics. A total of 46 pairs of trans-Neptunian objects with metric values below 0.1 AU were identified. The dynamical evolution of these pairs was investigated over the past 10 Myr using numerical methods based on their nominal orbits. The formation epochs of the trans-Neptunian object pairs were determined using the method of nodal and apsidal convergence analysis, as well as the orbital convergence method. For the pairs 2003 QX90 – 2000 ON67, 2005 CE81 – 2003 QY90, 2013 TG229 – 2009 YK32, 2013 UN17 – 2003 QX90 and 2019 QL111 – 2015 GF59, a probabilistic evolution study was conducted over a 2-Myr interval. For the pairs 2003 QX90 – 2000 ON67, 2013 TG229 – 2009 YK32, 2013 UN17 – 2003 QX90 and 2019 QL111 – 2015 GF59, their ages were estimated, and the fraction of formation orbits within the studied interval was calculated. The masses of trans-Neptunian objects that allow for their formation were determined using MOID analysis. The ages of the remaining 42 pairs exceed 10 Myr.
{"title":"Age estimation of Trans-Neptunian Object pairs in close orbits","authors":"V.D. Gusev, E.D. Kuznetsov","doi":"10.1016/j.icarus.2025.116838","DOIUrl":"10.1016/j.icarus.2025.116838","url":null,"abstract":"<div><div>A search for pairs of trans-Neptunian objects in close orbits with semi-major axes greater than 30 AU has been conducted. The proximity of the orbital pairs was determined using Kholshevnikov metrics. A total of 46 pairs of trans-Neptunian objects with metric values below 0.1 AU<span><math><msup><mrow></mrow><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msup></math></span> were identified. The dynamical evolution of these pairs was investigated over the past 10 Myr using numerical methods based on their nominal orbits. The formation epochs of the trans-Neptunian object pairs were determined using the method of nodal and apsidal convergence analysis, as well as the orbital convergence method. For the pairs 2003 QX90 – 2000 ON67, 2005 CE81 – 2003 QY90, 2013 TG229 – 2009 YK32, 2013 UN17 – 2003 QX90 and 2019 QL111 – 2015 GF59, a probabilistic evolution study was conducted over a 2-Myr interval. For the pairs 2003 QX90 – 2000 ON67, 2013 TG229 – 2009 YK32, 2013 UN17 – 2003 QX90 and 2019 QL111 – 2015 GF59, their ages were estimated, and the fraction of formation orbits within the studied interval was calculated. The masses of trans-Neptunian objects that allow for their formation were determined using MOID analysis. The ages of the remaining 42 pairs exceed 10 Myr.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"445 ","pages":"Article 116838"},"PeriodicalIF":3.0,"publicationDate":"2025-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145321771","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}
Pub Date : 2025-10-04DOI: 10.1016/j.icarus.2025.116837
Shaelyn M. Raposa , Sugata P. Tan , William M. Grundy , Gerrick E. Lindberg , Jordan K. Steckloff , Stephen C. Tegler , Jennifer Hanley , Anna E. Engle , Cecilia L. Thieberger
New data of a sub-solidus phase boundary that has never been detected before were derived from Raman spectroscopy for the binary mixture nitrogen-methane. The experimental data were then evaluated using a robust thermodynamic equation of state, CRYOCHEM 2.0. The consistency between experimental data and thermodynamics found in this work introduces a new phase diagram to be used in future applications at low temperatures.
This mixture is the major binary system that represents the most abundant volatiles on icy bodies, like Pluto, Triton, and Eris. The new phase diagram will lead to a better understanding of the atmospheres and surfaces of these bodies, at present, past, or future geophysical conditions.
{"title":"Discovery of a new sub-solidus phase boundary of the binary nitrogen-methane mixture","authors":"Shaelyn M. Raposa , Sugata P. Tan , William M. Grundy , Gerrick E. Lindberg , Jordan K. Steckloff , Stephen C. Tegler , Jennifer Hanley , Anna E. Engle , Cecilia L. Thieberger","doi":"10.1016/j.icarus.2025.116837","DOIUrl":"10.1016/j.icarus.2025.116837","url":null,"abstract":"<div><div>New data of a sub-solidus phase boundary that has never been detected before were derived from Raman spectroscopy for the binary mixture nitrogen-methane. The experimental data were then evaluated using a robust thermodynamic equation of state, CRYOCHEM 2.0. The consistency between experimental data and thermodynamics found in this work introduces a new phase diagram to be used in future applications at low temperatures.</div><div>This mixture is the major binary system that represents the most abundant volatiles on icy bodies, like Pluto, Triton, and Eris. The new phase diagram will lead to a better understanding of the atmospheres and surfaces of these bodies, at present, past, or future geophysical conditions.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"444 ","pages":"Article 116837"},"PeriodicalIF":3.0,"publicationDate":"2025-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145268263","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}
Pub Date : 2025-10-03DOI: 10.1016/j.icarus.2025.116831
E. Piacenti , A.J. Dombard
Exploring Europa, one of Jupiter's icy moons, is crucial for advancing our understanding of extraterrestrial geology and potential habitability. At present, study of gravity anomalies represents the best way to interrogate Europa's seafloor; however, current and expected global gravity models are insufficient for detecting and characterizing specific geologic features due to their coarse resolution. This study aims to determine whether Line-of-Sight (LoS) gravity signatures derived from Doppler residuals can be used to identify specific geological features on Europa's seafloor, such as mountain ranges, valleys, impact basins, rift zones, and subduction zones. Here, we assess the detectability of these features and evaluate whether the resolution from Europa Clipper would be sufficient to distinguish them. Our findings indicate that the expected LoS Doppler residual data likely will not provide sufficient resolution to differentiate between various geological formations on Europa's seafloor, primarily due to the spatial scale of the expected features compared to the spacecraft's distance from the surface. These limitations suggest that gravity signatures alone may not offer enough information for the interpretation of Europa's seafloor geology.
{"title":"Predictive modeling of gravitational anomalies for geological features along Europa's seafloor, utilizing line-of-sight Doppler residuals","authors":"E. Piacenti , A.J. Dombard","doi":"10.1016/j.icarus.2025.116831","DOIUrl":"10.1016/j.icarus.2025.116831","url":null,"abstract":"<div><div>Exploring Europa, one of Jupiter's icy moons, is crucial for advancing our understanding of extraterrestrial geology and potential habitability. At present, study of gravity anomalies represents the best way to interrogate Europa's seafloor; however, current and expected global gravity models are insufficient for detecting and characterizing specific geologic features due to their coarse resolution. This study aims to determine whether Line-of-Sight (LoS) gravity signatures derived from Doppler residuals can be used to identify specific geological features on Europa's seafloor, such as mountain ranges, valleys, impact basins, rift zones, and subduction zones. Here, we assess the detectability of these features and evaluate whether the resolution from Europa Clipper would be sufficient to distinguish them. Our findings indicate that the expected LoS Doppler residual data likely will not provide sufficient resolution to differentiate between various geological formations on Europa's seafloor, primarily due to the spatial scale of the expected features compared to the spacecraft's distance from the surface. These limitations suggest that gravity signatures alone may not offer enough information for the interpretation of Europa's seafloor geology.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"445 ","pages":"Article 116831"},"PeriodicalIF":3.0,"publicationDate":"2025-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145321770","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}
Pub Date : 2025-10-02DOI: 10.1016/j.icarus.2025.116839
N.S. Arnold , F.E.G. Butcher
Mars' mid latitudes contain thousands of ‘viscous flow features’ (VFFs), akin to debris-covered glaciers on Earth. They are thought to have formed during martian ‘ice ages’, driven by variations in Mars' spin-axis obliquity. Knowledge of the emplacement age of ice within VFFs is key to understanding the nature and timing of such glacial cycles, and the palaeoclimate histories they reflect. Current methods to estimate VFF surface ages, which place VFF formation broadly within the last few Myr to 100 s Myr, predominantly rely on the size-frequency distributions of impact craters across their surfaces. However, these ‘impact crater retention ages’ likely reflect the time since the emplacement or last major modification of the surficial debris layer; they implicitly assume a uniform age across the sampled area. They also provide no direct information about the emplacement ages of the underlying ice layers, the configurations (and hence age distributions) of which are likely to have been modified during transit by ice flow. Here, we develop a new, physically-based method to reconstruct the flow paths and transit times of ice within VFFs, and hence estimate variations in the minimum age of ice across their (now debris-covered) surfaces, and with depth. We use 3-dimensional ice flow modelling and particle tracking, and apply our method to a small VFF in Mars' southern mid-latitudes, north of Argyre Planitia. Our method produces spatially-variable near-surface ice age estimates which range from very young (< 1Myr) in the upper parts of the VFF to ∼500 Myr close to the VFF terminus, assuming current martian temperatures and a conventional ice rheology. Toward the terminus, the calculated surface ages increase rapidly over short distances as compressional ice flow transports old, deep ice upwards toward the surface. The distributed 3D age estimates provided by our method also allow prediction of the depths and configurations of isochronous layers within the VFF. The spatial patterns we find are insensitive to the assumed ice deformation mechanism, but the specific calculated ages are highly sensitive (> 2 orders of magnitude) to ice temperature and grain size, which emerge as the main controls on modelled ice flow velocities, and hence the estimated ages. Our results have significant implications for identifying landing sites and ice sampling strategies for future missions which could extract climate records potentially hosted within glacial ice layers on Mars. The significant variations we find in the age of ice across the VFF surface, arising from the flow-induced deflection of ice layers up to the surface, suggest that such missions could access ice with a large range of ages (and hence potentially longer-timespan climate records) by sampling from shallow depths across the surface a single VFF.
{"title":"Estimating the age of ice in a Martian mid-latitude debris-covered glacier from numerical modelling and particle tracking","authors":"N.S. Arnold , F.E.G. Butcher","doi":"10.1016/j.icarus.2025.116839","DOIUrl":"10.1016/j.icarus.2025.116839","url":null,"abstract":"<div><div>Mars' mid latitudes contain thousands of ‘viscous flow features’ (VFFs), akin to debris-covered glaciers on Earth. They are thought to have formed during martian ‘ice ages’, driven by variations in Mars' spin-axis obliquity. Knowledge of the emplacement age of ice within VFFs is key to understanding the nature and timing of such glacial cycles, and the palaeoclimate histories they reflect. Current methods to estimate VFF surface ages, which place VFF formation broadly within the last few Myr to 100 s Myr, predominantly rely on the size-frequency distributions of impact craters across their surfaces. However, these ‘impact crater retention ages’ likely reflect the time since the emplacement or last major modification of the surficial debris layer; they implicitly assume a uniform age across the sampled area. They also provide no direct information about the emplacement ages of the underlying ice layers, the configurations (and hence age distributions) of which are likely to have been modified during transit by ice flow. Here, we develop a new, physically-based method to reconstruct the flow paths and transit times of ice within VFFs, and hence estimate variations in the minimum age of ice across their (now debris-covered) surfaces, and with depth. We use 3-dimensional ice flow modelling and particle tracking, and apply our method to a small VFF in Mars' southern mid-latitudes, north of Argyre Planitia. Our method produces spatially-variable near-surface ice age estimates which range from very young (< 1Myr) in the upper parts of the VFF to ∼500 Myr close to the VFF terminus, assuming current martian temperatures and a conventional ice rheology. Toward the terminus, the calculated surface ages increase rapidly over short distances as compressional ice flow transports old, deep ice upwards toward the surface. The distributed 3D age estimates provided by our method also allow prediction of the depths and configurations of isochronous layers within the VFF. The spatial patterns we find are insensitive to the assumed ice deformation mechanism, but the specific calculated ages are highly sensitive (> 2 orders of magnitude) to ice temperature and grain size, which emerge as the main controls on modelled ice flow velocities, and hence the estimated ages. Our results have significant implications for identifying landing sites and ice sampling strategies for future missions which could extract climate records potentially hosted within glacial ice layers on Mars. The significant variations we find in the age of ice across the VFF surface, arising from the flow-induced deflection of ice layers up to the surface, suggest that such missions could access ice with a large range of ages (and hence potentially longer-timespan climate records) by sampling from shallow depths across the surface a single VFF.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"444 ","pages":"Article 116839"},"PeriodicalIF":3.0,"publicationDate":"2025-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145324918","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}
Pub Date : 2025-10-01DOI: 10.1016/j.icarus.2025.116836
Maxwell L. Craddock , Yasuhito Sekine , Maryse Napoleoni , Nozair Khawaja , Shuya Tan , Yamei Li , Zening Yang , Lucía Hortal Sánchez , Ruiqin Yi , Frank Postberg
In-situ observations of Enceladus' plume and Saturn's E ring by the Cassini spacecraft have revealed that some ice particles erupted from Enceladus contain a large inventory of organic materials. These include both high- and low-molecular-weight hydrocarbon chains, aromatic-, nitrogen-, and oxygen-bearing compounds. Here we report experimental results on organic synthesis through hydrothermal (up to 150 °C) and freezing (down to –40 °C) processes using starting solutions simulating Enceladus' ocean. We find that, owing to HCN and NH3 in the starting solutions, amino acids, together with aldehydes, carboxylic acids, amines, and nitriles, are the primary products of hydrothermal synthesis. Freezing of the starting solutions can also form simple amino acids, such as glycine. Comparing with Cassini's observations, most of our hydrothermal products are in good agreement with observations arguing for a deep plume source, but amino acid-relevant molecular signals in the experiments appear to be absent in Enceladus' organic-rich particles. One possibility for this discrepancy is that partitioning of amino acids into salt-rich plume particles may obscure detection. Macromolecules with aromatic constituents and long hydrocarbon chains in Enceladus cannot be replicated in our experiments. Primordial organic matter or catalytic reactions at elevated temperatures (>150 °C) might contribute to the formation of macromolecules in Enceladus.
{"title":"Laboratory simulations of organic synthesis in Enceladus: Implications for the origin of organic matter in the plume","authors":"Maxwell L. Craddock , Yasuhito Sekine , Maryse Napoleoni , Nozair Khawaja , Shuya Tan , Yamei Li , Zening Yang , Lucía Hortal Sánchez , Ruiqin Yi , Frank Postberg","doi":"10.1016/j.icarus.2025.116836","DOIUrl":"10.1016/j.icarus.2025.116836","url":null,"abstract":"<div><div>In-situ observations of Enceladus' plume and Saturn's E ring by the Cassini spacecraft have revealed that some ice particles erupted from Enceladus contain a large inventory of organic materials. These include both high- and low-molecular-weight hydrocarbon chains, aromatic-, nitrogen-, and oxygen-bearing compounds. Here we report experimental results on organic synthesis through hydrothermal (up to 150 °C) and freezing (down to –40 °C) processes using starting solutions simulating Enceladus' ocean. We find that, owing to HCN and NH<sub>3</sub> in the starting solutions, amino acids, together with aldehydes, carboxylic acids, amines, and nitriles, are the primary products of hydrothermal synthesis. Freezing of the starting solutions can also form simple amino acids, such as glycine. Comparing with Cassini's observations, most of our hydrothermal products are in good agreement with observations arguing for a deep plume source, but amino acid-relevant molecular signals in the experiments appear to be absent in Enceladus' organic-rich particles. One possibility for this discrepancy is that partitioning of amino acids into salt-rich plume particles may obscure detection. Macromolecules with aromatic constituents and long hydrocarbon chains in Enceladus cannot be replicated in our experiments. Primordial organic matter or catalytic reactions at elevated temperatures (>150 °C) might contribute to the formation of macromolecules in Enceladus.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"444 ","pages":"Article 116836"},"PeriodicalIF":3.0,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145268265","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}
Pub Date : 2025-09-30DOI: 10.1016/j.icarus.2025.116832
J.M. Burley , L.L. Tornabene , G.R. Osinski
Meteorite impact craters on Mars display a diverse range of ejecta morphologies. A number of studies have suggested the presence of impact ejecta deposits beyond the limit of the canonical proximal continuous ejecta blanket, which on Mars is often marked by a topographic high, or “rampart”. It is currently uncertain how such deposits beyond the rampart form, and under what conditions. With the goal of answering such questions, we identified and characterized extensive surface flow deposits beyond the proximal ejecta blanket of Tokmok Crater, a ∼ 9 km-diameter well-preserved crater in central Noachis Terra (29.405°S 351.319°E). We refer to these as Distal Flow Deposits (DFDs). We recognize two types: Type 1 flows develop at the base of source crater facing slopes as fan-like accumulations of smooth surfaced material. Type 2 flows form channel-fill like deposits within confining topography that funnel material from flat-lying regions. Through the identification, morphological mapping, and morphometric analysis of various impact units, the DFDs studied here are interpreted to represent the emplacement of outwardly mobilized ground-hugging flows subject to some form of impact-induced fluidization. DFD slope values are consistently below the dynamic angle of repose (Type 1 average = 6°; Type 2 average = 8.4°). DFDs are shown to accumulate where existing target topography captures more extended ejecta than surrounding flat-lying terrains that are resurfaced or obscured by the same deposits. Such deposits are shown to exist well beyond the proximal continuous ejecta blanket, which has important implications for geomorphological studies across Mars.
{"title":"Distal impact-related surface flows associated with the well-preserved Tokmok Crater, Noachis Terra, Mars","authors":"J.M. Burley , L.L. Tornabene , G.R. Osinski","doi":"10.1016/j.icarus.2025.116832","DOIUrl":"10.1016/j.icarus.2025.116832","url":null,"abstract":"<div><div>Meteorite impact craters on Mars display a diverse range of ejecta morphologies. A number of studies have suggested the presence of impact ejecta deposits beyond the limit of the canonical proximal continuous ejecta blanket, which on Mars is often marked by a topographic high, or “rampart”. It is currently uncertain how such deposits beyond the rampart form, and under what conditions. With the goal of answering such questions, we identified and characterized extensive surface flow deposits beyond the proximal ejecta blanket of Tokmok Crater, a ∼ 9 km-diameter well-preserved crater in central Noachis Terra (29.405°S 351.319°E). We refer to these as Distal Flow Deposits (DFDs). We recognize two types: Type 1 flows develop at the base of source crater facing slopes as fan-like accumulations of smooth surfaced material. Type 2 flows form channel-fill like deposits within confining topography that funnel material from flat-lying regions. Through the identification, morphological mapping, and morphometric analysis of various impact units, the DFDs studied here are interpreted to represent the emplacement of outwardly mobilized ground-hugging flows subject to some form of impact-induced fluidization. DFD slope values are consistently below the dynamic angle of repose (Type 1 average = 6°; Type 2 average = 8.4°). DFDs are shown to accumulate where existing target topography captures more extended ejecta than surrounding flat-lying terrains that are resurfaced or obscured by the same deposits. Such deposits are shown to exist well beyond the proximal continuous ejecta blanket, which has important implications for geomorphological studies across Mars.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"444 ","pages":"Article 116832"},"PeriodicalIF":3.0,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145268260","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}
Pub Date : 2025-09-29DOI: 10.1016/j.icarus.2025.116833
Márton Mester , R. John Wilson , Jeffery L. Hollingsworth , Melinda A. Kahre
Martian extratropical baroclinic waves exhibit a pronounced hemispheric asymmetry, with significantly more vigorous activity in the Northern Hemisphere (NH) compared to the Southern Hemisphere (SH). This study employs the NASA Ames Mars Global Climate Model (MGCM) to investigate the role of topography in driving this asymmetry. Through a series of simulations with varying topographic configurations, we demonstrate that continental-scale impact basins, lowlands, and highlands have a substantial influence on the intensity and distribution of baroclinic waves. Our findings reveal that the SH’s relatively weaker wave activity is partly attributable to the presence of the Hellas and Argyre impact basins, which act as barriers to baroclinic wave propagation. The hemispheric asymmetry is additionally amplified by an increased wave activity in the NH due to an intensification of baroclinic waves at the boundaries of Tharsis-Acidalia, Elysium-Arcadia, and Nilosyrtis-Utopia. It is determined that such highland-lowland west-east structures contribute to a weakening in wave activity above the highlands and a strengthening above the lowlands, with the influence of the latter propagating downstream to the east with a resulting net gain in wave energy. These results provide insight into how topography influences extratropical weather systems on Mars and highlight how impact basins and highlands may shape the climate of a rocky planet.
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