Icarus最新文献

{"title":"Magnetic topology dependence of ionizing electrons on the Martian nightside ionosphere","authors":"Arnob Sarkar ,&nbsp;N.V. Rao ,&nbsp;Pavan D. Gramapurohit ,&nbsp;Umesh R. Kadhane","doi":"10.1016/j.icarus.2025.116566","DOIUrl":"10.1016/j.icarus.2025.116566","url":null,"abstract":"<div><div>The interaction between the solar wind and Martian crustal magnetic fields plays a significant role in shaping electron precipitation in the ionosphere, particularly on the nightside. Using five years of data from the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, this study explores how magnetic topology influences the distribution of ionizing electrons, quantified through the electron impact ionization frequency (EIIF). Data from MAVEN's Solar Wind Electron Analyzer (SWEA) and magnetometer (MAG) were analyzed, with strong and weak crustal field regions defined at observation altitudes using a crustal field model. As expected, the results demonstrate that magnetic topology critically influences the altitude distribution of EIIF on the nightside. However, variations in EIIF across the terminator reveal dynamic and novel patterns. In open and draped topologies, EIIF decreases gradually from the dayside, across the terminator, and onto the nightside. Conversely, closed topologies exhibit a sharper decrease in EIIF across the terminator, characterized by strong altitude dependence. This is attributed to day-to-night transport along cross-terminator closed field lines. Below 600 km on the nightside, EIIF in closed topologies is up to two orders of magnitude lower than in open and draped topologies due to the shielding effect of crustal fields, with stronger shielding observed at lower altitudes. Above 240 km, EIIF in open and draped topologies shows no dependence on crustal field strength and weak dependence on solar wind dynamic pressure (P_sw). In contrast, the EIIF in closed topologies shows a strong dependence on magnetic field strength and a weak dependence on P_sw. These findings provide critical insights into the role of magnetic topology in electron precipitation, aiding the parameterization of electron dynamics in global circulation models of the Martian ionosphere.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"435 ","pages":"Article 116566"},"PeriodicalIF":2.5,"publicationDate":"2025-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143697851","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 role of planetary-scale waves on the stratospheric superrotation in Titan's atmosphere","authors":"Yuan Lian ,&nbsp;Cecilia Leung ,&nbsp;Claire Newman ,&nbsp;Leslie Tamppari","doi":"10.1016/j.icarus.2025.116561","DOIUrl":"10.1016/j.icarus.2025.116561","url":null,"abstract":"<div><div>We analyze simulation results from the TitanWRF global circulation model to understand the mechanisms that maintain the equatorial superrotation in Titan's stratosphere. We find that the eddies associated with wave activities can transport angular momentum upgradient to zonal flow, leading to acceleration of the equatorial superrotation. The dominant wave modes identified in this study are consistent with previous studies, with zonal wavenumber 1 being the major contributor to the prograde acceleration. Despite the same conclusion of maintenance of equatorial superrotation <em>via</em> wave-mean interactions, we find that the way waves interact with the zonal flow in TitanWRF is slightly different from some other studies. We confirm our previous findings that in TitanWRF this occurs primarily during a dozen or so annual, short-duration (a few Titan sols) angular momentum “transfer events,” which have a repeatable seasonal pattern but differ slightly in timing and magnitude between years. This is not the case in the Titan Atmosphere Model (TAM), which found milder angular momentum transfers that produced the strongest acceleration of superrotation around solstice in the upper stratosphere and more continuous year-around acceleration in the lower stratosphere. Despite differences in angular momentum transfer across models, we further find that, similar to the TAM wave analysis results, eddies generated by Rossby-Kelvin instabilities may be the major source of prograde angular momentum for the equatorial superrotation, although TitanWRF may also include contributions from the absorption of vertically propagating equatorial Kelvin waves. This differs from our previous work, which suggested barotropic waves were responsible for TitanWRF's solsticial transfer event.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"435 ","pages":"Article 116561"},"PeriodicalIF":2.5,"publicationDate":"2025-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143706120","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":"Characterization of lobate scarps at the western rim of the Apollo basin using high-resolution DEMs generated using generative adversarial network (GAN) based approach","authors":"Xijian Li ,&nbsp;Zongyu Yue ,&nbsp;Man Peng ,&nbsp;Kaichang Di ,&nbsp;Biao Wang ,&nbsp;Yexin Wang ,&nbsp;Gregory Michael ,&nbsp;Congzhe Wu ,&nbsp;Jianzhong Liu","doi":"10.1016/j.icarus.2025.116562","DOIUrl":"10.1016/j.icarus.2025.116562","url":null,"abstract":"<div><div>Chang'e-6 is the first sample-return mission from the lunar farside and has returned samples from the landing site within the Apollo basin on June 25, 2024. Lobate scarps have been identified approximately 300 km northwest of the Chang'e-6 landing site (and at western rim of the Apollo basin). The distribution and morphological characteristics of lobate scarps are crucial for understanding the lunar geological history of the landing area. In this research, we have analyzed the spatial distribution and formation age of lobate scarps at western rim of the Apollo basin. The morphology, dynamical models, and formation ages of lobate scarps are investigated through Mohr-Coulomb measurement and crater size-frequency distribution measurements (CSFD). We generated high-resolution digital elevation models by deep learning method using Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) imagery and Selenological and Engineering Explorer (SELENE) and Lunar Orbiter Laser Altimeter (LOLA) Digital Elevation Model (SLDEM), which enabled the study of lobate scarps in areas lacking NAC DTM coverage, and their accuracy were thoroughly validated. The displacement-length ratios of the lobate scarps are calculated, with an average of approximately 3.80 %. By calculating the morphological parameters of lobate scarps, inferring their formation ages, and studying their spatial distribution, we find that these lobate scarps are distributed in the highlands nearby the Apollo basin edge. They were formed under horizontal compressive stresses exceeding 400 MPa during the last 80 Ma, which is consistent with the initially totally molten (ITM) model. This finding is further supported by cross-validation with the ²³⁸U/²⁰⁴Pb ratios from lunar far-side samples by the Chang'e-6 mission, challenging the notion that the lunar magma ocean (LMO) can prolong magmatic activity through KREEP.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"435 ","pages":"Article 116562"},"PeriodicalIF":2.5,"publicationDate":"2025-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143697850","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":"Exobase and homopause altitudes in the Martian upper atmosphere: Solar cycle variability and response to the 2018 global dust storm","authors":"N.V. Rao ,&nbsp;V. Leelavathi ,&nbsp;Neha Gupta","doi":"10.1016/j.icarus.2025.116565","DOIUrl":"10.1016/j.icarus.2025.116565","url":null,"abstract":"<div><div>Understanding the composition of volatile gases in the Martian upper atmosphere and the mechanisms governing their escape into outer space is crucial for unraveling planetary evolution. Two critical neutral atmospheric boundaries, the exobase and the homopause, play key roles in this context. In this study, we conducted a detailed analysis of the exobase and homopause altitudes derived from measurements by the Neutral Gas and Ion Mass Spectrometer (NGIMS) aboard the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft. The exobase and homopause altitudes observed in this study range from 140 to 200 km and 90–135 km, respectively, broadly agreeing with values reported in previous studies. Using extended observations, this study reveals significant interannual variability in these altitudes. Both the exobase and homopause were found to be higher during moderate solar activity compared to solar minimum. During moderate solar activity, these two altitudes rise and fall nearly synchronously, while this coupling weakens during solar minimum. Seasonal trends are also pronounced, with elevated altitudes observed during perihelion and in the summer hemisphere, particularly during the southern summer. These findings suggest that enhanced solar activity during moderate solar periods increases atmospheric heating, elevating atmospheric scale heights and causing the exobase and homopause to rise and fall in-phase. In contrast, during solar minimum, weaker thermal forcing reduces the influence of atmospheric expansion, allowing gravity wave activity to dominate the variability of the homopause. During the 2018 global dust storm (GDS), exobase altitudes were elevated with reduced sinusoidal amplitude, while homopause altitudes exhibited significant fluctuations. These results indicate that thermospheric expansion raises the altitudes of both boundaries during the GDS, but enhanced gravity wave activity introduces substantial fluctuations in the homopause altitude, disrupting its coupling with the exobase and resulting in a phase shift between the variations of these two critical altitudes.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"435 ","pages":"Article 116565"},"PeriodicalIF":2.5,"publicationDate":"2025-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143697852","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":"Morphometrics of polygonal ground on Earth and Mars: Assessing formation mechanisms from orbit","authors":"Derek A. Berman ,&nbsp;Michael T. Mellon","doi":"10.1016/j.icarus.2025.116558","DOIUrl":"10.1016/j.icarus.2025.116558","url":null,"abstract":"<div><div>Polygonal ground patterns are meter-to-decameter-scale landforms commonly observed on Earth, Mars, and other planetary bodies. They can form through a variety of processes (periglacial, desiccation, volcanic, jointing) and provide insight into geological and environmental conditions that can influence habitability. We focus on the morphometric analysis of these patterns to determine diagnostic signatures which may be used to remotely distinguish between the different formation mechanisms, particularly when in-situ observations are not available. We conducted a survey of patterned ground at 17 Earth sites and 12 Mars sites to determine the diameter distributions, junction angles, junction valencies, circularities, and aspect ratios to determine the characteristics of each polygon type. Our results showed common clustering of morphometric characteristics amongst similar polygon types, though some ambiguities remain between formation endmembers. The size-frequency distributions and the ratio of 90° to 120° junction angles were strong indicators of formation process. The junction angle ratio also reveals the “maturity” of the networks due to periodic or episodic refracturing. Junction valency, circularity, and aspect ratios, also proved valuable as statistical indicators. Our analysis of polygonal patterns located in the Jezero crater floor and margin unit, along with two sites located at Terby crater, are consistent with both volcanic and tectonic jointing processes. Analysis of Mawrth Vallis is strongly suggestive of desiccation. These findings suggest that similar physical mechanisms control polygon formation across planetary bodies, and the study of these patterns on Mars can provide key insights into its geological and climate history, providing clues to potential habitability.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"435 ","pages":"Article 116558"},"PeriodicalIF":2.5,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143767473","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Masses of binary asteroid systems with strong solar perturbations","authors":"M.I. Varfolomeev ,&nbsp;N.V. Emelyanov","doi":"10.1016/j.icarus.2025.116546","DOIUrl":"10.1016/j.icarus.2025.116546","url":null,"abstract":"<div><div>We give refined values for the masses for the following binary asteroid systems with strong solar perturbations: (379) Huenna, (3548) Eurybates-Queta, (3749) Balam, (88611) Teharonhiawako-Sawiskera, (160256) 2002 PD₁₄₉, (341520) Mors-Somnus, (364171) 2006 JZ₈₁, (524531) 2002 XH₉₁, 1998 WW₃₁, and 2003 QY₉₀. The masses were refined by numeric integration of the equations of motion where perturbations from the Sun’s gravity were taken into account. Assuming the satellite orbits to be close to Keplerian, the initial integration parameters and the masses of the systems can be refined by the least-squares method in which the coefficients of the conditional equations are calculated using the Keplerian motion formulae. For some systems with strong solar perturbations (2001 QW₃₂₂, 2006 BR₂₈₄, 2006 CH₆₉, (525462) 2005 EO₃₀₄, (612147) 2000 CF₁₀₅, (612687) 2003 UN₂₈₄) the masses could not be refined since the rms residuals increase when solar perturbations are taken into account, which can be caused by insufficient interval or amount of observations. For most systems, the obtained values for masses are within the error limits of the values obtained using only Keplerian model. However, for a number of satellites, the Keplerian model of motion, which does not take into account solar perturbations, gives significant deviations in the apparent positions exceeding the accuracy of modern observations. These systems are (379) Huenna, (3548) Eurybates-Queta, (3749) Balam, (160256) 2002 PD₁₄₉, and (364171) 2006 JZ₈₁. For the systems for which it was possible to refine the masses, we give elements of their satellites’ osculating orbits for the epoch close to the date of their first observation.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"434 ","pages":"Article 116546"},"PeriodicalIF":2.5,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143644815","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":"Mars ionosphere TEC estimation from MARSIS data: A new approach","authors":"M. Cartacci ,&nbsp;B. Sánchez-Cano ,&nbsp;A. Cicchetti ,&nbsp;R. Noschese ,&nbsp;B. Langlais ,&nbsp;R. Orosei","doi":"10.1016/j.icarus.2025.116545","DOIUrl":"10.1016/j.icarus.2025.116545","url":null,"abstract":"<div><div>We describe a new implementation of the Contrast Method (CM) algorithm (<span><span>Picardi and Sorge, 2000</span></span>; <span><span>Ilyushin Ya and Kunitsyn, 2004</span></span>; <span><span>Cartacci et al., 2013</span></span>) used to correct the phase distortion of the echoes recorded by the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) (<span><span>Picardi et al., 2005</span></span>; <span><span>Jordan et al., 2009</span></span>) in its subsurface mode.</div><div>The New CM is designed following an improved approach which allows not only to perform its original task but also to estimate the Total Electron Content (TEC) of the Mars ionosphere with a better accuracy respect to the past (<span><span>Cartacci et al., 2013</span></span>; <span><span>Cartacci et al., 2017</span></span>), in the nightside when the transmitted frequency is close to the ionosphere plasma frequency as well as in the dayside, thanks to a lesser use of theoretical approximations in the method development.</div><div>Moreover, taking advantage of almost 16 years of MARSIS operations, corresponding to about 8700 orbits, we present an improved global map of the night side TEC variations due to the interaction with the Mars crustal magnetic field (<span><span>Safaeinili et al., 2007</span></span>; <span><span>Cartacci et al., 2013</span></span>).</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"434 ","pages":"Article 116545"},"PeriodicalIF":2.5,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143636296","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 impact of cometary outbursts on the orbits of comets in the Oort cloud","authors":"A.Y. Merkulova,&nbsp;A.K. Pavlov,&nbsp;D.V. Belousov","doi":"10.1016/j.icarus.2025.116547","DOIUrl":"10.1016/j.icarus.2025.116547","url":null,"abstract":"<div><div>The surface layers of cometary nuclei are intensively irradiated by high energy protons, α-particles and heavy ions of galactic cosmic ray (GCR), leading to the formation of ions and radicals in the comet's matter. At low temperatures, high concentrations of radicals accumulated in the ice can be followed by a rapid release of energy during spontaneous or induced recombination. This process can provoke a gas release from the comet's surface layers. The resulting gas flux leads to a change in the velocity of comets, which affects the stability of their orbits. Repeated outbursts can occur over the comet's lifetime in the Oort cloud. This mechanism depends on the comet's size, the initial eccentricity, and the ejected mass during the outburst. We modeled the impact of repeated cometary outbursts on the orbits of comets in the Oort cloud. The results indicate that 49.5 % of comets with radii R_c = 0.4 km and 72.4 % of comets with R_c = 0.3 km and initial eccentricities e_c ≥ 0.9 could leave the Oort cloud due to repeated outbursts. This fraction leaving comets for the initial eccentricities e_c &gt; 0 is 19.3 % for R_c = 0.4 km and 54.1 % for R_c = 0.3 km, respectively. The mechanism has the most effect on highly elongated orbits of comets.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"434 ","pages":"Article 116547"},"PeriodicalIF":2.5,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143620612","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":"Visible spectroscopy of 3 KBOs and 1 Centaur","authors":"R.K. Williams,&nbsp;J.P. Emery","doi":"10.1016/j.icarus.2025.116554","DOIUrl":"10.1016/j.icarus.2025.116554","url":null,"abstract":"<div><div>Material remaining from the formation of the outer Solar System congregated in the Kuiper Belt. Studying this material has provided key information about the formation of the Solar System, the distribution of planetary materials, and the compositions of different objects. Additional spectra of objects in the Kuiper Belt will provide further insight into Solar System formation and evolution. An important question is whether, and in what quantity, hydrated material formed in the outer Solar System. We address this question here with visible spectra of three Kuiper Belt Objects (KBOs) and one Centaur. We find moderately red spectral slopes for these four bodies, with no clear evidence for the 7000 Å feature due to Fe-rich phyllosilicates. These results extend the overall lack of detection of hydrated materials among KBOs and Centaurs. Although it is clear that hydrated silicates are not common in the outer Solar System, some hydration might be expected, and further observations will continue to refine its prevalence.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"434 ","pages":"Article 116554"},"PeriodicalIF":2.5,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143683298","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":"Insights for hydrated sulfuric acid on Europa's surface from a combined orbital – experimental approach.","authors":"T.W. Hayes ,&nbsp;S. Li","doi":"10.1016/j.icarus.2025.116543","DOIUrl":"10.1016/j.icarus.2025.116543","url":null,"abstract":"<div><div>Europa's non-water ice component may come from its interior ocean or from exotic processes (e.g. surface irradiation and/or impacts). We investigate these possible sources globally using all high spatial resolution (&lt;25 km/pixel) data acquired by the Near-Infrared Mapping Spectrometer (NIMS) onboard Galileo, which is more advantageous than previous studies that only used few selected high spatial resolution datasets, or those with global coverage yet low spatial resolution. We find that the slopes of NIMS spectra from 1.3 to 2.2 μm show the same hemispheric dichotomy displayed by incident radiation fluxes, with trailing hemisphere spectral slopes being much more negative, or “bluer”, than those of the leading hemisphere. Spectral slopes are also bluer locally in older terrains, further suggesting a surface exposure-age dependence. In our examined endmember library, only sulfuric acid octahydrate (H₂SO₄ • 8H₂O, “SAO”) can explain this blue slope. Water ice – SAO ice mixtures show blue slope strength increases with SAO abundance. We attribute the behavior of Europa's NIMS spectral slopes to indicate the likely presence of hydrated sulfuric acid. Weak blue slopes in Europa's endogenic features suggest minor SAO abundances.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"434 ","pages":"Article 116543"},"PeriodicalIF":2.5,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143683297","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}