Icarus最新文献

{"title":"Numerical model for the solidification of a chondrule melt","authors":"","doi":"10.1016/j.icarus.2024.116317","DOIUrl":"10.1016/j.icarus.2024.116317","url":null,"abstract":"<div><div>In this study, we propose a novel numerical method to simulate the growth dynamics of an olivine single crystal within an isolated, multicomponent silicate droplet. We aimed to theoretically replicate the solidification textures observed in chondrules. The method leverages the phase-field model, a well-established framework for simulating alloy solidification. This approach enables the calculation of the solidification process within the ternary MgO–FeO–SiO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> system. Furthermore, the model incorporates the anisotropic characteristics of interface free energy and growth kinetics inherent to the crystal structure. Here we investigated an anisotropy model capable of reproducing the experimentally observed dependence of the growth patterns of the olivine single crystal on the degree of supercooling under the constraints of two-dimensional modeling. By independently adjusting the degree of anisotropies of interface free energy and growth kinetics, we successfully achieved the qualitative replication of diverse olivine crystal morphologies, ranging from polyhedral shapes at low supercooling to elongated, needle-like structures at high supercooling. This computationally driven method offers a unique and groundbreaking approach for theoretically reproducing the solidification textures of chondrules.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":null,"pages":null},"PeriodicalIF":2.5,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142539185","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":"On the impact of the vertical structure of Martian water ice clouds on nadir atmospheric retrievals from simultaneous EMM/EXI and TGO/ACS-MIR observations.","authors":"","doi":"10.1016/j.icarus.2024.116335","DOIUrl":"10.1016/j.icarus.2024.116335","url":null,"abstract":"<div><div>Retrieving the optical depth of the Martian clouds (<span><math><msub><mrow><mi>τ</mi></mrow><mrow><mtext>cld</mtext></mrow></msub></math></span>) is a powerful way to monitor their spatial and temporal evolution. However, such retrievals from nadir imagery rely on several assumptions, including the vertical structure of the clouds in the atmosphere. Here we compare the results of cloud optical depth retrievals at 320 nm from the Emirates eXploration Imager (EXI) onboard the Emirates Mars Mission (EMM) “Hope” orbiter performed using a basic uniform cloud profile used in previous studies and using derived cloud profiles obtained from near-simultaneous Solar Occultation observations in the 3.1–3.4 <span><math><mrow><mi>μ</mi><mi>m</mi></mrow></math></span> spectral range from the Middle-Infrared channel of the Atmospheric Chemistry Suite (ACS) instrument onboard the ESA Trace Gas Orbiter (TGO). We show that the latitudinal dependence of the cloud vertical profiles can have a strong impact on the nadir retrievals; neglecting it can lead to a significant underestimation of <span><math><msub><mrow><mi>τ</mi></mrow><mrow><mtext>cld</mtext></mrow></msub></math></span> in the polar regions (up to 25 % to 50 %, depending on the vertical distribution of the dust in the atmosphere) and to a lesser extent, to an overestimation of <span><math><msub><mrow><mi>τ</mi></mrow><mrow><mtext>cld</mtext></mrow></msub></math></span> around the equator. We also discuss the impact of a vertically-dependent particle size profile, as previous studies have shown the presence of very small water ice particles at the top of the clouds. From this analysis, we provide recommendations for the improvement of water ice cloud parameterization in radiative transfer algorithms in nadir atmospheric retrievals.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":null,"pages":null},"PeriodicalIF":2.5,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142427336","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":"A conceptual model for the formation of ramparts on Martian impact crater ejecta","authors":"","doi":"10.1016/j.icarus.2024.116336","DOIUrl":"10.1016/j.icarus.2024.116336","url":null,"abstract":"<div><div>Mars Orbiter Laser Altimeter (MOLA) elevation measurements for 23 different impact craters and 12 different long runout landslides show rampart ridges on Martian fluidized ejecta flows are higher relief than those on Martian landslides. We propose a conceptual model to explain this height difference that is based on the effects of the impact and ejecta emplacement process on the development of ejecta ramparts. Our model explains the relatively high relief of the distal ramparts as well as the particle size distribution that is inferred from thermal inertia measurements. In this model, impact events produce ejecta curtains that advance radially at increasingly higher velocity outward excavating and roughening the surface as they impact. This produces an inertia-driven, ground-hugging ejecta flow composed of primary and secondary ejecta. This flow moves rapidly across the surface following closely behind the impacting ejecta curtain. The ejecta curtain continuously adds impact-generated debris to the flow front that includes large particles, some of which are overridden by the flow, but some accumulate at the flow front. These particles are pushed forward at the flow front as a high-friction “dam” with the accumulating material growing into a relatively high rampart as the ejecta curtain adds more large particles to it. In addition, the impact-roughened surface cause substantial vibrations and shear in the flows moving behind the ejecta curtain. This roughness results in kinetic sieving in the flows that brings large particles to the surface and transports them to the flow front where some are also overridden or accumulate to add the ones already at flow front. We propose that these processes combine to produce the observed high ejecta ramparts. The relatively high velocity of the ejecta flows pushes the load of coarse-grained debris to the top of even high developing ramparts. When the flow halts, it drains back from the accumulated coarse debris at the flow front, leaving a high rampart dominantly composed of large particles.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":null,"pages":null},"PeriodicalIF":2.5,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142427337","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 Palomar twilight survey of ‘Ayló’chaxnim, Atiras, and comets","authors":"","doi":"10.1016/j.icarus.2024.116333","DOIUrl":"10.1016/j.icarus.2024.116333","url":null,"abstract":"<div><div>Near-sun sky twilight observations allow for the detection of asteroids interior to the orbit of Venus (Aylos) and the Earth (Atiras) and comets. We present the results of observations with the Palomar 48-inch telescope (P48)/Zwicky Transient Facility (ZTF) camera in 30 s r-band exposures taken during evening astronomical twilight from 2019 Sep 20 to 2022 March 7 and during morning astronomical twilight sky from 2019 Sep 21 to 2022 Sep 29. More than 21,940 exposures were taken in evening astronomical twilight within 31° and 66° from the Sun with an r-band limiting magnitude between 18.0 and 20.8 (5th to 95th percentile), and more than 24,370 exposures were taken in morning astronomical twilight within 31° and 65° from the Sun with an r-band limiting magnitude between 18.2 and 20.9 (5th to 95th percentile). The morning and evening twilight pointings show a slight seasonal dependence in limiting magnitude and ability to point closer towards the Sun, with limiting magnitude improving by 0.5 magnitudes during the summer months and Sun-centric angular distances as small as 31–32° during the spring and fall months. In total, the one Aylo, (594913) ‘Ayló’chaxnim, and 4 Atiras, 2020 OV<span><math><msub><mrow></mrow><mrow><mn>1</mn></mrow></msub></math></span>, 2021 BS<span><math><msub><mrow></mrow><mrow><mn>1</mn></mrow></msub></math></span>, 2021 PB<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>, and 2021 VR<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span>, were discovered in evening and morning twilight observations. Additional twilight survey discoveries also include 6 long period comets: C/2020 T2, C/2020 V2, C/2021 D2, C/2021 E3, C/2022 E3 and C/2022 P3, and two short period comets: P/2021 N1 and P/2022 P2 using deep learning comet detection pipelines. The P48/ZTF twilight survey also recovered 11 known Atiras, one Aylo, three short period comes, two long period comets, one interstellar object, 45,536 Main Belt asteroids, and 265 near-Earth objects. Additionally, observations from the GROWTH network of telescopes were used to recover the Aylo, Atira, and comet discoveries made during the ZTF twilight survey. Lastly, we discuss the future twilight surveys for the discovery of Aylos such as with the Vera Rubin Observatory which will have a twilight survey starting in its first year of operations and will cover the sky as within 45 degrees from the Sun. Twilight surveys such as those by ZTF and future surveys will provide opportunities for the discovery of asteroids inside the orbits of the terrestrial planets that would otherwise be unavailable in conventional sky survey observations.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":null,"pages":null},"PeriodicalIF":2.5,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142356765","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":"Identification and analysis of interior and exterior resonant orbits in the Sun–Venus system","authors":"","doi":"10.1016/j.icarus.2024.116328","DOIUrl":"10.1016/j.icarus.2024.116328","url":null,"abstract":"<div><div>With Venus being Earth’s nearest neighbor and it being similar in size to Earth, it is the ideal candidate for certain mission types. These missions range from scientific, such as helio-physics and space weather monitoring, to defense focused, such as monitoring Earth’s orbital path for meteoroid threats. Limited research has been done on the periodic orbits in the Sun–Venus system. The first step to understanding which orbits could be useful for such a mission is to identify families of resonant periodic orbits in the Sun–Venus system and conduct a stability analysis on these orbits. This research work identifies 90 periodic, resonant orbits in the Sun–Venus system and their associated families of orbits. The orbits are found within the Circular Restricted 3 Body Problem (CR3BP) dynamical model with solar radiation pressure included as a perturbation. The periodic orbits are found using Poincaré maps, and the families are generated using a continuation method that steps through different Jacobi constants. The stability for each orbit in the family is calculated and the structure of the eigenvalues for each is assessed to determine when the family has crossed a bifurcation point. This research work seeks to generate a catalog of resonant orbits within the Sun–Venus system while providing stability and bifurcation information for each resonant orbit family.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":null,"pages":null},"PeriodicalIF":2.5,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142427335","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":"Alkali metal depletion in the deep Jovian atmosphere: The role of anions","authors":"","doi":"10.1016/j.icarus.2024.116334","DOIUrl":"10.1016/j.icarus.2024.116334","url":null,"abstract":"<div><div>The Juno Microwave Radiometer has allowed observation of Jupiter's atmosphere down to previously inaccessible depths, although the complexity of the atmospheric dynamics has complicated analysis. The longest-wavelength channel (600 MHz) is sensitive to pressure levels of hundreds of bars, and has observed opacity sources other than the known gaseous and cloud components, likely caused by thermally ionized free electrons from alkali metal vapor. We extend previous analysis of limb darkening at these wavelengths, using radiative transfer and thermal equilibrium modeling, by considering the effect of anions in the deep Jovian atmosphere, which act as a sink for free electrons and will thus decrease opacity for a given alkali metal abundance. We show that MWR observations are consistent with a sodium and potassium abundance on the order of 0.1× solar around the 1-kilobar level, higher than previously estimated but still substantially depleted compared to other heavy elements, a value that would be within the range of observed alkali metal abundances on giant exoplanets; alternatively, MWR observations may be consistent with 3× solar sodium abundance, but only if potassium is even more strongly depleted. Such depletion may be the result of either chemical processes yet deeper in the atmosphere, such as in the silicate clouds, or of a long-lived stable layer shallower than the alkali salt clouds.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":null,"pages":null},"PeriodicalIF":2.5,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142323119","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":"Radiative signatures of circumplanetary disks and envelopes during the late stages of giant planet formation","authors":"","doi":"10.1016/j.icarus.2024.116327","DOIUrl":"10.1016/j.icarus.2024.116327","url":null,"abstract":"<div><div>During the late stages of giant planet formation, protoplanets are surrounded by a circumplanetary disk and an infalling envelope of gas and dust. For systems with sufficient cooling, material entering the sphere of influence of the planet falls inward and approaches ballistic conditions. Due to conservation of angular momentum, most of the incoming material falls onto the disk rather than directly onto the planet. This paper determines the spectral energy distributions of forming planets in this stage of evolution. Generalizing previous work, we consider a range of possible geometries for the boundary conditions of the infall and determine the two-dimensional structure of the envelope, as well as the surface density of the disk. After specifying the luminosity sources for the planet and disk, we calculate the corresponding radiative signatures for the system, including the emergent spectral energy distributions and emission maps. These results show how the observational appearance of forming planets depend on the input parameters, including the instantaneous mass, mass accretion rate, semimajor axis of the orbit, and the planetary magnetic field strength (which sets the inner boundary condition for the disk). We also consider different choices for the form of the opacity law and attenuation due to the background circumstellar disk. Although observing forming planets will be challenging, these results show how the observational signatures depend on the underlying properties of the planet/disk/envelope system.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":null,"pages":null},"PeriodicalIF":2.5,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142326800","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":"Updated ultraviolet fluorescence efficiencies of CS: Evidence for model discrepancies in the enhancement of NUV-derived CS abundances in comets","authors":"","doi":"10.1016/j.icarus.2024.116326","DOIUrl":"10.1016/j.icarus.2024.116326","url":null,"abstract":"<div><div>Observations of carbon monosulfide (CS) have a long history serving as a remote proxy for atomic sulfur, and more broadly, one of the sulfur reservoirs in cometary bodies. Recently, systematic discrepancies between NUV- and radio-derived CS abundances have been found to exceed a factor of 2–5, with NUV-derived abundances appearing enhanced for a wide array of comets. Interpretation of cometary CS emission in the ultraviolet has relied on a murky and ill-documented lineage of calculations whose accuracy can be difficult to assess. We report new fluorescence efficiencies of the CS radical, utilizing a rovibrational structure with vibrational states up to <span><math><mrow><mi>v</mi><mo>=</mo><mn>8</mn></mrow></math></span> and rotational states up to <span><math><mrow><mi>N</mi><mo>=</mo><mn>100</mn></mrow></math></span>. The models utilize a new set of band transition rates derived from laboratory electron impact experiments. Benchmark comparisons to IUE observations of C/1979 Y1 (Bradfield) show favorable agreement with the fluorescence models. The present results affirm the accuracy of the historical record of CS abundances derived via ultraviolet CS emission in comets with IUE and HST, but do not explain the consistent enhancement of NUV-derived CS abundances relative to the radio measurements during the same apparitions. Alternative explanations of the factor of 2–5 discrepancy between NUV- and radio-derived CS abundances are discussed, as well as possible connections to sulfur reservoirs in protoplanetary disks. The model code and computed fluorescence efficiencies are made publicly available on the Zenodo service.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":null,"pages":null},"PeriodicalIF":2.5,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142326801","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":"Unlocking planetesimal magnetic field histories: A refined, versatile model for thermal evolution and dynamo generation","authors":"","doi":"10.1016/j.icarus.2024.116323","DOIUrl":"10.1016/j.icarus.2024.116323","url":null,"abstract":"<div><div>The thermal and magnetic histories of planetesimals provide unique insights into the formation and evolution of Earth’s building blocks. These histories can be gleaned from meteorites by using numerical models to translate measured properties into planetesimal behaviour. In this paper, we present a new 1D planetesimal thermal evolution and dynamo generation model. This magnetic field generation model is the first of a differentiated, mantled planetesimal that includes both mantle convection and sub-eutectic core solidification. We have improved fundamental aspects of mantle heat transport by including a more detailed viscosity model and stagnant lid convection parametrisations consistent with internal heating. We have also added radiogenic heating from ⁶⁰Fe in the metallic Fe-FeS core. Additionally, we implement a combined thermal and compositional buoyancy flux, as well as the latest magnetic field scaling laws to predict magnetic field strengths during the planetesimal’s thermal evolution until core solidification is complete. We illustrate the consequences of our model changes with an example run for a 500<!--> <!-->km radius planetesimal. These effects include more rapid erosion of core thermal stratification and longer duration of mantle convection compared to previous studies. The additional buoyancy from core solidification has a marginal effect on dynamo strength, but for some initial core sulfur contents it can prevent cessation of the dynamo when mantle convection ends. Our model can be used to investigate the effects of individual parameters on dynamo generation and constrain properties of specific meteorite parent bodies. Combined, these updates mean this model can predict the most reliable and complete magnetic field history for a planetesimal to date, so is a valuable tool for deciphering planetesimal behaviour from meteorite properties.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":null,"pages":null},"PeriodicalIF":2.5,"publicationDate":"2024-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142356766","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":"Low temperature phase transitions in the visible and near-infrared (VNIR) reflectance spectra of (NH4)2HPO4 and (NH4)HSO4 salts","authors":"","doi":"10.1016/j.icarus.2024.116321","DOIUrl":"10.1016/j.icarus.2024.116321","url":null,"abstract":"<div><div>The detection of ammonium bearing crystalline solids in salt-water systems on icy bodies and solar system bodies could provide information about the ascent of these salts from a deep reservoir within the hydrosphere. Due to their chemical-physical properties, NH₄⁺ compounds play a key role both in the internal dynamics of celestial bodies and in the potential habitability of ocean worlds. In this work we analysed the reflectance spectra of two synthetic NH₄⁺ salts: ammonium hydrogen phosphate (NH₄)₂HPO₄ and ammonium hydrogen sulphate (NH₄)HSO₄ in the 1–4.2 μm spectral range at low temperature, between 110 and 290 K. For (NH₄)₂HPO₄ we also examined the effect of three different grain sizes (150–125 μm; 125–80 μm; 80–32 μm). The collected reflectance spectra show absorption features related to NH₄⁺ group overtone and combination modes in the 1–2.5 μm range. In particular, the bands located at ∼1.09 μm (3ν₃), ∼1.30 μm (2ν₃ + ν₄), ∼1.58 μm (2ν₃), ∼2.02 μm (ν₂ + v₃) and ∼ 2.2 μm (<em>v</em>₃ + v₄) could be useful to discriminate these salts. The low temperature spectra, compared to those at ambient temperature, reveal finer structures, displaying sharper and narrower absorption bands. The selected NH₄⁺-bearing salts are subjected to reversible low temperature phase transitions, which are revealed in the spectra by a progressive growth and shift of the bands toward shorter wavelengths with a drastic change of their depth. We performed laboratory measurements of ammonium (NH₄⁺) compounds to address the limited data available expanding the existing database. The collected cryogenic spectra can be directly compared with remote sensing data from planetary missions of the upcoming decade such as NASA's Europa Clipper, and ESA's JUICE and the newly launched James Webb Space Telescope expanding the existing database of ammonium compounds at cryogenic temperature.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":null,"pages":null},"PeriodicalIF":2.5,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142326803","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}