Francis Nimmo, Jonathan Lunine, Kevin Zahnle and Lars Stixrude
The bulk of Uranus consists of a rock–ice core, but the relative proportions of rock and ice are unknown. Radioactive decay of potassium in the silicates produces 40Ar. If transport of argon from the core to the gaseous envelope is efficient, a measurement of 40Ar in the envelope will provide a direct constraint on the rock mass present (assuming a chondritic rock composition). The expected 40Ar concentrations in this case would be readily detectable by a mass spectrometer carried by a future atmospheric probe. For a given envelope concentration there is a trade-off between the rock mass present and the transport efficiency; this degeneracy could be overcome by making independent determinations of the rock mass (e.g., by gravity and seismology). Primordial 40Ar is a potential confounding factor, especially if Ar/H2 is significantly enhanced above solar or if degassing of radiogenic 40Ar were inefficient. Unfortunately, the primordial 40Ar/36Ar ratio is very uncertain; better constraints on this ratio through measurement or theory would be very helpful. Pollution of the envelope by silicates is another confounding factor but can be overcome by a measurement of the alkali metals in the envelope.
{"title":"Probing the Rock Mass Fraction and Transport Efficiency inside Uranus Using 40Ar Measurements","authors":"Francis Nimmo, Jonathan Lunine, Kevin Zahnle and Lars Stixrude","doi":"10.3847/psj/ad3b93","DOIUrl":"https://doi.org/10.3847/psj/ad3b93","url":null,"abstract":"The bulk of Uranus consists of a rock–ice core, but the relative proportions of rock and ice are unknown. Radioactive decay of potassium in the silicates produces 40Ar. If transport of argon from the core to the gaseous envelope is efficient, a measurement of 40Ar in the envelope will provide a direct constraint on the rock mass present (assuming a chondritic rock composition). The expected 40Ar concentrations in this case would be readily detectable by a mass spectrometer carried by a future atmospheric probe. For a given envelope concentration there is a trade-off between the rock mass present and the transport efficiency; this degeneracy could be overcome by making independent determinations of the rock mass (e.g., by gravity and seismology). Primordial 40Ar is a potential confounding factor, especially if Ar/H2 is significantly enhanced above solar or if degassing of radiogenic 40Ar were inefficient. Unfortunately, the primordial 40Ar/36Ar ratio is very uncertain; better constraints on this ratio through measurement or theory would be very helpful. Pollution of the envelope by silicates is another confounding factor but can be overcome by a measurement of the alkali metals in the envelope.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":"44 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140886779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Oriel A. Humes, Audrey C. Martin, Cristina A. Thomas and Joshua P. Emery
Primitive asteroids with low albedos and red slopes in the visible and near-infrared (VNIR) are found in both the main belt and the Jupiter Trojan clouds. In order to determine whether the VNIR spectral similarities of primitive main-belt asteroids and Jupiter Trojans are reflective of a true compositional similarity, we compare the mid-infrared silicate emission features of main-belt and Jupiter Trojan asteroids. Using archival data from the Spitzer Space Telescope’s Infrared Spectrograph and observations from the Stratospheric Observatory for Infrared Astronomy’s FORCAST instrument, we analyze the 5–40 μm spectra of 13 primitive main-belt asteroids and compare them to those of Jupiter Trojans in the literature. We find that while many primitive asteroids in the main belt resemble their Trojan counterparts with strong spectral signatures of olivine-rich high-porosity silicate regoliths, we identify (368) Haidea as a spectrally distinctive asteroid that lacks strong evidence of olivine in its mid-IR spectrum. Differences in silicate compositions among D-type asteroids imply a diversity of origins for primitive asteroids.
{"title":"Comparative Mid-infrared Spectroscopy of Dark, Primitive Asteroids: Does Shared Taxonomic Class Indicate Shared Silicate Composition?","authors":"Oriel A. Humes, Audrey C. Martin, Cristina A. Thomas and Joshua P. Emery","doi":"10.3847/psj/ad3a69","DOIUrl":"https://doi.org/10.3847/psj/ad3a69","url":null,"abstract":"Primitive asteroids with low albedos and red slopes in the visible and near-infrared (VNIR) are found in both the main belt and the Jupiter Trojan clouds. In order to determine whether the VNIR spectral similarities of primitive main-belt asteroids and Jupiter Trojans are reflective of a true compositional similarity, we compare the mid-infrared silicate emission features of main-belt and Jupiter Trojan asteroids. Using archival data from the Spitzer Space Telescope’s Infrared Spectrograph and observations from the Stratospheric Observatory for Infrared Astronomy’s FORCAST instrument, we analyze the 5–40 μm spectra of 13 primitive main-belt asteroids and compare them to those of Jupiter Trojans in the literature. We find that while many primitive asteroids in the main belt resemble their Trojan counterparts with strong spectral signatures of olivine-rich high-porosity silicate regoliths, we identify (368) Haidea as a spectrally distinctive asteroid that lacks strong evidence of olivine in its mid-IR spectrum. Differences in silicate compositions among D-type asteroids imply a diversity of origins for primitive asteroids.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":"43 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140886867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We examine high-spatial-resolution Galileo/Near-Infrared Mapping Spectrometer observations of the young (∼1 My–∼20 My) impact features, Pwyll and Manannán craters, on Europa’s trailing hemisphere in an effort to constrain irradiation timescales. We characterize their composition using a linear spectral modeling analysis, and find that both craters and their ejecta are depleted in hydrated sulfuric acid relative to nearby older terrain. This suggests that the radiolytic sulfur cycle has not yet had enough time to build up an equilibrium concentration of H2SO4, and places a strong lower limit of the age of the craters on the equilibrium timescale of the radiolytic sulfur cycle on Europa's trailing hemisphere. Additionally, we find that the dark and red material seen in the craters and proximal ejecta of Pwyll and Manannán show the spectroscopic signature of hydrated, presumably endogenic salts. This suggests that the irradiation-induced darkening and reddening of endogenic salts thought to occur on Europa’s trailing hemisphere has already happened at Pwyll and Manannán, thereby placing an upper limit on the timescale by which salts are irradiation reddened.
{"title":"Pwyll and Manannán Craters as a Laboratory for Constraining Irradiation Timescales on Europa","authors":"M. Ryleigh Davis and Michael E. Brown","doi":"10.3847/psj/ad3944","DOIUrl":"https://doi.org/10.3847/psj/ad3944","url":null,"abstract":"We examine high-spatial-resolution Galileo/Near-Infrared Mapping Spectrometer observations of the young (∼1 My–∼20 My) impact features, Pwyll and Manannán craters, on Europa’s trailing hemisphere in an effort to constrain irradiation timescales. We characterize their composition using a linear spectral modeling analysis, and find that both craters and their ejecta are depleted in hydrated sulfuric acid relative to nearby older terrain. This suggests that the radiolytic sulfur cycle has not yet had enough time to build up an equilibrium concentration of H2SO4, and places a strong lower limit of the age of the craters on the equilibrium timescale of the radiolytic sulfur cycle on Europa's trailing hemisphere. Additionally, we find that the dark and red material seen in the craters and proximal ejecta of Pwyll and Manannán show the spectroscopic signature of hydrated, presumably endogenic salts. This suggests that the irradiation-induced darkening and reddening of endogenic salts thought to occur on Europa’s trailing hemisphere has already happened at Pwyll and Manannán, thereby placing an upper limit on the timescale by which salts are irradiation reddened.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":"60 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140834223","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
William M. Farrell, P. Prem, D. M. Hurley, O. J. Tucker, R. M. Killen
This work assesses the potential of midsized and large human landing systems to deliver water from their exhaust plumes to cold traps within lunar polar craters. It has been estimated that a total of between 2 and 60 T of surficial water was sensed by the Lunar Reconnaissance Orbiter Lyman Alpha Mapping Project on the floors of the larger permanently shadowed south polar craters. This intrinsic surficial water sensed in the far-ultraviolet is thought to be in the form of a 0.3%–2% icy regolith in the top few hundred nanometers of the surface. We find that the six past Apollo Lunar Module midlatitude landings could contribute no more than 0.36 T of water mass to this existing, intrinsic surficial water in permanently shadowed regions (PSRs). However, we find that the Starship landing plume has the potential, in some cases, to deliver over 10 T of water to the PSRs, which is a substantial fraction (possibly >20%) of the existing intrinsic surficial water mass. This anthropogenic contribution could possibly overlay and mix with the naturally occurring icy regolith at the uppermost surface. A possible consequence is that the origin of the intrinsic surficial icy regolith, which is still undetermined, could be lost as it mixes with the extrinsic anthropogenic contribution. We suggest that existing and future orbital and landed assets be used to examine the effect of polar landers on the cold traps within PSRs.
这项工作评估了中型和大型人类着陆系统从其排出的羽流中向月球极地环形山内的冷阱输送水的潜力。据估计，月球勘测轨道器莱曼阿尔法测绘项目在较大的永久阴影南极陨石坑底部感应到的地表水总量在 2 到 60 T 之间。这种在远紫外线中感应到的固有地表水被认为是以 0.3%-2% 的冰质碎屑形式存在于地表顶部几百纳米的区域。我们发现，过去六次阿波罗登月舱中纬度着陆对永久阴影区（PSRs）现有的固有表层水的贡献不会超过 0.36 T。然而，我们发现星船着陆羽流在某些情况下有可能向永久阴影区提供超过 10 吨的水，这相当于现有固有表层水的很大一部分（可能是 20%）。这种人为的水可能会与最上层地表自然形成的冰壳岩相叠加和混合。一个可能的后果是，仍未确定的固有表层冰质碎屑岩的来源可能会因为与外来的人为成分混合而消失。我们建议利用现有和未来的轨道和着陆资产来研究极地着陆器对 PSR 内冷阱的影响。
{"title":"Possible Anthropogenic Contributions to the LAMP-observed Surficial Icy Regolith within Lunar Polar Craters: A Comparison of Apollo and Starship Landings","authors":"William M. Farrell, P. Prem, D. M. Hurley, O. J. Tucker, R. M. Killen","doi":"10.3847/psj/ad37f5","DOIUrl":"https://doi.org/10.3847/psj/ad37f5","url":null,"abstract":"This work assesses the potential of midsized and large human landing systems to deliver water from their exhaust plumes to cold traps within lunar polar craters. It has been estimated that a total of between 2 and 60 T of surficial water was sensed by the Lunar Reconnaissance Orbiter Lyman Alpha Mapping Project on the floors of the larger permanently shadowed south polar craters. This intrinsic surficial water sensed in the far-ultraviolet is thought to be in the form of a 0.3%–2% icy regolith in the top few hundred nanometers of the surface. We find that the six past Apollo Lunar Module midlatitude landings could contribute no more than 0.36 T of water mass to this existing, intrinsic surficial water in permanently shadowed regions (PSRs). However, we find that the Starship landing plume has the potential, in some cases, to deliver over 10 T of water to the PSRs, which is a substantial fraction (possibly >20%) of the existing intrinsic surficial water mass. This anthropogenic contribution could possibly overlay and mix with the naturally occurring icy regolith at the uppermost surface. A possible consequence is that the origin of the intrinsic surficial icy regolith, which is still undetermined, could be lost as it mixes with the extrinsic anthropogenic contribution. We suggest that existing and future orbital and landed assets be used to examine the effect of polar landers on the cold traps within PSRs.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140834423","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Julie A. Rathbun, Madeline Pettine, Moses Milazzo and Christian Tate
Recent ground-based Infrared Telescope Facility observations showed that a hot spot observed at the location of the surface feature Acala Fluctus was volcanically active for ∼18 months in 2019–2020 and exhibited two outbursts with a temperature of ∼1200 K. A high-temperature hot spot at Acala was also observed by Galileo SSI in the late 1990s over multiple flybys. Low-temperature hot spots in this area were detected in 2000 by the Galileo Photopolarimeter Radiometer and in 1979 by Voyager IRIS. However, neither the Galileo NIMS instrument nor any instrument on the New Horizons spacecraft, which flew by Io in 2007, saw any evidence of an Acala hot spot. It is also possible that earlier ground-based disk-integrated observations of hot spots are due to Acala, even though they were originally attributed to other volcanoes, such as Loki. These include outbursts in 1978 and 1990 and a persistent low-temperature source in the 1980 and 1990s. From these observations, we propose that Acala consists of highly variable high-temperature fire fountains and a large area of low-temperature, older flows. Due to these recent outbursts, we expect that any images of Acala obtained by JunoCam will show surface changes from Galileo images.
{"title":"The History of Eruptions at Acala Fluctus, Io: Source of Multiple Outbursts","authors":"Julie A. Rathbun, Madeline Pettine, Moses Milazzo and Christian Tate","doi":"10.3847/psj/ad38be","DOIUrl":"https://doi.org/10.3847/psj/ad38be","url":null,"abstract":"Recent ground-based Infrared Telescope Facility observations showed that a hot spot observed at the location of the surface feature Acala Fluctus was volcanically active for ∼18 months in 2019–2020 and exhibited two outbursts with a temperature of ∼1200 K. A high-temperature hot spot at Acala was also observed by Galileo SSI in the late 1990s over multiple flybys. Low-temperature hot spots in this area were detected in 2000 by the Galileo Photopolarimeter Radiometer and in 1979 by Voyager IRIS. However, neither the Galileo NIMS instrument nor any instrument on the New Horizons spacecraft, which flew by Io in 2007, saw any evidence of an Acala hot spot. It is also possible that earlier ground-based disk-integrated observations of hot spots are due to Acala, even though they were originally attributed to other volcanoes, such as Loki. These include outbursts in 1978 and 1990 and a persistent low-temperature source in the 1980 and 1990s. From these observations, we propose that Acala consists of highly variable high-temperature fire fountains and a large area of low-temperature, older flows. Due to these recent outbursts, we expect that any images of Acala obtained by JunoCam will show surface changes from Galileo images.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":"54 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140834222","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Bastian Knieling, Karsten Schindler, Amanda A. Sickafoose, Michael J. Person, Stephen E. Levine and Alfred Krabbe
Gaussian process (GP) regression is a nonparametric Bayesian approach that has been used successfully in various astronomical domains, especially in time-domain astronomy. The most common applications are the smoothing of data for interpolation and the detection of periodicities. The ability to create unbiased data-driven models without a predefined physical model can be a major advantage over conventional regression methods. Prior knowledge can be included by setting boundary conditions or constraining hyperparameter values, while unknown hyperparameters are optimized during the conditioning of the model. We have adapted and transformed previous approaches of GP regression and introduce three new applications for this regression method, especially in the context of stellar occultations: the modeling of occultation light curves, the correction of public JPL ephemerides of minor planets based on publicly available image data of the Zwicky Transient Facility, and the detection of natural satellites. We used data from observations of stellar occultations to validate the models and achieved promising results in all cases, and thus we confirmed the flexibility of GP regression models. Considering various existing use cases in addition to our novel applications, GP regression can be used to model diverse data sets addressing a wide range of problems. The accuracy of the model depends on the input data and on the set boundary conditions. Generally, high-quality data allow the usage of loose boundary conditions, while low-quality data require more restrictive boundary conditions to avoid overfitting.
高斯过程（GP）回归是一种非参数贝叶斯方法，已成功应用于各种天文领域，尤其是时域天文学。最常见的应用是平滑数据以进行插值和检测周期性。与传统回归方法相比，该方法的一大优势是能够在没有预定义物理模型的情况下创建无偏的数据驱动模型。通过设置边界条件或限制超参数值，可以将先验知识纳入其中，而未知超参数则在模型调节过程中进行优化。我们对以前的 GP 回归方法进行了调整和改造，并为这种回归方法引入了三个新的应用领域，尤其是在恒星掩星方面：掩星光曲线建模、根据公开的兹威基瞬变设施图像数据修正 JPL 小行星星历表，以及探测天然卫星。我们使用恒星掩星观测数据来验证模型，在所有情况下都取得了令人满意的结果，从而证实了 GP 回归模型的灵活性。考虑到现有的各种应用案例以及我们的新应用，GP 回归可用于对各种数据集进行建模，以解决广泛的问题。模型的准确性取决于输入数据和设定的边界条件。一般来说，高质量数据允许使用宽松的边界条件，而低质量数据则需要更严格的边界条件以避免过拟合。
{"title":"Stellar Occultations in the Era of Data Mining and Modern Regression Models: Using Gaussian Processes to Analyze Light Curves and Improve Predictions","authors":"Bastian Knieling, Karsten Schindler, Amanda A. Sickafoose, Michael J. Person, Stephen E. Levine and Alfred Krabbe","doi":"10.3847/psj/ad3819","DOIUrl":"https://doi.org/10.3847/psj/ad3819","url":null,"abstract":"Gaussian process (GP) regression is a nonparametric Bayesian approach that has been used successfully in various astronomical domains, especially in time-domain astronomy. The most common applications are the smoothing of data for interpolation and the detection of periodicities. The ability to create unbiased data-driven models without a predefined physical model can be a major advantage over conventional regression methods. Prior knowledge can be included by setting boundary conditions or constraining hyperparameter values, while unknown hyperparameters are optimized during the conditioning of the model. We have adapted and transformed previous approaches of GP regression and introduce three new applications for this regression method, especially in the context of stellar occultations: the modeling of occultation light curves, the correction of public JPL ephemerides of minor planets based on publicly available image data of the Zwicky Transient Facility, and the detection of natural satellites. We used data from observations of stellar occultations to validate the models and achieved promising results in all cases, and thus we confirmed the flexibility of GP regression models. Considering various existing use cases in addition to our novel applications, GP regression can be used to model diverse data sets addressing a wide range of problems. The accuracy of the model depends on the input data and on the set boundary conditions. Generally, high-quality data allow the usage of loose boundary conditions, while low-quality data require more restrictive boundary conditions to avoid overfitting.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":"66 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140800747","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Huazhi Ge, 华志 葛, Cheng Li, Xi Zhang and Chris Moeckel
Storms operated by moist convection and the condensation of CH4 or H2S have been observed on Uranus and Neptune. However, the mechanism of cloud formation, thermal structure, and mixing efficiency of ice giant weather layers remains unclear. In this paper, we show that moist convection is limited by heat transport on giant planets, especially on ice giants where planetary heat flux is weak. Latent heat associated with condensation and evaporation can efficiently bring heat across the weather layer through precipitations. This effect was usually neglected in previous studies without a complete hydrological cycle. We first derive analytical theories and show that the upper limit of cloud density is determined by the planetary heat flux and microphysics of clouds but is independent of the atmospheric composition. The eddy diffusivity of moisture depends on the planetary heat fluxes, atmospheric composition, and surface gravity but is not directly related to cloud microphysics. We then conduct convection- and cloud-resolving simulations with SNAP to validate our analytical theory. The simulated cloud density and eddy diffusivity are smaller than the results acquired from the equilibrium cloud condensation model and mixing length theory by several orders of magnitude but consistent with our analytical solutions. Meanwhile, the mass-loading effect of CH4 and H2S leads to superadiabatic and stable weather layers. Our simulations produced three cloud layers that are qualitatively similar to recent observations. This study has important implications for cloud formation and eddy mixing in giant planet atmospheres in general and observations for future space missions and ground-based telescopes.
{"title":"Heat-flux-limited Cloud Activity and Vertical Mixing in Giant Planet Atmospheres with an Application to Uranus and Neptune","authors":"Huazhi Ge, 华志 葛, Cheng Li, Xi Zhang and Chris Moeckel","doi":"10.3847/psj/ad0ed3","DOIUrl":"https://doi.org/10.3847/psj/ad0ed3","url":null,"abstract":"Storms operated by moist convection and the condensation of CH4 or H2S have been observed on Uranus and Neptune. However, the mechanism of cloud formation, thermal structure, and mixing efficiency of ice giant weather layers remains unclear. In this paper, we show that moist convection is limited by heat transport on giant planets, especially on ice giants where planetary heat flux is weak. Latent heat associated with condensation and evaporation can efficiently bring heat across the weather layer through precipitations. This effect was usually neglected in previous studies without a complete hydrological cycle. We first derive analytical theories and show that the upper limit of cloud density is determined by the planetary heat flux and microphysics of clouds but is independent of the atmospheric composition. The eddy diffusivity of moisture depends on the planetary heat fluxes, atmospheric composition, and surface gravity but is not directly related to cloud microphysics. We then conduct convection- and cloud-resolving simulations with SNAP to validate our analytical theory. The simulated cloud density and eddy diffusivity are smaller than the results acquired from the equilibrium cloud condensation model and mixing length theory by several orders of magnitude but consistent with our analytical solutions. Meanwhile, the mass-loading effect of CH4 and H2S leads to superadiabatic and stable weather layers. Our simulations produced three cloud layers that are qualitatively similar to recent observations. This study has important implications for cloud formation and eddy mixing in giant planet atmospheres in general and observations for future space missions and ground-based telescopes.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":"27 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140800668","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Francois-Xavier Schmider, Patrick Gaulme, Raúl Morales-Juberías, Jason Jackiewicz, Ivan Gonçalves, Tristan Guillot, Amy A. Simon, Michael H. Wong, Thomas Underwood, David Voelz, Cristo Sanchez, Riley DeColibus, Sarah A. Kovac, Sean Sellers, Doug Gilliam, Patrick Boumier, Thierry Appourchaux, Julien Dejonghe, Jean Pierre Rivet, Steve Markham, Saburo Howard, Lyu Abe, Djamel Mekarnia, Masahiro Ikoma, Hidekazu Hanayama, Bun’ei Sato, Masanobu Kunitomo, Hideyuki Izumiura
We present three-dimensional (3D) maps of Jupiter’s atmospheric circulation at cloud-top level from Doppler-imaging data obtained in the visible domain with JIVE, the second node of the JOVIAL network, which is mounted on the Dunn Solar Telescope at Sunspot, New Mexico. We report on 12 nights of observations between 2018 May 4 and May 30, representing a total of about 80 hr. First, the average zonal wind profile derived from our data is compatible with that derived from cloud-tracking measurements performed on Hubble Space Telescope images obtained in 2018 April from the Outer Planet Atmospheres Legacy program. Second, we present the first ever 2D maps of Jupiter’s atmospheric circulation from Doppler measurements. The zonal velocity map highlights well-known atmospheric features, such as the equatorial hot spots and the Great Red Spot (GRS). In addition to zonal winds, we derive meridional and vertical velocity fields from the Doppler data. The motions attributed to vertical flows are mainly located at the boundary between the equatorial belts and tropical zones, which could indicate active motion in theses regions. Qualitatively, these results compare well to recent Juno data that have unveiled the 3D structure of Jupiter’s wind field. To the contrary, the motions attributed to meridional circulation are very different from what is obtained by cloud tracking, except at the GRS. Because of limitations with data resolution and processing techniques, we acknowledge that our measurements of the vertical or meridional flows of Jupiter are still to be confirmed.
{"title":"Three-dimensional Atmospheric Dynamics of Jupiter from Ground-based Doppler Imaging Spectroscopy in the Visible","authors":"Francois-Xavier Schmider, Patrick Gaulme, Raúl Morales-Juberías, Jason Jackiewicz, Ivan Gonçalves, Tristan Guillot, Amy A. Simon, Michael H. Wong, Thomas Underwood, David Voelz, Cristo Sanchez, Riley DeColibus, Sarah A. Kovac, Sean Sellers, Doug Gilliam, Patrick Boumier, Thierry Appourchaux, Julien Dejonghe, Jean Pierre Rivet, Steve Markham, Saburo Howard, Lyu Abe, Djamel Mekarnia, Masahiro Ikoma, Hidekazu Hanayama, Bun’ei Sato, Masanobu Kunitomo, Hideyuki Izumiura","doi":"10.3847/psj/ad3066","DOIUrl":"https://doi.org/10.3847/psj/ad3066","url":null,"abstract":"We present three-dimensional (3D) maps of Jupiter’s atmospheric circulation at cloud-top level from Doppler-imaging data obtained in the visible domain with JIVE, the second node of the JOVIAL network, which is mounted on the Dunn Solar Telescope at Sunspot, New Mexico. We report on 12 nights of observations between 2018 May 4 and May 30, representing a total of about 80 hr. First, the average zonal wind profile derived from our data is compatible with that derived from cloud-tracking measurements performed on Hubble Space Telescope images obtained in 2018 April from the Outer Planet Atmospheres Legacy program. Second, we present the first ever 2D maps of Jupiter’s atmospheric circulation from Doppler measurements. The zonal velocity map highlights well-known atmospheric features, such as the equatorial hot spots and the Great Red Spot (GRS). In addition to zonal winds, we derive meridional and vertical velocity fields from the Doppler data. The motions attributed to vertical flows are mainly located at the boundary between the equatorial belts and tropical zones, which could indicate active motion in theses regions. Qualitatively, these results compare well to recent Juno data that have unveiled the 3D structure of Jupiter’s wind field. To the contrary, the motions attributed to meridional circulation are very different from what is obtained by cloud tracking, except at the GRS. Because of limitations with data resolution and processing techniques, we acknowledge that our measurements of the vertical or meridional flows of Jupiter are still to be confirmed.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":"126 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140610029","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Norbert Schorghofer, Robert Gaskell, Erwan Mazarico, John Weirich
Permanently shadowed regions (PSRs) in the north polar region of Ceres have been previously mapped by the Dawn spacecraft. Putative ice deposits are found in some of these PSRs, whereas most PSRs host no bright deposits, which is thought to be due to oscillations of the axis tilt with a ∼25 ka period. We use stereophotoclinometry to construct refined topographic models of PSR-hosting craters. Ray-tracing calculations reveal that no PSRs remain at the maximum axis tilt, which implies that the ice deposits are remarkably young. The bright ice deposits do not extend beyond PSRs at an axis tilt of 10°, which last occurred about 6 ka ago. This suggests that water is delivered to the polar regions or exposed within the craters by frequent and short-lived events. Surface temperatures are calculated with a terrain irradiance model to delineate cold traps. Based on maximum equilibrium temperatures, Cerean PSRs are too warm to trap supervolatiles.
黎明号宇宙飞船先前绘制了谷神星北极区域的永久阴影区（PSRs）。在其中一些永久阴影区发现了假定的冰沉积物，而大多数永久阴影区没有发现明亮的沉积物，这被认为是由于轴倾斜的振荡造成的，振荡周期为 25 ka。我们利用立体光度测量法构建了PSR环形山的精细地形模型。射线追踪计算显示，在最大轴倾角处没有PSR，这意味着冰沉积物非常年轻。在轴倾角为 10°时，明亮的冰沉积物没有延伸到 PSR 之外，而 PSR 最后一次出现是在大约 6 ka 年前。这表明，水是通过频繁而短暂的事件输送到极区或暴露在陨石坑内的。利用地形辐照度模型计算了地表温度，以划分冷阱。根据最高平衡温度，Cerean PSRs温度过高，无法捕获超巨星。
{"title":"History of Ceres’s Cold Traps Based on Refined Shape Models","authors":"Norbert Schorghofer, Robert Gaskell, Erwan Mazarico, John Weirich","doi":"10.3847/psj/ad3639","DOIUrl":"https://doi.org/10.3847/psj/ad3639","url":null,"abstract":"Permanently shadowed regions (PSRs) in the north polar region of Ceres have been previously mapped by the Dawn spacecraft. Putative ice deposits are found in some of these PSRs, whereas most PSRs host no bright deposits, which is thought to be due to oscillations of the axis tilt with a ∼25 ka period. We use stereophotoclinometry to construct refined topographic models of PSR-hosting craters. Ray-tracing calculations reveal that no PSRs remain at the maximum axis tilt, which implies that the ice deposits are remarkably young. The bright ice deposits do not extend beyond PSRs at an axis tilt of 10°, which last occurred about 6 ka ago. This suggests that water is delivered to the polar regions or exposed within the craters by frequent and short-lived events. Surface temperatures are calculated with a terrain irradiance model to delineate cold traps. Based on maximum equilibrium temperatures, Cerean PSRs are too warm to trap supervolatiles.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":"31 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140610089","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Siobhan Light, Mark Gurwell, Alexander Thelen, Nicholas A Lombardo, Conor Nixon
Saturn’s moon Titan possesses stratospheric zonal winds that places it among a sparse class of planetary bodies known to have superrotation in their atmospheres. Few measurements have been made of these speeds in the upper stratosphere, leaving their seasonal variations still not well understood. We examined observations made with the extended Submillimeter Array in 2009 March (Ls = 355°) and 2010 February (Ls = 5°), shortly before and after Titan's northern spring equinox. Cassini observations and atmospheric models find equinoctial periods to be especially dynamic. Zonal wind calculations, derived from the Doppler frequency shift of CH3CN near 349.4 GHz, yielded speeds of 128 ± 27 m s−1 in 2009 and 209 ± 48 m s−1 in 2010. We estimated the measured emission to originate from vertical altitudes of 336−88+112 km, equivalent to pressures of 3.8−3.4+19.2 Pa, commensurate with Titan’s upper stratosphere/lower mesosphere. This suggests a possible increase in zonal speeds during this period. The results are then compared to those from previous Cassini-inferred and direct-interferometric observations of winds, as well as general circulation model simulations, to form a more complete picture of the seasonal cycle of stratospheric zonal winds.
{"title":"Measurements of Titan’s Stratospheric Winds during the 2009 Equinox with the eSMA","authors":"Siobhan Light, Mark Gurwell, Alexander Thelen, Nicholas A Lombardo, Conor Nixon","doi":"10.3847/psj/ad3355","DOIUrl":"https://doi.org/10.3847/psj/ad3355","url":null,"abstract":"Saturn’s moon Titan possesses stratospheric zonal winds that places it among a sparse class of planetary bodies known to have superrotation in their atmospheres. Few measurements have been made of these speeds in the upper stratosphere, leaving their seasonal variations still not well understood. We examined observations made with the extended Submillimeter Array in 2009 March (<italic toggle=\"yes\">L</italic>\u0000<sub>\u0000<italic toggle=\"yes\">s</italic>\u0000</sub> = 355°) and 2010 February (<italic toggle=\"yes\">L</italic>\u0000<sub>\u0000<italic toggle=\"yes\">s</italic>\u0000</sub> = 5°), shortly before and after Titan's northern spring equinox. Cassini observations and atmospheric models find equinoctial periods to be especially dynamic. Zonal wind calculations, derived from the Doppler frequency shift of CH<sub>3</sub>CN near 349.4 GHz, yielded speeds of 128 ± 27 m s<sup>−1</sup> in 2009 and 209 ± 48 m s<sup>−1</sup> in 2010. We estimated the measured emission to originate from vertical altitudes of <inline-formula>\u0000<tex-math>\u0000<?CDATA ${336}_{-88}^{+112}$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:msubsup><mml:mrow><mml:mn>336</mml:mn></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>88</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mn>112</mml:mn></mml:mrow></mml:msubsup></mml:math>\u0000<inline-graphic xlink:href=\"psjad3355ieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> km, equivalent to pressures of <inline-formula>\u0000<tex-math>\u0000<?CDATA ${3.8}_{-3.4}^{+19.2}$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:msubsup><mml:mrow><mml:mn>3.8</mml:mn></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>3.4</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mn>19.2</mml:mn></mml:mrow></mml:msubsup></mml:math>\u0000<inline-graphic xlink:href=\"psjad3355ieqn2.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> Pa, commensurate with Titan’s upper stratosphere/lower mesosphere. This suggests a possible increase in zonal speeds during this period. The results are then compared to those from previous Cassini-inferred and direct-interferometric observations of winds, as well as general circulation model simulations, to form a more complete picture of the seasonal cycle of stratospheric zonal winds.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":"888 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140610608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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