Icarus最新文献_第4页

Preliminary investigation of debris propagation dynamics in the Jovian system using the circular restricted 3- and N-body problems

IF 2.5 2区物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS

Icarus

Pub Date : 2025-01-16 DOI: 10.1016/j.icarus.2025.116455

Annika J. Gilliam, Robert A. Bettinger, Nicholas S. Reid, Christina E. Paljug, Isabella G. Tebrugge

Jupiter’s many moons and the potentiality for water and life on these celestial bodies have significantly increased interest in the Jovian system. Missions to the Jovian system aim to limit “forward contamination” caused by human-made debris in order to preserve these moons for scientific discovery and exploration. Understanding the behavior and dynamics of debris in the system is vital to ensure limited impacts on the moons in the event of a debris-causing mishap. Additionally, the Jovian system presents highly complex dynamics based on the masses of the Galilean moons of Io, Europa, Ganymede, and Callisto. Incorporating the gravitational perturbations due to these additional system bodies ensures results that more accurately reflect real-world conditions. The Circular Restricted 3-Body Problem (CR3BP) and Circular Restricted N-Body Problem (CRNBP) may be used to propagate the motion of debris in the region, and this paper investigates the debris propagation dynamics associated with a catastrophic spacecraft breakup event occurring along trajectories within the orbital zone of Jupiter’s inner and Galilean moons. The NASA Standard Breakup Model (SBM) is used as the statistical means for debris generation for all analyses. This research presents four sample trajectories propagated using both the CR3BP and CRNBP models for comparison. Impacts on each of the four Galilean moons and four additional inner Jovian moons are analyzed for each sample trajectory case using 100 trials of the NASA SBM for each test. Preliminary results demonstrate that debris is mitigated in the out-of-plane and Europa-centric cases, while tested resonant trajectories result in up to 15% of produced debris impacting celestial bodies.

{"title":"Preliminary investigation of debris propagation dynamics in the Jovian system using the circular restricted 3- and N-body problems","authors":"Annika J. Gilliam, Robert A. Bettinger, Nicholas S. Reid, Christina E. Paljug, Isabella G. Tebrugge","doi":"10.1016/j.icarus.2025.116455","DOIUrl":"10.1016/j.icarus.2025.116455","url":null,"abstract":"<div><div>Jupiter’s many moons and the potentiality for water and life on these celestial bodies have significantly increased interest in the Jovian system. Missions to the Jovian system aim to limit “forward contamination” caused by human-made debris in order to preserve these moons for scientific discovery and exploration. Understanding the behavior and dynamics of debris in the system is vital to ensure limited impacts on the moons in the event of a debris-causing mishap. Additionally, the Jovian system presents highly complex dynamics based on the masses of the Galilean moons of Io, Europa, Ganymede, and Callisto. Incorporating the gravitational perturbations due to these additional system bodies ensures results that more accurately reflect real-world conditions. The Circular Restricted 3-Body Problem (CR3BP) and Circular Restricted N-Body Problem (CRNBP) may be used to propagate the motion of debris in the region, and this paper investigates the debris propagation dynamics associated with a catastrophic spacecraft breakup event occurring along trajectories within the orbital zone of Jupiter’s inner and Galilean moons. The NASA Standard Breakup Model (SBM) is used as the statistical means for debris generation for all analyses. This research presents four sample trajectories propagated using both the CR3BP and CRNBP models for comparison. Impacts on each of the four Galilean moons and four additional inner Jovian moons are analyzed for each sample trajectory case using 100 trials of the NASA SBM for each test. Preliminary results demonstrate that debris is mitigated in the out-of-plane and Europa-centric cases, while tested resonant trajectories result in up to 15% of produced debris impacting celestial bodies.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"429 ","pages":"Article 116455"},"PeriodicalIF":2.5,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134802","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}

引用次数: 0

Constraining volcanic vent parameters to understand the 2007 brightness surge in Io's Tvashtar plume: A DSMC approach

IF 2.5 2区物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS

Icarus

Pub Date : 2025-01-16 DOI: 10.1016/j.icarus.2025.116458

A.O. Adeloye , L.M. Trafton , D.B. Goldstein , P.L. Varghese , A. Mahieux

Io's Tvashtar volcanic plume displayed an irregular order of magnitude increase in brightness during the 2007 New Horizons (NH) flyby as the solar phase angle of Io relative to NH increased. High-resolution NH/LORRI images captured the Tvashtar plume's evolution throughout the flyby. We investigate potential causes for the brightness surge by examining whether changes in Tvashtar's volcanic vent properties could have explained the observed brightness increase.

Using the captured NH images, a robust method is developed to constrain some of Tvashtar's vent properties. This method involves a sensitivity study of free parameters at Tvashtar's vent using axisymmetric Direct Simulation Monte Carlo (DSMC) simulations incorporating both gas and grain radiation modeling. The analysis examines how variations in these parameters (such as vent stagnation temperature, area, mass flow rate, and grain mass loading) influence the plume canopy's height, width, and overall shape.

The sensitivity analysis identifies the vent stagnation temperature and area as the parameters most influential on the plume's canopy characteristics. Given the visibility of Tvashtar's plume canopy throughout the NH flyby, canopy spatial coordinates are extracted from each LORRI image. Subsequently, a Levenberg-Marquardt optimization algorithm is employed to fit DSMC simulation plume canopies, parameterized over a two-dimensional space of stagnation temperature and area, to each extracted canopy. This process yields the optimal pair of vent stagnation temperature and area that best models the observed plume canopy for each case.

From the fitting process, we hypothesize an asymmetric source region at Tvashtar, consistent with previous research findings. However, the fitting process also determines that the observed increase in brightness cannot be entirely attributed to changes in vent conditions during the flyby, as there appears to be no correlation between these changes and the surge in brightness. The most plausible explanation for the brightness surge lies in the optical scattering properties of the plume particulates.

{"title":"Constraining volcanic vent parameters to understand the 2007 brightness surge in Io's Tvashtar plume: A DSMC approach","authors":"A.O. Adeloye , L.M. Trafton , D.B. Goldstein , P.L. Varghese , A. Mahieux","doi":"10.1016/j.icarus.2025.116458","DOIUrl":"10.1016/j.icarus.2025.116458","url":null,"abstract":"<div><div>Io's Tvashtar volcanic plume displayed an irregular order of magnitude increase in brightness during the 2007 New Horizons (NH) flyby as the solar phase angle of Io relative to NH increased. High-resolution NH/LORRI images captured the Tvashtar plume's evolution throughout the flyby. We investigate potential causes for the brightness surge by examining whether changes in Tvashtar's volcanic vent properties could have explained the observed brightness increase.</div><div>Using the captured NH images, a robust method is developed to constrain some of Tvashtar's vent properties. This method involves a sensitivity study of free parameters at Tvashtar's vent using axisymmetric Direct Simulation Monte Carlo (DSMC) simulations incorporating both gas and grain radiation modeling. The analysis examines how variations in these parameters (such as vent stagnation temperature, area, mass flow rate, and grain mass loading) influence the plume canopy's height, width, and overall shape.</div><div>The sensitivity analysis identifies the vent stagnation temperature and area as the parameters most influential on the plume's canopy characteristics. Given the visibility of Tvashtar's plume canopy throughout the NH flyby, canopy spatial coordinates are extracted from each LORRI image. Subsequently, a Levenberg-Marquardt optimization algorithm is employed to fit DSMC simulation plume canopies, parameterized over a two-dimensional space of stagnation temperature and area, to each extracted canopy. This process yields the optimal pair of vent stagnation temperature and area that best models the observed plume canopy for each case.</div><div>From the fitting process, we hypothesize an asymmetric source region at Tvashtar, consistent with previous research findings. However, the fitting process also determines that the observed increase in brightness cannot be entirely attributed to changes in vent conditions during the flyby, as there appears to be no correlation between these changes and the surge in brightness. The most plausible explanation for the brightness surge lies in the optical scattering properties of the plume particulates.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"429 ","pages":"Article 116458"},"PeriodicalIF":2.5,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134801","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}

引用次数: 0

Quantifying lava surface heterogeneity on Mars using THEMIS brightness temperature data

IF 2.5 2区物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS

Icarus

Pub Date : 2025-01-12 DOI: 10.1016/j.icarus.2025.116456

B.E. McKeeby , T. Peterson , M.S. Ramsey

The analysis and characterization of any planetary surface relies heavily on orbital data. The Martian surface is dominated by extrusive volcanism with most of the younger rocks being either too rough or at altitudes that are commonly inaccessible to landers or rovers. Therefore, the accurate interpretation of orbital data is critical to understanding the planet's youngest magmatic conditions and subsequent cratering and eolian history. However, the cumulative effects of surface processes such as dust deposition spanning millions of years typically obscures observable features, posing challenges for data analysis. This study focuses on the igneous terrains from Arsia Mons and into Daedalia Planum using a unique off-nadir thermal infrared (TIR) dataset acquired through special tasking of the Mars Odyssey spacecraft. Prior studies of this region indicated compositional variations were present, yet the dust cover made conclusive results impossible. This study introduces a novel methodology that combines the KRC thermal model, quantitative thermal inertia data, and the off-axis TIR observations to predict surface temperature and quantify submeter-scale surface roughness. In doing so, we reveal changes in lava flow roughness that can be correlated to relative flow ages, flow dynamics, and preferential mantling of dust. These data are compared to older, nadir pointing, THEMIS emissivity data to quantify the anisothermality caused by surface roughness. The results underscore the significance of existing orbital data acquired and processed in novel ways to retrieve new information about Martian volcanology and the ongoing dynamics acting on these surfaces.

{"title":"Quantifying lava surface heterogeneity on Mars using THEMIS brightness temperature data","authors":"B.E. McKeeby , T. Peterson , M.S. Ramsey","doi":"10.1016/j.icarus.2025.116456","DOIUrl":"10.1016/j.icarus.2025.116456","url":null,"abstract":"<div><div>The analysis and characterization of any planetary surface relies heavily on orbital data. The Martian surface is dominated by extrusive volcanism with most of the younger rocks being either too rough or at altitudes that are commonly inaccessible to landers or rovers. Therefore, the accurate interpretation of orbital data is critical to understanding the planet's youngest magmatic conditions and subsequent cratering and eolian history. However, the cumulative effects of surface processes such as dust deposition spanning millions of years typically obscures observable features, posing challenges for data analysis. This study focuses on the igneous terrains from Arsia Mons and into Daedalia Planum using a unique off-nadir thermal infrared (TIR) dataset acquired through special tasking of the Mars Odyssey spacecraft. Prior studies of this region indicated compositional variations were present, yet the dust cover made conclusive results impossible. This study introduces a novel methodology that combines the KRC thermal model, quantitative thermal inertia data, and the off-axis TIR observations to predict surface temperature and quantify submeter-scale surface roughness. In doing so, we reveal changes in lava flow roughness that can be correlated to relative flow ages, flow dynamics, and preferential mantling of dust. These data are compared to older, nadir pointing, THEMIS emissivity data to quantify the anisothermality caused by surface roughness. The results underscore the significance of existing orbital data acquired and processed in novel ways to retrieve new information about Martian volcanology and the ongoing dynamics acting on these surfaces.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"429 ","pages":"Article 116456"},"PeriodicalIF":2.5,"publicationDate":"2025-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134787","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}

引用次数: 0

Discovery of carbonaceous chondritic fragment in Chang'e-5 regolith samples

IF 2.5 2区物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS

Icarus

Pub Date : 2025-01-06 DOI: 10.1016/j.icarus.2025.116454

Linxi Li , Hejiu Hui , Sen Hu , Qiuli Li , Yi Chen , Wei Yang , Guoqiang Tang , Lihui Jia , Xiaoguang Li , Lixin Gu , Fuyuan Wu

Lunar regolith samples contain fragments of endogenic rocks and exogenous meteorites. We report the first discovery of a chondrule fragment preserved in Chang'e-5 (CE-5) regolith samples. Forsterite and enstatite phenocrysts have extremely high Mg# (> 99) and high Mn/Fe ratios in this chondrule fragment. Its glass mesostasis is heterogeneous and contains hydrogen and carbon, as indicated by Raman peaks. The mineral assemblage, chemical composition, and oxygen isotope anomaly of this fragment are similar to those of type-I chondrules from carbonaceous chondrites. This fragment and other chondritic relics with < 3.0 Ga impact ages exhibit compositional similarities to micrometeorites on Earth, but are different from ultramagnesian mafic fragments (UMMFs) discovered on the Moon with impact ages > 3.4 Ga. This contrast suggests that there may have been a change of impactors to the Earth–Moon system during the Imbrian period. Furthermore, this CE-5 chondrule fragment is a direct record of volatile addition to the Moon's surface from meteorites during the Eratosthenian period.

{"title":"Discovery of carbonaceous chondritic fragment in Chang'e-5 regolith samples","authors":"Linxi Li , Hejiu Hui , Sen Hu , Qiuli Li , Yi Chen , Wei Yang , Guoqiang Tang , Lihui Jia , Xiaoguang Li , Lixin Gu , Fuyuan Wu","doi":"10.1016/j.icarus.2025.116454","DOIUrl":"10.1016/j.icarus.2025.116454","url":null,"abstract":"<div><div>Lunar regolith samples contain fragments of endogenic rocks and exogenous meteorites. We report the first discovery of a chondrule fragment preserved in Chang'e-5 (CE-5) regolith samples. Forsterite and enstatite phenocrysts have extremely high Mg# (> 99) and high Mn/Fe ratios in this chondrule fragment. Its glass mesostasis is heterogeneous and contains hydrogen and carbon, as indicated by Raman peaks. The mineral assemblage, chemical composition, and oxygen isotope anomaly of this fragment are similar to those of type-I chondrules from carbonaceous chondrites. This fragment and other chondritic relics with < 3.0 Ga impact ages exhibit compositional similarities to micrometeorites on Earth, but are different from ultramagnesian mafic fragments (UMMFs) discovered on the Moon with impact ages > 3.4 Ga. This contrast suggests that there may have been a change of impactors to the Earth–Moon system during the Imbrian period. Furthermore, this CE-5 chondrule fragment is a direct record of volatile addition to the Moon's surface from meteorites during the Eratosthenian period.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"429 ","pages":"Article 116454"},"PeriodicalIF":2.5,"publicationDate":"2025-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134776","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}

引用次数: 0

Distinct types of C-H-O-N atmospheres and surface pressures depending on melt redox state and outgassing efficiency

IF 2.5 2区物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS

Icarus

Pub Date : 2025-01-03 DOI: 10.1016/j.icarus.2024.116450

Caroline Brachmann , Lena Noack , Philipp Alexander Baumeister , Frank Sohl

After the magma ocean state, secondary atmospheres build up via early volcanic degassing of planetary interiors. The terrestrial planets Venus, Earth, and Mars are believed to have originated from similar source material but reveal distinct present-day atmospheric compositions, pressures, and temperatures. To investigate how such diverse atmospheres emerge, we have built a three-step model coupling mantle and atmospheric composition. The model incorporates mantle melting, melt ascent, and volcanic degassing. Additionally, it includes atmospheric equilibrium chemistry, taking into account processes such as water condensation and hydrogen escape. Key parameters such as mantle oxygen fugacity, melt production rates, surface temperature, and volatile abundance in the mantle, were varied to understand their impact on atmospheric composition and pressure. For reduced mantles with redox states below IW +1, atmospheric pressures remain strongly limited to a maximum of 2 bar due to the outgassing of predominantly light species that are prone to atmospheric escape or condensation. Above IW +1, atmospheric pressure can reach several tens of bars depending on the outgassing efficiency. For high-pressure atmospheres, CO₂ is the main atmospheric species observed in our models. For oxidized low-pressure atmospheres, depending on temperature, atmospheres can be either water-rich or also CO₂-dominated. For reducing atmospheres, nitrogen species tend to dominate the atmospheres, with NH₃ for colder atmospheres and N₂ for warmer atmospheres. CH₄ becomes dominant only in a narrow parameter space at redox states around IW +0.5 to IW +2 and is favored by lower atmospheric temperatures.

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引用次数: 0

Modeling studies of dust/gas non-thermal equilibrium in the Martian atmosphere

IF 2.5 2区物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS

Icarus

Pub Date : 2025-01-03 DOI: 10.1016/j.icarus.2024.116452

Robert M. Haberle , Melinda A. Kahre , Tanguy Bertrand , Michael J. Wolff

We discuss and implement the physics of dust-gas non-equilibrium processes into 1-D radiative-convective and 3-D climate models to assess at what altitude dust and gas temperatures in the Martian atmosphere diverge and to what extent it affects the thermal structure, dynamics, and transport capabilities of the upper atmosphere. As found in an earlier paper by Goldenson et al. (2008), we find (using a different approach) that dust and gas temperatures diverge above 40 km as collisions between dust particles and gas molecules are too infrequent to equilibrate these two components. With our 1-D model we show that when dust-gas non-equilibrium physics is included, gas temperatures above 40 km cool and heating rates are reduced. The magnitude of the effect depends mostly on the size and abundance of the dust particles and is proportional to each. With our 3-D model we show that this physics is important mainly during times of intense dust lifting events such as local rocket storms, or regional or global storms when dust quickly penetrates to high altitudes and particle sizes can be somewhat larger at least initially. During such times upper atmosphere temperatures cool, wind systems are weakened, and vertical and meridional transport is diminished when compared to simulation assuming thermal equilibrium.

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引用次数: 0

Attribute recognition: A new method for grouping planetary images by visual characteristics, using the example of Mn-rich rocks in the floor of Gale crater, Mars

IF 2.5 2区物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS

Icarus

Pub Date : 2025-01-01 DOI: 10.1016/j.icarus.2024.116451

Ari Essunfeld , Jade M. Comellas , Reid A. Morris , Patrick J. Gasda , Dorothea Delapp , Diane Oyen , Candice C. Bedford , Benton C. Clark , Erwin Dehouck , Ryan B. Anderson , Ana Lomashvili , Roger C. Wiens , Samuel M. Clegg , Olivier Gasnault , Nina L. Lanza

Classifying images is particularly challenging when working with large datasets without predefined groups. We present a new method for grouping images by visual similarity using relatively simple terminology and apply this method to the process of grouping NASA Curiosity rover ChemCam target images into visually similar groups. This method is designed for offline use, rather than on-board applications where power constraints are a consideration. Given the large quantity of data from ChemCam, we narrow the scope of our study to consider only rock targets that are early-mission and contain elevated manganese. A standard list of visual attributes is assessed for each target, and for each attribute on the list, a 1 is recorded if the ChemCam target image exhibits the attribute, and a 0 otherwise. The binary number resulting from this analysis encodes the visual characteristics of each image and is also used to determine similarity between images. Images are modeled as nodes in a network, and similarities between images are modeled as edges between nodes in the network. We find that when using a conservative threshold for similarity and an undirected, unweighted graph to represent the network, visually similar images cluster effectively into disjoint connected components. To improve the geologic usefulness of the resulting target groupings, we define a metric for weak component connectivity and explore methods for automatically partitioning weakly connected components. We compare these results to weighted-graph approaches, as well as to control tests using random partitions. Starting with a dataset of 201 ChemCam Remote Micro Imager mosaics, we found that the “automatic partitioning” method divided these images into 13 groups and resulted in better intra-group visual coherence than the other methods assessed. These results may be applied to motivate machine learning models for automatic attribute recognition to expand data labeling, as well as future classification efforts, including citizen science endeavors.

{"title":"Attribute recognition: A new method for grouping planetary images by visual characteristics, using the example of Mn-rich rocks in the floor of Gale crater, Mars","authors":"Ari Essunfeld , Jade M. Comellas , Reid A. Morris , Patrick J. Gasda , Dorothea Delapp , Diane Oyen , Candice C. Bedford , Benton C. Clark , Erwin Dehouck , Ryan B. Anderson , Ana Lomashvili , Roger C. Wiens , Samuel M. Clegg , Olivier Gasnault , Nina L. Lanza","doi":"10.1016/j.icarus.2024.116451","DOIUrl":"10.1016/j.icarus.2024.116451","url":null,"abstract":"<div><div>Classifying images is particularly challenging when working with large datasets without predefined groups. We present a new method for grouping images by visual similarity using relatively simple terminology and apply this method to the process of grouping NASA <em>Curiosity</em> rover ChemCam target images into visually similar groups. This method is designed for offline use, rather than on-board applications where power constraints are a consideration. Given the large quantity of data from ChemCam, we narrow the scope of our study to consider only rock targets that are early-mission and contain elevated manganese. A standard list of visual attributes is assessed for each target, and for each attribute on the list, a 1 is recorded if the ChemCam target image exhibits the attribute, and a 0 otherwise. The binary number resulting from this analysis encodes the visual characteristics of each image and is also used to determine similarity between images. Images are modeled as nodes in a network, and similarities between images are modeled as edges between nodes in the network. We find that when using a conservative threshold for similarity and an undirected, unweighted graph to represent the network, visually similar images cluster effectively into disjoint connected components. To improve the geologic usefulness of the resulting target groupings, we define a metric for weak component connectivity and explore methods for automatically partitioning weakly connected components. We compare these results to weighted-graph approaches, as well as to control tests using random partitions. Starting with a dataset of 201 ChemCam Remote Micro Imager mosaics, we found that the “automatic partitioning” method divided these images into 13 groups and resulted in better intra-group visual coherence than the other methods assessed. These results may be applied to motivate machine learning models for automatic attribute recognition to expand data labeling, as well as future classification efforts, including citizen science endeavors.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"429 ","pages":"Article 116451"},"PeriodicalIF":2.5,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134730","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}

引用次数: 0

High spectral resolution observations of Uranus' near-IR thermospheric H2 emission spectrum using the IGRINS spectrograph during the 2018 and 2023 apparitions

IF 2.5 2区物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS

Icarus

Pub Date : 2024-12-28 DOI: 10.1016/j.icarus.2024.116453

L.M. Trafton, K.F. Kaplan

Ground-based near-IR observations have revealed that Uranus' anomalously hot upper atmosphere, detected by Voyager II, has been steadily cooling. The observed H₃⁺ and H₂ emission-line spectra probe Uranus' ionosphere and thermosphere, respectively. Previous observations have shown that the cooling has continued well past the 2007 vernal equinox, when the seasonal solar forcing turned positive, resulting in net heating of the IAU northern hemisphere. Most of them, especially for H₂, were obtained at moderate spectral resolution, R ∼ 1000 to 3000, which admits more sky background, with its associated noise, per spectral resolution element relative to spectrographs having higher spectral resolution. We report the first instance of high spectral resolution being used to observe Uranus' fundamental-band rovibrational quadrupole H₂ emission spectrum; where the sky background is suppressed and narrow planetary emission lines stand out against the planetary continuum. The IGRINS spectrograph with spectral resolution R ∼ 45,000 was used to observe Uranus in the K-band on Oct 26 & 27, 2018 at the Lowell Discovery Telescope, and on Nov 27, 2023 at Gemini South. These observations reveal rovibrational temperatures of Uranus' thermosphere of 542 ± 25 K and 397 ± 32 K at these two epochs, respectively. The consecutive-nights at elevated temperature observed at the Discovery Telescope suggest that Uranus' near-IR H₂ aurora was detected over each of the northern and southern magnetic poles, respectively. The collective IGRINS results support the continued cooling of Uranus' thermosphere through the 2023 apparition, 73 % through the spring season.

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引用次数: 0

How much earlier would LSST have discovered currently known long-period comets?

IF 2.5 2区物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS

Icarus

Pub Date : 2024-12-28 DOI: 10.1016/j.icarus.2024.116443

Laura Inno , Margherita Scuderi , Ivano Bertini , Marco Fulle , Elena Mazzotta Epifani , Vincenzo Della Corte , Alice Maria Piccirillo , Antonio Vanzanella , Pedro Lacerda , Chiara Grappasonni , Eleonora Ammanito , Giuseppe Sindoni , Alessandra Rotundi

Among solar system objects, comets coming from the Oort Cloud are an elusive population, intrinsically rare and difficult to detect. Nonetheless, as the more pristine objects we can observe, they encapsulate critical cues on the formation of planetary systems and are the focus of many scientific investigations and science missions. The Legacy Survey of Space and Time (LSST), which will start to operate from the Vera C. Rubin Observatory in 2025, is expected to dramatically improve our detection ability of these comets by performing regular monitoring of the Southern sky deep down to magnitude 24.5 with excellent astrometry. However, making straightforward predictions on future LSST detection rates is challenging due to our biased knowledge of the underlying population. This is because identifications to date have been conducted by various surveys or individual observers, often without detailed information on their respective selection functions. Recent efforts (see e.g. Vokrouhlickỳ et al., 2019) to predict incoming flux of Long Period Comets still suffer of the lack of systematic, well-characterized, homogeneous cometary surveys. Here, we adopt a different point of view by asking how much earlier on known comets on long-period or hyperbolic orbits would have been discovered by a LSST-like survey if it was already in place 10 years prior to their perihelion epoch. In this case, we are not simulating a real flux of incoming comet, as all comets in our sample reach the perihelion simultaneously, but we can analyze the impact of a LSST-like survey on individual objects. We find that LSST would have found about 40% of comets in our sample at least 5 years prior to their perihelion epoch, and at double (at least) the distance at which they were actually discovered. Based on this approach, we find that LSST has the potentiality to at least twofold the current discovery rate of long-period and hyperbolic comets.

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引用次数: 0

Rotating convection with a melting boundary: An application to the icy moons

IF 2.5 2区物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS

Icarus

Pub Date : 2024-12-27 DOI: 10.1016/j.icarus.2024.116441

T. Gastine , B. Favier

A better understanding of the ice-ocean couplings is required to better characterise the hydrosphere of the icy moons. Using global numerical simulations in spherical geometry, we have investigated here the interplay between rotating convection and a melting boundary. To do so, we have implemented and validated a phase field formulation in the open-source code MagIC. We have conducted a parameter study varying the influence of rotation, the vigour of the convective forcing and the melting temperature. We have evidenced different regimes akin to those already found in previous monophasic models in which the mean axisymmetric ice crust transits from pole-ward thinning to equator-ward thinning with the increase of the rotational constraint on the flow. The derivation of a perturbative model of heat conduction in the ice layer enabled us to relate those mean topographic changes to the underlying latitudinal heat flux variations at the top of the ocean. The phase change has also been found to yield the formation of sizeable non-axisymmetric topography at the solid–liquid interface with a typical size close to that of the convective columns. We have shown that the typical evolution timescale of the interface increases linearly with the crest-to-trough amplitude and quadratically with the mean melt radius. In the case of the largest topographic changes, the convective flows become quasi locked in the topography due to the constructive coupling between convection and ice melting. The tentative extrapolation to the planetary regimes yields

O (1 0^{2} - 1 0^{3})

meters for the amplitude of non-axisymmetric topography at the base of the ice layer of Enceladus and

O (1 0^{3} - 1 0^{4})

meters for Titan.

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引用次数: 0