Jacob Haqq-Misra, Eric T. Wolf, Thomas J. Fauchez and Ravi K. Kopparapu
This paper highlights methods from geostatistics that are relevant to the interpretation, intercomparison, and synthesis of atmospheric model data, with a specific application to exoplanet atmospheric modeling. Climate models are increasingly used to study theoretical and observational properties of exoplanets, which include a hierarchy of models ranging from fast and idealized models to those that are slower but more comprehensive. Exploring large parameter spaces with computationally expensive models can be accomplished with sparse sampling techniques, but analyzing such sparse samples can pose challenges for conventional interpolation functions. Ordinary kriging is a statistical method for describing the spatial distribution of a data set in terms of the variogram function, which can be used to interpolate sparse samples across any number of dimensions. Variograms themselves may also be useful diagnostic tools for describing the spatial distribution of model data in exoplanet atmospheric model intercomparison projects. Universal kriging is another method that can synthesize data calculated by models of different complexity, which can be used to combine sparse samples of data from slow models with larger samples of data from fast models. Ordinary and universal kriging can also provide a way to synthesize model predictions with sparse samples of exoplanet observations and may have other applications in exoplanet science.
{"title":"Interpolation and Synthesis of Sparse Samples in Exoplanet Atmospheric Modeling","authors":"Jacob Haqq-Misra, Eric T. Wolf, Thomas J. Fauchez and Ravi K. Kopparapu","doi":"10.3847/psj/ad50a7","DOIUrl":"https://doi.org/10.3847/psj/ad50a7","url":null,"abstract":"This paper highlights methods from geostatistics that are relevant to the interpretation, intercomparison, and synthesis of atmospheric model data, with a specific application to exoplanet atmospheric modeling. Climate models are increasingly used to study theoretical and observational properties of exoplanets, which include a hierarchy of models ranging from fast and idealized models to those that are slower but more comprehensive. Exploring large parameter spaces with computationally expensive models can be accomplished with sparse sampling techniques, but analyzing such sparse samples can pose challenges for conventional interpolation functions. Ordinary kriging is a statistical method for describing the spatial distribution of a data set in terms of the variogram function, which can be used to interpolate sparse samples across any number of dimensions. Variograms themselves may also be useful diagnostic tools for describing the spatial distribution of model data in exoplanet atmospheric model intercomparison projects. Universal kriging is another method that can synthesize data calculated by models of different complexity, which can be used to combine sparse samples of data from slow models with larger samples of data from fast models. Ordinary and universal kriging can also provide a way to synthesize model predictions with sparse samples of exoplanet observations and may have other applications in exoplanet science.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141504676","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}
Megan T. Gialluca, Rory Barnes, Victoria S. Meadows, Rodolfo Garcia, Jessica Birky, Eric Agol
JWST observations of the seven-planet TRAPPIST-1 system will provide an excellent opportunity to test outcomes of stellar-driven evolution of terrestrial planetary atmospheres, including atmospheric escape, ocean loss, and abiotic oxygen production. While most previous studies use a single luminosity evolution for the host star, we incorporate observational uncertainties in stellar mass, luminosity evolution, system age, and planetary parameters to statistically explore the plausible range of planetary atmospheric escape outcomes. We present probabilistic distributions of total water loss and oxygen production as a function of initial water content, for planets with initially pure water atmospheres and no interior–atmosphere exchange. We find that the interior planets are desiccated for initial water contents below 50 Earth oceans. For TRAPPIST-1e, f, g, and h, we report maximum water-loss ranges of 8.0−0.9+1.3, 4.8−0.4+0.6, 3.4−0.3+0.3, and 0.8−0.1+0.2 Earth oceans, respectively, with corresponding maximum oxygen retention of 1290−75+75
{"title":"The Implications of Thermal Hydrodynamic Atmospheric Escape on the TRAPPIST-1 Planets","authors":"Megan T. Gialluca, Rory Barnes, Victoria S. Meadows, Rodolfo Garcia, Jessica Birky, Eric Agol","doi":"10.3847/psj/ad4454","DOIUrl":"https://doi.org/10.3847/psj/ad4454","url":null,"abstract":"JWST observations of the seven-planet TRAPPIST-1 system will provide an excellent opportunity to test outcomes of stellar-driven evolution of terrestrial planetary atmospheres, including atmospheric escape, ocean loss, and abiotic oxygen production. While most previous studies use a single luminosity evolution for the host star, we incorporate observational uncertainties in stellar mass, luminosity evolution, system age, and planetary parameters to statistically explore the plausible range of planetary atmospheric escape outcomes. We present probabilistic distributions of total water loss and oxygen production as a function of initial water content, for planets with initially pure water atmospheres and no interior–atmosphere exchange. We find that the interior planets are desiccated for initial water contents below 50 Earth oceans. For TRAPPIST-1e, f, g, and h, we report maximum water-loss ranges of <inline-formula>\u0000<tex-math>\u0000<?CDATA ${8.0}_{-0.9}^{+1.3}$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:msubsup><mml:mrow><mml:mn>8.0</mml:mn></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>0.9</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mn>1.3</mml:mn></mml:mrow></mml:msubsup></mml:math>\u0000<inline-graphic xlink:href=\"psjad4454ieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>, <inline-formula>\u0000<tex-math>\u0000<?CDATA ${4.8}_{-0.4}^{+0.6}$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:msubsup><mml:mrow><mml:mn>4.8</mml:mn></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>0.4</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mn>0.6</mml:mn></mml:mrow></mml:msubsup></mml:math>\u0000<inline-graphic xlink:href=\"psjad4454ieqn2.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>, <inline-formula>\u0000<tex-math>\u0000<?CDATA ${3.4}_{-0.3}^{+0.3}$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:msubsup><mml:mrow><mml:mn>3.4</mml:mn></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>0.3</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mn>0.3</mml:mn></mml:mrow></mml:msubsup></mml:math>\u0000<inline-graphic xlink:href=\"psjad4454ieqn3.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>, and <inline-formula>\u0000<tex-math>\u0000<?CDATA ${0.8}_{-0.1}^{+0.2}$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:msubsup><mml:mrow><mml:mn>0.8</mml:mn></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>0.1</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mn>0.2</mml:mn></mml:mrow></mml:msubsup></mml:math>\u0000<inline-graphic xlink:href=\"psjad4454ieqn4.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> Earth oceans, respectively, with corresponding maximum oxygen retention of <inline-formula>\u0000<tex-math>\u0000<?CDATA ${1290}_{-75}^{+75}$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:msubsup><mml:mrow><mml:mn>1290</mml:mn></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>75</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mn>75</mml:mn></mml:mrow></mml:msubsup></mml:math>\u0000<inline-graphic xlink:href=\"psjad4454ieqn5.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formul","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141504677","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}
Proton auroras are widely observed on the dayside of Mars, identified as a significant intensity enhancement in the hydrogen Lyα (121.6 nm) emission at altitudes of ∼110 and 150 km. Solar wind protons penetrating as energetic neutral atoms into Mars’ thermosphere are thought to be primarily responsible for these auroras. Recent observations of spatially localized “patchy” proton auroras suggest a possible direct deposition of protons into Mars’ atmosphere during unstable solar wind conditions. Improving our understanding of proton auroras is therefore important for characterizing the interaction of the solar wind with Mars’ atmosphere. Here, we develop a first purely data-driven model of proton auroras using Mars Atmosphere and Volatile Evolution (MAVEN) in situ observations and limb scans of Lyα emissions between 2014 and 2022. We train an artificial neural network that reproduces individual Lyα intensities and relative Lyα peak intensity enhancements with Pearson correlations of ∼94% and ∼60% respectively for the test data, along with a faithful reconstruction of the shape of the observed altitude profiles of Lyα emission. By performing a Shapley Additive Explanations (SHAP) analysis, we find that solar zenith angle, solar longitude, CO2 atmosphere variability, solar wind speed, and temperature are the most important features for the modeled Lyα peak intensity enhancements. Additionally, we find that the modeled peak intensity enhancements are high for early local-time hours, particularly near polar latitudes, and the induced magnetic fields are weaker. Through SHAP analysis, we also identify the influence of biases in the training data and interdependences between the measurements used for the modeling, and an improvement of those aspects can significantly improve the performance and applicability of the ANN model.
{"title":"An Explainable Deep-learning Model of Proton Auroras on Mars","authors":"Dattaraj B. Dhuri, Dimitra Atri, Ahmed AlHantoobi","doi":"10.3847/psj/ad45ff","DOIUrl":"https://doi.org/10.3847/psj/ad45ff","url":null,"abstract":"Proton auroras are widely observed on the dayside of Mars, identified as a significant intensity enhancement in the hydrogen Ly<italic toggle=\"yes\">α</italic> (121.6 nm) emission at altitudes of ∼110 and 150 km. Solar wind protons penetrating as energetic neutral atoms into Mars’ thermosphere are thought to be primarily responsible for these auroras. Recent observations of spatially localized “patchy” proton auroras suggest a possible direct deposition of protons into Mars’ atmosphere during unstable solar wind conditions. Improving our understanding of proton auroras is therefore important for characterizing the interaction of the solar wind with Mars’ atmosphere. Here, we develop a first purely data-driven model of proton auroras using Mars Atmosphere and Volatile Evolution (MAVEN) in situ observations and limb scans of Ly<italic toggle=\"yes\">α</italic> emissions between 2014 and 2022. We train an artificial neural network that reproduces individual Ly<italic toggle=\"yes\">α</italic> intensities and relative Ly<italic toggle=\"yes\">α</italic> peak intensity enhancements with Pearson correlations of ∼94% and ∼60% respectively for the test data, along with a faithful reconstruction of the shape of the observed altitude profiles of Ly<italic toggle=\"yes\">α</italic> emission. By performing a Shapley Additive Explanations (SHAP) analysis, we find that solar zenith angle, solar longitude, CO<sub>2</sub> atmosphere variability, solar wind speed, and temperature are the most important features for the modeled Ly<italic toggle=\"yes\">α</italic> peak intensity enhancements. Additionally, we find that the modeled peak intensity enhancements are high for early local-time hours, particularly near polar latitudes, and the induced magnetic fields are weaker. Through SHAP analysis, we also identify the influence of biases in the training data and interdependences between the measurements used for the modeling, and an improvement of those aspects can significantly improve the performance and applicability of the ANN model.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141504697","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}
Neptune’s external mean-motion resonances play an important role in sculpting the observed population of trans-Neptunian objects (TNOs). The population of scattering TNOs is known to “stick” to Neptune's resonances while evolving in semimajor axis (a), though simulations show that resonance sticking is less prevalent at a ≳ 200–250 au. Here we present an extensive numerical exploration of the strengths of Neptune's resonances for scattering TNOs with perihelion distances q = 33 au. We show that the drop-off in resonance sticking for the large a scattering TNOs is not a generic feature of scattering dynamics but can instead be attributed to the specific configuration of Neptune and Uranus in our solar system. In simulations with just Uranus removed from the giant planet system, Neptune's resonances are strong in the scattering population out to at least ∼300 au. Uranus and Neptune are near a 2:1 period ratio, and the variations in Neptune's orbit resulting from this near-resonance are responsible for destabilizing Neptune's resonances for high-e TNO orbits beyond the ∼20:1 resonance at a ≈ 220 au. Direct interactions between Uranus and the scattering population are responsible for slightly weakening Neptune's closer-in resonances. In simulations where Neptune and Uranus are placed in their mutual 2:1 resonance, we see almost no stable libration of scattering particles in Neptune's external resonances. Our results have important implications for how the strengths of Neptune's distant resonances varied during the epoch of planet migration when the Neptune–Uranus period ratio was evolving. These strength variations likely affected the distant scattering, resonant, and detached TNO populations.
海王星的外部平均运动共振在形成观测到的跨海王星天体（TNOs）群方面起着重要作用。众所周知，在半长轴（a）的演化过程中，散射的 TNO 物体群会 "粘附 "在海王星的共振上，不过模拟结果表明，共振粘附在 ≳ 200-250 au 时并不那么普遍。在这里，我们对近日点距离 q = 33 au 的散射 TNO 的海王星共振强度进行了广泛的数值探索。我们的研究表明，大a散射TNOs共振粘性的下降并不是散射动力学的一般特征，而是由于海王星和天王星在太阳系中的特殊构造造成的。在只将天王星从巨行星系统中移除的模拟中，海王星的共振在至少 ∼300 au 范围内的散射群体中是很强的。天王星和海王星的周期比接近 2:1，这种近共振导致海王星轨道的变化，从而破坏了海王星在 ≈ 220 au 处的∼20:1 共振之外的高 e TNO 轨道共振的稳定性。天王星和散射群之间的直接相互作用会稍微削弱海王星的近距离共振。在海王星和天王星处于2:1共振的模拟中，我们发现海王星外部共振中几乎没有稳定的散射粒子天平动。我们的研究结果对海王星-天王星周期比演变的行星迁移时代海王星遥远共振的强度如何变化具有重要意义。这些强度变化很可能会影响到遥远的散射、共振和分离的尘埃粒子群。
{"title":"Uranus’s Influence on Neptune’s Exterior Mean-motion Resonances","authors":"Severance Graham, Kathryn Volk","doi":"10.3847/psj/ad4707","DOIUrl":"https://doi.org/10.3847/psj/ad4707","url":null,"abstract":"Neptune’s external mean-motion resonances play an important role in sculpting the observed population of trans-Neptunian objects (TNOs). The population of scattering TNOs is known to “stick” to Neptune's resonances while evolving in semimajor axis (<italic toggle=\"yes\">a</italic>), though simulations show that resonance sticking is less prevalent at <italic toggle=\"yes\">a</italic> ≳ 200–250 au. Here we present an extensive numerical exploration of the strengths of Neptune's resonances for scattering TNOs with perihelion distances <italic toggle=\"yes\">q</italic> = 33 au. We show that the drop-off in resonance sticking for the large <italic toggle=\"yes\">a</italic> scattering TNOs is not a generic feature of scattering dynamics but can instead be attributed to the specific configuration of Neptune and Uranus in our solar system. In simulations with just Uranus removed from the giant planet system, Neptune's resonances are strong in the scattering population out to at least ∼300 au. Uranus and Neptune are near a 2:1 period ratio, and the variations in Neptune's orbit resulting from this near-resonance are responsible for destabilizing Neptune's resonances for high-<italic toggle=\"yes\">e</italic> TNO orbits beyond the ∼20:1 resonance at <italic toggle=\"yes\">a</italic> ≈ 220 au. Direct interactions between Uranus and the scattering population are responsible for slightly weakening Neptune's closer-in resonances. In simulations where Neptune and Uranus are placed in their mutual 2:1 resonance, we see almost no stable libration of scattering particles in Neptune's external resonances. Our results have important implications for how the strengths of Neptune's distant resonances varied during the epoch of planet migration when the Neptune–Uranus period ratio was evolving. These strength variations likely affected the distant scattering, resonant, and detached TNO populations.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141504696","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}
Juan A. Sanchez, Vishnu Reddy, Audrey Thirouin, William F. Bottke, Theodore Kareta, Mario De Florio, Benjamin N. L. Sharkey, Adam Battle, David C. Cantillo, Neil Pearson
The study of small (<300 m) near-Earth objects (NEOs) is important because they are more closely related than larger objects to the precursors of meteorites that fall on Earth. Collisions of these bodies with Earth are also more frequent. Although such collisions cannot produce massive extinction events, they can still produce significant local damage. Here we present the results of a photometric and spectroscopic survey of small NEOs that include near-infrared spectra of 84 objects with a mean diameter of 126 m and photometric data of 59 objects with a mean diameter of 87 m. We found that S-complex asteroids are the most abundant among the NEOs, comprising ∼66% of the sample. Most asteroids in the S-complex were found to have compositions consistent with LL-chondrites. Our study revealed the existence of NEOs with spectral characteristics similar to those in the S-complex but that could be hidden within the C- or X-complex due to their weak absorption bands. We suggest that the presence of metal or shock darkening could be responsible for the attenuation of the absorption bands. These objects have been grouped into a new subclass within the S-complex called Sx-types. The dynamical modeling showed that 83% of the NEOs escaped from the ν6 resonance, 16% from the 3:1, and just 1% from the 5:2 resonance. Lightcurves and rotational periods were derived from the photometric data. No clear trend between the axis ratio and the absolute magnitude or rotational period of the NEOs was found.
{"title":"The Population of Small Near-Earth Objects: Composition, Source Regions, and Rotational Properties","authors":"Juan A. Sanchez, Vishnu Reddy, Audrey Thirouin, William F. Bottke, Theodore Kareta, Mario De Florio, Benjamin N. L. Sharkey, Adam Battle, David C. Cantillo, Neil Pearson","doi":"10.3847/psj/ad445f","DOIUrl":"https://doi.org/10.3847/psj/ad445f","url":null,"abstract":"The study of small (<300 m) near-Earth objects (NEOs) is important because they are more closely related than larger objects to the precursors of meteorites that fall on Earth. Collisions of these bodies with Earth are also more frequent. Although such collisions cannot produce massive extinction events, they can still produce significant local damage. Here we present the results of a photometric and spectroscopic survey of small NEOs that include near-infrared spectra of 84 objects with a mean diameter of 126 m and photometric data of 59 objects with a mean diameter of 87 m. We found that S-complex asteroids are the most abundant among the NEOs, comprising ∼66% of the sample. Most asteroids in the S-complex were found to have compositions consistent with LL-chondrites. Our study revealed the existence of NEOs with spectral characteristics similar to those in the S-complex but that could be hidden within the C- or X-complex due to their weak absorption bands. We suggest that the presence of metal or shock darkening could be responsible for the attenuation of the absorption bands. These objects have been grouped into a new subclass within the S-complex called Sx-types. The dynamical modeling showed that 83% of the NEOs escaped from the <italic toggle=\"yes\">ν</italic>\u0000<sub>6</sub> resonance, 16% from the 3:1, and just 1% from the 5:2 resonance. Lightcurves and rotational periods were derived from the photometric data. No clear trend between the axis ratio and the absolute magnitude or rotational period of the NEOs was found.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141504698","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}
Catherine E. Regan, Andrew J. Coates, Mark Lester, Anne Wellbrock, Geraint H. Jones, Beatriz Sánchez-Cano, Philippe Garnier, Richard P. Haythornthwaite, Dikshita Meggi, Rudy A. Frahm and Mats Holmström
Mars's magnetosphere is a sensitive system, varying due to external and internal factors, such as solar wind conditions and crustal magnetic fields. A signature of this influence can be seen in the position of two boundaries; the bow shock and the induced magnetospheric boundary (IMB). The bow shock moves closer to Mars during times of high solar activity, and both the bow shock and IMB bulge away from Mars over crustal magnetic fields in the southern hemisphere. This study investigates whether large-scale atmospheric events at Mars have any signature in these two magnetic boundaries, by investigating the 2007 storm. The 2007 global storm lasted for several months and increased atmospheric temperatures and densities of both water vapor and carbon dioxide in the atmosphere, leading to an increase in atmospheric escape. Using Mars Express, we identified boundary locations before, during, and after the event, and compared these to modeled boundary locations and areographical locations on Mars. We find that, while it is unclear whether the bow shock position is impacted by the storm, the IMB location does change significantly, despite the orbital bias introduced by Mars Express. The terminator distance for the IMB peaks at longitudes 0°–40° and 310°–360°, leaving a depression around 180° longitude, where the boundary usually extends to higher altitudes due to the crustal magnetic fields. We suggest this may be due to the confinement of ionospheric plasma over crustal fields preventing mixing with the dust, creating a dip in ionospheric pressure here.
{"title":"Effects of the 2007 Martian Global Dust Storm on Boundary Positions in the Induced Magnetosphere","authors":"Catherine E. Regan, Andrew J. Coates, Mark Lester, Anne Wellbrock, Geraint H. Jones, Beatriz Sánchez-Cano, Philippe Garnier, Richard P. Haythornthwaite, Dikshita Meggi, Rudy A. Frahm and Mats Holmström","doi":"10.3847/psj/ad4116","DOIUrl":"https://doi.org/10.3847/psj/ad4116","url":null,"abstract":"Mars's magnetosphere is a sensitive system, varying due to external and internal factors, such as solar wind conditions and crustal magnetic fields. A signature of this influence can be seen in the position of two boundaries; the bow shock and the induced magnetospheric boundary (IMB). The bow shock moves closer to Mars during times of high solar activity, and both the bow shock and IMB bulge away from Mars over crustal magnetic fields in the southern hemisphere. This study investigates whether large-scale atmospheric events at Mars have any signature in these two magnetic boundaries, by investigating the 2007 storm. The 2007 global storm lasted for several months and increased atmospheric temperatures and densities of both water vapor and carbon dioxide in the atmosphere, leading to an increase in atmospheric escape. Using Mars Express, we identified boundary locations before, during, and after the event, and compared these to modeled boundary locations and areographical locations on Mars. We find that, while it is unclear whether the bow shock position is impacted by the storm, the IMB location does change significantly, despite the orbital bias introduced by Mars Express. The terminator distance for the IMB peaks at longitudes 0°–40° and 310°–360°, leaving a depression around 180° longitude, where the boundary usually extends to higher altitudes due to the crustal magnetic fields. We suggest this may be due to the confinement of ionospheric plasma over crustal fields preventing mixing with the dust, creating a dip in ionospheric pressure here.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141257302","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}
O. Agiwal, Hao Cao, Hsiang-Wen Hsu, L. Moore, A. Sulaiman, James O’Donoghue, Michele K. Dougherty
This study presents a synthesized analysis of in situ and ground-based observations to investigate electromagnetic coupling between Saturn and its rings. During the Cassini Grand Finale, the magnetometer detected gradients in the azimuthal magnetic field B ϕ connected to Saturn’s B-ring on 17 out of 21 orbits. The B ϕ gradients indicate that field-aligned currents are flowing into Saturn’s B-ring at ∼1.55–1.67 R S in the ring plane, preferentially in the southern hemisphere. On average, these currents are magnetically conjugate with ground-based observations of nonsolar enhancements in H3+ emissions from Saturn’s ionosphere and detected contemporaneously with ring-sourced, planetward electron beams and field-aligned charged dust grain inflow from the C- and B-rings into Saturn’s atmosphere. Collectively, these observations align with Voyager-era predictions of a phenomenon known as “ring rain,” where charged ring material generated inward of a nominal “critical radius” is drawn into Saturn’s upper atmosphere along the magnetic field. However, we show that the B-ring currents are not likely to be a direct signature of infalling field-aligned ring grains. Instead, we propose that the ring rain generation mechanism naturally results in a sharp gradient in the ionospheric Pedersen conductance at the ∼1.57–1.67 R S boundary, which, combined with a v × B electric field in the ring ionosphere, could drive the observed B-ring currents. The Pedersen conductance in the high-conductance region of the southern ring ionosphere is constrained to ∼0.07–2 S and is observed to vary within this range on week-long timescales.
本研究综合分析了现场和地面观测数据，以研究土星与其星环之间的电磁耦合。在 "卡西尼大结局 "期间，磁强计在 21 个轨道中的 17 个轨道上探测到了与土星 B 环相连的方位磁场 B ϕ 的梯度。B ϕ梯度表明，在环平面的 1.55-1.67 R S 处，有场对齐电流流入土星的 B 环，主要是在南半球。平均而言，这些电流与地面观测到的土星电离层非太阳H3+发射增强的情况在磁场上是共轭的，并与环源的行星向电子束和从C环和B环流入土星大气的场对齐带电尘粒同时被探测到。总体而言，这些观测结果与旅行者号时代对 "环雨 "现象的预测相吻合。"环雨 "现象是指在标称的 "临界半径 "内产生的带电环物质沿着磁场被吸入土星上层大气。不过，我们的研究表明，B 环电流不太可能是下沉的磁场对齐环粒的直接特征。相反，我们认为环雨产生机制自然会导致电离层佩德森电导在 1.57-1.67 R S 边界处出现急剧梯度，再加上环电离层中的 v × B 电场，可能会驱动观测到的 B 环电流。南环电离层高电导区的 Pedersen 电导被限制在 ∼0.07-2 S，并且观测到在这一范围内以周为时间尺度变化。
{"title":"Current Events at Saturn: Ring–Planet Electromagnetic Coupling","authors":"O. Agiwal, Hao Cao, Hsiang-Wen Hsu, L. Moore, A. Sulaiman, James O’Donoghue, Michele K. Dougherty","doi":"10.3847/PSJ/ad4343","DOIUrl":"https://doi.org/10.3847/PSJ/ad4343","url":null,"abstract":"This study presents a synthesized analysis of in situ and ground-based observations to investigate electromagnetic coupling between Saturn and its rings. During the Cassini Grand Finale, the magnetometer detected gradients in the azimuthal magnetic field B ϕ connected to Saturn’s B-ring on 17 out of 21 orbits. The B ϕ gradients indicate that field-aligned currents are flowing into Saturn’s B-ring at ∼1.55–1.67 R S in the ring plane, preferentially in the southern hemisphere. On average, these currents are magnetically conjugate with ground-based observations of nonsolar enhancements in H3+ emissions from Saturn’s ionosphere and detected contemporaneously with ring-sourced, planetward electron beams and field-aligned charged dust grain inflow from the C- and B-rings into Saturn’s atmosphere. Collectively, these observations align with Voyager-era predictions of a phenomenon known as “ring rain,” where charged ring material generated inward of a nominal “critical radius” is drawn into Saturn’s upper atmosphere along the magnetic field. However, we show that the B-ring currents are not likely to be a direct signature of infalling field-aligned ring grains. Instead, we propose that the ring rain generation mechanism naturally results in a sharp gradient in the ionospheric Pedersen conductance at the ∼1.57–1.67 R S boundary, which, combined with a v × B electric field in the ring ionosphere, could drive the observed B-ring currents. The Pedersen conductance in the high-conductance region of the southern ring ionosphere is constrained to ∼0.07–2 S and is observed to vary within this range on week-long timescales.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141412735","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}
Vishnu Reddy, Michael S. Kelley, L. Benner, J. Dotson, N. Erasmus, Davide Farnocchia, Tyler Linder, Joseph R. Masiero, Cristina Thomas, J. Bauer, M. R. Alarcon, P. Bacci, D. Bamberger, Adam Battle, Z. Benkhaldoun, Guido Betti, M. Birlan, Marina Brozovic, B. Burt, D. Cantillo, Sunil Chandra, Grégoire Chomette, Ashley Coates, F. DeMeo, M. Devogéle, P. Fatka, M. Ferrais, P. Fini, Carel van Gend, J. Giorgini, Dmitry Glamazda, Robert Holmes, Joseph L. Hora, Shinji Horiuchi, K. Hornoch, Marco Iozzi, Cristóvão Jacques, E. Jehin, Hai Jiang, Galina Kaiser, P. Kušnirák, Eduard Kuznetsov, J. de León, A. Liakos, J. Licandro, Tim A. Lister, Jing Liu, A. López-Oquendo, M. Maestripieri, D. Mathias, Marco Micheli, S. Naidu, A. Nastasi, A. Nedelcu, E. Petrescu, M. Popescu, Stephen B Potter, P. Pravec, Juan A. Sanchez, T. Santana-Ros, M. Serra-Ricart, N. Sioulas, A. Sonka, Alessio Squilloni, M. Tombelli, M. Trelia, D. Trilling, Elizabeth M. Warner, G. Wells, L. Wheeler, Mike Wiles
We present the results of a fourth planetary defense exercise, focused this time on the small near-Earth asteroid (NEA) 2023 DZ2 and conducted during its close approach to the Earth in 2023 March. The International Asteroid Warning Network (IAWN), with support from NASA's Planetary Defense Coordination Office (PDCO), has been coordinating planetary defense observational campaigns since 2017 to test the operational readiness of the global planetary defense capabilities. The last campaign focused on the NEA Apophis, and an outcome of that exercise was the need for a short burst campaign to replicate a real-life near-Earth object impact hazard scenario. The goal of the 2023 DZ2 campaign was to characterize the small NEA as a potential impactor and exercise the planetary defense system including observations, hypothetical risk assessment and risk prediction, and hazard communication with a short notice of just 24 hr. The entire campaign lasted about 10 days. The campaign team was divided into several working groups based on the characterization method: photometry, spectroscopy, thermal IR photometry and optical polarimetry, radar, and risk assessment. Science results from the campaign show that 2023 DZ2 has a rotation period of 6.2745 ± 0.0030 minutes; visible wavelength color photometry/spectroscopy/polarimetry and near-IR spectroscopy all point to an E-type taxonomic classification with surface composition analogous to aubrite meteorites; and radar observations show that the object has a diameter of 30 ± 10 m, consistent with the high albedo (0.49) derived from polarimetric and thermal IR observations.
{"title":"2023 DZ2 Planetary Defense Campaign","authors":"Vishnu Reddy, Michael S. Kelley, L. Benner, J. Dotson, N. Erasmus, Davide Farnocchia, Tyler Linder, Joseph R. Masiero, Cristina Thomas, J. Bauer, M. R. Alarcon, P. Bacci, D. Bamberger, Adam Battle, Z. Benkhaldoun, Guido Betti, M. Birlan, Marina Brozovic, B. Burt, D. Cantillo, Sunil Chandra, Grégoire Chomette, Ashley Coates, F. DeMeo, M. Devogéle, P. Fatka, M. Ferrais, P. Fini, Carel van Gend, J. Giorgini, Dmitry Glamazda, Robert Holmes, Joseph L. Hora, Shinji Horiuchi, K. Hornoch, Marco Iozzi, Cristóvão Jacques, E. Jehin, Hai Jiang, Galina Kaiser, P. Kušnirák, Eduard Kuznetsov, J. de León, A. Liakos, J. Licandro, Tim A. Lister, Jing Liu, A. López-Oquendo, M. Maestripieri, D. Mathias, Marco Micheli, S. Naidu, A. Nastasi, A. Nedelcu, E. Petrescu, M. Popescu, Stephen B Potter, P. Pravec, Juan A. Sanchez, T. Santana-Ros, M. Serra-Ricart, N. Sioulas, A. Sonka, Alessio Squilloni, M. Tombelli, M. Trelia, D. Trilling, Elizabeth M. Warner, G. Wells, L. Wheeler, Mike Wiles","doi":"10.3847/PSJ/ad4a6d","DOIUrl":"https://doi.org/10.3847/PSJ/ad4a6d","url":null,"abstract":"We present the results of a fourth planetary defense exercise, focused this time on the small near-Earth asteroid (NEA) 2023 DZ2 and conducted during its close approach to the Earth in 2023 March. The International Asteroid Warning Network (IAWN), with support from NASA's Planetary Defense Coordination Office (PDCO), has been coordinating planetary defense observational campaigns since 2017 to test the operational readiness of the global planetary defense capabilities. The last campaign focused on the NEA Apophis, and an outcome of that exercise was the need for a short burst campaign to replicate a real-life near-Earth object impact hazard scenario. The goal of the 2023 DZ2 campaign was to characterize the small NEA as a potential impactor and exercise the planetary defense system including observations, hypothetical risk assessment and risk prediction, and hazard communication with a short notice of just 24 hr. The entire campaign lasted about 10 days. The campaign team was divided into several working groups based on the characterization method: photometry, spectroscopy, thermal IR photometry and optical polarimetry, radar, and risk assessment. Science results from the campaign show that 2023 DZ2 has a rotation period of 6.2745 ± 0.0030 minutes; visible wavelength color photometry/spectroscopy/polarimetry and near-IR spectroscopy all point to an E-type taxonomic classification with surface composition analogous to aubrite meteorites; and radar observations show that the object has a diameter of 30 ± 10 m, consistent with the high albedo (0.49) derived from polarimetric and thermal IR observations.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141416081","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}
R. Nakano, M. Hirabayashi, S. Raducan, P. Pravec, S. Naidu, H. Agrusa, S. Chesley, F. Ferrari, M. Jutzi, C. C. Merrill, A. J. Meyer, P. Michel, Derek C. Richardson, P. Sánchez, Peter Scheirich, S. R. Schwartz, Yun Zhang, A. C. Bagatin, Po-Yen Liu, A. F. Cheng
On 2022 September 26 (UTC), NASA's Double Asteroid Redirection Test (DART) mission achieved a successful impact on Dimorphos, the secondary component of the near-Earth binary asteroid system (65803) Didymos. Subsequent ground-based observations suggest a significant reshaping of Dimorphos, with its equatorial axis ratio changing from 1.06 to ∼1.3. Here we report the effects of this reshaping event on Dimorphos's orbit and attitude. Given the reported reshaping magnitude, our mutual dynamics simulations show that approximately 125 s of the observed 33 minute orbit period change after the DART impact may have resulted from reshaping. This value, however, is sensitive to the precise values of Dimorphos's post-impact axis ratios and may vary by up to 2 times that amount, reaching approximately 250 s within the current uncertainty range. While the rotational state of the body is stable at the currently estimated axis ratios, even minor changes in these ratios or the introduction of shape asymmetry can render its attitude unstable. The perturbation to Dimorphos’s orbital and rotational state delivered by the impact directly, combined with any reshaping, leads to a strong possibility for a tumbling rotation state. To accurately determine the momentum enhancement factor (β) through measurements by the European Space Agency’s Hera spacecraft and to evaluate the effectiveness of the kinetic deflection technique for future planetary defense initiatives, the effects of reshaping should not be overlooked.
{"title":"Dimorphos’s Orbit Period Change and Attitude Perturbation due to Its Reshaping after the DART Impact","authors":"R. Nakano, M. Hirabayashi, S. Raducan, P. Pravec, S. Naidu, H. Agrusa, S. Chesley, F. Ferrari, M. Jutzi, C. C. Merrill, A. J. Meyer, P. Michel, Derek C. Richardson, P. Sánchez, Peter Scheirich, S. R. Schwartz, Yun Zhang, A. C. Bagatin, Po-Yen Liu, A. F. Cheng","doi":"10.3847/PSJ/ad4350","DOIUrl":"https://doi.org/10.3847/PSJ/ad4350","url":null,"abstract":"On 2022 September 26 (UTC), NASA's Double Asteroid Redirection Test (DART) mission achieved a successful impact on Dimorphos, the secondary component of the near-Earth binary asteroid system (65803) Didymos. Subsequent ground-based observations suggest a significant reshaping of Dimorphos, with its equatorial axis ratio changing from 1.06 to ∼1.3. Here we report the effects of this reshaping event on Dimorphos's orbit and attitude. Given the reported reshaping magnitude, our mutual dynamics simulations show that approximately 125 s of the observed 33 minute orbit period change after the DART impact may have resulted from reshaping. This value, however, is sensitive to the precise values of Dimorphos's post-impact axis ratios and may vary by up to 2 times that amount, reaching approximately 250 s within the current uncertainty range. While the rotational state of the body is stable at the currently estimated axis ratios, even minor changes in these ratios or the introduction of shape asymmetry can render its attitude unstable. The perturbation to Dimorphos’s orbital and rotational state delivered by the impact directly, combined with any reshaping, leads to a strong possibility for a tumbling rotation state. To accurately determine the momentum enhancement factor (β) through measurements by the European Space Agency’s Hera spacecraft and to evaluate the effectiveness of the kinetic deflection technique for future planetary defense initiatives, the effects of reshaping should not be overlooked.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141396610","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}
D. Cantillo, Kaycee I. Ridenhour, Adam Battle, Thomas Joyce, Juliana Nunez Breceda, Neil Pearson, Vishnu Reddy
Characterization of near-Earth objects (NEOs) is critical for Earth-impact hazard assessment. Particularly crucial to our physical understanding of NEOs are laboratory spectral measurements of meteorites as they are the best and most widely available analog materials, barring sample return missions. However, most meteorites do not have direct orbital links to specific asteroids, making it challenging to identify their source body in the NEO or main-belt asteroid populations. Near-Earth asteroid (NEA) 2024 BX1 was discovered on 2024 January 20 at 21:48 UTC from MPC code K88, impacting the Earth (west of Berlin, Germany) 165 minutes later. The incoming bolide was observed by multiple meteor cameras, which enabled successful reconstruction of its exo-atmospheric orbit and quick recovery. We present results from laboratory spectral characterization of the Ribbeck meteorite in the UV–mid-infrared wavelengths (0.2–14.2 μm) over seven grain size bins (<45 μm–slab). Our results suggest that Ribbeck has spectral properties consistent with enstatite achondrite (aubrite) meteorites. Our grain-size spectral analysis shows that albedo and spectral slope decrease as grain size increases. In addition, increasing grain size also shifts the taxonomic type in the Bus–DeMeo system from Xn to B types, suggesting the limitations of taxonomy in classifying small, regolith-free NEAs. We also present results of our comparison between Ribbeck data and spectra of E types in the main-belt and NEA populations. Principal component analysis of our Ribbeck samples shows variations parallel to the α line, which can be confused with space weathering in PC space.
近地天体（NEOs）的特征描述对于地球撞击危险评估至关重要。陨石的实验室光谱测量对我们了解近地天体的物理特性尤为重要，因为除样本返回任务外，陨石是最好和最广泛可用的模拟材料。然而，大多数陨石与特定的小行星没有直接的轨道联系，因此在近地小行星或主带小行星群中确定其源体具有挑战性。近地小行星（NEA）2024 BX1 于 2024 年 1 月 20 日 21:48 UTC 发现，来自 MPC 代码 K88，165 分钟后撞击地球（德国柏林以西）。多台流星照相机观测到了这颗来袭的长尾天体，从而成功地重建了它的大气层外轨道并使其迅速恢复。我们展示了里贝克陨石在七个粒度分段（<45 μm-slab）的紫外-中红外波段（0.2-14.2 μm）的实验室光谱特性分析结果。我们的结果表明，Ribbeck 的光谱特性与软玉（enstatite achondrite）陨石一致。我们的粒度光谱分析显示，反照率和光谱斜率随着粒度的增大而减小。此外，晶粒尺寸的增大也会使 Bus-DeMeo 系统中的分类类型从 Xn 类型转变为 B 类型，这表明分类学在对小型、不含残积岩的近地天体进行分类时存在局限性。我们还介绍了里贝克数据与主带和近地小行星群中 E 类型光谱的比较结果。对我们的里贝克样本进行的主成分分析显示了与α线平行的变化，这可能与PC空间的空间风化相混淆。
{"title":"Laboratory Spectral Characterization of Ribbeck Aubrite: Meteorite Sample of Earth-impacting Near-Earth Asteroid 2024 BX1","authors":"D. Cantillo, Kaycee I. Ridenhour, Adam Battle, Thomas Joyce, Juliana Nunez Breceda, Neil Pearson, Vishnu Reddy","doi":"10.3847/PSJ/ad4885","DOIUrl":"https://doi.org/10.3847/PSJ/ad4885","url":null,"abstract":"Characterization of near-Earth objects (NEOs) is critical for Earth-impact hazard assessment. Particularly crucial to our physical understanding of NEOs are laboratory spectral measurements of meteorites as they are the best and most widely available analog materials, barring sample return missions. However, most meteorites do not have direct orbital links to specific asteroids, making it challenging to identify their source body in the NEO or main-belt asteroid populations. Near-Earth asteroid (NEA) 2024 BX1 was discovered on 2024 January 20 at 21:48 UTC from MPC code K88, impacting the Earth (west of Berlin, Germany) 165 minutes later. The incoming bolide was observed by multiple meteor cameras, which enabled successful reconstruction of its exo-atmospheric orbit and quick recovery. We present results from laboratory spectral characterization of the Ribbeck meteorite in the UV–mid-infrared wavelengths (0.2–14.2 μm) over seven grain size bins (<45 μm–slab). Our results suggest that Ribbeck has spectral properties consistent with enstatite achondrite (aubrite) meteorites. Our grain-size spectral analysis shows that albedo and spectral slope decrease as grain size increases. In addition, increasing grain size also shifts the taxonomic type in the Bus–DeMeo system from Xn to B types, suggesting the limitations of taxonomy in classifying small, regolith-free NEAs. We also present results of our comparison between Ribbeck data and spectra of E types in the main-belt and NEA populations. Principal component analysis of our Ribbeck samples shows variations parallel to the α line, which can be confused with space weathering in PC space.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141403348","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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