Pub Date : 2024-11-27DOI: 10.1016/j.icarus.2024.116400
M.D. Cashion , B.C. Johnson , R. Deienno , K.A. Kretke , K.J. Walsh , A.N. Krot
Chondrules, igneous spherules found in most meteorites, formed throughout the protoplanetary disk, but their formation is largely unexplored beyond the water snowline, in the outer disk. Combining simulations of giant planet core accretion with simulations of planetesimal collisions, we find that impact jetting can produce chondrules to distances of ∼15 AU from the Sun. In our simulations, chondrule formation ceases by the time the first giant planet core exceeds isolation mass, ∼10 Earth masses. The time it takes to reach this mass is sensitive to the total mass of the disk, and how the mass is distributed within planetesimals and small pebbles. Measured chondrule ages subsequently constrain the time of Jupiter's core formation to approximately 3–4 Myr after the first solar system solids. This protracted growth indicates the separation of non‑carbonaceous and carbonaceous material reservoirs predates the formation of Jupiter's core.
{"title":"Chondrule formation indicates protracted growth of giant planet cores","authors":"M.D. Cashion , B.C. Johnson , R. Deienno , K.A. Kretke , K.J. Walsh , A.N. Krot","doi":"10.1016/j.icarus.2024.116400","DOIUrl":"10.1016/j.icarus.2024.116400","url":null,"abstract":"<div><div>Chondrules, igneous spherules found in most meteorites, formed throughout the protoplanetary disk, but their formation is largely unexplored beyond the water snowline, in the outer disk. Combining simulations of giant planet core accretion with simulations of planetesimal collisions, we find that impact jetting can produce chondrules to distances of ∼15 AU from the Sun. In our simulations, chondrule formation ceases by the time the first giant planet core exceeds isolation mass, ∼10 Earth masses. The time it takes to reach this mass is sensitive to the total mass of the disk, and how the mass is distributed within planetesimals and small pebbles. Measured chondrule ages subsequently constrain the time of Jupiter's core formation to approximately 3–4 Myr after the first solar system solids. This protracted growth indicates the separation of non‑carbonaceous and carbonaceous material reservoirs predates the formation of Jupiter's core.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"429 ","pages":"Article 116400"},"PeriodicalIF":2.5,"publicationDate":"2024-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134538","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}
Pub Date : 2024-11-26DOI: 10.1016/j.icarus.2024.116386
Larry W. Esposito , Joshua Ε. Colwell , Stephanie Eckert , Melody R. Green , Richard G. Jerousek , Sreenivas Madhusudhanan
The varying geometry of Cassini star occultations by Saturn's rings constrains both the size and shape of structures that block starlight. We extend the approach of Showalter and Nicholson (1990, who first used the observed variance of the stellar counts to calculate the size of the ring particles from the Voyager ring occultation) to higher moments and remove their restrictions on fractional particle area δ < < 1 and line-of-sight optical depth τ < < 1. We calculate the excess variance, skewness and kurtosis including the effects of irregular particle shadows, adopting a rectangular parallelepiped model of self-gravity wakes which can also be extended to model irregularly spaced gaps, ghosts, and clumps. Particles in Saturn's background C ring and the C ring ramp are matched by spheres with effective radius aeff = 2.5 m, with no evidence for gaps or ghosts in these 2 regions. The A ring statistics are dominated by self-gravity wakes. The skewness and kurtosis require transparent regions like those seen in high resolution Cassini occultations and indicated by numerical simulations. Transparent gaps between self-gravity wakes demonstrate dynamic processes which prevent the rings from achieving uniformity. The changing wake structures show density waves can trigger aggregation, consistent with a Predator-Prey model of ring dynamics (Esposito et al. 2012). Perturbed by passing density waves, self-gravity wakes grow and erode on orbital timescales with a full amplitude of 50 %, and a phase lag Δϕ ∼ 60°. We speculate that the collisions or azimuthal instabilities of these wakes may lead to the straw features seen in Cassini images. Ejecta from collisions and erosion may be forming the dusty haloes around the density waves. Similar resonant perturbations from a forming protoplanet could trigger growth at its resonant locations in a debris disk.
{"title":"Statistics of Saturn's ring occultations: Implications for structure, dynamics, and origins","authors":"Larry W. Esposito , Joshua Ε. Colwell , Stephanie Eckert , Melody R. Green , Richard G. Jerousek , Sreenivas Madhusudhanan","doi":"10.1016/j.icarus.2024.116386","DOIUrl":"10.1016/j.icarus.2024.116386","url":null,"abstract":"<div><div>The varying geometry of Cassini star occultations by Saturn's rings constrains both the size and shape of structures that block starlight. We extend the approach of Showalter and Nicholson (1990, who first used the observed variance of the stellar counts to calculate the size of the ring particles from the Voyager ring occultation) to higher moments and remove their restrictions on fractional particle area <em>δ</em> < < 1 and line-of-sight optical depth <em>τ</em> < < 1. We calculate the excess variance, skewness and kurtosis including the effects of irregular particle shadows, adopting a rectangular parallelepiped model of self-gravity wakes which can also be extended to model irregularly spaced gaps, ghosts, and clumps. Particles in Saturn's background C ring and the C ring ramp are matched by spheres with effective radius a<sub>eff</sub> = 2.5 m, with no evidence for gaps or ghosts in these 2 regions. The A ring statistics are dominated by self-gravity wakes. The skewness and kurtosis require transparent regions like those seen in high resolution Cassini occultations and indicated by numerical simulations. Transparent gaps between self-gravity wakes demonstrate dynamic processes which prevent the rings from achieving uniformity. The changing wake structures show density waves can trigger aggregation, consistent with a Predator-Prey model of ring dynamics (Esposito et al. 2012). Perturbed by passing density waves, self-gravity wakes grow and erode on orbital timescales with a full amplitude of 50 %, and a phase lag Δϕ ∼ 60°. We speculate that the collisions or azimuthal instabilities of these wakes may lead to the straw features seen in Cassini images. Ejecta from collisions and erosion may be forming the dusty haloes around the density waves. Similar resonant perturbations from a forming protoplanet could trigger growth at its resonant locations in a debris disk.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"429 ","pages":"Article 116386"},"PeriodicalIF":2.5,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134793","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}
Pub Date : 2024-11-26DOI: 10.1016/j.icarus.2024.116379
Jose Daniel Castro-Cisneros , Renu Malhotra , Aaron J. Rosengren
Lunar ejecta, produced by meteoroidal impacts, have been proposed for the origin of the near-Earth asteroid (469219) Kamo’oalewa, supported by its unusually Earth-like orbit and L-type reflectance spectrum (Sharkey et al., 2021). In a recent study (Castro-Cisneros et al. 2023), we found with N-body numerical simulations that the orbit of Kamo’oalewa is dynamically compatible with rare pathways of lunar ejecta captured into Earth’s co-orbital region, persistently transitioning between horseshoe and quasi-satellite (HS-QS) states. Subsequently, Jiao et al. (2024) found with hydrodynamic and N-body simulations that the geologically young lunar crater Giordano Bruno generated up to 300 Kamo’oalewa-sized escaping fragments, and up to three of those could have become Earth co-orbitals. However, these results are based upon specific initial conditions of the major planets in the Solar System, close to the current epoch. In particular, over megayear time spans, Earth’s eccentricity undergoes excursions up to five times its current value, potentially affecting the chaotic orbital evolution of lunar ejecta and their capture into Earth’s co-orbital regions. In the present work, we carry out additional numerical simulations to compute the statistics of co-orbital outcomes across different launch epochs, representative of the full range of Earth’s eccentricity values. Our main results are as follows: Kamo’oalewa-like co-orbital outcomes of lunar ejecta vary only slightly across the range of Earth’s orbital eccentricity, suggesting no privileged ejecta launching epoch for such objects; the probability of co-orbital outcomes decreases rapidly with increasing launch speed, but long-lived HS-QS states are favored at higher launch speeds.
{"title":"The sensitivity to initial conditions of the co-orbital outcomes of lunar ejecta","authors":"Jose Daniel Castro-Cisneros , Renu Malhotra , Aaron J. Rosengren","doi":"10.1016/j.icarus.2024.116379","DOIUrl":"10.1016/j.icarus.2024.116379","url":null,"abstract":"<div><div>Lunar ejecta, produced by meteoroidal impacts, have been proposed for the origin of the near-Earth asteroid (469219) Kamo’oalewa, supported by its unusually Earth-like orbit and L-type reflectance spectrum (Sharkey et al., 2021). In a recent study (Castro-Cisneros et al. 2023), we found with N-body numerical simulations that the orbit of Kamo’oalewa is dynamically compatible with rare pathways of lunar ejecta captured into Earth’s co-orbital region, persistently transitioning between horseshoe and quasi-satellite (HS-QS) states. Subsequently, Jiao et al. (2024) found with hydrodynamic and N-body simulations that the geologically young lunar crater Giordano Bruno generated up to 300 Kamo’oalewa-sized escaping fragments, and up to three of those could have become Earth co-orbitals. However, these results are based upon specific initial conditions of the major planets in the Solar System, close to the current epoch. In particular, over megayear time spans, Earth’s eccentricity undergoes excursions up to five times its current value, potentially affecting the chaotic orbital evolution of lunar ejecta and their capture into Earth’s co-orbital regions. In the present work, we carry out additional numerical simulations to compute the statistics of co-orbital outcomes across different launch epochs, representative of the full range of Earth’s eccentricity values. Our main results are as follows: Kamo’oalewa-like co-orbital outcomes of lunar ejecta vary only slightly across the range of Earth’s orbital eccentricity, suggesting no privileged ejecta launching epoch for such objects; the probability of co-orbital outcomes decreases rapidly with increasing launch speed, but long-lived HS-QS states are favored at higher launch speeds.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"429 ","pages":"Article 116379"},"PeriodicalIF":2.5,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134800","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}
Pub Date : 2024-11-26DOI: 10.1016/j.icarus.2024.116380
Ilgmars Eglitis, Darja Svincicka
In the present study, the Lomb–Scargle Scargle (L–S) method was employed for the analysis of brightness measurements from multiple observatories as published in the Minor Planet Center (MPC) circulars, as well as brightness measurements from the Baldone Observatory, to determine the periods of asteroids. The periods of fifteen asteroids were determined. The research yielded results for both asteroids with previously known periods and those without listed periods in the ALCDEF lightcurve database. The results revealed the potential for this approach to be used in the subsequent identification of yet-unknown periods of asteroids. This was demonstrated by the confirmation of periods for four of the five asteroids with known periods from the ALCDEF lightcurve database, namely 1951, 1963, 2134 and 2150. In the case of the fifth asteroid, 2174, for which a previously determined rotation period had been provided, an additional, possible shorter rotation period was identified. As has been shown, the use of the L–S method in conjunction with independent analysis of many series of brightness measurements from different observatories is a suitable approach, even for a small series of samples of brightness observations unevenly spread over a long time, for the determination of periods. Furthermore, this approach is effective even when there are significant intervals between measurements, which is not the case with the classical Fourier method. Additionally, the exclusion of observations that deviate significantly from the linear relationship of the phase diagram, by the three-sigma criterion, markedly enhanced the efficacy and precision of the method. As a result, periods were identified for the first time for asteroids 1779, 1818, 2128, 2318, 2497, 2503, 2538, 2539, and 2583.
{"title":"Rotation period estimates for 14 asteroids with the Earth MOID less than 1.1 AU","authors":"Ilgmars Eglitis, Darja Svincicka","doi":"10.1016/j.icarus.2024.116380","DOIUrl":"10.1016/j.icarus.2024.116380","url":null,"abstract":"<div><div>In the present study, the Lomb–Scargle Scargle (L–S) method was employed for the analysis of brightness measurements from multiple observatories as published in the Minor Planet Center (MPC) circulars, as well as brightness measurements from the Baldone Observatory, to determine the periods of asteroids. The periods of fifteen asteroids were determined. The research yielded results for both asteroids with previously known periods and those without listed periods in the ALCDEF lightcurve database. The results revealed the potential for this approach to be used in the subsequent identification of yet-unknown periods of asteroids. This was demonstrated by the confirmation of periods for four of the five asteroids with known periods from the ALCDEF lightcurve database, namely 1951, 1963, 2134 and 2150. In the case of the fifth asteroid, 2174, for which a previously determined rotation period had been provided, an additional, possible shorter rotation period was identified. As has been shown, the use of the L–S method in conjunction with independent analysis of many series of brightness measurements from different observatories is a suitable approach, even for a small series of samples of brightness observations unevenly spread over a long time, for the determination of periods. Furthermore, this approach is effective even when there are significant intervals between measurements, which is not the case with the classical Fourier method. Additionally, the exclusion of observations that deviate significantly from the linear relationship of the phase diagram, by the three-sigma criterion, markedly enhanced the efficacy and precision of the method. As a result, periods were identified for the first time for asteroids 1779, 1818, 2128, 2318, 2497, 2503, 2538, 2539, and 2583.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"428 ","pages":"Article 116380"},"PeriodicalIF":2.5,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142745842","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}
Pub Date : 2024-11-26DOI: 10.1016/j.icarus.2024.116384
Ivy Ettenborough, Anna Szynkiewicz
Secondary sulfate minerals are common throughout the sedimentary deposits of Mount Sharp, located within Gale crater on Mars. However, the source of sulfate (SO42−) and past climatic conditions during their formation are not well understood. Therefore, we investigated the δ34S, δ18O, and δ2H of gypsum veins and other Mg- and Ca- sulfates forming as salt crusts and cement within the shallow sediments of the Rio Puerco watershed in central New Mexico. The δ34S values of vein gypsum and acid-soluble SO42− (cement) varied over the same range (−33.3 to −12.9 ‰ and −34.6 to −12.1 ‰, respectively), which was similar to the δ34S of bedrock sulfide minerals (−37.4 to −5.9 ‰). This implies that sulfide oxidation is the main source of SO42− in the Rio Puerco aqueous system. The measured δ18O values of SO42− (−8.9 to +3.1 ‰) as well as δ18O and δ2H values of gypsum hydration water (−8.9 to +0.6 ‰, and −112 to −82 ‰, respectively) overlapped with the isotope composition of local meteoric precipitation, suggesting that sulfide oxidation to SO42− and gypsum formation have occurred under semi-arid climate conditions. The isotope results suggest the top-down infiltration of meteoric water leads to leaching of SO42−, Mg+, and Ca2+ from bedrock sulfide weathering followed by abundant formation of Mg- and Ca-sulfates in surface deposits and gypsum veins with depth. Because of spatial and mineralogical similarities in the secondary Mg- and Ca-sulfate mineral occurrences, we hypothesize that chemical weathering of sulfide minerals could have been the main source of SO42− in the aqueous system of Gale crater.
{"title":"Investigating formation processes of secondary sulfate minerals in the semi-arid climate of the Rio Puerco watershed, New Mexico using sulfur and oxygen isotopes – Implications for the origin of gypsum veins in Gale crater on Mars","authors":"Ivy Ettenborough, Anna Szynkiewicz","doi":"10.1016/j.icarus.2024.116384","DOIUrl":"10.1016/j.icarus.2024.116384","url":null,"abstract":"<div><div>Secondary sulfate minerals are common throughout the sedimentary deposits of Mount Sharp, located within Gale crater on Mars. However, the source of sulfate (SO<sub>4</sub><sup>2−</sup>) and past climatic conditions during their formation are not well understood. Therefore, we investigated the δ<sup>34</sup>S, δ<sup>18</sup>O, and δ<sup>2</sup>H of gypsum veins and other Mg- and Ca- sulfates forming as salt crusts and cement within the shallow sediments of the Rio Puerco watershed in central New Mexico. The δ<sup>34</sup>S values of vein gypsum and acid-soluble SO<sub>4</sub><sup>2−</sup> (cement) varied over the same range (−33.3 to −12.9 ‰ and −34.6 to −12.1 ‰, respectively), which was similar to the δ<sup>34</sup>S of bedrock sulfide minerals (−37.4 to −5.9 ‰). This implies that sulfide oxidation is the main source of SO<sub>4</sub><sup>2−</sup> in the Rio Puerco aqueous system. The measured δ<sup>18</sup>O values of SO<sub>4</sub><sup>2−</sup> (−8.9 to +3.1 ‰) as well as δ<sup>18</sup>O and δ<sup>2</sup>H values of gypsum hydration water (−8.9 to +0.6 ‰, and −112 to −82 ‰, respectively) overlapped with the isotope composition of local meteoric precipitation, suggesting that sulfide oxidation to SO<sub>4</sub><sup>2−</sup> and gypsum formation have occurred under semi-arid climate conditions. The isotope results suggest the top-down infiltration of meteoric water leads to leaching of SO<sub>4</sub><sup>2−</sup>, Mg<sup>+</sup>, and Ca<sup>2+</sup> from bedrock sulfide weathering followed by abundant formation of Mg- and Ca-sulfates in surface deposits and gypsum veins with depth. Because of spatial and mineralogical similarities in the secondary Mg- and Ca-sulfate mineral occurrences, we hypothesize that chemical weathering of sulfide minerals could have been the main source of SO<sub>4</sub><sup>2−</sup> in the aqueous system of Gale crater.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"428 ","pages":"Article 116384"},"PeriodicalIF":2.5,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142759678","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}
Pub Date : 2024-11-26DOI: 10.1016/j.icarus.2024.116375
L. Šachl, J. Kvorka, O. Čadek, J. Velímský
Movements of Europa in Jupiter’s magnetic field generate an induced magnetic field in the moon’s interior. Its measurements by the Galileo space probe led to the discovery of Europa’s subsurface ocean. However, interactions of the ocean flow with Jupiter’s background magnetic field also generate the motionally induced electrical currents in the ocean and the corresponding ocean-induced magnetic field (OIMF), which has not yet been studied in detail. A single study estimated the OIMF nT using a simplified scaling relation. In this paper, we revisit this estimate using a physically consistent modeling setup. Based on the numerical simulations of ocean convection, we show that two modes can exist in Europa’s ocean. Mode I is dominated by a prograde zonal flow at the equator with negligible radial and meridional flows. Mode II is characterized by Hadley-like meridional circulation cells in both hemispheres and a retrograde zonal flow at the equator. The scaling analysis based on our dataset strongly indicates that Mode II is appropriate for Europa’s ocean with velocities around m/s. We then calculate Europa’s OIMF using a time-domain EM induction solver, which properly accounts for self-induction and diffusion of the magnetic field in the silicate and ice layers, and implicitly covers the full temporal spectrum. Our calculations suggest that even under the most favorable circumstances ( km thick ocean with a conductivity of S/m located under a 1 km thick ice layer) the magnitude of Europa’s OIMF forced by the flow in Mode II is approximately nT, at the lower bound of the sensitivity of the Europa Clipper measurements and more than one order of magnitude smaller than previously predicted. The discrepancy is primarily caused by a more sluggish ocean flow and a correct treatment of EM induction. Moreover, Europa’s OIMF is affected by the electrical conductivity and thickness of ice and ocean, which we demonstrate in a parametric study.
{"title":"Magnetic field induced by convective flow in Europa’s subsurface ocean","authors":"L. Šachl, J. Kvorka, O. Čadek, J. Velímský","doi":"10.1016/j.icarus.2024.116375","DOIUrl":"10.1016/j.icarus.2024.116375","url":null,"abstract":"<div><div>Movements of Europa in Jupiter’s magnetic field generate an induced magnetic field in the moon’s interior. Its measurements by the Galileo space probe led to the discovery of Europa’s subsurface ocean. However, interactions of the ocean flow with Jupiter’s background magnetic field also generate the motionally induced electrical currents in the ocean and the corresponding ocean-induced magnetic field (OIMF), which has not yet been studied in detail. A single study estimated the OIMF <span><math><mo>≤</mo></math></span> <!--> <span><math><mrow><mn>20</mn></mrow></math></span> <!--> <!-->nT using a simplified scaling relation. In this paper, we revisit this estimate using a physically consistent modeling setup. Based on the numerical simulations of ocean convection, we show that two modes can exist in Europa’s ocean. Mode I is dominated by a prograde zonal flow at the equator with negligible radial and meridional flows. Mode II is characterized by Hadley-like meridional circulation cells in both hemispheres and a retrograde zonal flow at the equator. The scaling analysis based on our dataset strongly indicates that Mode II is appropriate for Europa’s ocean with velocities around <span><math><mrow><mn>0</mn><mo>.</mo><mn>3</mn></mrow></math></span> <!--> <!-->m/s. We then calculate Europa’s OIMF using a time-domain EM induction solver, which properly accounts for self-induction and diffusion of the magnetic field in the silicate and ice layers, and implicitly covers the full temporal spectrum. Our calculations suggest that even under the most favorable circumstances (<span><math><mrow><mn>150</mn></mrow></math></span> <!--> <!-->km thick ocean with a conductivity of <span><math><mrow><mn>18</mn></mrow></math></span> <!--> <!-->S/m located under a 1 km thick ice layer) the magnitude of Europa’s OIMF forced by the flow in Mode II is approximately <span><math><mn>1</mn></math></span> <!--> <!-->nT, at the lower bound of the sensitivity of the Europa Clipper measurements and more than one order of magnitude smaller than previously predicted. The discrepancy is primarily caused by a more sluggish ocean flow and a correct treatment of EM induction. Moreover, Europa’s OIMF is affected by the electrical conductivity and thickness of ice and ocean, which we demonstrate in a parametric study.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"429 ","pages":"Article 116375"},"PeriodicalIF":2.5,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134727","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}
Pub Date : 2024-11-26DOI: 10.1016/j.icarus.2024.116401
B. Hubert , L. Soret , J.-C. Gérard , G. Wautelet , G. Munhoven , A. Piccialli , A.-C. Vandaele
Over the last two decades, important efforts have been undertaken by the most prominent space agencies to explore and analyze the interior, ground and atmosphere of Mars. A series of remote sensing instruments have been deployed and operated to characterize the atmospheric composition and dynamics. Several techniques have been used including solar occultation spectroscopy recording the sun spectrum attenuated through the atmosphere. We present three different methods dedicated to the analysis of occultation observations in the ultraviolet (UV) wavelength range covering the Hartley band of ozone. These methods are designed to account for several absorbing gases as well as aerosols responsible for extinction along the observing line-of-sight passing through the atmosphere. The aerosols are described using a local extinction parameter at a reference wavelength and a so-called Angström α-parameter to express the wavelength dependency of extinction with a power law.
In a first method, inverse Abel transform of the total extinction parameter (or optical thickness) of the atmosphere is conducted at each wavelength using a least-squares fitting technique, followed by a second least squares estimate of the local atmospheric properties at all fitting altitudes, separately.
A second method is derived in which all the atmospheric gas concentrations and aerosol extinction coefficient at reference wavelength vary with altitude in a piecewise linear manner. The α parameter is however assumed to be a piecewise linear function of ln(r), allowing for numerical and analytic developments. For the sake of inversion of the observation, the gas densities and aerosol reference extinction parameters are expressed as a function of the α parameters using a linear least-squares fitting expression, so that the α parameters can be estimated using a non-linear least-squares fitting method.
A third method is derived in which the gas species are approximated using piecewise exponential branches. Tests are conducted to evaluate the efficiency of all methods against retrieval of a prescribed atmospheric profile.
It is found that the first two methods can readily retrieve the atmospheric properties, the second one allowing for more consistent uncertainty estimates. The third method is found to be computationally expensive with a difficult-to-reach fitting convergence. Preliminary tests are conducted using TGO-NOMAD-UVIS observations in the O3 Hartley band wavelength range. It is found that the CO2 extinction is too weak to allow retrieval of the CO2 density profile from observations at those wavelengths, while the O3 density and dust properties can be successfully retrieved.
{"title":"Inversion of ultraviolet occultation profiles in a dusty atmosphere: Analytic and numerical methods","authors":"B. Hubert , L. Soret , J.-C. Gérard , G. Wautelet , G. Munhoven , A. Piccialli , A.-C. Vandaele","doi":"10.1016/j.icarus.2024.116401","DOIUrl":"10.1016/j.icarus.2024.116401","url":null,"abstract":"<div><div>Over the last two decades, important efforts have been undertaken by the most prominent space agencies to explore and analyze the interior, ground and atmosphere of Mars. A series of remote sensing instruments have been deployed and operated to characterize the atmospheric composition and dynamics. Several techniques have been used including solar occultation spectroscopy recording the sun spectrum attenuated through the atmosphere. We present three different methods dedicated to the analysis of occultation observations in the ultraviolet (UV) wavelength range covering the Hartley band of ozone. These methods are designed to account for several absorbing gases as well as aerosols responsible for extinction along the observing line-of-sight passing through the atmosphere. The aerosols are described using a local extinction parameter at a reference wavelength and a so-called Angström α-parameter to express the wavelength dependency of extinction with a power law.</div><div>In a first method, inverse Abel transform of the total extinction parameter (or optical thickness) of the atmosphere is conducted at each wavelength using a least-squares fitting technique, followed by a second least squares estimate of the local atmospheric properties at all fitting altitudes, separately.</div><div>A second method is derived in which all the atmospheric gas concentrations and aerosol extinction coefficient at reference wavelength vary with altitude in a piecewise linear manner. The α parameter is however assumed to be a piecewise linear function of ln(r), allowing for numerical and analytic developments. For the sake of inversion of the observation, the gas densities and aerosol reference extinction parameters are expressed as a function of the α parameters using a linear least-squares fitting expression, so that the α parameters can be estimated using a non-linear least-squares fitting method.</div><div>A third method is derived in which the gas species are approximated using piecewise exponential branches. Tests are conducted to evaluate the efficiency of all methods against retrieval of a prescribed atmospheric profile.</div><div>It is found that the first two methods can readily retrieve the atmospheric properties, the second one allowing for more consistent uncertainty estimates. The third method is found to be computationally expensive with a difficult-to-reach fitting convergence. Preliminary tests are conducted using TGO-NOMAD-UVIS observations in the O<sub>3</sub> Hartley band wavelength range. It is found that the CO<sub>2</sub> extinction is too weak to allow retrieval of the CO<sub>2</sub> density profile from observations at those wavelengths, while the O<sub>3</sub> density and dust properties can be successfully retrieved.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"429 ","pages":"Article 116401"},"PeriodicalIF":2.5,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134794","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}
Pub Date : 2024-11-26DOI: 10.1016/j.icarus.2024.116382
Jianhua Cui, Geng Li, Yongheng Zhao
The historical observations of East Asia provide a systematic and accurate record of bright periodic comets and could help us understand their past states. However, except for these comets, few other comets have been successfully associated with historical observations. Here we report that the sunskirter 322P/SOHO is probably associated with a historical comet in 254 CE, although it appeared no visible cometary activity in recent observations. By analyzing astrometric data from the IAU Minor Planet Center, we determine the orbit of 322P and suggest that its motion is affected by non-gravitational forces based on sodium sublimation, indicating its high devolatilization. The orbital integration shows that the position and perihelion date of 322P are highly corresponding to a historical comet in 254 CE. This comet had an extremely long tail that stretched across the sky, indicating the intense activity outburst. The dynamical properties of 322P and its similarity to dark comets suggests that it possibly originated from a volatile object in the main belt, but has undergone the rotational splitting and devolatilization. Previous studies have also suggested the possible splitting. Given that splitting is a common cause of activity outburst, we suggest that 322P might have experienced a fragmentation in 254 CE and released a large amount of material, which led to the spectacular tail and devolatilization. Only faint sodium-driven activity remained afterwards, which could explain the lack of historical observations after 254 CE.
{"title":"322P/SOHO: The counterpart of a historical comet in 254 CE?","authors":"Jianhua Cui, Geng Li, Yongheng Zhao","doi":"10.1016/j.icarus.2024.116382","DOIUrl":"10.1016/j.icarus.2024.116382","url":null,"abstract":"<div><div>The historical observations of East Asia provide a systematic and accurate record of bright periodic comets and could help us understand their past states. However, except for these comets, few other comets have been successfully associated with historical observations. Here we report that the sunskirter 322P/SOHO is probably associated with a historical comet in 254 CE, although it appeared no visible cometary activity in recent observations. By analyzing astrometric data from the IAU Minor Planet Center, we determine the orbit of 322P and suggest that its motion is affected by non-gravitational forces based on sodium sublimation, indicating its high devolatilization. The orbital integration shows that the position and perihelion date of 322P are highly corresponding to a historical comet in 254 CE. This comet had an extremely long tail that stretched across the sky, indicating the intense activity outburst. The dynamical properties of 322P and its similarity to dark comets suggests that it possibly originated from a volatile object in the main belt, but has undergone the rotational splitting and devolatilization. Previous studies have also suggested the possible splitting. Given that splitting is a common cause of activity outburst, we suggest that 322P might have experienced a fragmentation in 254 CE and released a large amount of material, which led to the spectacular tail and devolatilization. Only faint sodium-driven activity remained afterwards, which could explain the lack of historical observations after 254 CE.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"429 ","pages":"Article 116382"},"PeriodicalIF":2.5,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142757600","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}
Pub Date : 2024-11-22DOI: 10.1016/j.icarus.2024.116378
James W. Head , Lionel Wilson , Yuqi Qian
Three anomalously young, ∼120 Ma old lunar mare pyroclastic beads have recently been reported (Wang et al., 2024) from Chang'e-5 (CE-5 soils, particularly distinguished from impact melt beads by sulfur isotope (34S/32S) composition and correlations with sulfur concentration. We examine lunar pyroclastic eruption theory and candidate eruption conditions in order to locate the vent and assess its geological context, finding that the estimated maximum pyroclast dispersal range from a candidate source vent is likely to be ∼200 km, placing it within the area of the CE-5–2.0 Ga sampled Em4 unit. The greatest predicted dispersal distances are associated with an explosive eruption from a stalled dike several kilometers below the surface, creating an elongated, multi-km-scale pit crater potentially surrounded by a dark pyroclastic ring. We assessed the Chang'e-5 region for such candidates and found none. This raises the possibility that the ∼120 Ma pyroclastic beads might have been delivered to the site from an impact crater outside Em4, but the most likely candidates are sufficiently large and at such great distances that they are likely to have reset the ages of any young pyroclastic beads thus delivered. Lacking a clear source for extraordinarily young pyroclastic beads, we reassess the possibility that the ∼120 Ma beads may be of local impact melt origin. Evidence favoring this hypothesis includes the abundant CE-5 impact glass bead ages in the 100–200 Ma year range previously reported (Long et al., 2022), and the similarities in composition and characteristics of the three beads and those of local impact origin. To address these conundra, further regional searches for a source vent and continued geochemical characterization and dating of CE-5 regolith glass beads should be undertaken.
最近从嫦娥五号(CE-5)土壤中报道了三个异常年轻的,~ 120 Ma的月海火山碎屑珠(Wang et al., 2024),特别是通过硫同位素(34S/32S)组成和与硫浓度的相关性将其与撞击熔融珠区分出来。我们研究了月球火山碎屑喷发理论和候选喷发条件,以定位喷口并评估其地质背景,发现估计候选源喷口的最大火山碎屑扩散范围可能为~ 200公里,将其放置在CE-5-2.0 Ga采样的Em4单元区域内。预测的最大扩散距离与地表以下几公里处的一个停滞的岩脉爆发有关,形成了一个细长的、多公里规模的坑坑,可能被一个黑暗的火山碎屑环包围。我们对嫦娥五号区域进行了这样的评估,但没有发现。这就提出了这样一种可能性,即这些~ 120毫安的火山碎屑珠可能是从Em4外的一个撞击坑运到这里的,但最有可能的候选者是足够大的,而且距离如此之远,以至于它们很可能重置了这样运到的任何年轻火山碎屑珠的年龄。由于缺乏非常年轻的火山碎屑珠的明确来源,我们重新评估了~ 120 Ma珠可能是局部撞击熔体起源的可能性。支持这一假设的证据包括先前报道的丰富的CE-5撞击玻璃珠年龄在100-200 Ma年范围内(Long et al., 2022),以及三颗珠的成分和特征与当地撞击起源的相似之处。为了解决这些难题,应该进行进一步的区域搜索,寻找源喷口,并继续进行CE-5风化层玻璃珠的地球化学表征和定年。
{"title":"Where on the Moon was the eruption that produced the recently reported ∼ 120 million year old volcanic glass beads?","authors":"James W. Head , Lionel Wilson , Yuqi Qian","doi":"10.1016/j.icarus.2024.116378","DOIUrl":"10.1016/j.icarus.2024.116378","url":null,"abstract":"<div><div>Three anomalously young, ∼120 Ma old lunar mare pyroclastic beads have recently been reported (Wang et al., 2024) from Chang'e-5 (CE-5 soils, particularly distinguished from impact melt beads by sulfur isotope (<sup>34</sup>S/<sup>32</sup>S) composition and correlations with sulfur concentration. We examine lunar pyroclastic eruption theory and candidate eruption conditions in order to locate the vent and assess its geological context, finding that the estimated maximum pyroclast dispersal range from a candidate source vent is likely to be ∼200 km, placing it within the area of the CE-5–2.0 Ga sampled Em4 unit. The greatest predicted dispersal distances are associated with an explosive eruption from a stalled dike several kilometers below the surface, creating an elongated, multi-km-scale pit crater potentially surrounded by a dark pyroclastic ring. We assessed the Chang'e-5 region for such candidates and found none. This raises the possibility that the ∼120 Ma pyroclastic beads might have been delivered to the site from an impact crater outside Em4, but the most likely candidates are sufficiently large and at such great distances that they are likely to have reset the ages of any young pyroclastic beads thus delivered. Lacking a clear source for extraordinarily young pyroclastic beads, we reassess the possibility that the ∼120 Ma beads may be of local impact melt origin. Evidence favoring this hypothesis includes the abundant CE-5 impact glass bead ages in the 100–200 Ma year range previously reported (Long et al., 2022), and the similarities in composition and characteristics of the three beads and those of local impact origin. To address these conundra, further regional searches for a source vent and continued geochemical characterization and dating of CE-5 regolith glass beads should be undertaken.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"428 ","pages":"Article 116378"},"PeriodicalIF":2.5,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142745837","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-21DOI: 10.1016/j.icarus.2024.116367
J. Michael Battalio
Mars’s atmosphere shares many of the same types of oscillations exhibited in Earth’s climate, like the Semiannual Oscillation and Annular Modes, but using two Martian reanalysis datasets derived from Mars Climate Sounder observations, we find that Mars fails to generate a Quasi-Biennial Oscillation (QBO). The lack of a QBO may stem from the absence of a stratosphere on Mars — as the background flow is critical for setting the altitude that vertically propagating waves deposit momentum — or the extreme latitudinal variation of the overturning circulation disrupts waves sources. The lack of a QBO on Mars may enable unique comparisons between Earth’s and Mars’s atmospheres.
{"title":"Quasi-Biennial Oscillation absent in Mars atmospheric reanalysis datasets","authors":"J. Michael Battalio","doi":"10.1016/j.icarus.2024.116367","DOIUrl":"10.1016/j.icarus.2024.116367","url":null,"abstract":"<div><div>Mars’s atmosphere shares many of the same types of oscillations exhibited in Earth’s climate, like the Semiannual Oscillation and Annular Modes, but using two Martian reanalysis datasets derived from Mars Climate Sounder observations, we find that Mars fails to generate a Quasi-Biennial Oscillation (QBO). The lack of a QBO may stem from the absence of a stratosphere on Mars — as the background flow is critical for setting the altitude that vertically propagating waves deposit momentum — or the extreme latitudinal variation of the overturning circulation disrupts waves sources. The lack of a QBO on Mars may enable unique comparisons between Earth’s and Mars’s atmospheres.</div></div>","PeriodicalId":13199,"journal":{"name":"Icarus","volume":"427 ","pages":"Article 116367"},"PeriodicalIF":2.5,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142706043","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}