Derek C. Richardson, Harrison F. Agrusa, Brent Barbee, Rachel H. Cueva, Fabio Ferrari, Seth A. Jacobson, Rahil Makadia, Alex J. Meyer, Patrick Michel, Ryota Nakano, Yun Zhang, Paul Abell, Colby C. Merrill, Adriano Campo Bagatin, Olivier Barnouin, Nancy L. Chabot, Andrew F. Cheng, Steven R. Chesley, R. Terik Daly, Siegfried Eggl, Carolyn M. Ernst, Eugene G. Fahnestock, Tony L. Farnham, Oscar Fuentes-Muñoz, Edoardo Gramigna, Douglas P. Hamilton, Masatoshi Hirabayashi, Martin Jutzi, Josh Lyzhoft, Riccardo Lasagni Manghi, Jay McMahon, Fernando Moreno, Naomi Murdoch, Shantanu P. Naidu, Eric E. Palmer, Paolo Panicucci, Laurent Pou, Petr Pravec, Sabina D. Raducan, Andrew S. Rivkin, Alessandro Rossi, Paul Sánchez, Daniel J. Scheeres, Peter Scheirich, Stephen R. Schwartz, Damya Souami, Gonzalo Tancredi, Paolo Tanga, Paolo Tortora, Josep M. Trigo-Rodríguez, Kleomenis Tsiganis, John Wimarsson, Marco Zannoni
NASA’s Double Asteroid Redirection Test (DART) spacecraft impacted Dimorphos, the natural satellite of (65803) Didymos, on 2022 September 26, as a first successful test of kinetic impactor technology for deflecting a potentially hazardous object in space. The experiment resulted in a small change to the dynamical state of the Didymos system consistent with expectations and Level 1 mission requirements. In the preencounter paper, predictions were put forward regarding the pre- and postimpact dynamical state of the Didymos system. Here we assess these predictions, update preliminary findings published after the impact, report on new findings related to dynamics, and provide implications for ESA’s Hera mission to Didymos, scheduled for launch in 2024 October with arrival in 2026 December. Preencounter predictions tested to date are largely in line with observations, despite the unexpected, flattened appearance of Didymos compared to the radar model and the apparent preimpact oblate shape of Dimorphos (with implications for the origin of the system that remain under investigation). New findings include that Dimorphos likely became prolate due to the impact and may have entered a tumbling rotation state. A possible detection of a postimpact transient secular decrease in the binary orbital period suggests possible dynamical coupling with persistent ejecta. Timescales for damping of any tumbling and clearing of any debris are uncertain. The largest uncertainty in the momentum transfer enhancement factor of the DART impact remains the mass of Dimorphos, which will be resolved by the Hera mission.
{"title":"The Dynamical State of the Didymos System before and after the DART Impact","authors":"Derek C. Richardson, Harrison F. Agrusa, Brent Barbee, Rachel H. Cueva, Fabio Ferrari, Seth A. Jacobson, Rahil Makadia, Alex J. Meyer, Patrick Michel, Ryota Nakano, Yun Zhang, Paul Abell, Colby C. Merrill, Adriano Campo Bagatin, Olivier Barnouin, Nancy L. Chabot, Andrew F. Cheng, Steven R. Chesley, R. Terik Daly, Siegfried Eggl, Carolyn M. Ernst, Eugene G. Fahnestock, Tony L. Farnham, Oscar Fuentes-Muñoz, Edoardo Gramigna, Douglas P. Hamilton, Masatoshi Hirabayashi, Martin Jutzi, Josh Lyzhoft, Riccardo Lasagni Manghi, Jay McMahon, Fernando Moreno, Naomi Murdoch, Shantanu P. Naidu, Eric E. Palmer, Paolo Panicucci, Laurent Pou, Petr Pravec, Sabina D. Raducan, Andrew S. Rivkin, Alessandro Rossi, Paul Sánchez, Daniel J. Scheeres, Peter Scheirich, Stephen R. Schwartz, Damya Souami, Gonzalo Tancredi, Paolo Tanga, Paolo Tortora, Josep M. Trigo-Rodríguez, Kleomenis Tsiganis, John Wimarsson, Marco Zannoni","doi":"10.3847/psj/ad62f5","DOIUrl":"https://doi.org/10.3847/psj/ad62f5","url":null,"abstract":"NASA’s Double Asteroid Redirection Test (DART) spacecraft impacted Dimorphos, the natural satellite of (65803) Didymos, on 2022 September 26, as a first successful test of kinetic impactor technology for deflecting a potentially hazardous object in space. The experiment resulted in a small change to the dynamical state of the Didymos system consistent with expectations and Level 1 mission requirements. In the preencounter paper, predictions were put forward regarding the pre- and postimpact dynamical state of the Didymos system. Here we assess these predictions, update preliminary findings published after the impact, report on new findings related to dynamics, and provide implications for ESA’s Hera mission to Didymos, scheduled for launch in 2024 October with arrival in 2026 December. Preencounter predictions tested to date are largely in line with observations, despite the unexpected, flattened appearance of Didymos compared to the radar model and the apparent preimpact oblate shape of Dimorphos (with implications for the origin of the system that remain under investigation). New findings include that Dimorphos likely became prolate due to the impact and may have entered a tumbling rotation state. A possible detection of a postimpact transient secular decrease in the binary orbital period suggests possible dynamical coupling with persistent ejecta. Timescales for damping of any tumbling and clearing of any debris are uncertain. The largest uncertainty in the momentum transfer enhancement factor of the DART impact remains the mass of Dimorphos, which will be resolved by the Hera mission.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142200768","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}
Stephanie G. Jarmak, Tracy M. Becker, Charles E. Woodward, Casey I. Honniball, Andrew S. Rivkin, Margaret M. McAdam, Zoe A. Landsman, Saverio Cambioni, Thomas G. Müller, Driss Takir, Kurt D. Retherford, Anicia Arredondo, Linda T. Elkins-Tanton
Our understanding of solar system evolution is closely tied to interpretations of asteroid composition, particularly the M-class asteroids. These asteroids were initially thought to be the exposed cores of differentiated planetesimals, a hypothesis based on their spectral similarity to iron meteorites. However, recent astronomical observations have revealed hydration on their surface through the detection of 3 μm absorption features associated with OH and potentially H2O. We present evidence of hydration due mainly to OH on asteroid (16) Psyche, the largest M-class asteroid, using data from the James Webb Space Telescope (JWST) spanning 1.1–6.63 μm. Our observations include two detections of the full 3 μm feature associated with OH and H2O resembling those found in CY-, CH-, and CB-type carbonaceous chondrites, and no 6 μm feature uniquely associated with H2O across two observations. We observe 3 μm depths of between 4.3% and 6% across two observations, values consistent with hydrogen abundance estimates on other airless bodies of 250–400 ppm. We place an upper limit of 39 ppm on the water abundance from the standard deviation around the 6 μm feature region. The presence of hydrated minerals suggests a complex history for Psyche. Exogenous sources of OH-bearing minerals could come from hydrated impactors. Endogenous OH-bearing minerals would indicate a composition more similar to E- or P-class asteroids. If the hydration is endogenous, it supports the theory that Psyche originated beyond the snow line and later migrated to the outer main belt.
{"title":"Estimate of Water and Hydroxyl Abundance on Asteroid (16) Psyche from JWST Data","authors":"Stephanie G. Jarmak, Tracy M. Becker, Charles E. Woodward, Casey I. Honniball, Andrew S. Rivkin, Margaret M. McAdam, Zoe A. Landsman, Saverio Cambioni, Thomas G. Müller, Driss Takir, Kurt D. Retherford, Anicia Arredondo, Linda T. Elkins-Tanton","doi":"10.3847/psj/ad66b9","DOIUrl":"https://doi.org/10.3847/psj/ad66b9","url":null,"abstract":"Our understanding of solar system evolution is closely tied to interpretations of asteroid composition, particularly the M-class asteroids. These asteroids were initially thought to be the exposed cores of differentiated planetesimals, a hypothesis based on their spectral similarity to iron meteorites. However, recent astronomical observations have revealed hydration on their surface through the detection of 3 <italic toggle=\"yes\">μ</italic>m absorption features associated with OH and potentially H<sub>2</sub>O. We present evidence of hydration due mainly to OH on asteroid (16) Psyche, the largest M-class asteroid, using data from the James Webb Space Telescope (JWST) spanning 1.1–6.63 <italic toggle=\"yes\">μ</italic>m. Our observations include two detections of the full 3 <italic toggle=\"yes\">μ</italic>m feature associated with OH and H<sub>2</sub>O resembling those found in CY-, CH-, and CB-type carbonaceous chondrites, and no 6 <italic toggle=\"yes\">μ</italic>m feature uniquely associated with H<sub>2</sub>O across two observations. We observe 3 <italic toggle=\"yes\">μ</italic>m depths of between 4.3% and 6% across two observations, values consistent with hydrogen abundance estimates on other airless bodies of 250–400 ppm. We place an upper limit of 39 ppm on the water abundance from the standard deviation around the 6 <italic toggle=\"yes\">μ</italic>m feature region. The presence of hydrated minerals suggests a complex history for Psyche. Exogenous sources of OH-bearing minerals could come from hydrated impactors. Endogenous OH-bearing minerals would indicate a composition more similar to E- or P-class asteroids. If the hydration is endogenous, it supports the theory that Psyche originated beyond the snow line and later migrated to the outer main belt.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":"43 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142200770","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}
Ion pickup by the solar wind is ubiquitous in space plasma. Because pickup ions are originally produced by ionization of an exospheric neutral atmosphere, their measurements contain information on the exospheric neutral abundance. Here we established a method to retrieve exospheric number densities, by analyzing the ion velocity distribution functions of pickup ions measured by the Mars Atmosphere and Volatile EvolutioN spacecraft. We successfully retrieved exospheric oxygen density distributions at altitudes ranging from 1000 to 10,000 km around Mars except for the vicinity of the bow shock. This method can be applied to other space missions to study the upper atmosphere of planets, moons, and other small bodies in our solar system, where pickup ions exist.
{"title":"A Technique for Retrieving the Exospheric Number Density Distribution from Pickup Ion Ring Distributions","authors":"Kei Masunaga, Naoki Terada, François Leblanc, Yuki Harada, Takuya Hara, Shotaro Sakai, Shoichiro Yokota, Kanako Seki, Atsushi Yamazaki, James. P. McFadden, Tomohiro Usui","doi":"10.3847/psj/ad65d4","DOIUrl":"https://doi.org/10.3847/psj/ad65d4","url":null,"abstract":"Ion pickup by the solar wind is ubiquitous in space plasma. Because pickup ions are originally produced by ionization of an exospheric neutral atmosphere, their measurements contain information on the exospheric neutral abundance. Here we established a method to retrieve exospheric number densities, by analyzing the ion velocity distribution functions of pickup ions measured by the Mars Atmosphere and Volatile EvolutioN spacecraft. We successfully retrieved exospheric oxygen density distributions at altitudes ranging from 1000 to 10,000 km around Mars except for the vicinity of the bow shock. This method can be applied to other space missions to study the upper atmosphere of planets, moons, and other small bodies in our solar system, where pickup ions exist.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":"16 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142200769","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}
Alex J. Meyer, Oscar Fuentes-Muñoz, Ioannis Gkolias, Kleomenis Tsiganis, Petr Pravec, Shantanu Naidu, Daniel J. Scheeres
Among binary asteroids, (35107) 1991VH stands out as unique given the likely chaotic rotation within its secondary component. The source of this excited dynamical state is unknown. In this work, we demonstrate that a past close encounter with Earth could have provided the necessary perturbation to allow the natural internal dynamics, characterized by spin–orbit coupling, to evolve the system into its current dynamical state. In this hypothesis, the secondary of 1991VH was previously in a classical 1:1 spin–orbit resonance with an orbit period likely between 28 and 35 hr before being perturbed by an Earth encounter within ∼80,000 km. We find that if the energy dissipation within the secondary is relatively inefficient, this excited dynamical state could persist to today and produce the observed ground-based measurements. Coupled with the orbital history of 1991VH, we can then place a constraint on the tidal dissipation parameters of the secondary.
{"title":"An Earth Encounter as the Cause of Chaotic Dynamics in Binary Asteroid (35107) 1991VH","authors":"Alex J. Meyer, Oscar Fuentes-Muñoz, Ioannis Gkolias, Kleomenis Tsiganis, Petr Pravec, Shantanu Naidu, Daniel J. Scheeres","doi":"10.3847/psj/ad6605","DOIUrl":"https://doi.org/10.3847/psj/ad6605","url":null,"abstract":"Among binary asteroids, (35107) 1991VH stands out as unique given the likely chaotic rotation within its secondary component. The source of this excited dynamical state is unknown. In this work, we demonstrate that a past close encounter with Earth could have provided the necessary perturbation to allow the natural internal dynamics, characterized by spin–orbit coupling, to evolve the system into its current dynamical state. In this hypothesis, the secondary of 1991VH was previously in a classical 1:1 spin–orbit resonance with an orbit period likely between 28 and 35 hr before being perturbed by an Earth encounter within ∼80,000 km. We find that if the energy dissipation within the secondary is relatively inefficient, this excited dynamical state could persist to today and produce the observed ground-based measurements. Coupled with the orbital history of 1991VH, we can then place a constraint on the tidal dissipation parameters of the secondary.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142200772","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}
Damanveer S. Grewal, Yoshinori Miyazaki, Nicole X. Nie
The timing and mechanism by which the present-day inventory of life-essential volatiles hydrogen–carbon–nitrogen–sulfur (H–C–N–S) in the bulk silicate Earth (BSE) was established are debated. In this study we have modeled the equilibrium partitioning of H–C–N–S between core, magma ocean (MO), and atmosphere to determine whether the Moon-forming impactor (MFI) was the primary source of volatiles in the BSE. Our findings suggest that the MFI’s core and MO-degassed atmosphere were its primary H–C–N–S reservoirs. Since the MFI likely lost its MO-degassed atmosphere before the giant impact, most of the BSE’s volatiles must come from the small fraction of the MFI’s core which reequilibrated with Earth’s post-impact MO. This implies a high H–C–N–S inventory in the MFI (up to 50% of volatile-rich carbonaceous chondrites) to establish the BSE’s volatile budget. Although isotopic compositions of nonvolatile elements do not rule out the possibility of substantial volatile-rich, carbonaceous material accretion, MFI’s collisional growth from thermally metamorphosed/differentiated planetesimals makes it improbable that it contained ∼50% carbonaceous chondrite equivalent of H–C–N during its differentiation. Therefore, the MFI was unlikely the primary source of volatiles in the BSE. A significant portion of the BSE’s volatile inventory (especially H and C) likely predates the Moon-forming event. To prevent loss to space and segregation into Earth’s core, volatile-bearing materials must be delivered during the final accretion event(s) preceding the Moon-forming event. The substantial size of the proto-Earth at this stage, combined with limited metal–silicate equilibration during the Moon-forming event, facilitated the retention of these volatiles within the BSE.
{"title":"Contribution of the Moon-forming Impactor to the Volatile Inventory in the Bulk Silicate Earth","authors":"Damanveer S. Grewal, Yoshinori Miyazaki, Nicole X. Nie","doi":"10.3847/psj/ad5b5d","DOIUrl":"https://doi.org/10.3847/psj/ad5b5d","url":null,"abstract":"The timing and mechanism by which the present-day inventory of life-essential volatiles hydrogen–carbon–nitrogen–sulfur (H–C–N–S) in the bulk silicate Earth (BSE) was established are debated. In this study we have modeled the equilibrium partitioning of H–C–N–S between core, magma ocean (MO), and atmosphere to determine whether the Moon-forming impactor (MFI) was the primary source of volatiles in the BSE. Our findings suggest that the MFI’s core and MO-degassed atmosphere were its primary H–C–N–S reservoirs. Since the MFI likely lost its MO-degassed atmosphere before the giant impact, most of the BSE’s volatiles must come from the small fraction of the MFI’s core which reequilibrated with Earth’s post-impact MO. This implies a high H–C–N–S inventory in the MFI (up to 50% of volatile-rich carbonaceous chondrites) to establish the BSE’s volatile budget. Although isotopic compositions of nonvolatile elements do not rule out the possibility of substantial volatile-rich, carbonaceous material accretion, MFI’s collisional growth from thermally metamorphosed/differentiated planetesimals makes it improbable that it contained ∼50% carbonaceous chondrite equivalent of H–C–N during its differentiation. Therefore, the MFI was unlikely the primary source of volatiles in the BSE. A significant portion of the BSE’s volatile inventory (especially H and C) likely predates the Moon-forming event. To prevent loss to space and segregation into Earth’s core, volatile-bearing materials must be delivered during the final accretion event(s) preceding the Moon-forming event. The substantial size of the proto-Earth at this stage, combined with limited metal–silicate equilibration during the Moon-forming event, facilitated the retention of these volatiles within the BSE.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":"83 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142200764","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}
Mingbao Li, Ke Zhu, Yan Fan, P. M. Ranjith, Chao Wang, Wen Yu, Shijie Li
A comprehensive study of an ungrouped achondrite meteorite, North West Africa (NWA) 11562, was conducted, involving petrology, mineralogy, and mass-independent chromium isotopic composition. NWA 11562 comprises 34.9 vol% olivine, 56.1 vol% pyroxenes, 6.7 vol% Fe–Ni metal and oxides, 2.2 vol% carbon, and 0.2 vol% anhydrite. The oxygen isotopic composition (δ