Marina Brozović, Lance A. M. Benner, Shantanu P. Naidu, Nicholas Moskovitz, Jon D. Giorgini, Anne K. Virkki, Sean E. Marshall, Lord R. Dover, Agata Rożek, Stephen C. Lowry, Brian D. Warner, Patrick A. Taylor, Edgard G. Rivera-Valentin, Timothy A. Lister, Joseph P. Chatelain, Michael W. Busch, Christopher Magri, Joseph S. Jao, Lawrence G. Snedeker and Kenneth J. Lawrence
We report radar, photometric, and visible-wavelength spectrophotometry observations of NEA 2018 EB obtained in 2018. The radar campaign started at Goldstone (8560 MHz, 3.5 cm) on April 7, and it was followed by more extensive observations from October 5 to 9 by both Arecibo (2380 MHz, 12.6 cm) and Goldstone. 2018 EB was observed optically on April 5, 8, and 9 and again on October 18. Spectrophotometry was obtained on October 19 with the SOAR telescope, and the data suggest that 2018 EB is an Xk-class object. The echo power spectra and delay-Doppler radar images revealed that 2018 EB is a binary system. Radar images constrained the satellite's diameter to km, but the data were not sufficient for shape modeling. Shape modeling of lightcurves and radar data yielded an oblate primary with an effective diameter D = 0.30 ± 0.04 km and a sidereal rotation period of hr. Measurements of delay-Doppler separations between the centers of mass of the primary and the satellite, along with the timing of a radar eclipse observed on October 9, resulted in an orbit fit for the satellite with a semimajor axis of km, an eccentricity of 0.15 ± 0.04, a period of hr, and an orbit pole constrained to the ecliptic longitudes and latitudes of and . The system mass was estimated to be kg, which yielded a bulk density of g cm−3. Our analysis suggests that 2018 EB has a low optical albedo of pV = 0.028 ± 0.016 and a relatively high radar albedo of ηOC = 0.29 ± 0.11 at Arecibo and η = 0.22 ± 0.10 at Goldstone.
{"title":"Radar and Optical Observations and Physical Modeling of Binary Near-Earth Asteroid 2018 EB","authors":"Marina Brozović, Lance A. M. Benner, Shantanu P. Naidu, Nicholas Moskovitz, Jon D. Giorgini, Anne K. Virkki, Sean E. Marshall, Lord R. Dover, Agata Rożek, Stephen C. Lowry, Brian D. Warner, Patrick A. Taylor, Edgard G. Rivera-Valentin, Timothy A. Lister, Joseph P. Chatelain, Michael W. Busch, Christopher Magri, Joseph S. Jao, Lawrence G. Snedeker and Kenneth J. Lawrence","doi":"10.3847/psj/ad4342","DOIUrl":"https://doi.org/10.3847/psj/ad4342","url":null,"abstract":"We report radar, photometric, and visible-wavelength spectrophotometry observations of NEA 2018 EB obtained in 2018. The radar campaign started at Goldstone (8560 MHz, 3.5 cm) on April 7, and it was followed by more extensive observations from October 5 to 9 by both Arecibo (2380 MHz, 12.6 cm) and Goldstone. 2018 EB was observed optically on April 5, 8, and 9 and again on October 18. Spectrophotometry was obtained on October 19 with the SOAR telescope, and the data suggest that 2018 EB is an Xk-class object. The echo power spectra and delay-Doppler radar images revealed that 2018 EB is a binary system. Radar images constrained the satellite's diameter to km, but the data were not sufficient for shape modeling. Shape modeling of lightcurves and radar data yielded an oblate primary with an effective diameter D = 0.30 ± 0.04 km and a sidereal rotation period of hr. Measurements of delay-Doppler separations between the centers of mass of the primary and the satellite, along with the timing of a radar eclipse observed on October 9, resulted in an orbit fit for the satellite with a semimajor axis of km, an eccentricity of 0.15 ± 0.04, a period of hr, and an orbit pole constrained to the ecliptic longitudes and latitudes of and . The system mass was estimated to be kg, which yielded a bulk density of g cm−3. Our analysis suggests that 2018 EB has a low optical albedo of pV = 0.028 ± 0.016 and a relatively high radar albedo of ηOC = 0.29 ± 0.11 at Arecibo and η = 0.22 ± 0.10 at Goldstone.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141165565","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}
Ashley Gerard Davies, Jason E. Perry, David A. Williams, Glenn J. Veeder and David M. Nelson
By combining multiple spacecraft and telescope data sets, the first fully global volcanic heat flow map of Io has been created, incorporating data down to spatial resolutions of ∼10 km pixel−1 in Io’s polar regions. Juno Jovian Infrared Auroral Mapper data have filled coverage gaps in Io’s polar regions and other areas poorly imaged by Galileo instruments. A total of 343 thermal sources are identified in data up to mid-2023. While poor correlations are found between the longitudinal distribution of volcanic thermal emission and radially integrated end-member models of internal heating, the best correlations are found with shallow asthenospheric tidal heating and magma ocean models and negative correlations with the deep-mantle heating model. The presence of polar volcanoes supports, but does not necessarily confirm, the presence of a magma ocean on Io. We find that the number of active volcanoes per unit area in polar regions is no different from that at lower latitudes, but we find that Io’s polar volcanoes are smaller, in terms of thermal emission, than those at lower latitudes. Half as much energy is emitted from polar volcanoes as from those at lower latitudes, and the thermal emission from the north polar cap volcanoes is twice that of those in the south polar cap. Apparent dichotomies in terms of volcanic advection and resulting power output exist between sub- and anti-Jovian hemispheres, between polar regions and lower latitudes, and between the north and south polar regions, possibly due to internal asymmetries or variations in lithospheric thickness.
{"title":"New Global Map of Io’s Volcanic Thermal Emission and Discovery of Hemispherical Dichotomies","authors":"Ashley Gerard Davies, Jason E. Perry, David A. Williams, Glenn J. Veeder and David M. Nelson","doi":"10.3847/psj/ad4346","DOIUrl":"https://doi.org/10.3847/psj/ad4346","url":null,"abstract":"By combining multiple spacecraft and telescope data sets, the first fully global volcanic heat flow map of Io has been created, incorporating data down to spatial resolutions of ∼10 km pixel−1 in Io’s polar regions. Juno Jovian Infrared Auroral Mapper data have filled coverage gaps in Io’s polar regions and other areas poorly imaged by Galileo instruments. A total of 343 thermal sources are identified in data up to mid-2023. While poor correlations are found between the longitudinal distribution of volcanic thermal emission and radially integrated end-member models of internal heating, the best correlations are found with shallow asthenospheric tidal heating and magma ocean models and negative correlations with the deep-mantle heating model. The presence of polar volcanoes supports, but does not necessarily confirm, the presence of a magma ocean on Io. We find that the number of active volcanoes per unit area in polar regions is no different from that at lower latitudes, but we find that Io’s polar volcanoes are smaller, in terms of thermal emission, than those at lower latitudes. Half as much energy is emitted from polar volcanoes as from those at lower latitudes, and the thermal emission from the north polar cap volcanoes is twice that of those in the south polar cap. Apparent dichotomies in terms of volcanic advection and resulting power output exist between sub- and anti-Jovian hemispheres, between polar regions and lower latitudes, and between the north and south polar regions, possibly due to internal asymmetries or variations in lithospheric thickness.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141165634","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}
Matthew Belyakov, M. Ryleigh Davis, Zachariah Milby, Ian Wong and Michael E. Brown
We use 1.4–4.6 μm multiband photometry of the small inner Uranian and Neptunian satellites obtained with the James Webb Space Telescope’s near-infrared imager NIRCam to characterize their surface compositions. We find that the satellites of the ice giants have, to first order, similar compositions to one another, with a 3.0 μm absorption feature possibly associated with an O-H stretch, indicative of water ice or hydrated minerals. Additionally, the spectrophotometry for the small ice-giant satellites matches spectra of some Neptune Trojans and excited Kuiper Belt objects, suggesting shared properties. Future spectroscopy of these small satellites is necessary to identify and better constrain their specific surface compositions.
{"title":"JWST Spectrophotometry of the Small Satellites of Uranus and Neptune","authors":"Matthew Belyakov, M. Ryleigh Davis, Zachariah Milby, Ian Wong and Michael E. Brown","doi":"10.3847/psj/ad3d55","DOIUrl":"https://doi.org/10.3847/psj/ad3d55","url":null,"abstract":"We use 1.4–4.6 μm multiband photometry of the small inner Uranian and Neptunian satellites obtained with the James Webb Space Telescope’s near-infrared imager NIRCam to characterize their surface compositions. We find that the satellites of the ice giants have, to first order, similar compositions to one another, with a 3.0 μm absorption feature possibly associated with an O-H stretch, indicative of water ice or hydrated minerals. Additionally, the spectrophotometry for the small ice-giant satellites matches spectra of some Neptune Trojans and excited Kuiper Belt objects, suggesting shared properties. Future spectroscopy of these small satellites is necessary to identify and better constrain their specific surface compositions.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141147134","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}
Andy J. López-Oquendo, Mark J. Loeffler and David E. Trilling
Surfaces of carbonaceous asteroids (C-complex) have shown diverse, contrasting spectral variations, which may be related to space weathering. We performed laser irradiation experiments on CI and CM simulant material under vacuum to mimic the spectral alteration induced by micrometeorite impacts. We used in situ ultraviolet-visible and near-infrared reflectance spectroscopy to analyze spectral alterations in response to pulsed laser irradiation, as well as scanning electron microscopy and X-ray photoelectron spectroscopy to search for microstructural and compositional changes. Laser irradiation causes an increase in spectral slope (reddening) and a decrease in the albedo (darkening), and these changes are stronger in the ultraviolet-visible region. These spectral changes are likely driven by the excess iron found in the altered surface region although other factors, such as the observed structural changes, may also contribute. Additionally, while the 0.27 μm band appears relatively stable under laser irradiation, a broad feature at 0.6 μm rapidly disappears with laser irradiation, suggesting that space weathering may inhibit the detection of any feature in this spectral region, including the 0.7 μm band, which has typically been used an indicator of hydration. Comparing our laboratory results with optical spectrophotometry observations of C-complex asteroids, we find that the majority of objects are spectrally red and possess colors that are similar to our irradiated material rather than our fresh samples. Furthermore, we also find that “younger” and “older” C-complex families have similar colors, suggesting that the space-weathering process is near equal or faster than the time it takes to refresh the surfaces of these airless bodies.
碳质小行星（C-complex）的表面显示出多种多样、对比强烈的光谱变化，这可能与空间风化有关。我们在真空环境下对碳质小行星和碳质小行星模拟材料进行了激光辐照实验，以模拟微陨石撞击引起的光谱变化。我们使用原位紫外-可见光和近红外反射光谱分析脉冲激光辐照引起的光谱变化，并使用扫描电子显微镜和 X 射线光电子能谱寻找微观结构和成分变化。激光辐照会导致光谱斜率增加（变红）和反照率降低（变黑），这些变化在紫外-可见光区域更为强烈。这些光谱变化很可能是由改变表面区域发现的过量铁引起的，尽管其他因素，如观测到的结构变化，也可能起作用。此外，虽然 0.27 μm 波段在激光照射下显得相对稳定，但 0.6 μm 波段的宽特征在激光照射下迅速消失，这表明空间风化可能会抑制对该光谱区域任何特征的探测，包括 0.7 μm 波段，该波段通常被用作水化指标。将我们的实验室结果与 C 复合小行星的光学分光光度观测结果进行比较，我们发现大多数天体的光谱都是红色的，其颜色类似于我们的辐照物质，而不是我们的新鲜样本。此外，我们还发现 "年轻 "和 "年长 "的 C-复合族具有相似的颜色，这表明空间风化过程与这些无空气天体表面刷新所需的时间几乎相等或更快。
{"title":"Laser Irradiation of Carbonaceous Chondrite Simulants: Space-weathering Implications for C-complex Asteroids","authors":"Andy J. López-Oquendo, Mark J. Loeffler and David E. Trilling","doi":"10.3847/psj/ad4028","DOIUrl":"https://doi.org/10.3847/psj/ad4028","url":null,"abstract":"Surfaces of carbonaceous asteroids (C-complex) have shown diverse, contrasting spectral variations, which may be related to space weathering. We performed laser irradiation experiments on CI and CM simulant material under vacuum to mimic the spectral alteration induced by micrometeorite impacts. We used in situ ultraviolet-visible and near-infrared reflectance spectroscopy to analyze spectral alterations in response to pulsed laser irradiation, as well as scanning electron microscopy and X-ray photoelectron spectroscopy to search for microstructural and compositional changes. Laser irradiation causes an increase in spectral slope (reddening) and a decrease in the albedo (darkening), and these changes are stronger in the ultraviolet-visible region. These spectral changes are likely driven by the excess iron found in the altered surface region although other factors, such as the observed structural changes, may also contribute. Additionally, while the 0.27 μm band appears relatively stable under laser irradiation, a broad feature at 0.6 μm rapidly disappears with laser irradiation, suggesting that space weathering may inhibit the detection of any feature in this spectral region, including the 0.7 μm band, which has typically been used an indicator of hydration. Comparing our laboratory results with optical spectrophotometry observations of C-complex asteroids, we find that the majority of objects are spectrally red and possess colors that are similar to our irradiated material rather than our fresh samples. Furthermore, we also find that “younger” and “older” C-complex families have similar colors, suggesting that the space-weathering process is near equal or faster than the time it takes to refresh the surfaces of these airless bodies.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141147133","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}
Impact-derived ejecta covers most of the lunar surface, originating from recent impacts through to the beginning of the geologic record. Despite how common ejecta is, accurate measurements of ejecta thickness are difficult to obtain, and existing estimates of ejecta thickness vary widely. This study uses excavation by meter-scale impacts on the fresh ejecta blankets of larger, kilometer-scale impacts to make point measurements of ejecta thickness. We estimate ejecta thickness at the rims of 73 lunar craters (0.1–4.8 km diameter) and create isopach maps of ejecta thickness for three craters. We derive an equation for ejecta thickness, , where r is the horizontal distance from the center of the crater, R is the center-to-rim crater radius, and B describes the rate at which ejecta thickness decays with radial distance. Our average value for B (2.8 ± 0.1) is similar to previous work, though we observe that B can vary significantly within an ejecta blanket.
{"title":"Ejecta Blankets at Small Craters on the Moon","authors":"Trevor Austin, Mark Robinson and Prasun Mahanti","doi":"10.3847/psj/ad3827","DOIUrl":"https://doi.org/10.3847/psj/ad3827","url":null,"abstract":"Impact-derived ejecta covers most of the lunar surface, originating from recent impacts through to the beginning of the geologic record. Despite how common ejecta is, accurate measurements of ejecta thickness are difficult to obtain, and existing estimates of ejecta thickness vary widely. This study uses excavation by meter-scale impacts on the fresh ejecta blankets of larger, kilometer-scale impacts to make point measurements of ejecta thickness. We estimate ejecta thickness at the rims of 73 lunar craters (0.1–4.8 km diameter) and create isopach maps of ejecta thickness for three craters. We derive an equation for ejecta thickness, , where r is the horizontal distance from the center of the crater, R is the center-to-rim crater radius, and B describes the rate at which ejecta thickness decays with radial distance. Our average value for B (2.8 ± 0.1) is similar to previous work, though we observe that B can vary significantly within an ejecta blanket.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140936841","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}
Joseph R. Masiero, Yuna G. Kwon, Dar W. Dahlen, Frank J. Masci, Amy K. Mainzer
Asteroids with low orbital perihelion distances experience extreme heating from the Sun that can modify their surfaces and trigger nontypical activity mechanisms. These objects are generally difficult to observe from ground-based telescopes due to their frequent proximity to the Sun. The Near-Earth Object (NEO) Surveyor mission, however, will regularly survey down to solar elongations of 45° and is well suited for the detection and characterization of low-perihelion asteroids. Here, we use the survey simulation software tools developed for mission verification to explore the expected sensitivity of NEO Surveyor to these objects. We find that NEO Surveyor is expected to be >90% complete for near-Sun objects larger than D ∼ 300 m. Additionally, if the asteroid (3200) Phaethon underwent a disruption event in the past to form the Geminid meteor stream, Surveyor will be >90% complete to any fragments larger than D ∼ 200 m. For probable disruption models, NEO Surveyor would be expected to detect dozens of objects on Phaethon-like orbits, compared to a predicted background population of only a handful of asteroids, setting strong constraints on the likelihood of this scenario.
轨道近日点距离较低的小行星会受到来自太阳的极端加热，从而改变其表面并引发非典型的活动机制。这些天体由于经常接近太阳，一般很难从地面望远镜观测到。然而，近地天体巡天探测器（NEO Surveyor）任务将定期巡天至太阳45度，非常适合低近日点小行星的探测和定性。在此，我们使用为任务验证而开发的巡天模拟软件工具来探索近地天体巡天者对这些天体的预期灵敏度。此外，如果小行星（3200）Phaethon 在过去经历了一次扰动事件，形成了双子座流星群，那么对于任何大于 D ∼ 200 米的碎片，近地天体巡天者的探测将达到 90%的完整度。对于可能的破坏模型，近地天体勘测者预计将探测到数十个位于类似辉卫一轨道上的天体，而预测的背景天体数量仅为少数几个小行星，这对这种情况发生的可能性提出了强有力的限制。
{"title":"The Sensitivity of NEO Surveyor to Low-perihelion Asteroids","authors":"Joseph R. Masiero, Yuna G. Kwon, Dar W. Dahlen, Frank J. Masci, Amy K. Mainzer","doi":"10.3847/psj/ad42a2","DOIUrl":"https://doi.org/10.3847/psj/ad42a2","url":null,"abstract":"Asteroids with low orbital perihelion distances experience extreme heating from the Sun that can modify their surfaces and trigger nontypical activity mechanisms. These objects are generally difficult to observe from ground-based telescopes due to their frequent proximity to the Sun. The Near-Earth Object (NEO) Surveyor mission, however, will regularly survey down to solar elongations of 45° and is well suited for the detection and characterization of low-perihelion asteroids. Here, we use the survey simulation software tools developed for mission verification to explore the expected sensitivity of NEO Surveyor to these objects. We find that NEO Surveyor is expected to be >90% complete for near-Sun objects larger than <italic toggle=\"yes\">D</italic> ∼ 300 m. Additionally, if the asteroid (3200) Phaethon underwent a disruption event in the past to form the Geminid meteor stream, Surveyor will be >90% complete to any fragments larger than <italic toggle=\"yes\">D</italic> ∼ 200 m. For probable disruption models, NEO Surveyor would be expected to detect dozens of objects on Phaethon-like orbits, compared to a predicted background population of only a handful of asteroids, setting strong constraints on the likelihood of this scenario.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140936961","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}
Much of what we know about Neptune’s moon Triton was inferred from the analysis of images returned by the Voyager 2 mission, the only spacecraft to have visited that putative ocean world. Unfortunately, the highest-resolution images (scales < 2 km pixel−1) are difficult to use because they are only available in nonstandard formats, and the locations of the images on Triton’s surface are incorrect by up to 200 km. Although image mosaics of Triton are publicly available, these do not include the highest-resolution data. Here we describe our effort to improve the usability and accessibility of Voyager 2 images of Triton. We used the USGS’s ISIS software to process 41 Triton images, including geometric calibration, radiometric calibration, and reseau removal. We improved the image locations using a photogrammetric control network with 958 points and 3910 image measurements. Least-squares bundle adjustment of the network yielded rms uncertainty of 0.50, 0.52, and 0.51 pixels in latitude, longitude, and radius, respectively, and maximum residuals of −4.21 and +3.20 pixels, respectively. Image-to-image alignment is therefore vastly improved. We have released these processed images as cloud-optimized GeoTIFFs in orthographic projection at the original pixel scale of each image. Associated mosaics have also been created and released to provide geologic context for the individual images. These products provide the science community with analysis-ready data that enable new investigations of Triton, increase accessibility to this unique data set, and continue to enhance the scientific return from the Voyager 2 mission.
{"title":"Increasing the Usability and Accessibility of Voyager 2 Images of Triton","authors":"Michael T. Bland, Emily S. Martin, Alex Patthoff","doi":"10.3847/psj/ad33ca","DOIUrl":"https://doi.org/10.3847/psj/ad33ca","url":null,"abstract":"Much of what we know about Neptune’s moon Triton was inferred from the analysis of images returned by the Voyager 2 mission, the only spacecraft to have visited that putative ocean world. Unfortunately, the highest-resolution images (scales < 2 km pixel<sup>−1</sup>) are difficult to use because they are only available in nonstandard formats, and the locations of the images on Triton’s surface are incorrect by up to 200 km. Although image mosaics of Triton are publicly available, these do not include the highest-resolution data. Here we describe our effort to improve the usability and accessibility of Voyager 2 images of Triton. We used the USGS’s ISIS software to process 41 Triton images, including geometric calibration, radiometric calibration, and reseau removal. We improved the image locations using a photogrammetric control network with 958 points and 3910 image measurements. Least-squares bundle adjustment of the network yielded rms uncertainty of 0.50, 0.52, and 0.51 pixels in latitude, longitude, and radius, respectively, and maximum residuals of −4.21 and +3.20 pixels, respectively. Image-to-image alignment is therefore vastly improved. We have released these processed images as cloud-optimized GeoTIFFs in orthographic projection at the original pixel scale of each image. Associated mosaics have also been created and released to provide geologic context for the individual images. These products provide the science community with analysis-ready data that enable new investigations of Triton, increase accessibility to this unique data set, and continue to enhance the scientific return from the Voyager 2 mission.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140936918","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}
NH3 has long been predicted to be an important component of outer solar system bodies, yet detection of this compound suggests a low abundance or absence on many objects where it would be expected. Here, we demonstrate that a thermally driven oxidation reaction between ammonia (NH3) and ozone (O3) in a H2O + NH3 + O3 mixture may contribute to the low abundance of NH3 on some of these objects, as this reaction efficiently occurs at temperatures as low as 70 K. We determined the overall activation energy for this reaction to be 17 ± 2 kJ mol−1, which is consistent with other chemical systems that react at cryogenic temperatures. The loss of these two compounds coincides with the formation of NH4+ and NO3− at low temperatures, both of which are observable with infrared spectroscopy. Warming our H2O + NH3 + O3 mixtures through sublimation, we find a number of higher-temperature phases, such as ammonia hemihydrate, nitric acid, and ammonium nitrate (NH4NO3). The most stable of these is NH4NO3, which remains on the substrate until temperatures near 270 K. The salt product within this sample contains near-infrared spectral features between 2.0 and 2.22 μm, which is a spectral region of interest for several outer solar system objects, including the Uranian satellites Miranda, Ariel and Umbriel, and Pluto's satellite Charon.
{"title":"Thermal Oxidation Reaction between NH3 and O3: Low-temperature Formation of an NH4+ -bearing Salt","authors":"Patrick D. Tribbett, Mark J. Loeffler","doi":"10.3847/psj/ad394a","DOIUrl":"https://doi.org/10.3847/psj/ad394a","url":null,"abstract":"NH<sub>3</sub> has long been predicted to be an important component of outer solar system bodies, yet detection of this compound suggests a low abundance or absence on many objects where it would be expected. Here, we demonstrate that a thermally driven oxidation reaction between ammonia (NH<sub>3</sub>) and ozone (O<sub>3</sub>) in a H<sub>2</sub>O + NH<sub>3</sub> + O<sub>3</sub> mixture may contribute to the low abundance of NH<sub>3</sub> on some of these objects, as this reaction efficiently occurs at temperatures as low as 70 K. We determined the overall activation energy for this reaction to be 17 ± 2 kJ mol<sup>−1</sup>, which is consistent with other chemical systems that react at cryogenic temperatures. The loss of these two compounds coincides with the formation of <inline-formula>\u0000<tex-math>\u0000<?CDATA ${mathrm{NH}}_{4}^{+}$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:msubsup><mml:mrow><mml:mi>NH</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msubsup></mml:math>\u0000<inline-graphic xlink:href=\"psjad394aieqn3.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> and <inline-formula>\u0000<tex-math>\u0000<?CDATA ${mathrm{NO}}_{3}^{-}$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:msubsup><mml:mrow><mml:mi>NO</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow><mml:mrow><mml:mo>−</mml:mo></mml:mrow></mml:msubsup></mml:math>\u0000<inline-graphic xlink:href=\"psjad394aieqn4.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> at low temperatures, both of which are observable with infrared spectroscopy. Warming our H<sub>2</sub>O + NH<sub>3</sub> + O<sub>3</sub> mixtures through sublimation, we find a number of higher-temperature phases, such as ammonia hemihydrate, nitric acid, and ammonium nitrate (NH<sub>4</sub>NO<sub>3</sub>). The most stable of these is NH<sub>4</sub>NO<sub>3</sub>, which remains on the substrate until temperatures near 270 K. The salt product within this sample contains near-infrared spectral features between 2.0 and 2.22 <italic toggle=\"yes\">μ</italic>m, which is a spectral region of interest for several outer solar system objects, including the Uranian satellites Miranda, Ariel and Umbriel, and Pluto's satellite Charon.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140941961","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}
Rogerio Deienno, David Nesvorný, Matthew S. Clement, William F. Bottke, André Izidoro, Kevin J. Walsh
The main asteroid belt (MAB) is known to be primarily composed of objects from two distinct taxonomic classes, generically defined here as S- and C-complex. The former probably originated from the inner solar system (interior to Jupiter’s orbit), while the latter probably originated from the outer solar system. Following this definition, (4) Vesta, a V-type residing in the inner MAB (a < 2.5 au), is the sole D > 500 km object akin to the S-complex that potentially formed in situ. This provides a useful constraint on the number of D > 500 km bodies that could have formed, or grown, within the primordial MAB. In this work, we numerically simulate the accretion of objects in the MAB region during the time when gas in the protoplanetary disk still existed while assuming different MAB primordial masses. We then account for the depletion of that population happening after gas disk dispersal. In our analysis, we subdivided the MAB into five subregions and showed that the depletion factor varies throughout the MAB. This results in uneven radial- and size-dependent depletion of the MAB. We show that the MAB primordial mass has to be ≲2.14 × 10−3M⊕. Larger primordial masses would lead to the accretion of tens to thousands of S-complex objects with D > 500 km in the MAB. Such large objects would survive depletion even in the outer subregions (a > 2.5 au), thus being inconsistent with observations. Our results also indicate that S-complex objects with D > 200–300 km, including (4) Vesta, are likely to be terrestrial planetesimals implanted into the MAB rather than formed in situ.
众所周知，主小行星带（MAB）主要由两个不同分类学类别的天体组成，这里一般定义为S-和C-复合天体。前者可能来自内太阳系（木星轨道内部），后者可能来自外太阳系。根据这一定义，(4) 灶神星，一个位于内MAB（a < 2.5 au）的V型天体，是唯一一个可能在原地形成的类似于S型复合天体的D > 500 km天体。这为原始 MAB 中可能形成或生长的 D > 500 公里天体的数量提供了一个有用的约束。在这项工作中，我们用数值模拟了在原行星盘中气体仍然存在的时期，MAB区域内的天体吸积情况，同时假设了不同的MAB原始质量。然后，我们对气体盘散开后发生的种群耗竭进行了核算。在分析中，我们将人与生物圈细分为五个子区域，结果表明整个人与生物圈的损耗因子是不同的。这导致了 MAB 不均匀的径向损耗和尺寸损耗。我们表明，人与生物圈的原始质量必须是 ≲2.14 × 10-3M⊕。更大的原始质量将导致数以万计的S-复合天体在MAB中增生，其D > 500公里。这样大的天体即使在外层子区域（a > 2.5 au）也能存活下来，因此与观测结果不符。我们的研究结果还表明，包括(4)灶神星在内的D > 200-300千米的S-复合天体很可能是植入人与生物圈的陆地行星，而不是在原地形成的。
{"title":"Accretion and Uneven Depletion of the Main Asteroid Belt","authors":"Rogerio Deienno, David Nesvorný, Matthew S. Clement, William F. Bottke, André Izidoro, Kevin J. Walsh","doi":"10.3847/psj/ad3a68","DOIUrl":"https://doi.org/10.3847/psj/ad3a68","url":null,"abstract":"The main asteroid belt (MAB) is known to be primarily composed of objects from two distinct taxonomic classes, generically defined here as S- and C-complex. The former probably originated from the inner solar system (interior to Jupiter’s orbit), while the latter probably originated from the outer solar system. Following this definition, (4) Vesta, a V-type residing in the inner MAB (<italic toggle=\"yes\">a</italic> < 2.5 au), is the sole <italic toggle=\"yes\">D</italic> > 500 km object akin to the S-complex that potentially formed in situ. This provides a useful constraint on the number of <italic toggle=\"yes\">D</italic> > 500 km bodies that could have formed, or grown, within the primordial MAB. In this work, we numerically simulate the accretion of objects in the MAB region during the time when gas in the protoplanetary disk still existed while assuming different MAB primordial masses. We then account for the depletion of that population happening after gas disk dispersal. In our analysis, we subdivided the MAB into five subregions and showed that the depletion factor varies throughout the MAB. This results in uneven radial- and size-dependent depletion of the MAB. We show that the MAB primordial mass has to be ≲2.14 × 10<sup>−3</sup>\u0000<italic toggle=\"yes\">M</italic>\u0000<sub>⊕</sub>. Larger primordial masses would lead to the accretion of tens to thousands of S-complex objects with <italic toggle=\"yes\">D</italic> > 500 km in the MAB. Such large objects would survive depletion even in the outer subregions (<italic toggle=\"yes\">a</italic> > 2.5 au), thus being inconsistent with observations. Our results also indicate that S-complex objects with <italic toggle=\"yes\">D</italic> > 200–300 km, including (4) Vesta, are likely to be terrestrial planetesimals implanted into the MAB rather than formed in situ.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140936842","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}
Francis Nimmo, Jonathan Lunine, Kevin Zahnle and Lars Stixrude
The bulk of Uranus consists of a rock–ice core, but the relative proportions of rock and ice are unknown. Radioactive decay of potassium in the silicates produces 40Ar. If transport of argon from the core to the gaseous envelope is efficient, a measurement of 40Ar in the envelope will provide a direct constraint on the rock mass present (assuming a chondritic rock composition). The expected 40Ar concentrations in this case would be readily detectable by a mass spectrometer carried by a future atmospheric probe. For a given envelope concentration there is a trade-off between the rock mass present and the transport efficiency; this degeneracy could be overcome by making independent determinations of the rock mass (e.g., by gravity and seismology). Primordial 40Ar is a potential confounding factor, especially if Ar/H2 is significantly enhanced above solar or if degassing of radiogenic 40Ar were inefficient. Unfortunately, the primordial 40Ar/36Ar ratio is very uncertain; better constraints on this ratio through measurement or theory would be very helpful. Pollution of the envelope by silicates is another confounding factor but can be overcome by a measurement of the alkali metals in the envelope.
{"title":"Probing the Rock Mass Fraction and Transport Efficiency inside Uranus Using 40Ar Measurements","authors":"Francis Nimmo, Jonathan Lunine, Kevin Zahnle and Lars Stixrude","doi":"10.3847/psj/ad3b93","DOIUrl":"https://doi.org/10.3847/psj/ad3b93","url":null,"abstract":"The bulk of Uranus consists of a rock–ice core, but the relative proportions of rock and ice are unknown. Radioactive decay of potassium in the silicates produces 40Ar. If transport of argon from the core to the gaseous envelope is efficient, a measurement of 40Ar in the envelope will provide a direct constraint on the rock mass present (assuming a chondritic rock composition). The expected 40Ar concentrations in this case would be readily detectable by a mass spectrometer carried by a future atmospheric probe. For a given envelope concentration there is a trade-off between the rock mass present and the transport efficiency; this degeneracy could be overcome by making independent determinations of the rock mass (e.g., by gravity and seismology). Primordial 40Ar is a potential confounding factor, especially if Ar/H2 is significantly enhanced above solar or if degassing of radiogenic 40Ar were inefficient. Unfortunately, the primordial 40Ar/36Ar ratio is very uncertain; better constraints on this ratio through measurement or theory would be very helpful. Pollution of the envelope by silicates is another confounding factor but can be overcome by a measurement of the alkali metals in the envelope.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140886779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：