N. Kumari, T. Glotch, Jean-Pierre Williams, M. Sullivan, Shuai Li, B. Greenhagen, Dany Waller, Tyler Powell, Catherine M. Elder, Benjamin D. Byron, K. Shirley
The formation mechanisms, extent, and compositions of red spots on the lunar surface have intrigued the lunar community for decades. By identifying a new dome and another silicic crater in the highlands nearby, we find that the silicic volcanism in the Gruithuisen region extends beyond the three major domes. Our observations indicate that the Gruithuisen domes have low iron and titanium contents. They are enveloped by ejecta from surrounding regions and host silica-rich material excavated by the young craters consistent with previous work. Our boulder maps of the Gamma dome display a high boulder count and indicate that the Diviner rock abundance maps are only sensitive to boulders larger than ∼2 m. The H-parameter values are sensitive to presence of rocks and may be a better indicator of rocks at submeter scales. The Delta dome has gentle slopes, lower rock abundance, and one young crater, and it could serve as a safe and scientifically valuable site for landing and exploration of the domes and nearby region. The dome also displays anomalously high H-parameter in the same region as the crater, indicating the potential presence of pyroclastic materials. We observe up to 200 ppm of OH/H2O on the domes and nearby mare despite the presence of a weak magnetic field to the south of Delta dome, further supporting the potential presence of pyroclastics in the region. This study could potentially aid in logistical and scientific decisions of the future NASA missions in the region.
数十年来，月球表面红斑的形成机制、范围和成分一直令月球学界感到好奇。我们在附近的高地发现了一个新的圆顶和另一个硅质陨石坑，从而发现格鲁伊图森地区的硅质火山活动超出了三个主要圆顶的范围。我们的观测结果表明，格鲁伊图森穹丘的铁和钛含量较低。它们被周围地区的喷出物所包围，并承载着年轻陨石坑挖掘出的富含二氧化硅的物质，这与之前的研究结果是一致的。我们在伽马穹顶绘制的巨石图显示了较高的巨石数量，表明占卜者岩石丰度图仅对大于 2 米的巨石敏感。德尔塔穹丘坡度平缓，岩石丰度较低，有一个年轻的陨石坑，可以作为一个安全和有科学价值的地点，用于着陆和探索穹丘及附近地区。在与陨石坑相同的区域，穹顶还显示出异常高的 H 参数，表明可能存在火成碎屑物质。尽管德尔塔穹顶南侧存在弱磁场，但我们在穹顶和附近的红土上观测到了高达 200 ppm 的 OH/H2O，这进一步证明了该地区可能存在火成碎屑。这项研究可能有助于美国国家航空航天局未来在该地区执行任务的后勤和科学决策。
{"title":"Extended Silicic Volcanism in the Gruithuisen Region—Revisiting the Composition and Thermophysical Properties of Gruithuisen Domes on the Moon","authors":"N. Kumari, T. Glotch, Jean-Pierre Williams, M. Sullivan, Shuai Li, B. Greenhagen, Dany Waller, Tyler Powell, Catherine M. Elder, Benjamin D. Byron, K. Shirley","doi":"10.3847/PSJ/ad4352","DOIUrl":"https://doi.org/10.3847/PSJ/ad4352","url":null,"abstract":"The formation mechanisms, extent, and compositions of red spots on the lunar surface have intrigued the lunar community for decades. By identifying a new dome and another silicic crater in the highlands nearby, we find that the silicic volcanism in the Gruithuisen region extends beyond the three major domes. Our observations indicate that the Gruithuisen domes have low iron and titanium contents. They are enveloped by ejecta from surrounding regions and host silica-rich material excavated by the young craters consistent with previous work. Our boulder maps of the Gamma dome display a high boulder count and indicate that the Diviner rock abundance maps are only sensitive to boulders larger than ∼2 m. The H-parameter values are sensitive to presence of rocks and may be a better indicator of rocks at submeter scales. The Delta dome has gentle slopes, lower rock abundance, and one young crater, and it could serve as a safe and scientifically valuable site for landing and exploration of the domes and nearby region. The dome also displays anomalously high H-parameter in the same region as the crater, indicating the potential presence of pyroclastic materials. We observe up to 200 ppm of OH/H2O on the domes and nearby mare despite the presence of a weak magnetic field to the south of Delta dome, further supporting the potential presence of pyroclastics in the region. This study could potentially aid in logistical and scientific decisions of the future NASA missions in the region.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141408284","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}
S. Porter, S. Benecchi, A. Verbiscer, W. M. Grundy, K. S. Noll, A. H. Parker
Binaries in the Kuiper Belt are common. Here we present our analysis of the Solar System Origins Legacy Survey (SSOLS) to show that using a point-spread function (PSF)-fitting method can roughly double the number of binaries identified in that data set. Out of 198 Kuiper Belt objects (KBOs) observed by SSOLS, we find 23 to be visually separated binaries, while a further 19 are blended PSF binaries detectable with the method we present here. This is an overall binary fraction of 21% for the SSOLS data set of cold classical KBOs. In addition, we tested our fitting methods on synthetic data, and while we were able to show them to be very effective at detecting certain blended-PSF binary KBOs, fainter or closer binary KBOs may easily be missed, suggesting that the close binary KBO fraction could be even higher. These results strongly support the idea that most (if not all) KBOs were formed through the streaming instability process, and as a consequence, most KBOs were formed as near-equal mass binaries.
{"title":"Detection of Close Kuiper Belt Binaries with HST WFC3","authors":"S. Porter, S. Benecchi, A. Verbiscer, W. M. Grundy, K. S. Noll, A. H. Parker","doi":"10.3847/PSJ/ad3f19","DOIUrl":"https://doi.org/10.3847/PSJ/ad3f19","url":null,"abstract":"Binaries in the Kuiper Belt are common. Here we present our analysis of the Solar System Origins Legacy Survey (SSOLS) to show that using a point-spread function (PSF)-fitting method can roughly double the number of binaries identified in that data set. Out of 198 Kuiper Belt objects (KBOs) observed by SSOLS, we find 23 to be visually separated binaries, while a further 19 are blended PSF binaries detectable with the method we present here. This is an overall binary fraction of 21% for the SSOLS data set of cold classical KBOs. In addition, we tested our fitting methods on synthetic data, and while we were able to show them to be very effective at detecting certain blended-PSF binary KBOs, fainter or closer binary KBOs may easily be missed, suggesting that the close binary KBO fraction could be even higher. These results strongly support the idea that most (if not all) KBOs were formed through the streaming instability process, and as a consequence, most KBOs were formed as near-equal mass binaries.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141404330","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}
L. Pou, M. Panning, M. Styczinski, M. Melwani Daswani, C. Nunn, S. Vance
Seismology is a powerful tool for probing the deep interiors of planetary bodies. Just as deep moonquakes triggered by Earth’s tides occur on the Moon, as observed by the Apollo seismometers, icy moons of the giant planets may also have seismically active deep interiors, opening up future prospects for in situ seismic investigations at their surfaces. Of notable interest is Jupiter’s moon Europa, with its dynamic ice shell and potentially habitable subsurface ocean. In this work, we use different interior models of the Moon and model the tidal stress inside them to determine the most likely times and locations for the triggering of tidal moonquakes. Using the Mohr–Coulomb failure criterion, we derive cohesion and friction values for the lunar interior to match the observations of deep moonquakes by Apollo at a depth between 700 and 1200 km. By extending the same approach to different interior models of Europa, we show that Europa quakes triggered by the tides of Jupiter are 10 times more likely to occur than tidal moonquakes. The strength and depth of these tidal Europa quakes (euroquakes) strongly depend on the interior structure, with stronger events at the core–mantle boundary for liquid core models, while solid core models can be more prone to failure at the bottom of the ocean floor. Models without a metallic core favor failure in the upper third of the mantle with event strength similar to that in the solid core models.
{"title":"Tidal Seismicity in the Moon and Implications for the Rocky Interior of Europa","authors":"L. Pou, M. Panning, M. Styczinski, M. Melwani Daswani, C. Nunn, S. Vance","doi":"10.3847/PSJ/ad47bc","DOIUrl":"https://doi.org/10.3847/PSJ/ad47bc","url":null,"abstract":"Seismology is a powerful tool for probing the deep interiors of planetary bodies. Just as deep moonquakes triggered by Earth’s tides occur on the Moon, as observed by the Apollo seismometers, icy moons of the giant planets may also have seismically active deep interiors, opening up future prospects for in situ seismic investigations at their surfaces. Of notable interest is Jupiter’s moon Europa, with its dynamic ice shell and potentially habitable subsurface ocean. In this work, we use different interior models of the Moon and model the tidal stress inside them to determine the most likely times and locations for the triggering of tidal moonquakes. Using the Mohr–Coulomb failure criterion, we derive cohesion and friction values for the lunar interior to match the observations of deep moonquakes by Apollo at a depth between 700 and 1200 km. By extending the same approach to different interior models of Europa, we show that Europa quakes triggered by the tides of Jupiter are 10 times more likely to occur than tidal moonquakes. The strength and depth of these tidal Europa quakes (euroquakes) strongly depend on the interior structure, with stronger events at the core–mantle boundary for liquid core models, while solid core models can be more prone to failure at the bottom of the ocean floor. Models without a metallic core favor failure in the upper third of the mantle with event strength similar to that in the solid core models.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141403245","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}
Tim Lister, Cora Constantinescu, William Ryan, Eileen Ryan, Edward Gomez, Liz Phillips, Agata Rożek, Helen Usher, Brian P. Murphy, Joseph Chatelain and Sarah Greenstreet
The world’s first planetary defense test mission was carried out in late 2022 by NASA’s Double Asteroid Redirection Test (DART) mission. The main DART spacecraft, which was accompanied by the ASI-provided LICIACube cubesat, intentionally impacted Dimorphos, the smaller secondary of the near-Earth object binary system (65803) Didymos, on 2022 September 26. The impact released a large amount of ejecta, which, combined with the spacecraft’s momentum, produced the observed 33 ± 1 minute period change that was subsequently observed from ground-based telescopes. The DART mission, in addition to having successfully changed the orbital period of Dimorphos, also activated the asteroid as a result of the impact but under known conditions, unlike other impacts on asteroids. We have conducted long-term monitoring over 5 months following the impact with the Las Cumbres Observatory Global Telescope (LCOGT) network and Magdalena Ridge Observatory (MRO). This was supplemented by almost 3 months of more sparsely sampled data, primarily from educational users of the LCOGT network during the period from 2022 July 5 to 2022 September 25, prior to the impact date of 2022 September 26. Here we report the observations of the Didymos system and DART impact ejecta with the telescopes of the LCOGT network from T+1.93 days to T+151.3 days after impact, and we study the evolving morphology of the ejecta cloud and evolving tail over the entire length of the data set. In addition, we combined these intensive data sets with the earlier sparse observations over the ∼90 days prior to impact to derive a new disk-integrated phase function model using the H, G1, G2 parameterization.
{"title":"Long-term Monitoring of Didymos with the LCOGT Network and MRO after the DART Impact","authors":"Tim Lister, Cora Constantinescu, William Ryan, Eileen Ryan, Edward Gomez, Liz Phillips, Agata Rożek, Helen Usher, Brian P. Murphy, Joseph Chatelain and Sarah Greenstreet","doi":"10.3847/psj/ad4345","DOIUrl":"https://doi.org/10.3847/psj/ad4345","url":null,"abstract":"The world’s first planetary defense test mission was carried out in late 2022 by NASA’s Double Asteroid Redirection Test (DART) mission. The main DART spacecraft, which was accompanied by the ASI-provided LICIACube cubesat, intentionally impacted Dimorphos, the smaller secondary of the near-Earth object binary system (65803) Didymos, on 2022 September 26. The impact released a large amount of ejecta, which, combined with the spacecraft’s momentum, produced the observed 33 ± 1 minute period change that was subsequently observed from ground-based telescopes. The DART mission, in addition to having successfully changed the orbital period of Dimorphos, also activated the asteroid as a result of the impact but under known conditions, unlike other impacts on asteroids. We have conducted long-term monitoring over 5 months following the impact with the Las Cumbres Observatory Global Telescope (LCOGT) network and Magdalena Ridge Observatory (MRO). This was supplemented by almost 3 months of more sparsely sampled data, primarily from educational users of the LCOGT network during the period from 2022 July 5 to 2022 September 25, prior to the impact date of 2022 September 26. Here we report the observations of the Didymos system and DART impact ejecta with the telescopes of the LCOGT network from T+1.93 days to T+151.3 days after impact, and we study the evolving morphology of the ejecta cloud and evolving tail over the entire length of the data set. In addition, we combined these intensive data sets with the earlier sparse observations over the ∼90 days prior to impact to derive a new disk-integrated phase function model using the H, G1, G2 parameterization.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141197576","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}
Tomas Kohout, Maurizio Pajola, Assi-Johanna Soini, Alice Lucchetti, Arto Luttinen, Alexia Duchêne, Naomi Murdoch, Robert Luther, Nancy L. Chabot, Sabina D. Raducan, Paul Sánchez, Olivier S. Barnouin and Andrew S. Rivkin
The ∼200 m s−1 impact of a single 400 kg Bjurböle L/LL ordinary chondrite meteorite onto sea ice resulted in the catastrophic disruption of the projectile. This resulted in a significant fraction of decimeter-sized fragments that exhibit power-law cumulative size and mass distributions. This size range is underrepresented in impact experiments and asteroid boulder studies. The Bjurböle projectile fragments share similarities in shape (sphericity and roughness at small and large scales) with asteroid boulders. However, the mean aspect ratio (3D measurement) and apparent aspect ratio (2D measurement) of the Bjurböle fragments is 0.83 and 0.77, respectively, indicating that Bjurböle fragments are more equidimensional compared to both fragments produced in smaller-scale impact experiments and asteroid boulders. These differences may be attributed either to the fragment source (projectile versus target), to the high porosity and low strength of Bjurböle, to the lower impact velocity compared with typical asteroid collision velocities, or potentially to fragment erosion during sea sediment penetration or cleaning.
{"title":"Impact Disruption of Bjurböle Porous Chondritic Projectile","authors":"Tomas Kohout, Maurizio Pajola, Assi-Johanna Soini, Alice Lucchetti, Arto Luttinen, Alexia Duchêne, Naomi Murdoch, Robert Luther, Nancy L. Chabot, Sabina D. Raducan, Paul Sánchez, Olivier S. Barnouin and Andrew S. Rivkin","doi":"10.3847/psj/ad4266","DOIUrl":"https://doi.org/10.3847/psj/ad4266","url":null,"abstract":"The ∼200 m s−1 impact of a single 400 kg Bjurböle L/LL ordinary chondrite meteorite onto sea ice resulted in the catastrophic disruption of the projectile. This resulted in a significant fraction of decimeter-sized fragments that exhibit power-law cumulative size and mass distributions. This size range is underrepresented in impact experiments and asteroid boulder studies. The Bjurböle projectile fragments share similarities in shape (sphericity and roughness at small and large scales) with asteroid boulders. However, the mean aspect ratio (3D measurement) and apparent aspect ratio (2D measurement) of the Bjurböle fragments is 0.83 and 0.77, respectively, indicating that Bjurböle fragments are more equidimensional compared to both fragments produced in smaller-scale impact experiments and asteroid boulders. These differences may be attributed either to the fragment source (projectile versus target), to the high porosity and low strength of Bjurböle, to the lower impact velocity compared with typical asteroid collision velocities, or potentially to fragment erosion during sea sediment penetration or cleaning.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141188410","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}
Marc Rovira-Navarro, Isamu Matsuyama and Alexander Berne
Body tides reveal information about planetary interiors and affect their evolution. Most models to compute body tides rely on the assumption of a spherically symmetric interior. However, several processes can lead to lateral variations of interior properties. We present a new spectral method to compute the tidal response of laterally heterogeneous bodies. Compared to previous spectral methods, our approach is not limited to small-amplitude lateral variations; compared to finite element codes, this approach is more computationally efficient. While the tidal response of a spherically symmetric body has the same wavelength as the tidal force; lateral heterogeneities produce an additional tidal response with a spectra that depends on the spatial pattern of such variations. For Mercury, the Moon, and Io, the amplitude of this signal is as high as 1%–10% of the main tidal response for long-wavelength shear modulus variations higher than ∼10% of the mean shear modulus. For Europa, Ganymede, and Enceladus, shell-thickness variations of 50% of the mean shell thickness can cause an additional signal of ∼1% and ∼10% for the Jovian moons and Encelaudus, respectively. Future missions, such as BepiColombo and JUICE, might measure these signals. Lateral variations of viscosity affect the distribution of tidal heating. This can drive the thermal evolution of tidally active bodies and affect the distribution of active regions.
{"title":"A Spectral Method to Compute the Tides of Laterally Heterogeneous Bodies","authors":"Marc Rovira-Navarro, Isamu Matsuyama and Alexander Berne","doi":"10.3847/psj/ad381f","DOIUrl":"https://doi.org/10.3847/psj/ad381f","url":null,"abstract":"Body tides reveal information about planetary interiors and affect their evolution. Most models to compute body tides rely on the assumption of a spherically symmetric interior. However, several processes can lead to lateral variations of interior properties. We present a new spectral method to compute the tidal response of laterally heterogeneous bodies. Compared to previous spectral methods, our approach is not limited to small-amplitude lateral variations; compared to finite element codes, this approach is more computationally efficient. While the tidal response of a spherically symmetric body has the same wavelength as the tidal force; lateral heterogeneities produce an additional tidal response with a spectra that depends on the spatial pattern of such variations. For Mercury, the Moon, and Io, the amplitude of this signal is as high as 1%–10% of the main tidal response for long-wavelength shear modulus variations higher than ∼10% of the mean shear modulus. For Europa, Ganymede, and Enceladus, shell-thickness variations of 50% of the mean shell thickness can cause an additional signal of ∼1% and ∼10% for the Jovian moons and Encelaudus, respectively. Future missions, such as BepiColombo and JUICE, might measure these signals. Lateral variations of viscosity affect the distribution of tidal heating. This can drive the thermal evolution of tidally active bodies and affect the distribution of active regions.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141197795","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}
Norbert Schörghofer, Jean-Pierre Williams and Erwan Mazarico
Lunar cold traps are defined by extremely low sublimation rates, such that water ice could have accumulated in them. Here time-averaged sublimation rates are calculated for the north polar region of the Moon based on over 14 years of Diviner surface temperature measurements. Data for each spatial pixel are binned according to subsolar (diurnal) and ecliptic (seasonal) longitude. The cold trap area poleward of 80°N is about 32% larger when defined by a time-average sublimation rate instead of by peak temperature. Apparently sunlit cold traps are identified, e.g., in Lenard Crater, where modeling of direct illumination reveals that the Sun briefly rises above the horizon each Draconic year. The true cold trap area is smaller than what can be determined from Diviner data. Also presented are north polar maps for the potential sublimation rate of relic buried ice and for subsurface cold trapping.
{"title":"Lunar North Polar Cold Traps Based on Diurnally and Seasonally Varying Temperatures","authors":"Norbert Schörghofer, Jean-Pierre Williams and Erwan Mazarico","doi":"10.3847/psj/ad49a8","DOIUrl":"https://doi.org/10.3847/psj/ad49a8","url":null,"abstract":"Lunar cold traps are defined by extremely low sublimation rates, such that water ice could have accumulated in them. Here time-averaged sublimation rates are calculated for the north polar region of the Moon based on over 14 years of Diviner surface temperature measurements. Data for each spatial pixel are binned according to subsolar (diurnal) and ecliptic (seasonal) longitude. The cold trap area poleward of 80°N is about 32% larger when defined by a time-average sublimation rate instead of by peak temperature. Apparently sunlit cold traps are identified, e.g., in Lenard Crater, where modeling of direct illumination reveals that the Sun briefly rises above the horizon each Draconic year. The true cold trap area is smaller than what can be determined from Diviner data. Also presented are north polar maps for the potential sublimation rate of relic buried ice and for subsurface cold trapping.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141188469","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}
Alexander E. Thelen, Conor A. Nixon, Martin A. Cordiner, Emmanuel Lellouch, Sandrine Vinatier, Nicholas A. Teanby, Bryan Butler, Steven B. Charnley, Richard G. Cosentino, Katherine de Kleer, Patrick G. J. Irwin, Mark A. Gurwell, Zbigniew Kisiel and Raphael Moreno
Titan’s atmospheric composition and dynamical state have previously been studied over numerous epochs by both ground- and space-based facilities. However, stratospheric measurements remain sparse during Titan’s northern summer and fall. The lack of seasonal symmetry in observations of Titan’s temperature field and chemical abundances raises questions about the nature of the middle atmosphere’s meridional circulation and evolution over Titan’s 29 yr seasonal cycle that can only be answered through long-term monitoring campaigns. Here, we present maps of Titan’s stratospheric temperature, acetonitrile (or methyl cyanide; CH3CN) abundance, and monodeuterated methane (CH3D) abundance following Titan’s northern summer solstice obtained with Band 9 (∼0.43 mm) Atacama Large Millimeter/submillimeter Array observations. We find that increasing temperatures toward high southern latitudes, currently in winter, resemble those observed during Titan’s northern winter by the Cassini mission. Acetonitrile abundances have changed significantly since previous (sub)millimeter observations, and we find that the species is now highly concentrated at high southern latitudes. The stratospheric CH3D content is found to range between 4 and 8 ppm in these observations, and we infer the CH4 abundance to vary between ∼0.9% and 1.6% through conversion with previously measured D/H values. A global value of CH4 = 1.15% was retrieved, lending further evidence to the temporal and spatial variability of Titan’s stratospheric methane when compared with previous measurements. Additional observations are required to determine the cause and magnitude of stratospheric enhancements in methane during these poorly understood seasons on Titan.
{"title":"Observations of Titan’s Stratosphere during Northern Summer: Temperatures, CH3CN and CH3D Abundances","authors":"Alexander E. Thelen, Conor A. Nixon, Martin A. Cordiner, Emmanuel Lellouch, Sandrine Vinatier, Nicholas A. Teanby, Bryan Butler, Steven B. Charnley, Richard G. Cosentino, Katherine de Kleer, Patrick G. J. Irwin, Mark A. Gurwell, Zbigniew Kisiel and Raphael Moreno","doi":"10.3847/psj/ad47bd","DOIUrl":"https://doi.org/10.3847/psj/ad47bd","url":null,"abstract":"Titan’s atmospheric composition and dynamical state have previously been studied over numerous epochs by both ground- and space-based facilities. However, stratospheric measurements remain sparse during Titan’s northern summer and fall. The lack of seasonal symmetry in observations of Titan’s temperature field and chemical abundances raises questions about the nature of the middle atmosphere’s meridional circulation and evolution over Titan’s 29 yr seasonal cycle that can only be answered through long-term monitoring campaigns. Here, we present maps of Titan’s stratospheric temperature, acetonitrile (or methyl cyanide; CH3CN) abundance, and monodeuterated methane (CH3D) abundance following Titan’s northern summer solstice obtained with Band 9 (∼0.43 mm) Atacama Large Millimeter/submillimeter Array observations. We find that increasing temperatures toward high southern latitudes, currently in winter, resemble those observed during Titan’s northern winter by the Cassini mission. Acetonitrile abundances have changed significantly since previous (sub)millimeter observations, and we find that the species is now highly concentrated at high southern latitudes. The stratospheric CH3D content is found to range between 4 and 8 ppm in these observations, and we infer the CH4 abundance to vary between ∼0.9% and 1.6% through conversion with previously measured D/H values. A global value of CH4 = 1.15% was retrieved, lending further evidence to the temporal and spatial variability of Titan’s stratospheric methane when compared with previous measurements. Additional observations are required to determine the cause and magnitude of stratospheric enhancements in methane during these poorly understood seasons on Titan.","PeriodicalId":34524,"journal":{"name":"The Planetary Science Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141188470","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}
Ryan T. Walker, Michael K. Barker, Erwan Mazarico, Xiaoli Sun, Gregory A. Neumann, David E. Smith, James W. Head and Maria T. Zuber
Examining the reflectance of the Moon's surface across a broad range of viewing geometries through photometric analysis can reveal physical and geological properties of its regolith. Since 2013 December, the Lunar Orbiter Laser Altimeter (LOLA) on board the Lunar Reconnaissance Orbiter (LRO) has been operating as a near-infrared (1064 nm) passive radiometer when its laser is turned off. We present a new analysis of this data set spanning roughly 8 yr and covering the surface up to high latitudes in both hemispheres. We apply semiempirical phase functions to find a lower photometric slope and a narrower opposition effect for the highlands than the maria, consistent with theoretical expectations given the higher albedo of the highlands. Examining various geological properties at global scales shows that, in the highlands, iron abundance (FeO) and optical maturity (OMAT) are the dominant factors affecting the phase function, with a smaller influence from surface slope. In the maria, FeO is the dominant factor, with smaller influences from OMAT, surface slope, and TiO2. Submicroscopic iron abundance (SMFe) has a similar effect to OMAT in both highlands and maria. Analysis at specific sites, including the Reiner Gamma swirl and several silicic anomalies, indicates that the phase functions are consistent with the global data for similar FeO and OMAT. Thermophysical properties inferred from surface temperature observations by the Diviner Lunar Radiometer Experiment on board LRO do not affect the 1064 nm phase function, possibly due to a difference between their depth scale and LOLA's sensing depth.
{"title":"Near-infrared Photometry of the Moon's Surface with Passive Radiometry from the Lunar Orbiter Laser Altimeter (LOLA)","authors":"Ryan T. Walker, Michael K. Barker, Erwan Mazarico, Xiaoli Sun, Gregory A. Neumann, David E. Smith, James W. Head and Maria T. Zuber","doi":"10.3847/psj/ad4467","DOIUrl":"https://doi.org/10.3847/psj/ad4467","url":null,"abstract":"Examining the reflectance of the Moon's surface across a broad range of viewing geometries through photometric analysis can reveal physical and geological properties of its regolith. Since 2013 December, the Lunar Orbiter Laser Altimeter (LOLA) on board the Lunar Reconnaissance Orbiter (LRO) has been operating as a near-infrared (1064 nm) passive radiometer when its laser is turned off. We present a new analysis of this data set spanning roughly 8 yr and covering the surface up to high latitudes in both hemispheres. We apply semiempirical phase functions to find a lower photometric slope and a narrower opposition effect for the highlands than the maria, consistent with theoretical expectations given the higher albedo of the highlands. Examining various geological properties at global scales shows that, in the highlands, iron abundance (FeO) and optical maturity (OMAT) are the dominant factors affecting the phase function, with a smaller influence from surface slope. In the maria, FeO is the dominant factor, with smaller influences from OMAT, surface slope, and TiO2. Submicroscopic iron abundance (SMFe) has a similar effect to OMAT in both highlands and maria. Analysis at specific sites, including the Reiner Gamma swirl and several silicic anomalies, indicates that the phase functions are consistent with the global data for similar FeO and OMAT. Thermophysical properties inferred from surface temperature observations by the Diviner Lunar Radiometer Experiment on board LRO do not affect the 1064 nm phase function, possibly due to a difference between their depth scale and LOLA's sensing depth.","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":"141165507","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}
The Lunar Reconnaissance Orbiter (LRO) has returned a wealth of remotely sensed data of the Moon over the past 15 years. As preparations are under way to return humans to the lunar surface with the Artemis campaign, LRO data have become a cornerstone for the characterization of potential sites of scientific and exploration interest on the Moon's surface. One critical aspect of landing site selection is knowledge of topography, slope, and surface hazards. Digital elevation models derived from the Lunar Orbiter Laser Altimeter (LOLA) and Lunar Reconnaissance Orbiter Camera (LROC) instruments can provide this information at scales of meters to decameters. Shape-from-shading (SfS), or photoclinometry, is a technique for independently deriving surface height information by correlating surface reflectance with incidence angle and can theoretically approach an effective resolution equivalent to the input images themselves, typically better than 1 m per pixel with the LROC Narrow Angle Camera (NAC). We present a high-level, semiautomated pipeline that utilizes preexisting Ames Stereo Pipeline tools along with image alignment and parallel processing routines to generate SfS-refined digital elevation models using LRO data. In addition to the present focus on the lunar south pole with Artemis, we also demonstrate the usefulness of SfS for characterizing meter-scale lunar topography at lower equatorial latitudes.
{"title":"Shape-from-shading Refinement of LOLA and LROC NAC Digital Elevation Models: Applications to Upcoming Human and Robotic Exploration of the Moon","authors":"Benjamin D. Boatwright and James W. Head","doi":"10.3847/psj/ad41b4","DOIUrl":"https://doi.org/10.3847/psj/ad41b4","url":null,"abstract":"The Lunar Reconnaissance Orbiter (LRO) has returned a wealth of remotely sensed data of the Moon over the past 15 years. As preparations are under way to return humans to the lunar surface with the Artemis campaign, LRO data have become a cornerstone for the characterization of potential sites of scientific and exploration interest on the Moon's surface. One critical aspect of landing site selection is knowledge of topography, slope, and surface hazards. Digital elevation models derived from the Lunar Orbiter Laser Altimeter (LOLA) and Lunar Reconnaissance Orbiter Camera (LROC) instruments can provide this information at scales of meters to decameters. Shape-from-shading (SfS), or photoclinometry, is a technique for independently deriving surface height information by correlating surface reflectance with incidence angle and can theoretically approach an effective resolution equivalent to the input images themselves, typically better than 1 m per pixel with the LROC Narrow Angle Camera (NAC). We present a high-level, semiautomated pipeline that utilizes preexisting Ames Stereo Pipeline tools along with image alignment and parallel processing routines to generate SfS-refined digital elevation models using LRO data. In addition to the present focus on the lunar south pole with Artemis, we also demonstrate the usefulness of SfS for characterizing meter-scale lunar topography at lower equatorial latitudes.","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":"141165615","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：