This document reports on high-resolution images from the MESSENGER spacecraft that reveal unusual landforms on Mercury characterized by irregular, shallow depressions known as hollows. The hollows range in size and are commonly found in clusters associated with high-reflectance materials within impact craters. The most likely formation mechanisms involve recent loss of volatile materials through processes like sublimation or pyroclastic volcanism. These features suggest Mercury's interior contains more volatile materials than predicted, challenging models of the planet's formation.
- Hollows on Mercury range from tens of meters to kilometers across and are irregular depressions found within impact craters.
- Many hollows have high-reflectance interiors and halos and are associated with crater central peaks, peak rings, floors, and walls.
- The most likely formation mechanisms involve recent loss of volatiles through processes like sublimation, outgassing, or pyroclastic volcanism.
- The discovery of hollows provides evidence that Mercury has higher abundances of volatile materials than predicted.
The GRAIL spacecraft measured the gravity field of the Moon at high resolution, allowing determination of the bulk density and porosity of the lunar crust. The analysis found:
1) The bulk density of the lunar highlands crust is 2550 kg/m3, substantially lower than previous estimates due to impact-induced porosity.
2) The average porosity of the crust is 12%, varying regionally from 4-21% and correlated with impact basins.
3) A new global crustal thickness model was constructed satisfying seismic constraints with an average thickness of 34-43 km, indicating the Moon's composition is not highly enriched compared to Earth.
This document examines four Venusian shield fields through geological mapping using Synthetic Aperture Radar imagery. It finds that each field displays a distinct morphology, possibly related to differences in magma properties or eruption styles. Mapping allowed trends in shield morphologies to be recorded across different areas of Venus' surface. However, due to the resolution of imagery, establishing detailed stratigraphy within individual fields is challenging.
The document summarizes the analysis of layered deposits inside the 174 km diameter Terby impact crater located on Mars. Stratigraphic and mineralogical analysis using multiple datasets suggests the deposits were formed subaqueously during the Noachian period. The thickest sequences display fan delta morphologies indicative of prograding/onlapping sedimentation over time. Phyllosilicates detected within layers support a sedimentary environment with sustained liquid water. Erosion during the Hesperian sculpted the current landforms, with later fluvial and then aeolian activity. Terby crater thus preserves a geologic record spanning multiple periods of Mars' history.
This document discusses implications of new images of the Sculptured Hills unit on the Moon for understanding the relative ages of impact basins. Key points:
1) Sculptured Hills was thought to be ejecta from the Serenitatis basin, but new images show it is widespread and overlies craters postdating Serenitatis.
2) Sculptured Hills transitions into the Alpes Formation north of Mare Serenitatis, suggesting it is actually ejecta from the younger Imbrium basin.
3) If true, this implies Serenitatis is relatively old, pre-Nectarian, and that the Apollo 17 impact melts may sample the older Serenitat
Ages and stratigraphy of lunar mare basalts a synthesisSérgio Sacani
This document summarizes ages and stratigraphy of lunar mare basalts based on a synthesis of crater counting efforts over more than 10 years. The key points are:
1) Lunar volcanism was active for almost 3 billion years, starting around 3.9-4 billion years ago and ceasing around 1.2 billion years ago.
2) Most basalts erupted during the late Imbrian period around 3.6-3.8 billion years ago.
3) Significantly fewer basalts were emplaced during the Eratosthenian period.
4) Basalts of possible Copernican age have only been found in limited areas of Oceanus Procellarum.
Non mare silicic volcanism on the lunar farside at compton–belkovichSérgio Sacani
1. Images from the Lunar Reconnaissance Orbiter reveal a central feature within the Compton–Belkovich thorium anomaly on the lunar farside characterized by elevated topography and relatively high reflectance.
2. The central feature contains several volcanic domes ranging from less than 1 km to over 6 km across, as well as arcuate and irregular depressions interpreted as collapse features associated with volcanism.
3. Spectral data indicates the volcanic feature is enriched in silica and alkali-feldspar, suggesting a composition of rhyolitic volcanic materials. This provides evidence for rare non-basaltic volcanism on the lunar farside far from the Procellarum
The document summarizes findings from images and data collected by the Lunar Reconnaissance Orbiter regarding the Compton-Belkovich thorium anomaly on the lunar farside. Key findings include:
1) A central feature covering 25 by 35 km is identified, characterized by elevated topography and relatively high reflectance, including several volcanic domes from less than 1 km to over 6 km across.
2) Arcuate to irregular circular depressions observed are interpreted as collapse features associated with volcanism.
3) Spectral data finds the volcanic feature enriched in silica or alkali-feldspar, indicative of compositionally evolved, rhyolitic volcanic materials.
4)
- Hollows on Mercury range from tens of meters to kilometers across and are irregular depressions found within impact craters.
- Many hollows have high-reflectance interiors and halos and are associated with crater central peaks, peak rings, floors, and walls.
- The most likely formation mechanisms involve recent loss of volatiles through processes like sublimation, outgassing, or pyroclastic volcanism.
- The discovery of hollows provides evidence that Mercury has higher abundances of volatile materials than predicted.
The GRAIL spacecraft measured the gravity field of the Moon at high resolution, allowing determination of the bulk density and porosity of the lunar crust. The analysis found:
1) The bulk density of the lunar highlands crust is 2550 kg/m3, substantially lower than previous estimates due to impact-induced porosity.
2) The average porosity of the crust is 12%, varying regionally from 4-21% and correlated with impact basins.
3) A new global crustal thickness model was constructed satisfying seismic constraints with an average thickness of 34-43 km, indicating the Moon's composition is not highly enriched compared to Earth.
This document examines four Venusian shield fields through geological mapping using Synthetic Aperture Radar imagery. It finds that each field displays a distinct morphology, possibly related to differences in magma properties or eruption styles. Mapping allowed trends in shield morphologies to be recorded across different areas of Venus' surface. However, due to the resolution of imagery, establishing detailed stratigraphy within individual fields is challenging.
The document summarizes the analysis of layered deposits inside the 174 km diameter Terby impact crater located on Mars. Stratigraphic and mineralogical analysis using multiple datasets suggests the deposits were formed subaqueously during the Noachian period. The thickest sequences display fan delta morphologies indicative of prograding/onlapping sedimentation over time. Phyllosilicates detected within layers support a sedimentary environment with sustained liquid water. Erosion during the Hesperian sculpted the current landforms, with later fluvial and then aeolian activity. Terby crater thus preserves a geologic record spanning multiple periods of Mars' history.
This document discusses implications of new images of the Sculptured Hills unit on the Moon for understanding the relative ages of impact basins. Key points:
1) Sculptured Hills was thought to be ejecta from the Serenitatis basin, but new images show it is widespread and overlies craters postdating Serenitatis.
2) Sculptured Hills transitions into the Alpes Formation north of Mare Serenitatis, suggesting it is actually ejecta from the younger Imbrium basin.
3) If true, this implies Serenitatis is relatively old, pre-Nectarian, and that the Apollo 17 impact melts may sample the older Serenitat
Ages and stratigraphy of lunar mare basalts a synthesisSérgio Sacani
This document summarizes ages and stratigraphy of lunar mare basalts based on a synthesis of crater counting efforts over more than 10 years. The key points are:
1) Lunar volcanism was active for almost 3 billion years, starting around 3.9-4 billion years ago and ceasing around 1.2 billion years ago.
2) Most basalts erupted during the late Imbrian period around 3.6-3.8 billion years ago.
3) Significantly fewer basalts were emplaced during the Eratosthenian period.
4) Basalts of possible Copernican age have only been found in limited areas of Oceanus Procellarum.
Non mare silicic volcanism on the lunar farside at compton–belkovichSérgio Sacani
1. Images from the Lunar Reconnaissance Orbiter reveal a central feature within the Compton–Belkovich thorium anomaly on the lunar farside characterized by elevated topography and relatively high reflectance.
2. The central feature contains several volcanic domes ranging from less than 1 km to over 6 km across, as well as arcuate and irregular depressions interpreted as collapse features associated with volcanism.
3. Spectral data indicates the volcanic feature is enriched in silica and alkali-feldspar, suggesting a composition of rhyolitic volcanic materials. This provides evidence for rare non-basaltic volcanism on the lunar farside far from the Procellarum
The document summarizes findings from images and data collected by the Lunar Reconnaissance Orbiter regarding the Compton-Belkovich thorium anomaly on the lunar farside. Key findings include:
1) A central feature covering 25 by 35 km is identified, characterized by elevated topography and relatively high reflectance, including several volcanic domes from less than 1 km to over 6 km across.
2) Arcuate to irregular circular depressions observed are interpreted as collapse features associated with volcanism.
3) Spectral data finds the volcanic feature enriched in silica or alkali-feldspar, indicative of compositionally evolved, rhyolitic volcanic materials.
4)
The document summarizes research on the origin of lunar concentric craters. The researchers analyzed data from Clementine, SELENE, and LRO to study 58 known concentric craters. They identified three morphological types and found concentric craters have shallower depths and smaller rim heights than fresh simple craters, suggesting impact degradation or uplift. Distribution near mare/highland boundaries and similarities to floor-fractured craters supports igneous intrusion as the most probable formation mechanism, rather than exogenic processes like simultaneous impacts or impact into layered targets.
1) The study mapped an area in southern Margaritifer Terra, Mars containing 5 large impact craters to understand the geologic history and role of water.
2) The craters showed evidence of alluvial fans, aeolian deposits, and fluvial erosion indicating water once flowed on the surface. Older fans within Crater 1 suggest the presence of an ancient lake.
3) Overall, the features revealed the area experienced impact cratering, mass wasting, and fluvial erosion and deposition from water in the past like rainfall, snowmelt, or groundwater. Mapping helped decipher the complex geologic processes that shaped the landscape over time.
This document analyzes structural mapping data of the central uplift region of Martin Crater on Mars to test predictions of acoustic fluidization models of central peak formation. The mapping shows the megablocks in the uplift are intricately interconnected with correlated bedding planes across boundaries, forming large folds accommodated by fracturing with little internal strain. Block separation measurements are far less than required for acoustic fluidization. The data are inconsistent with the block model of fluidization and suggest fluidization played a minor role, while not proposing an alternative formation mechanism.
The document discusses different types of geologic maps. It describes classifications of maps including qualitative maps that show shape, composition, and evolution over time and quantitative maps that show geometric configuration, thickness variations, and composition. Specific map types are outlined under each classification, such as geological maps, photogeological maps, structure contour maps, isopach maps, and geophysical maps. Key elements of geologic maps like strata patterns, folds, faults, and symbols are also reviewed.
Okay, here are the steps to solve this problem:
(a) (i) Using the equation: Depth = 2.5 km + 0.3(Age)1/2
Set Depth = 4700 m
4700 = 2.5 + 0.3(Age)1/2
4700 - 2.5 = 0.3(Age)1/2
4697.5 = 0.3(Age)1/2
(4697.5/0.3)2 = Age
Age = 80 Myr
(ii) Spreading rate = Distance from ridge / Age
= 1600 km / 80 Myr
= 20 km/Myr
(b) This is a half
The document summarizes a study that presents the first panoramic view of the outskirts of the Milky Way analogue galaxy NGC 891 based on ground-based imaging. The key findings are:
1) Numerous stellar overdensities and coherent substructures were detected out to distances of ~90 kpc from the center of NGC 891, including a giant stream looping around the galaxy up to ~50 kpc.
2) A previously undetected large, flat, and thick cocoon-like stellar structure was found surrounding the bulge and disk of NGC 891 out to radial distances of ~40 kpc and vertical distances of ~15 kpc.
3) The properties of the substructures suggest NGC
The document discusses the tools used for subsurface analysis in geology, including well logs, cores, seismic data, and gravity and magnetic surveys. It focuses on well logs and seismic data. Well logs provide high vertical resolution and help delimit bounding surfaces and establish lithology. Seismic data provide high lateral continuity and resolution to define sediment geometries. Together these tools are used for allostratigraphy and sequence stratigraphy by identifying bounding discontinuities and sequences reflecting changes in relative sea level.
Boon et al 2015 Geomorphology 248 pp296-310David Boon
The document describes a landslide that occurred on the Jurassic Escarpment in Great Fryup Dale, North Yorkshire, UK. A combined geomorphological mapping, LiDAR, borehole, and electrical resistivity tomography (ERT) approach was used to characterize the landslide. The landslide involved the failure of around 1 million cubic meters of bedrock, displacing it up to 50 meters deep. Radiocarbon dating indicates the frontal mudflow area was last active around 2270 years ago in the Late Holocene. While currently dormant, slope stability modeling suggests the slope is less stable than assumed and could reactivate during future wet climate phases, posing a landslide hazard for the region.
1) Gale Crater is a potential landing site for the Mars Science Laboratory rover. It contains a large mound of layered sediment in the crater's center over 5 km thick.
2) Previous studies have proposed various origins for the mound materials, including lacustrine, aeolian, pyroclastic, and spring deposits. However, the exact origin remains uncertain.
3) This study uses high-resolution imagery and spectral data to characterize the geomorphology and stratigraphy of the mound and crater in order to better understand the depositional environment(s) and evaluate hypotheses for the mound's origin.
This document discusses sedimentary basins, including their definition, formation, and analysis. Key points:
- Sedimentary basins form in low areas of the crust where sediments accumulate due to tectonic activity that creates relief. They range in size from hundreds of meters to ocean basins.
- Tectonics is the primary control on sedimentation, affecting factors like sediment supply and depositional environment. Sedimentation also influences tectonics by increasing lithospheric loading.
- Basins can be formed by processes including faulting, thermal subsidence of extended lithosphere, and flexural subsidence caused by loading of the lithosphere.
- Analyzing features of sedimentary
1. The document analyzes the spatial distribution and size-frequency of rayed impact craters on the Moon using Clementine image data.
2. It finds that the size-frequency distribution of rayed craters indicates an average surface age of 750 million years, with compositional rays potentially persisting longer.
3. Small craters below 5 km in diameter show evidence of faster fading of ejecta rays, with an average retention time of only about 5 million years for craters 1-500m in size.
This document discusses seismic stratigraphy, which uses seismic data to extract stratigraphic information about subsurface rock layers. It defines seismic waves and methods, including refraction and reflection. Reflection seismic is more commonly used to identify structures like folds and faults beneath the surface. Key parameters for interpretation are reflection configuration, continuity, amplitude, frequency, and interval velocity. Depositional environments are also identified based on their relationship to the wave base.
The document discusses techniques for seismic stratigraphy analysis and interpretation. It describes delineating depositional sequences using reflection termination mapping. Reflection terminations indicate strata discontinuities and can be truncation, toplap, baselap, onlap, or downlap. Seismic sequence analysis involves analyzing seismic sequences, facies, and interpreting depositional environments. Reflection configurations, continuity, amplitude, and frequency are used to define seismic facies units representing depositional environments and lithofacies.
Ancient igneous intrusions_and_early_expansion_of_the_moon_revealed_by_grailSérgio Sacani
1) Application of gravity gradiometry to data from the GRAIL mission revealed numerous linear gravity anomalies on the Moon with lengths of hundreds of kilometers.
2) Inversion of the anomalies indicates they are dense vertical intrusions or dikes formed by ancient magmatism during extension of the lunar lithosphere before the end of heavy bombardment.
3) The distribution, orientation, and size of the intrusions suggest they formed as the Moon's radius increased by 0.6-4.9 km early in its history, consistent with predictions of thermal evolution models.
This document summarizes geological investigations for engineering projects and disaster prevention in Japan. It describes various surface and subsurface investigation techniques used to characterize soil and rock conditions, including mapping, drilling, testing, and laboratory analysis. Examples of natural hazards like earthquakes, landslides, and floods are presented, along with case studies of slope failures in cuts and fills. The importance of geological mapping, stratigraphy, and regional hazard assessments are emphasized for understanding site conditions and designing safe structures.
This document discusses engineering geological mapping and provides details on:
1) The purpose of engineering geological maps is to provide basic information for land use planning, engineering works planning/design/construction/maintenance, and environmental planning.
2) Engineering geological maps represent characteristics of rocks/soils, hydrogeological conditions, geomorphological conditions, and active geodynamic phenomena.
3) Classification of rocks and soils on maps is based on properties indicating physical/engineering characteristics, such as mineralogy, texture, structure, and weathering state.
This document is a student's geological map project report on fieldwork conducted on the Isle of Rum, Scotland. It includes descriptions of the lithologies mapped in the area, including igneous rocks of the Igneous Layered Intrusion and sedimentary rocks of the Mullach Ard Formation. Detailed descriptions are provided of the mineralogy, textures, orientations, boundaries and inferred origins of the different rock units. Cross-sections were produced to interpret the subsurface relationships between the lithologies and understand the geological history of the area. Comparative analysis was also conducted on minor structures within the igneous and sedimentary rocks.
The document summarizes a geological field study conducted in Malekhu, Nepal. Key points:
- The study aimed to familiarize students with geological structures, engineering significance, and different rock and soil types. Measurements of dip, strike, and attitudes of bedding planes were taken.
- Engineering geology is important for civil engineering projects to understand subsurface conditions and design earthworks and foundations. Site investigations assess natural hazards.
- The field study location was selected for its accessible rocks, river morphology, natural topography, and mass movements. Objectives included learning identification and mapping techniques.
- Field observations and measurements of planar features like bedding, foliation, and joints were made using a Brunt
The document summarizes the first results from an ambitious HARPS program to detect Earth-like planets around nearby solar-type stars using high-precision radial velocity measurements. It reports the discovery of five new low-mass planets around the stars HD 20794, HD 85512, and HD 192310, including a system of three super-Earths and a planet with a mass of 3.6 Earth masses located at the inner edge of the habitable zone. This confirms previous indications that low-mass planets seem to be very frequent around solar-type stars, with an occurrence rate that may be higher than 30%.
1. Conformal cyclic cosmology (CCC) predicts the existence of concentric circles of anomalously low temperature variance in the cosmic microwave background (CMB) that would provide evidence of violent events prior to the Big Bang.
2. Analysis of WMAP and BOOMERANG CMB data reveals families of concentric circles up to 6 standard deviations below the mean temperature variance, consistent with CCC predictions.
3. These circles are not easily explained by standard inflationary cosmology, as the events that could cause some of the largest circles observed would need to occur before the end of inflation in the previous aeon.
The document summarizes research on the origin of lunar concentric craters. The researchers analyzed data from Clementine, SELENE, and LRO to study 58 known concentric craters. They identified three morphological types and found concentric craters have shallower depths and smaller rim heights than fresh simple craters, suggesting impact degradation or uplift. Distribution near mare/highland boundaries and similarities to floor-fractured craters supports igneous intrusion as the most probable formation mechanism, rather than exogenic processes like simultaneous impacts or impact into layered targets.
1) The study mapped an area in southern Margaritifer Terra, Mars containing 5 large impact craters to understand the geologic history and role of water.
2) The craters showed evidence of alluvial fans, aeolian deposits, and fluvial erosion indicating water once flowed on the surface. Older fans within Crater 1 suggest the presence of an ancient lake.
3) Overall, the features revealed the area experienced impact cratering, mass wasting, and fluvial erosion and deposition from water in the past like rainfall, snowmelt, or groundwater. Mapping helped decipher the complex geologic processes that shaped the landscape over time.
This document analyzes structural mapping data of the central uplift region of Martin Crater on Mars to test predictions of acoustic fluidization models of central peak formation. The mapping shows the megablocks in the uplift are intricately interconnected with correlated bedding planes across boundaries, forming large folds accommodated by fracturing with little internal strain. Block separation measurements are far less than required for acoustic fluidization. The data are inconsistent with the block model of fluidization and suggest fluidization played a minor role, while not proposing an alternative formation mechanism.
The document discusses different types of geologic maps. It describes classifications of maps including qualitative maps that show shape, composition, and evolution over time and quantitative maps that show geometric configuration, thickness variations, and composition. Specific map types are outlined under each classification, such as geological maps, photogeological maps, structure contour maps, isopach maps, and geophysical maps. Key elements of geologic maps like strata patterns, folds, faults, and symbols are also reviewed.
Okay, here are the steps to solve this problem:
(a) (i) Using the equation: Depth = 2.5 km + 0.3(Age)1/2
Set Depth = 4700 m
4700 = 2.5 + 0.3(Age)1/2
4700 - 2.5 = 0.3(Age)1/2
4697.5 = 0.3(Age)1/2
(4697.5/0.3)2 = Age
Age = 80 Myr
(ii) Spreading rate = Distance from ridge / Age
= 1600 km / 80 Myr
= 20 km/Myr
(b) This is a half
The document summarizes a study that presents the first panoramic view of the outskirts of the Milky Way analogue galaxy NGC 891 based on ground-based imaging. The key findings are:
1) Numerous stellar overdensities and coherent substructures were detected out to distances of ~90 kpc from the center of NGC 891, including a giant stream looping around the galaxy up to ~50 kpc.
2) A previously undetected large, flat, and thick cocoon-like stellar structure was found surrounding the bulge and disk of NGC 891 out to radial distances of ~40 kpc and vertical distances of ~15 kpc.
3) The properties of the substructures suggest NGC
The document discusses the tools used for subsurface analysis in geology, including well logs, cores, seismic data, and gravity and magnetic surveys. It focuses on well logs and seismic data. Well logs provide high vertical resolution and help delimit bounding surfaces and establish lithology. Seismic data provide high lateral continuity and resolution to define sediment geometries. Together these tools are used for allostratigraphy and sequence stratigraphy by identifying bounding discontinuities and sequences reflecting changes in relative sea level.
Boon et al 2015 Geomorphology 248 pp296-310David Boon
The document describes a landslide that occurred on the Jurassic Escarpment in Great Fryup Dale, North Yorkshire, UK. A combined geomorphological mapping, LiDAR, borehole, and electrical resistivity tomography (ERT) approach was used to characterize the landslide. The landslide involved the failure of around 1 million cubic meters of bedrock, displacing it up to 50 meters deep. Radiocarbon dating indicates the frontal mudflow area was last active around 2270 years ago in the Late Holocene. While currently dormant, slope stability modeling suggests the slope is less stable than assumed and could reactivate during future wet climate phases, posing a landslide hazard for the region.
1) Gale Crater is a potential landing site for the Mars Science Laboratory rover. It contains a large mound of layered sediment in the crater's center over 5 km thick.
2) Previous studies have proposed various origins for the mound materials, including lacustrine, aeolian, pyroclastic, and spring deposits. However, the exact origin remains uncertain.
3) This study uses high-resolution imagery and spectral data to characterize the geomorphology and stratigraphy of the mound and crater in order to better understand the depositional environment(s) and evaluate hypotheses for the mound's origin.
This document discusses sedimentary basins, including their definition, formation, and analysis. Key points:
- Sedimentary basins form in low areas of the crust where sediments accumulate due to tectonic activity that creates relief. They range in size from hundreds of meters to ocean basins.
- Tectonics is the primary control on sedimentation, affecting factors like sediment supply and depositional environment. Sedimentation also influences tectonics by increasing lithospheric loading.
- Basins can be formed by processes including faulting, thermal subsidence of extended lithosphere, and flexural subsidence caused by loading of the lithosphere.
- Analyzing features of sedimentary
1. The document analyzes the spatial distribution and size-frequency of rayed impact craters on the Moon using Clementine image data.
2. It finds that the size-frequency distribution of rayed craters indicates an average surface age of 750 million years, with compositional rays potentially persisting longer.
3. Small craters below 5 km in diameter show evidence of faster fading of ejecta rays, with an average retention time of only about 5 million years for craters 1-500m in size.
This document discusses seismic stratigraphy, which uses seismic data to extract stratigraphic information about subsurface rock layers. It defines seismic waves and methods, including refraction and reflection. Reflection seismic is more commonly used to identify structures like folds and faults beneath the surface. Key parameters for interpretation are reflection configuration, continuity, amplitude, frequency, and interval velocity. Depositional environments are also identified based on their relationship to the wave base.
The document discusses techniques for seismic stratigraphy analysis and interpretation. It describes delineating depositional sequences using reflection termination mapping. Reflection terminations indicate strata discontinuities and can be truncation, toplap, baselap, onlap, or downlap. Seismic sequence analysis involves analyzing seismic sequences, facies, and interpreting depositional environments. Reflection configurations, continuity, amplitude, and frequency are used to define seismic facies units representing depositional environments and lithofacies.
Ancient igneous intrusions_and_early_expansion_of_the_moon_revealed_by_grailSérgio Sacani
1) Application of gravity gradiometry to data from the GRAIL mission revealed numerous linear gravity anomalies on the Moon with lengths of hundreds of kilometers.
2) Inversion of the anomalies indicates they are dense vertical intrusions or dikes formed by ancient magmatism during extension of the lunar lithosphere before the end of heavy bombardment.
3) The distribution, orientation, and size of the intrusions suggest they formed as the Moon's radius increased by 0.6-4.9 km early in its history, consistent with predictions of thermal evolution models.
This document summarizes geological investigations for engineering projects and disaster prevention in Japan. It describes various surface and subsurface investigation techniques used to characterize soil and rock conditions, including mapping, drilling, testing, and laboratory analysis. Examples of natural hazards like earthquakes, landslides, and floods are presented, along with case studies of slope failures in cuts and fills. The importance of geological mapping, stratigraphy, and regional hazard assessments are emphasized for understanding site conditions and designing safe structures.
This document discusses engineering geological mapping and provides details on:
1) The purpose of engineering geological maps is to provide basic information for land use planning, engineering works planning/design/construction/maintenance, and environmental planning.
2) Engineering geological maps represent characteristics of rocks/soils, hydrogeological conditions, geomorphological conditions, and active geodynamic phenomena.
3) Classification of rocks and soils on maps is based on properties indicating physical/engineering characteristics, such as mineralogy, texture, structure, and weathering state.
This document is a student's geological map project report on fieldwork conducted on the Isle of Rum, Scotland. It includes descriptions of the lithologies mapped in the area, including igneous rocks of the Igneous Layered Intrusion and sedimentary rocks of the Mullach Ard Formation. Detailed descriptions are provided of the mineralogy, textures, orientations, boundaries and inferred origins of the different rock units. Cross-sections were produced to interpret the subsurface relationships between the lithologies and understand the geological history of the area. Comparative analysis was also conducted on minor structures within the igneous and sedimentary rocks.
The document summarizes a geological field study conducted in Malekhu, Nepal. Key points:
- The study aimed to familiarize students with geological structures, engineering significance, and different rock and soil types. Measurements of dip, strike, and attitudes of bedding planes were taken.
- Engineering geology is important for civil engineering projects to understand subsurface conditions and design earthworks and foundations. Site investigations assess natural hazards.
- The field study location was selected for its accessible rocks, river morphology, natural topography, and mass movements. Objectives included learning identification and mapping techniques.
- Field observations and measurements of planar features like bedding, foliation, and joints were made using a Brunt
The document summarizes the first results from an ambitious HARPS program to detect Earth-like planets around nearby solar-type stars using high-precision radial velocity measurements. It reports the discovery of five new low-mass planets around the stars HD 20794, HD 85512, and HD 192310, including a system of three super-Earths and a planet with a mass of 3.6 Earth masses located at the inner edge of the habitable zone. This confirms previous indications that low-mass planets seem to be very frequent around solar-type stars, with an occurrence rate that may be higher than 30%.
1. Conformal cyclic cosmology (CCC) predicts the existence of concentric circles of anomalously low temperature variance in the cosmic microwave background (CMB) that would provide evidence of violent events prior to the Big Bang.
2. Analysis of WMAP and BOOMERANG CMB data reveals families of concentric circles up to 6 standard deviations below the mean temperature variance, consistent with CCC predictions.
3. These circles are not easily explained by standard inflationary cosmology, as the events that could cause some of the largest circles observed would need to occur before the end of inflation in the previous aeon.
This document reports the detection of a low-mass dark satellite galaxy in a gravitational lens system. Using pixelated lens modeling of adaptive optics images, the researchers detected a positive density correction indicating the presence of a mass substructure. They estimate the mass of the substructure to be 1.9 x 108 solar masses located 600 parsecs from the density peak. Combining this detection with a previous one, they constrain the logarithmic slope of the mass function for dark matter substructure in elliptical galaxies to be 1.1-0.4 with an average mass fraction of 3.3-1.8%. This is consistent with predictions from cold dark matter simulations.
This article reports the detection of two gas clouds with no discernible elements heavier than hydrogen, representing the lowest heavy-element abundance observed in the early universe. One cloud at z=3.4 exhibits a deuterium abundance matching predictions from Big Bang nucleosynthesis, providing direct evidence for the standard cosmological model. The sparse metal enrichment of these clouds implies an inhomogeneous process for transporting heavy elements from galaxies into the surrounding intergalactic medium.
This document appears to be a citation to a 1996 Astrophysical Journal paper with the volume number 458 and page number 600, but it provides no other contextual information about the content or findings of the cited paper. The summary is limited due to the lack of substantive information in the given document.
The document discusses the training that Apollo astronauts received for making observations and taking photographs from lunar orbit. It summarizes that (1) astronauts were trained to add to scientific knowledge by describing lunar features from their unique viewpoint in orbit, and (2) photographs from orbit could provide regional context for detailed surface exploration findings. The training grew over missions from briefings to extensive classroom sessions. Outstanding results from astronaut observations and photos included realizing limitations of depicting lunar surface colors photographically and discovering previously unknown farside features.
Characterizing interstellar filaments with herschel in ic5146Sérgio Sacani
This document summarizes early results from the Herschel Gould Belt survey of the IC5146 molecular cloud. It reveals a complex network of filaments identified in the cloud, which are shown to be the main sites of prestellar core formation. Analysis of 27 filaments finds that their radial column density profiles fall off with radii as r^-1.5 to r^-2.5. Remarkably, the filaments seem to have a narrow distribution of widths centered around 0.1 pc, in contrast to a broader distribution of central Jeans lengths. This characteristic width corresponds to the sonic scale below which turbulence becomes subsonic, supporting the argument that filaments may form from dissipating large-scale turbulence.
This document summarizes a study that uses ab initio calculations to examine the solubility of magnesium oxide (MgO) in fluid hydrogen at conditions relevant to giant planet cores like Jupiter. The study finds that MgO is highly soluble in hydrogen for temperatures exceeding around 10,000 K, indicating rocky core materials would significantly redistribute within Jupiter and larger exoplanets. Free energy calculations based on density functional theory molecular dynamics and coupling constant integration techniques were used to determine the Gibbs free energy of solubilizing MgO in hydrogen at pressures from 10 to 40 megabars and temperatures from 10,000 to 20,000 K.
This document summarizes the discovery of a luminous quasar (ULAS J112001.481064124.3) with a redshift of z=7.085, located approximately 777 million years after the Big Bang. It has a luminosity of 6.3 x 10^13 solar luminosities and hosts a black hole with a mass of 2 x 10^9 solar masses. The radius of its ionized region is 1.9 megaparsecs, smaller than typical quasars from z=6.0 to z=6.4. Analysis of its spectrum is consistent with a high neutral fraction (>0.1) of the intergalactic medium in front of it. This makes it the most
The article provides a plausible explanation for reports of red glows seen in the Aristarchus crater on the moon. It details observations from 1963 of reddish spots near Aristarchus seen through a telescope. The authors recreate the illumination conditions and take their own image of the area. Their image shows chromatic dispersion that causes a reddish tint on the western rim of Aristarchus. When the color channels are properly aligned, no color is actually present. They conclude that atmospheric or chromatic dispersion is a logical explanation for the reported red color sightings in Aristarchus described in the 1963 observations.
The study examines a post-starburst galaxy outflow using ultraviolet spectroscopy of multiple ions including hydrogen. It finds the outflow extends at least 160,000 light-years from the galaxy and contains a hidden mass of at least 6x10^9 times the mass of our Sun. This challenges previous assumptions about the extent and mass of galaxy outflows, suggesting they may play a larger role in regulating galaxy evolution than thought.
The document summarizes research on the South Pole-Aitken basin, the largest impact crater on the Moon. It is over 2,500 km in diameter and more than 12 km deep. Spacecraft data show the basin has a higher concentration of iron than surrounding lunar highlands, suggesting it may expose deeper mantle rocks. However, the exact composition is debated, with some researchers arguing mantle rocks are not present based on mineral analysis. Understanding the basin's composition could provide insights into the Moon's interior structure and composition from the impact that formed the giant crater.
This document summarizes VLBI observations of supernova SN 2011dh made 14 days after its discovery, providing the earliest radio image of a supernova. The observations detected SN 2011dh at 22 GHz using a subset of the EVN array. The recovered flux density was approximately half the value measured by the EVLA at the same frequency and epoch, possibly due to extended emission or calibration issues. Precise coordinates for SN 2011dh were determined, linked to the ICRF, which may help improve future VLBI observations of the supernova.
The document summarizes a study of tungsten isotope ratios in lunar metals. The key findings are:
1) All lunar metal samples studied have identical tungsten isotope ratios within measurement error, indicating the lunar magma ocean did not crystallize within the first 60 million years as previously suggested.
2) Tungsten isotope ratios in lunar metals are identical to those in the Earth's mantle, suggesting the Moon and Earth mantles equilibrated after the giant impact that formed the Moon.
3) Together with previous samarium-neodymium dating of oldest lunar rocks, the results constrain the age of the Moon and Earth to 62 ± 10 million years after solar system formation.
1) Newly-born pulsars offer favorable conditions for accelerating heavy nuclei like iron to ultrahigh energies via unipolar induction. However, these nuclei must escape the surrounding dense supernova envelope.
2) The paper analytically and numerically examines the escape of ultrahigh energy cosmic rays (UHECRs) from supernova envelopes. It finds that at early times when protons could reach energies above 10^20 eV, the envelope prevents their escape. However, heavier iron nuclei can still reach the highest observed energies at later times when the envelope has thinned.
3) The authors conclude that a small fraction (0.01%) of extragalactic rapidly rotating young pulsars embedded in supernov
1. Chandra observations of the galaxy NGC 3351 revealed X-ray emission from its circumnuclear star-forming ring that is composed of numerous point-like sources embedded in diffuse hot gas.
2. The morphology of the X-ray emission is similar to but not identical with UV and H-alpha hot spots in the ring, which can be understood if star formation occurs through intermittent starbursts around the ring with different emissions tracing later evolutionary stages.
3. X-ray emission also extends beyond the ring, which is interpreted as outflowing gas from the ring into the disk and halo of NGC 3351, providing evidence for confined outflow near the plane but less restricted outflow perpendicular to
Measuring solar radius_from_space_during_the_2003_2006_mercury_transitsSérgio Sacani
This document describes measurements of the solar radius taken from images of the 2003 and 2006 transits of Mercury captured by the Michelson Doppler Imager aboard the Solar and Heliospheric Observatory. The authors measured contact times between Mercury and the solar limb to an accuracy of 0.09 arcseconds, finding a solar radius of 960”.12 ± 0”.09 or 696,342 ± 65km. This value is consistent between the two transits and after accounting for systematic effects between different instrument focus settings. The measurements represent some of the most accurate to date due to being taken from space above the Earth's atmosphere.
Neowise observations of near earth objects- preliminary resultsSérgio Sacani
The NEOWISE survey observed near-Earth objects at infrared wavelengths, detecting over 130 new NEOs. Analysis of the 428 NEOs detected allows estimates of the total NEO population between 100m and 1km in size. The survey found an estimated 981±19 NEOs larger than 1km have been detected, meeting the Spaceguard goal of detecting 90% of objects this size. It also estimates 20,500±3000 NEOs larger than 100m. The cumulative size distribution is best represented by a broken power law.
Herschel space telescope observations reveal cold dust emitting from Supernova 1987A at a temperature of 17-23 K, indicating a dust mass of 0.4-0.7 solar masses. The dust must originate from the supernova ejecta, requiring efficient precipitation of refractory elements into dust. This implies that supernovae can produce the large dust masses seen in early galaxies.
Our deep, wide-field imaging of M101 and its surrounding environment reveals:
1) M101's disk extends to nearly 25 arcminutes (50 kpc), three times the measured optical radius, with an asymmetric plume of light to the northeast following the extended HI disk.
2) This outer plume has very blue colors, suggesting a somewhat evolved young stellar population, while another redder spur is detected to the east.
3) No evidence is found of very extended tidal tails around M101 or its companions despite signs of past interactions shaping M101's asymmetry.
4) The detection of starlight at such large radii allows studying the stellar populations and star formation histories in M101's outer disk
The two largest impact basins recently discovered at Vesta's south pole are Rheasilvia and Veneneia. Rheasilvia is ~500 km wide and 19 km deep, making it one of the largest impact features on Vesta. It has a central massif and spiral ridge patterns on its floor. Veneneia is an older, partially buried ~400 km basin located beneath Rheasilvia. Crater counts date both basins to 1-2 billion years old, indicating major geological resetting of Vesta occurred relatively recently.
The unexpected surface of asteroid (101955) BennuSérgio Sacani
Bennu's surface was found to be more diverse and rugged than expected based on pre-encounter data. While its global properties like composition, shape and density matched predictions, high-resolution images revealed an unexpectedly wide range of albedos across its surface as well as many more large boulders than anticipated. This poses challenges for selecting a safe sample site. Magnetite detected on darker regions may indicate fresher material from aqueous alteration. More data is needed to understand Bennu's surface evolution and guide sample acquisition.
Color and albedo_heterogeneity_on_vestaSérgio Sacani
The document summarizes findings from the Dawn spacecraft about the composition and geology of Vesta. It found that Vesta's surface has significant heterogeneity in color and albedo. Spectroscopic data revealed variations in the mineralogy and composition, with the Oppia region showing differences possibly related to mass movements. Craters exposed layers with different mineral and chemical compositions, providing insights into Vesta's complex, stratified crust formed from magmatic processes during planetary differentiation.
Science laser altimetry of small scale features on 433 eros from near-shoemakerFelipe Correa
This article summarizes findings from laser altimetry observations of asteroid 433 Eros made by the NEAR spacecraft during its close flyby. The laser observations revealed surface features on scales of meters to hundreds of meters, showing that the surface has a fractal structure dominated by blocks, structural features, and small crater walls. This fractal structure suggests a single process, likely impacts, dominates the surface morphology on these scales. Laser altimetry also measured local surface elevations and slopes, correlating elevations with morphological evidence of downslope movement of loose surface materials.
The document summarizes findings from studying asteroid 4 Vesta using data from NASA's Dawn spacecraft. It finds that Vesta has experienced a violent collisional history, with large impacts creating steep slopes and resurfacing much of the surface. While no unambiguous volcanic deposits were found, some dark material in impact craters may be from excavated subsurface volcanic features. Smooth ponds found on Vesta are also seen on asteroid Eros and are thought to form from impact ejecta collecting in depressions.
Venus and Earth have remarkably diferent
surface conditions, yet the lithospheric
thickness and heat fow on Venus may be
Earth-like. This fnding supports a tectonic
regime with limited surface mobility and
dominated by intrusive magmatism.
Craters, boulders and regolith of (101955) Bennu indicative of an old and dyn...Sérgio Sacani
- NASA's OSIRIS-REx mission arrived at the near-Earth asteroid Bennu in December 2018 and obtained images revealing its shape and surface features.
- Bennu has a diameter of 492 meters and is classified as a rubble pile asteroid, consisting of loosely bound fragments with high porosity.
- Images show numerous large boulders on Bennu's surface, some over 50 meters in size, indicating impacts in its past. Fractured boulders and impact breccias further suggest a dynamic history.
- The surface shows signs of both ancient features from the main asteroid belt as well as more recent mass movement, with clusters of boulders in low areas and incomplete crater
Detection of intact lava tubes at Marius Hills on the Moon by SELENE (Kaguya)...Sérgio Sacani
Intact lunar lava tubes offer a pristine environment to conduct scientific examination of the Moon’s composition and potentially serve as secure shelters for humans and instruments. We investigated the SELENE Lunar Radar Sounder (LRS) data at locations close to the Marius Hills Hole (MHH), a skylight potentially leading to an intact lava tube, and found a distinctive echo pattern exhibiting a precipitous decrease in echo power, subsequently followed by a large second echo peak that may be evidence for the existence of a lava tube. The search area was further expanded to 13.00–15.005°N, 301.85–304.01°E around the MHH and similar LRS echo patterns were observed at several locations. Most of the locations are in regions of underground mass deficit suggested by GRAIL gravity data analysis. Some of the observed echo patterns are along rille A, where the MHH was discovered, or on the southwest underground extension of the rille.
A Morphological and Spatial Analysis of Volcanoes on VenusSérgio Sacani
Venus is home to many thousands of volcanic landforms that range in size from much less than 5 km to well over 100 km in diameter. Volcanism is clearly a major, widespread process on Venus, and is a principal expression of the planet's secular loss of interior heat. Without sufficient in situ data to clearly determine its internal structure, we can use the morphological and spatial properties of volcanoes across the planet to help place constraints on our understanding of the volcanic characteristics and history of Venus. With the Magellan synthetic-aperture radar full-resolution radar map left- and right-look global mosaics at 75 m-per-pixel resolution, we developed a global catalog of volcanoes on Venus that contains ∼85,000 edifices, ∼99% of which are <5 km in diameter. We find that Venus hosts far more volcanoes than previously mapped, and that although they are distributed across virtually the entire planet, size–frequency distribution analysis reveals a relative lack of edifices in the 20–100 km diameter range, which could be related to magma availability and eruption rate. Through spatial density analysis of volcanoes alongside assessments of geophysical data sets and proximal tectonic and volcanic structures, we report on the morphological and spatial patterns of volcanism on Venus to help gain new insights into the planet's geological evolution
A Tale of 3 Dwarf Planets: Ices and Organics on Sedna, Gonggong, and Quaoar f...Sérgio Sacani
The dwarf planets Sedna, Gonggong, and Quaoar are interesting in being somewhat smaller than
the methane-rich bodies of the Kuiper Belt (Pluto, Eris, Makemake), yet large enough to be
spherical and to have possibly undergone interior melting and differentiation. They also reside
on very different orbits, making them an ideal suite of bodies for untangling effects of size and
orbit on present day surface composition. We observed Sedna, Gonggong, and Quaoar with the
NIRSpec instrument on the James Webb Space Telescope (JWST). All three bodies were
observed in the low-resolution prism mode at wavelengths spanning 0.7 to 5.2 μm. Quaoar was
additionally observed at 10x higher spectral resolution from 0.97 to 3.16 μm using mediumresolution gratings. Sedna’s spectrum shows a large number of absorption features due to ethane
(C2H6), as well as acetylene (C2H2), ethylene (C2H4), H2O, and possibly minor CO2.
Gonggong’s spectrum also shows several, but fewer and weaker, ethane features, along with
stronger and cleaner H2O features and CO2 complexed with other molecules. Quaoar’s prism
spectrum shows even fewer and weaker ethane features, the deepest and cleanest H2O features, a
feature at 3.2 μm possibly due to HCN, and CO2 ice. The higher-resolution medium grating
spectrum of Quaoar reveals several overtone and combination bands of ethane and methane
(CH4). Spectra of all three objects show steep red spectral slopes and strong, broad absorptions
between 2.7 and 3.6 μm indicative of complex organic molecules. The suite of light
hydrocarbons and complex organic molecules are interpreted as the products of irradiation of
methane. The differences in apparent abundances of irradiation products among these three
similarly-sized bodies are likely due to their distinctive orbits, which lead to different timescales
of methane retention and to different charged particle irradiation environments. In all cases,
however, the continued presence of light hydrocarbons implies a resupply of methane to the
2
surface. We suggest that these three bodies have undergone internal melting and geochemical
evolution similar to the larger dwarf planets and distinct from all smaller KBOs. The feature
identification presented in this paper is the first step of analysis, and additional insight into the
relative abundances and mixing states of materials on these surfaces will come from future
spectral modeling of these data.
Candels the correlation_between_galaxy_morphology_and_star_formation_activity...Sérgio Sacani
This document summarizes a study investigating the relationship between galaxy morphology and star formation activity at z ~ 2 using a sample of 1,671 galaxies from CANDELS images in the GOODS-South field. The sample separates into massive, red, passive galaxies and less massive, blue, star-forming galaxies, correlating well with morphological properties. Star-forming galaxies show a variety of morphologies including clumpy structures and bulges mixed with faint disks, while passive galaxies often have compact morphologies resembling local spheroids. Similar trends are seen in local massive galaxies, suggesting the Hubble sequence was in place by z ~ 2.
This document introduces the VLT-FLAMES Tarantula Survey, which obtained multi-epoch optical spectroscopy of over 800 massive stars in the 30 Doradus region of the Large Magellanic Cloud. The survey aims to detect massive binary systems through variations in radial velocities and to characterize the properties of O- and B-type stars, addressing questions about stellar and cluster evolution. Spectral classifications are provided for newly discovered emission-line stars, including a new Wolf-Rayet star. The survey data and reduction procedures are overviewed, and upcoming analyses of the massive star properties are announced.
A super earth transiting a naked-eye starSérgio Sacani
This document summarizes the detection of transits of an exoplanet orbiting the star 55 Cnc, using photometry from the MOST space telescope. The transits match the period, phase, duration, and depth predicted for the innermost planet of 55 Cnc, designated 55 Cnc e. Analysis of the transit data indicates the planet has a mass of 8.57 Earth masses, a radius of 1.63 Earth radii, and a dense composition of rock and iron. This makes 55 Cnc e similar to other dense super-Earth exoplanets in short orbits, unlike lower-density super-Earths further from their stars. The brightness of 55 Cnc will enable further study of this transiting exoplanet system.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Shape of (101955) Bennu indicative of a rubble pile with internal stiffnessSérgio Sacani
The document describes new findings about the asteroid Bennu based on images from the OSIRIS-REx spacecraft. It finds that Bennu has a top-like shape with considerable macroporosity and prominent boulders, suggesting it is a rubble pile. However, it also has high-standing ridges and surface features indicating some level of internal stiffness. The shape and features suggest Bennu formed by reaccumulation and past fast spin, but now its interior allows surface cracking and mass wasting. Key parameters of Bennu such as size, volume, density are consistent with prior estimates from Earth-based radar.
Properties of rubble-pile asteroid (101955) Bennu from OSIRIS-REx imaging and...Sérgio Sacani
This document summarizes findings from imaging and thermal analysis of asteroid Bennu by NASA's OSIRIS-REx spacecraft. It finds that Bennu's surface is globally rough, dense with boulders over 1 meter in size, and has a low albedo of 4.4%. Thermal data indicates a moderate global thermal inertia of 350 J m-2 K-1 s-1/2, suggesting surface particle sizes of 0.5-5 cm by simple models, however images show the surface is dominated by boulders over 1 meter. Over 80% of the surface was analyzed, finding a power law distribution of boulder sizes with an index of -2.9 for boulders 8 meters
Martian soil as revealed by ground-penetrating radar at the Tianwen-1 landing...Sérgio Sacani
Much of the Martian surface is covered by a weathering layer (regolith or soil) produced
by long-term surface processes such as impact gardening, eolian erosion, water weathering,
and glacial modifications. China’s first Martian mission, Tianwen-1, employed the Mars
Rover Penetrating Radar (RoPeR) to unveil the detailed structure of the regolith layer and
assess its loss tangent. The RoPeR radargram revealed the local regolith layer to be highly
heterogeneous and geologically complex and characterized by structures that resemble partial
or complete crater walls and near-surface impact lenses at a very shallow depth. However,
comparable radar data from the Lunar far side are rather uniform, despite the two surfaces
being geologically contemporary. The close-to-surface crater presented in this study shows
no detectable surface expression, which suggests an accelerated occultation rate for small
craters on the surface of Mars as compared to the rate on the Moon. This is probably due to
the relentless eolian processes on the Martian surface that led to the burial of the crater and
thus shielded it from further erosion. The high loss tangent indicates that the regolith at the
Tianwen-1 landing site is not dominated by water ice.
Linne simple lunar mare crater geometry from lro observationsSérgio Sacani
This document analyzes the geometry of Linne crater on the Moon using high-resolution topographic data from LRO. The key findings are:
1) Linne's crater cavity is best described as a truncated cone, not a "bowl" as previously thought, with an inner wall slope of 33 degrees.
2) Linne's continuous ejecta blanket thickness decays with a power law exponent of -3.84, steeper than the typical -2.75 for craters on Earth.
3) When compared to other simple craters on the Moon, Mars, and Earth, Linne's normalized crater shape parameter suggests it represents an archetypal, well-preserved simple mare
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for...Sérgio Sacani
Mars is a particularly attractive candidate among known astronomical objects
to potentially host life. Results from space exploration missions have provided
insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to
its toxicity. However, it can also provide potential benefits, such as producing
brines by deliquescence, like those thought to exist on present-day Mars. Here
we show perchlorate brines support folding and catalysis of functional RNAs,
while inactivating representative protein enzymes. Additionally, we show
perchlorate and other oxychlorine species enable ribozyme functions,
including homeostasis-like regulatory behavior and ribozyme-catalyzed
chlorination of organic molecules. We suggest nucleic acids are uniquely wellsuited to hypersaline Martian environments. Furthermore, Martian near- or
subsurface oxychlorine brines, and brines found in potential lifeforms, could
provide a unique niche for biomolecular evolution.
Continuum emission from within the plunging region of black hole discsSérgio Sacani
The thermal continuum emission observed from accreting black holes across X-ray bands has the potential to be leveraged as a
powerful probe of the mass and spin of the central black hole. The vast majority of existing ‘continuum fitting’ models neglect
emission sourced at and within the innermost stable circular orbit (ISCO) of the black hole. Numerical simulations, however,
find non-zero emission sourced from these regions. In this work, we extend existing techniques by including the emission
sourced from within the plunging region, utilizing new analytical models that reproduce the properties of numerical accretion
simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component,
but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component
has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum
of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional
models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of
intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin
which must be low a• < 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission
component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our
continuum fitting model is made publicly available.
WASP-69b’s Escaping Envelope Is Confined to a Tail Extending at Least 7 RpSérgio Sacani
Studying the escaping atmospheres of highly irradiated exoplanets is critical for understanding the physical
mechanisms that shape the demographics of close-in planets. A number of planetary outflows have been observed
as excess H/He absorption during/after transit. Such an outflow has been observed for WASP-69b by multiple
groups that disagree on the geometry and velocity structure of the outflow. Here, we report the detection of this
planet’s outflow using Keck/NIRSPEC for the first time. We observed the outflow 1.28 hr after egress until the
target set, demonstrating the outflow extends at least 5.8 × 105 km or 7.5 Rp This detection is significantly longer
than previous observations, which report an outflow extending ∼2.2 planet radii just 1 yr prior. The outflow is
blueshifted by −23 km s−1 in the planetary rest frame. We estimate a current mass-loss rate of 1 M⊕ Gyr−1
. Our
observations are most consistent with an outflow that is strongly sculpted by ram pressure from the stellar wind.
However, potential variability in the outflow could be due to time-varying interactions with the stellar wind or
differences in instrumental precision.
Infrastructure Challenges in Scaling RAG with Custom AI modelsZilliz
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“An Outlook of the Ongoing and Future Relationship between Blockchain Technologies and Process-aware Information Systems.” Invited talk at the joint workshop on Blockchain for Information Systems (BC4IS) and Blockchain for Trusted Data Sharing (B4TDS), co-located with with the 36th International Conference on Advanced Information Systems Engineering (CAiSE), 3 June 2024, Limassol, Cyprus.
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Driving Business Innovation: Latest Generative AI Advancements & Success StorySafe Software
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During the hour, we’ll take you through:
Guest Speaker Segment with Hannah Barrington: Dive into the world of dynamic real estate marketing with Hannah, the Marketing Manager at Workspace Group. Hear firsthand how their team generates engaging descriptions for thousands of office units by integrating diverse data sources—from PDF floorplans to web pages—using FME transformers, like OpenAIVisionConnector and AnthropicVisionConnector. This use case will show you how GenAI can streamline content creation for marketing across the board.
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Hollows in mercury_science
1. REPORTS
28. K. J. Hon, J. Kauahikaua, R. Denlinger, K. Mackay, D. A. Williams, Eds. (Special Paper 477, Geological Supporting Online Material
Geol. Soc. Am. Bull. 106, 351 (1994). Society of America, Boulder, CO, 2011), pp. 1–51. www.sciencemag.org/cgi/content/full/333/6051/1853/DC1
29. L. R. Nittler et al., Science 333, 1847 (2011). Acknowledgments: We thank the MESSENGER team for SOM Text
30. C. I. Fassett et al., Earth Planet. Sci. Lett. 285, 297 development and flight operations. The NASA Discovery Figs. S1 to S3
(2009). Program supports the MESSENGER mission through
31. H. Hiesinger, J. W. Head III, U. Wolf, R. Jaumann, contract NAS5-97271 to The Johns Hopkins University
G. Neukum, in Recent Advances and Current Research Applied Physics Laboratory and NASW-00002 to the 1 August 2011; accepted 5 September 2011
Issues in Lunar Stratigraphy, W. A. Ambrose, Carnegie Institution of Washington. 10.1126/science.1211997
Hollows on Mercury: MESSENGER with spectral properties such as those of the hol-
lows in Figs. 1D and 2A were also seen in lower-
spatial-resolution multispectral images from the
Evidence for Geologically Recent Mariner 10 and MESSENGER flybys (3–7).
Materials with high reflectance and extremely
Volatile-Related Activity blue color are global spectral outliers and have
been termed “bright crater-floor deposits” (BCFDs)
(5–7). MESSENGER flyby images indicated that
David T. Blewett,1* Nancy L. Chabot,1 Brett W. Denevi,1 Carolyn M. Ernst,1 James W. Head,2 BCFDs occur in several morphologic types, in-
Noam R. Izenberg,1 Scott L. Murchie,1 Sean C. Solomon,3 Larry R. Nittler,3 Timothy J. McCoy,4 cluding varieties that have lobate outlines and
Zhiyong Xiao,5,6 David M. H. Baker,2 Caleb I. Fassett,2 Sarah E. Braden,7 Jürgen Oberst,8 those on central peaks and peak rings. Apart from
Frank Scholten,8 Frank Preusker,8 Debra M. Hurwitz2 Raditladi, Tyagaraja, and Sander (Figs. 1C and 2,
A and B), prominent named examples include
High-resolution images of Mercury’s surface from orbit reveal that many bright deposits within the deposits on the floors of the craters Balzac,
impact craters exhibit fresh-appearing, irregular, shallow, rimless depressions. The depressions, or de Graft, Kertesz, and Zeami and on the central
hollows, range from tens of meters to a few kilometers across, and many have high-reflectance peaks or peak rings of Eminescu and Vivaldi.
interiors and halos. The host rocks, which are associated with crater central peaks, peak rings, floors, MESSENGER’s orbital high-resolution and
and walls, are interpreted to have been excavated from depth by the crater-forming process. The color imaging reveals that the areas identified as
most likely formation mechanisms for the hollows involve recent loss of volatiles through some BCFDs are composed of hollows and etched
combination of sublimation, space weathering, outgassing, or pyroclastic volcanism. These features terrain; hence, hollows are widespread across the
support the inference that Mercury’s interior contains higher abundances of volatile materials than planet (Fig. 3). Hollows have been found be-
predicted by most scenarios for the formation of the solar system’s innermost planet. tween ~66° N and 54° S and across all longitudes
covered so far by orbital imaging. Many hollows
he MESSENGER spacecraft entered orbit orbit is closest to Mercury. Several of the targeted occur in areas where there are exposures of low-
T about Mercury on 18 March 2011, after
which the Mercury Dual Imaging System
(MDIS) (1) acquired high-spatial-resolution images.
areas (Figs. 1, A and B) show depressions, or hol-
lows, that are irregular in shape with generally
rounded edges. Horizontal dimensions range from
reflectance material (LRM) (5, 6), a major global
color-compositional unit thought to have been
originally emplaced at depth (8).
Many of the images reveal an unusual landform tens of meters to several kilometers. The hollows Volcanism, explosive outgassing, collapse
on Mercury, characterized by irregularly shaped, are shallow and rimless, and many have high- into a subsurface void, and loss of volatile-rich
shallow, rimless depressions, commonly in clusters reflectance interiors and diffuse bright halos. The material through sublimation are capable of creat-
and in association with high-reflectance materials. interiors are mostly smooth and flat, but some have ing irregularly shaped depressions on planetary
Here, we describe this class of landform and its small bumps, hills, or mesas, the tops of which surfaces. Volcanism was an important and wide-
distribution and suggest that it indicates recent may be remnants of the original surface. Many spread process on Mercury (9–14). Extrusive
volatile-related activity. form clusters, although some are isolated. The and explosive volcanism can produce rimless
MESSENGER is engaged in global imaging hollows appear fresh and lack superposed impact depressions in the form of calderas, vents, and
of Mercury’s surface at a pixel dimension of craters, implying that they are relatively young. collapse pits. A number of probable pyroclastic
~250 m. As part of this mapping, targeted ob- To date, we have found hollows within im- vents and deposits have been identified on Mercury
servations of selected areas are made using the pact craters that span a range of sizes. The exam- (12, 13, 15–17). Also, an intrusive magmatic
MDIS, with pixel dimensions of ~10 m for mono- ples in Fig. 1, A and B, are on impact crater process has been proposed as the source for a
chrome imaging and 80 m for multispectral im- central peaks or the peak rings of impact basins. class of pit craters on Mercury (18), via collapse
ages. Resolution is greatest—more than a factor Additional examples on basin peak rings are after withdrawal of magma from a near-surface
of 10 better than with standard mapping—for shown in Fig. 1, C and D. Similar high-reflectance chamber. However, the size and morphology of
areas northward of 20° N, where the spacecraft hollows occur on the floors, walls, and rims of the pyroclastic vents and pit craters identified to
some medium-sized impact craters (Fig. 1, E date on Mercury differ from those of the hollows.
1
The Johns Hopkins University Applied Physics Laboratory, and F). The hollows are found in comparatively Most of the irregular depressions associated with
Laurel, MD 20723, USA. 2Department of Geological Sci- fresh (Kuiperian) rayed craters, more degraded pyroclastic deposits are large [several tens of
ences, Brown University, Providence, RI 02912, USA. 3De- craters, and basins in a variety of states of erosion. kilometers (16, 17)] relative to the hollows and
partment of Terrestrial Magnetism, Carnegie Institution of
Craters such as Tyagaraja and Sander (Fig. 2, typically occur as isolated depressions rather than
Washington, Washington, DC 20015, USA. 4Smithsonian In-
stitution, Washington, DC 20013, USA. 5Lunar and Planetary A and B) exhibit extensive fields of coalescing in clusters. Moreover, the hollows occur on the
Laboratory, University of Arizona, Tucson, AZ 85721, USA. bright-interior/bright-halo hollows on their floors, tops and sides of central peak mountains as well
6
Faculty of Earth Sciences, China University of Geosciences, lending an etched appearance to the terrain. The as across impact crater walls and rims, which are
Wuhan, Hubei, 430074, P. R. China. 7School of Earth and etched terrain on Tyagaraja’s floor displays some unlikely locations for volcanic eruptions. The rec-
Space Exploration, Arizona State University, Tempe, AZ 85251,
USA. 8Institute of Planetary Research, German Aerospace of the highest reflectance on the planet (~2.5 ognized pyroclastic deposits are associated with
Center, D-12489 Berlin, Germany. times the global average), has a relatively shallow strong positive (“red”) spectral slope across the
*To whom correspondence should be addressed. E-mail: (“blue”) spectral slope (2), and lacks clear spec- visible and near-infrared (5, 6, 15–17) in contrast
david.blewett@jhuapl.edu tral features in MDIS multispectral data. Surfaces to the “blue” character of the hollows. Thus, if the
1856 30 SEPTEMBER 2011 VOL 333 SCIENCE www.sciencemag.org
2. REPORTS
hollows and etched terrain are products of vol- suggested as the origin of the bright, blue patches temperature environment of the surface or shal-
canism, it must be a form that is physically and first observed in Mariner 10 images. The location low subsurface, leading to sublimation and subse-
compositionally different from that which produced of hollows and etched terrain within impact cra- quent collapse. The example in Fig. 1F is instructive.
the recognized pyroclastic vents and deposits. In ters is consistent with the idea that deep-seated The crater is at a high northern latitude. High-
some cases, such as Praxiteles and Tyagaraja gases gain access to the surface along impact- reflectance material is present on the upper por-
(Figs. 1D and 2A), the blue materials are found induced fractures (3). tion of the northern wall, and several bright-halo
together with red materials. The association of hollows with impact cra- hollows are located in a slump in the middle of
Episodic minor explosive release of gas with ters and basins indicates a link with material that the wall. Solar heating would be maximal on these
no ejected juvenile material, as was proposed for has been brought near or to the surface from south-facing surfaces, suggesting that develop-
an unusual lunar feature [Ina (19)], could disrupt depth. For example, the peak rings of the 170-km- ment of the hollows and associated bright material
the country rock and maintain a fresh, high- diameter basin in Fig. 1A originated at depths of is correlated with peaks in diurnal temperature. The
albedo surface against space weathering by solar ~14 to 20 km (21), whereas the walls and ejecta of steep slopes on the crater wall and slump should
wind and micrometeoroid bombardment. How- the crater in Fig. 1E probably were derived from promote mass-wasting movement and continu-
ever, energetic outgassing alone may not account depths of ≲2 km. Whether the material asso- ously expose new material, so the bright material
for the differences in color between the hollows ciated with the hollows is derived from greater or and hollows are likely to be young features.
and ordinary immature local materials (20). Fu- shallower depths, it could be that a component is The hollows share morphological similari-
marolic deposition and chemical alteration (3) were unstable when it experiences the low-pressure, high- ties with portions of the “Swiss-cheese” terrain
Fig. 1. Examples of hollows on Mercury,
characterized by irregular rimless depres-
sions and associated high-reflectance ma-
terials. (A) Portion of a peak ring of a
170-km-diameter impact basin (inset).
White arrows indicate depressions with
high-reflectance interiors and halos. The
floor of the hollow indicated by the yel-
low arrow has a reflectance similar to the
surroundings. Image EN0213851669M,
15 m/pixel, centered at 34.4° N, 282.0° E.
(B) Hollows on and around the central peak
of a 36-km-diameter impact crater (inset).
High-reflectance material is also visible on the northern rim of the small crater at top left. Image
EN0215894066M, 15 m/pixel, 46.1° N, 134.8° E. (C) Portion of the peak ring of the 265-km-diameter
Raditladi basin (inset). White arrows indicate hollows on the basin floor; yellow arrows show those on the
peak mountains. Images EN0220979987M and -9993M, 17 m/pixel. (D) Interior of Praxiteles crater, 198
km in diameter. Enhanced-color image in which red-to-blue variations indicate relative color; the green
channel is a measure of overall albedo (34). Hollows (yellow arrows) appear bright blue; the large depression (red arrow) is a likely volcanic vent and the source of the
reddish pyroclastic deposit. Inset is image EN0211416219M (53 m/pixel), showing details of the bright depressions. (E) High-reflectance depressions on the floor,
walls, and rim of a partially degraded 25-km-diameter impact crater. Image EN0213154023M, 149 m/pixel, 23.3° N, 179.4° E. (F) Portion of a morphologically fresh
15-km-diameter crater (inset) with bright material on the upper wall and hollows on a wall slump. Image EN0218374376M, 18 m/pixel, 66.5° N, 153.2° E.
www.sciencemag.org SCIENCE VOL 333 30 SEPTEMBER 2011 1857
3. REPORTS
found in the south polar region of Mars (fig. S1): degradation of a component susceptible to space Whatever the identity of the sputtered or sub-
elongated, rounded depressions with flat floors weathering (by micrometeoroid bombardment limated material, hollows lacking high-reflectance
that occur in spatially extensive groups simi- and/or solar-wind sputtering). Impact vaporization halos or interiors (Fig. 1A) could be inactive, re-
lar to those in Raditladi, Tyagaraja, and Sander followed by sputtering of sulfide minerals has been sulting from exhaustion of the volatile-bearing
(Figs. 1C and 2, A and B). The martian terrain is invoked (23, 24) to explain the deficit of sulfur phase or development of a protective lag, whereas
produced by sublimation of CO2 ice (22). The measured at the surface of asteroid Eros by the the nearby depressions with bright interiors and
resemblance suggests that a sublimation process Near Earth Asteroid Rendezvous-Shoemaker space- halos probably are sites of current activity.
may be responsible for formation of the hollows. craft’s x-ray spectrometer (25). The MESSENGER Other volatile elements or compounds could
Rather than via a temperature or pressure ef- X-Ray Spectrometer has found a surprisingly high be involved in formation of the hollows. For
fect, the hollows on Mercury could form through abundance of sulfur in Mercury’s regolith (26). example, large volcanic eruptions that occurred
A
A B
25 km
25 km
Fig. 2. (A) Tyagaraja crater, 97 km in diameter. Bright areas with blue color
and etched texture correspond to a high density of hollows (inset). The central
10 km
pit surrounded by reddish material is probably a pyroclastic vent. From mono-
chrome image EN0212327089M, 111 m/pixel, with enhanced color from the
eight-filter set EW0217266882I (34). (B) Sander crater, 47 km in diameter. A
high density of hollows occurs in the high-reflectance portions of the crater floor; others are found on the northern crater rim and wall terraces. Stereo analysis
(35) indicates that any elevation differences between the high-reflectance and darker areas of the floor are ≲20 m. Image EN0218289182M, 30 m/pixel.
Fig. 3. Global distribution (simple
cylindrical projection) of hollows
seen at high spatial resolution (yel-
low dots) and materials with high
reflectance and strong blue color
(BCFDs, blue squares). Some por-
tions of the planet have not yet
been imaged at high resolution with
illumination and viewing conditions
best suited for morphological or col-
or analysis (supporting online ma-
terial text).
1858 30 SEPTEMBER 2011 VOL 333 SCIENCE www.sciencemag.org
4. REPORTS
when the surface was below the sublimation tem- The involvement of volatiles in candidate 19. P. H. Schultz, M. I. Staid, C. M. Pieters, Nature 444, 184
perature (that is, at night) may have produced formation mechanisms for the hollows fits with (2006).
20. Fresh (immature) materials in young crater ejecta and
volatile-rich deposits when magmatic gases or growing evidence (16, 17, 26, 29) that Mer- rays have spectral slopes that are less steep (“bluer”)
fumarolic minerals condensed onto the cold sur- cury’s interior contains higher abundances of than the global average. However, the BCFDs have more
roundings. These materials could then have been volatile elements than are predicted by several extreme blue color (5, 6).
21. The minimum depth of excavation of the central peak
sequestered through burial by extensive thick- planetary formation models for the innermost
material is assumed to be the maximum depth of impact
nesses of pyroclastic deposits or lava. Subsequent planet (30–32). Mercury is a small rocky-metal melting, which was estimated with methods described
impact cratering could have exhumed these ma- world whose internal geological activity was gen- earlier (33).
terials to the shallow subsurface, followed by erally thought to have ended long ago. The pres- 22. M. C. Malin, M. A. Caplinger, S. D. Davis, Science 294,
2146 (2001).
formation of depressions by scarp retreat as the ence of potentially recent surface modification 23. A. Kracher, D. W. G. Sears, Icarus 174, 36 (2005).
volatile component sublimated. implies that Mercury’s nonimpact geological evo- 24. M. J. Loeffler, C. A. Dukes, W. Y. Chang, L. A. McFadden,
To estimate the rate at which hollows may be lution may still be ongoing. R. A. Baragiola, Icarus 195, 622 (2008).
forming, we used shadow-length measurements 25. L. R. Nittler et al., Meteorit. Planet. Sci. 36, 1673 (2001).
26. L. R. Nittler et al., Science 333, 1847 (2011).
to determine the average depth of the hollows on References and Notes 27. R. G. Strom, C. R. Chapman, W. J. Merline, S. C. Solomon,
the floor of the Raditladi basin (Fig. 1C). This 1. S. E. Hawkins III et al., Space Sci. Rev. 131, 247 (2007). J. W. Head III, Science 321, 79 (2008).
2. Mercury’s surface reflectance spectrum has a positive 28. D. G. Ashworth, Lunar and planetary impact erosion,
value (44 m), combined with the age of the basin slope from ultraviolet to near-infrared wavelengths. in Cosmic Dust, J. A. M. McDonnell, Ed. (Wiley, Hoboken,
as constrained by the crater size-frequency dis- Spectral slopes less steep than the global average are NJ, 1977), pp. 427–526.
tribution [109 years (27)] yields an erosion rate of said to be “blue,” and those with greater slopes are 29. P. N. Peplowski et al., Science 333, 1850 (2011).
0.04 mm/year, or 1 cm in 200,000 years, under the termed “red.” The reflectance in 559-nm filter images is 30. J. S. Lewis, Annu. Rev. Phys. Chem. 24, 339 (1973).
0.140 for the hollows on Tyagaraja’s floor versus 0.057 31. B. Fegley Jr., A. G. W. Cameron, Earth Planet. Sci. Lett.
assumption that erosion proceeds only downwards.
for the Mercury global average. The normalized 559-nm 82, 207 (1987).
In many areas, however, the flat floors and rounded reflectance was measured for the continuous ejecta of 32. W. W. Benz, W. L. Slattery, A. G. W. Cameron, Icarus 74,
outlines suggest that the hollows are enlarged 23 rayed (Kuiperian) craters and 20 BCFDs. For the 516 (1988).
through radial growth—down to a resistant base, Kuiperian craters, the mean reflectance is 0.09 T 0.01. For 33. C. M. Ernst et al., Icarus 209, 210 (2010).
then laterally by scarp retreat. We determined the the BCFDs, the mean reflectance is 0.107 T 0.018. 34. During orbital mapping, the MDIS wide-angle camera
3. D. Dzurisin, Geophys. Res. Lett. 4, 383 (1977). collects images through filters with central wavelengths
characteristic average radius (137 m) for isolated 4. B. Rava, B. Hapke, Icarus 71, 397 (1987). of 430, 480, 559, 629, 749, 829, 898, and 997 nm.
hollows and individual hollows that form merged 5. M. S. Robinson et al., Science 321, 66 (2008). Red–green–blue presentation is the inverse of principal
groups on the floor of Raditladi. Under strictly 6. D. T. Blewett et al., Earth Planet. Sci. Lett. 285, 272 (2009). component two (iPC2)–PC1–(430-nm/629-nm ratio) (5, 8).
7. D. T. Blewett et al., Icarus 209, 239 (2010). 35. F. Preusker et al., Planet. Space Sci., 28 July 2011
radial growth, the erosion rate is 0.14 mm/year, or 8. B. W. Denevi et al., Science 324, 613 (2009). (10.1016/j.pss.2011.07.005).
1 cm in 70,000 years. For comparison, estimates 9. R. G. Strom, N. J. Trask, J. E. Guest, J. Geophys. Res. 80, Acknowledgments: This work was supported by NASA through
for the rate of scarp retreat in the martian “Swiss- 2478 (1975). the MESSENGER project and by a Participating Scientist
cheese” terrain are ~1 m per Earth year (22), and 10. P. D. Spudis, J. E. Guest, in Mercury, F. Vilas, C. R. Chapman, grant to D.T.B. M. Robinson offered helpful comments
M. S. Matthews, Eds. (Univ. of Arizona Press, Tucson, AZ, on the manuscript. We thank N. Fontanella, S. Peel,
the rate of abrasion of kilogram-sized lunar rocks 1988), pp. 118–164. E. Zhong, P. Pashai, and E. Coman for assistance with
by micrometeoroid bombardment is ~1 cm per 11. M. S. Robinson, P. G. Lucey, Science 275, 197 (1997). data processing and compilation. MESSENGER data are
107 years (28). Although the uncertainties in the 12. J. W. Head et al., Science 321, 69 (2008). archived with the NASA Planetary Data System.
13. J. W. Head et al., Earth Planet. Sci. Lett. 285, 227 (2009).
formation rate are large, the existence on Mercury 14. J. W. Head et al., Science 333, 1853 (2011). Supporting Online Material
of a process modifying the terrain faster than lunar 15. S. L. Murchie et al., Science 321, 73 (2008).
www.sciencemag.org/cgi/content/full/333/6051/1856/DC1
micrometeoroid erosion but more slowly than 16. L. Kerber et al., Earth Planet. Sci. Lett. 285, 263 (2009).
SOM Text
17. L. Kerber et al., Planet. Space Sci., 8 April 2011
martian CO2 ice sublimation can account for why (10.1016/j.pss.2011.03.020).
Fig. S1
the hollows appear to be much younger than the 18. J. J. Gillis-Davis et al., Earth Planet. Sci. Lett. 285, 243 25 July 2011; accepted 5 September 2011
impact structures in which they are found. (2009). 10.1126/science.1211681
The Global Magnetic Field of Mercury ing Mercury flybys by the Mariner 10 (1) and
MESSENGER (2, 3) spacecraft indicate that the
planet’s internal field is consistent with an axially
from MESSENGER Orbital Observations aligned dipole displaced northward by ~0.16 RM,
where RM is Mercury’s mean radius, 2440 km.
Brian J. Anderson,1* Catherine L. Johnson,2,3 Haje Korth,1 Michael E. Purucker,4 However, because of limited geographical cov-
Reka M. Winslow,2 James A. Slavin,5 Sean C. Solomon,6 Ralph L. McNutt Jr.,1 erage afforded by the flybys, the estimated di-
Jim M. Raines,5 Thomas H. Zurbuchen5 pole and quadrupole coefficients were highly
correlated (7, 8) such that the solutions were not
Magnetometer data acquired by the MESSENGER spacecraft in orbit about Mercury permit the separation unique. Moreover, signatures of plasma pressure
of internal and external magnetic field contributions. The global planetary field is represented as a near the equator raised questions about the field
southward-directed, spin-aligned, offset dipole centered on the spin axis. Positions where the cylindrical magnitudes recorded near the equator, imply-
radial magnetic field component vanishes were used to map the magnetic equator and reveal an offset ing that the inferred offset could have been the
of 484 T 11 kilometers northward of the geographic equator. The magnetic axis is tilted by less than 3°
from the rotation axis. A magnetopause and tail-current model was defined by using 332 magnetopause 1
The Johns Hopkins University Applied Physics Laboratory,
crossing locations. Residuals of the net external and offset-dipole fields from observations north of 30°N Laurel, MD 20723, USA. 2University of British Columbia,
yield a best-fit planetary moment of 195 T 10 nanotesla-RM3, where RM is Mercury’s mean radius. Vancouver, BC V6T 1Z4, Canada. 3Planetary Science Insti-
tute, Tucson, AZ 85719, USA. 4Goddard Space Flight Center,
ercury and Earth are the only terrestrial Earth-like magnetic dynamo in the fluid outer Greenbelt, MD 20771, USA. 5Department of Atmospheric, Oce-
M planets with global magnetic fields of
internal origin, but Mercury’s field is
weak compared with Earth’s (1–3). Explaining
core has proven challenging (4), and innovative
theoretical solutions have been proposed (5, 6)
that can potentially be distinguished by the field
anic and Space Sciences, University of Michigan, Ann Arbor,
MI 48109, USA. 6Department of Terrestrial Magnetism, Carne-
gie Institution of Washington, Washington, DC 20015, USA.
*To whom correspondence should be addressed. E-mail:
the comparatively weak field at Mercury with an geometry. Magnetometer observations made dur- brian.anderson@jhuapl.edu
www.sciencemag.org SCIENCE VOL 333 30 SEPTEMBER 2011 1859