This work focuses on the effect of the interval between two shocks on the ejecta formation from the grooved aluminum(Al_(1100))surface by using smoothed particle hydrodynamics numerical simulation.Two unsupported shoc...This work focuses on the effect of the interval between two shocks on the ejecta formation from the grooved aluminum(Al_(1100))surface by using smoothed particle hydrodynamics numerical simulation.Two unsupported shocks are obtained by the plate-impact between sample and two flyers at interval,with a peak pressure of approximately 30 GPa for each shock.When the shock interval varies from 2.11 to 7.67 times the groove depth,the bubble velocity reduces to a constant,and the micro jetting factor R_(J) from spike to bubble exhibits a non-monotonic change that decreases initially and then increases.At a shock interval of 3.6 times the groove depth,micro jetting factor R_(J) from spike to bubble reaches its minimum value of approximately 0.6.While,the micro jetting factor R_(F) from spike to free surface decreases linearly at first,and stabilizes around 0.25 once the shock interval surpasses 4.18 times the groove depth.When the shock interval is less than 4.18 times the groove depth,the unloading wave generated by the breakout of the first shock wave is superimpose with the unloading part of the second shock wave to form a large tensile area.展开更多
Dynamic failure and ejection characteristics of a periodic grooved Sn surface under unsupported shock loading are studied using a smoothed particle hydrodynamics method. An ＂Eiffel Tower＂ spatial structure is observ...Dynamic failure and ejection characteristics of a periodic grooved Sn surface under unsupported shock loading are studied using a smoothed particle hydrodynamics method. An ＂Eiffel Tower＂ spatial structure is observed, which is com- posed of high-speed jet tip, high-density jet slug, longitudinal tensile sparse zone, and complex broken zone between grooves. It is very different from the spike-bubble structure under supported shocks, and has been validated by detonation loading experiments. In comparison with that under supported shocks at the same peak pressure, the high-speed ejecta decreases obviously, whereas the truncated location of ejecta moves towards the interior of the sample and the total mass of ejecta increases due to the vast existence of low-speed broken materials. The shock wave profile determines mainly the total ejection amount, while the variation of V-groove angle will significantly alter the distribution of middle- and high-speed ejecta, and the maximum ejecta velocity has a linear corretation with the groove angle.展开更多
The Chinese Chang’e-3 mission landed close to the eastern rim of the ~450 m diameter Ziwei crater. Regional stratigraphy of the landing site and impact excavation model suggest that the bulk continuous ejecta deposit...The Chinese Chang’e-3 mission landed close to the eastern rim of the ~450 m diameter Ziwei crater. Regional stratigraphy of the landing site and impact excavation model suggest that the bulk continuous ejecta deposits of the Ziwei crater are composed by Erathothenian-aged mare basalts. Along the traverse of the Yutu rover, the western segment features a gentle topographic uplift(~0.5 m high over ~4 m), which is spatially connected with the structurally-uplifted crater rim. Assuming that this broad topographic uplift has physical properties discontinuous with materials below, we use data returned by the high-frequency lunar penetrating radar onboard the Yutu rover to estimate the possible range of relative permittivity for this topographic uplift. Only when the relative permittivity is ~9 is the observed radar reflection consistent with the observed topography, suggesting that the topographic uplift is composed of basaltic blocks that were excavated by the Ziwei crater. This result is consistent both with the impact excavation model that predicts deeper basaltic materials being deposited closer to the crater rim, and with observation of numerous half-buried boulders on the surface of this hill. We note that this study is the first to use topography and radargram data to estimate the relative permittivity of lunar surface uplifts, an approach that has had many successful applications on Mars. Similar approaches can apply other ground penetrating radar data for the Moon, such as will be available from the ongoing Chang’e-4 mission.展开更多
We conduct molecular dynamics simulations of the ejection process from a grooved Pb surface subjected to supported and unsupported shock waves with various shock-breakout pressures（PSB） inducing a solid–liquid phas...We conduct molecular dynamics simulations of the ejection process from a grooved Pb surface subjected to supported and unsupported shock waves with various shock-breakout pressures（PSB） inducing a solid–liquid phase transition upon shock or release. It is found that the total ejecta mass changing with PSBunder a supported shock reveals a similar trend with that under an unsupported shock and the former is always less than the latter at the same PSB. The origin of such a discrepancy could be unraveled that for an unsupported shock, a larger velocity difference between the jet tip and its bottom at an early stage of jet formation results in more serious damage, and therefore a greater amount of ejected particles are produced. The cumulative areal density distributions also display the discrepancy. In addition, we discuss the difference of these simulated results compared to the experimental findings.展开更多
The photon Doppler velocimetry(PDV) spectrum is investigated in an attempt to reveal the particle parameters of ejecta from shock-loaded samples in a vacuum. A GPU-accelerated Monte–Carlo algorithm, which considers t...The photon Doppler velocimetry(PDV) spectrum is investigated in an attempt to reveal the particle parameters of ejecta from shock-loaded samples in a vacuum. A GPU-accelerated Monte–Carlo algorithm, which considers the multiplescattering effects of light, is applied to reconstruct the light field of the ejecta and simulate the corresponding PDV spectrum.The influence of the velocity profile, total area mass, and particle size of the ejecta on the simulated spectra is discussed qualitatively. To facilitate a quantitative discussion, a novel theoretical optical model is proposed in which the singlescattering assumption is applied. With this model, the relationships between the particle parameters of ejecta and the peak information of the PDV spectrum are derived, enabling direct extraction of the particle parameters from the PDV spectrum.The values of the ejecta parameters estimated from the experimental spectrum are in good agreement with those measured by a piezoelectric probe.展开更多
Numerous linear grooves have long been recognized as covering the surface of Phobos, but the mechanisms of their formation are still unclear. One possible mechanism is related to the largest crater on Phobos, the Stic...Numerous linear grooves have long been recognized as covering the surface of Phobos, but the mechanisms of their formation are still unclear. One possible mechanism is related to the largest crater on Phobos, the Stickney crater, whose impact ejecta may slide,roll, bounce, and engrave groove-like features on Phobos. When the launch velocity is higher than the escape velocity, the impact ejecta can escape Phobos. A portion of these high-velocity ejecta are dragged by the gravitational force of Mars, fall back, and reimpact Phobos.In this research, we numerically test the hypothesis that the orbital ejecta of the Stickney crater that reimpact Phobos could be responsible for a particular subset of the observed grooves on Phobos. We adopt impact hydrocode i SALE-2 D(impact-Simplified Arbitrary Lagrangian Eulerian, two-dimensional) to simulate the formation of the Stickney crater and track its impact ejecta, with a focus on orbital ejecta with launch velocities greater than the escape velocity of Phobos. The launch velocity distribution of the ejecta particles is then used to calculate their trajectories in space and determine their fates. For orbital ejecta reimpacting Phobos, we then apply the sliding boulder model to calculate the ejecta paths, which are compared with the observed groove distribution and length to search for causal relationships. Our ejecta trajectory calculations suggest that only ~1% of the orbital ejecta from the Stickney crater can reimpact Phobos. Applying the sliding boulder model, we predict ejecta sliding paths of 9-20 km in a westward direction to the east of the zone of avoidance, closely matching the observed grooves in that region. The best-fit model assumes an ejecta radius of ~150 m and a speed restitution coefficient of 0.3, consistent with the expected ejecta and regolith properties. Our calculations thus suggest the groove class located to the east of the zone of avoidance may have been caused by reimpact orbital ejecta from the Stickney crater.展开更多
Many Propositions are made about the mechanism of emplacement of volcanoclastic material in the Bombay volcanic complex. The present paper deals exclusively with the physical features of the deposits laid by a complex...Many Propositions are made about the mechanism of emplacement of volcanoclastic material in the Bombay volcanic complex. The present paper deals exclusively with the physical features of the deposits laid by a complex tectono-magmatic process by making detailed inventory of the different kind of volcanic ejecta exposed in the Bomay Volcanic Complex (BVC), and an attempt has been made to classify the deposits genetically. A subsidenace which was hinted at earlier, may be a possible cauldron in BVC has been proposed, which might be responsible for producing such a varied and complex lithology.展开更多
We conducted numerical simulations of the related processes of interface instability, tensile fragmentation, and jetting resulting from four kinds of typical macro defect perturbations (chevron, sine wave, rectangle, ...We conducted numerical simulations of the related processes of interface instability, tensile fragmentation, and jetting resulting from four kinds of typical macro defect perturbations (chevron, sine wave, rectangle, and square) on a Cu free surface under a reflected shock wave when Cu impacts a solid wall at a speed of 2.5 km/s and found that, for the chevron and sine wave cases, the ejecta velocities of the head are 6.28 and 5.88 km/s, respectively. Some parts of the inner material are in a tensile state without any fragmentation, which is observed only in the main body of the material owing to the tension effect. Furthermore, for the other two initial perturbations (rectangle and square), the highest ejecta velocities may even reach 9.14 and 9.59 km/s, respectively. Fragmentation caused by multilayer spallation can be observed on a large scale in the Cu main body, and there are granules in the front area of the ejecta but the degree to which fragmentation occurs is much less in the Cu main body and there is a notable high-speed, low-density granule area in the ejecta head. Finally, we present a detailed analysis of the spatial distribution of the granules, ejecta mass, pressure, temperature, and grid convergence.展开更多
The Yutu-2 rover of the Chang'e-4 mission has been exploring the lunar farside since January 2019.By analyzing the visible and near-infrared spectra collected by Yutu-2 during its first five years of operation,we ...The Yutu-2 rover of the Chang'e-4 mission has been exploring the lunar farside since January 2019.By analyzing the visible and near-infrared spectra collected by Yutu-2 during its first five years of operation,we have identified that the pyroxene in the surrounding lunar regolith is primarily low-Ca clinopyroxene.Findings from spectral absorption analyses and mineralogical quantification indicate that the lunar regolith in the Chang'e-4 landing area predominantly consists of local mare basaltic materials rather than Finsen's ejecta.These mare basaltic substances were likely excavated by Finsen's secondary crater from the local basalt layer located at depths below about 8 m.Collaborative analyses of the mineralogy and topography along the Yutu-2 traverse suggest that the southern wall and western wall of Finsen's secondary crater may have experienced different degradation processes.Additionally,the Finsen's ejecta may be predominantly deposited at the center of its secondary crater.Our results reveal that the distal impact ejecta are capable of substantially excavating the local materials.These findings reveal the complex evolutionary processes of the lunar regolith and highlight the significance of meticulous analysis for the provenance of lunar surface materials.展开更多
Scientific interest in asteroids and their physical characteristics is growing.These bodies provide insights into the primordial solar system and represent a valuable source of metals,silicates,and water.Several missi...Scientific interest in asteroids and their physical characteristics is growing.These bodies provide insights into the primordial solar system and represent a valuable source of metals,silicates,and water.Several missions over the past few years have aimed to improve and better identify the main properties of these poorly known celestial bodies.However,these missions relied on touchdown(s)on the target asteroid to gather samples,which is complicated owing to the difficulty of accurately reaching and rendezvousing with the body.This study aims to assess the feasibility of an in-orbit asteroid sample collection mission.Such a strategy could prevent complex operations related to landing and touchdown maneuvers and avoid the dead times present in a mission requiring several landings.The presented collection scenario,which focuses on the asteroid Ryugu,proposes gathering samples using a spacecraft injected into a halo orbit around the second libration point,L2.For this purpose,the orbits in the neck region of the zero velocity curves are analyzed.A novel methodology to characterize bouncing behavior is introduced.An interpolation-based approach was used to recover the appropriate restitution coefficients for each collision occurring at a specific impact angle.This was applied to both the rigid body model and the point mass approximation studied for two different sites on the asteroid.Furthermore,the study enlarged the region of interest from only L2 to its neighboring zones to return a more global and realistic point of view.Considering the solar radiation pressure and asteroid aspherical potential,particles of different sizes ejected from different longitudes and with different ejection angles were classified according to their trajectories to finally build a database.Based on this analysis,an aerogel-based collection strategy inspired by that used in the Stardust-NExT(NASA)mission was investigated to assess its possible applicability to the analyzed scenario.展开更多
The lunar magma ocean hypothesis suggests that the primordial KREEP(an acronym of potassium(K),rare earth element(REE),and phosphorus(P))was the final product of fractional crystallization.However,the primordial KREEP...The lunar magma ocean hypothesis suggests that the primordial KREEP(an acronym of potassium(K),rare earth element(REE),and phosphorus(P))was the final product of fractional crystallization.However,the primordial KREEP(a.k.a.urKREEP)has never been identified in previous lunar samples or meteorites.The Moon is the focus of many countries’and agencies’space exploration plans,and with the advancement of technology,crewed missions have been proposed.We propose two candidate landing sites,located respectively in the northwest(9.5°W,0.9°S)and southeast(11.1°W,6.2°S)of Lalande crater(8.6°W,4.5°S),for future crewed missions,with the primary goal of sampling the speculated urKREEP.Both sites are situated on the Th-(a critical marker of KREEP)and silica-rich Lalande ejecta in the Mare Insularum and Mare Nubium,respectively.Their geolocations at the low latitude on the lunar nearside,the flat surface,and the low rock abundance suggest the sites are safe for landing and meet the needs of real-time Earth-Moon communication.The astronauts could perform many extravehicular activities,such as collecting KREEP-rich samples,screening clast samples,and drilling regolith cores,to gather a variety of samples,such as Lalande ejecta,basalts,Copernicus ejecta,and regolith.The returned samples are valuable to explore the speculated urKREEP,to reveal the relationship between heat-producing elements and volcanism,to refine the lunar cratering chronology function,and to investigate volatiles in the regolith.展开更多
基金supported by the Doctoral Research Launch Foundation of Liaoning Province(Grant No.2022-BS-185),Chinathe Science Challenge Project(Grant No.TZ2016001),China+2 种基金the National Natural Science Foundation of China(Grant Nos.11972092,12172056,12002049),Chinathe key Laboratory of Computational Physics(Gant No.HX02021-24)720-24)Shenyang Ligong University Talent Introduction Support Fund,China。
文摘This work focuses on the effect of the interval between two shocks on the ejecta formation from the grooved aluminum(Al_(1100))surface by using smoothed particle hydrodynamics numerical simulation.Two unsupported shocks are obtained by the plate-impact between sample and two flyers at interval,with a peak pressure of approximately 30 GPa for each shock.When the shock interval varies from 2.11 to 7.67 times the groove depth,the bubble velocity reduces to a constant,and the micro jetting factor R_(J) from spike to bubble exhibits a non-monotonic change that decreases initially and then increases.At a shock interval of 3.6 times the groove depth,micro jetting factor R_(J) from spike to bubble reaches its minimum value of approximately 0.6.While,the micro jetting factor R_(F) from spike to free surface decreases linearly at first,and stabilizes around 0.25 once the shock interval surpasses 4.18 times the groove depth.When the shock interval is less than 4.18 times the groove depth,the unloading wave generated by the breakout of the first shock wave is superimpose with the unloading part of the second shock wave to form a large tensile area.
基金Project supported by the Joint Fund of the National Natural Science Foundation of China and the China Academy of Engineering Physics(Grant No.U1530261)the National Natural Science Foundation of China(Grant Nos.11402032 and 11502030)the Science Challenge Project,China(Grant No.TZ2016001)
文摘Dynamic failure and ejection characteristics of a periodic grooved Sn surface under unsupported shock loading are studied using a smoothed particle hydrodynamics method. An ＂Eiffel Tower＂ spatial structure is observed, which is com- posed of high-speed jet tip, high-density jet slug, longitudinal tensile sparse zone, and complex broken zone between grooves. It is very different from the spike-bubble structure under supported shocks, and has been validated by detonation loading experiments. In comparison with that under supported shocks at the same peak pressure, the high-speed ejecta decreases obviously, whereas the truncated location of ejecta moves towards the interior of the sample and the total mass of ejecta increases due to the vast existence of low-speed broken materials. The shock wave profile determines mainly the total ejection amount, while the variation of V-groove angle will significantly alter the distribution of middle- and high-speed ejecta, and the maximum ejecta velocity has a linear corretation with the groove angle.
基金supported by the National Natural Science Foundation of China (41773063, 41525015 and 41830214)the Science and Technology Development Fund of Macao (0042/2018/A2)the Opening Fund of the Key Laboratory of Lunar and Deep Space Exploration, CAS (no.ldse201702)
文摘The Chinese Chang’e-3 mission landed close to the eastern rim of the ~450 m diameter Ziwei crater. Regional stratigraphy of the landing site and impact excavation model suggest that the bulk continuous ejecta deposits of the Ziwei crater are composed by Erathothenian-aged mare basalts. Along the traverse of the Yutu rover, the western segment features a gentle topographic uplift(~0.5 m high over ~4 m), which is spatially connected with the structurally-uplifted crater rim. Assuming that this broad topographic uplift has physical properties discontinuous with materials below, we use data returned by the high-frequency lunar penetrating radar onboard the Yutu rover to estimate the possible range of relative permittivity for this topographic uplift. Only when the relative permittivity is ~9 is the observed radar reflection consistent with the observed topography, suggesting that the topographic uplift is composed of basaltic blocks that were excavated by the Ziwei crater. This result is consistent both with the impact excavation model that predicts deeper basaltic materials being deposited closer to the crater rim, and with observation of numerous half-buried boulders on the surface of this hill. We note that this study is the first to use topography and radargram data to estimate the relative permittivity of lunar surface uplifts, an approach that has had many successful applications on Mars. Similar approaches can apply other ground penetrating radar data for the Moon, such as will be available from the ongoing Chang’e-4 mission.
基金supported by the National Natural Science Foundation of China(Grant Nos.11472254 and 11272006)
文摘We conduct molecular dynamics simulations of the ejection process from a grooved Pb surface subjected to supported and unsupported shock waves with various shock-breakout pressures（PSB） inducing a solid–liquid phase transition upon shock or release. It is found that the total ejecta mass changing with PSBunder a supported shock reveals a similar trend with that under an unsupported shock and the former is always less than the latter at the same PSB. The origin of such a discrepancy could be unraveled that for an unsupported shock, a larger velocity difference between the jet tip and its bottom at an early stage of jet formation results in more serious damage, and therefore a greater amount of ejected particles are produced. The cumulative areal density distributions also display the discrepancy. In addition, we discuss the difference of these simulated results compared to the experimental findings.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11902043 and 11772065)the Science Challenge Project (Grant No. TZ2016001)。
文摘The photon Doppler velocimetry(PDV) spectrum is investigated in an attempt to reveal the particle parameters of ejecta from shock-loaded samples in a vacuum. A GPU-accelerated Monte–Carlo algorithm, which considers the multiplescattering effects of light, is applied to reconstruct the light field of the ejecta and simulate the corresponding PDV spectrum.The influence of the velocity profile, total area mass, and particle size of the ejecta on the simulated spectra is discussed qualitatively. To facilitate a quantitative discussion, a novel theoretical optical model is proposed in which the singlescattering assumption is applied. With this model, the relationships between the particle parameters of ejecta and the peak information of the PDV spectrum are derived, enabling direct extraction of the particle parameters from the PDV spectrum.The values of the ejecta parameters estimated from the experimental spectrum are in good agreement with those measured by a piezoelectric probe.
基金supported by the Science and Technology Development Fund, Macao (Grant No. 0020/2021/A1)the National Natural Science Foundation of China (Grant No. 12173106)supported by the Science and Technology Development Fund, Macao (Grant No. 0079/2018/A2)
文摘Numerous linear grooves have long been recognized as covering the surface of Phobos, but the mechanisms of their formation are still unclear. One possible mechanism is related to the largest crater on Phobos, the Stickney crater, whose impact ejecta may slide,roll, bounce, and engrave groove-like features on Phobos. When the launch velocity is higher than the escape velocity, the impact ejecta can escape Phobos. A portion of these high-velocity ejecta are dragged by the gravitational force of Mars, fall back, and reimpact Phobos.In this research, we numerically test the hypothesis that the orbital ejecta of the Stickney crater that reimpact Phobos could be responsible for a particular subset of the observed grooves on Phobos. We adopt impact hydrocode i SALE-2 D(impact-Simplified Arbitrary Lagrangian Eulerian, two-dimensional) to simulate the formation of the Stickney crater and track its impact ejecta, with a focus on orbital ejecta with launch velocities greater than the escape velocity of Phobos. The launch velocity distribution of the ejecta particles is then used to calculate their trajectories in space and determine their fates. For orbital ejecta reimpacting Phobos, we then apply the sliding boulder model to calculate the ejecta paths, which are compared with the observed groove distribution and length to search for causal relationships. Our ejecta trajectory calculations suggest that only ~1% of the orbital ejecta from the Stickney crater can reimpact Phobos. Applying the sliding boulder model, we predict ejecta sliding paths of 9-20 km in a westward direction to the east of the zone of avoidance, closely matching the observed grooves in that region. The best-fit model assumes an ejecta radius of ~150 m and a speed restitution coefficient of 0.3, consistent with the expected ejecta and regolith properties. Our calculations thus suggest the groove class located to the east of the zone of avoidance may have been caused by reimpact orbital ejecta from the Stickney crater.
文摘Many Propositions are made about the mechanism of emplacement of volcanoclastic material in the Bombay volcanic complex. The present paper deals exclusively with the physical features of the deposits laid by a complex tectono-magmatic process by making detailed inventory of the different kind of volcanic ejecta exposed in the Bomay Volcanic Complex (BVC), and an attempt has been made to classify the deposits genetically. A subsidenace which was hinted at earlier, may be a possible cauldron in BVC has been proposed, which might be responsible for producing such a varied and complex lithology.
文摘We conducted numerical simulations of the related processes of interface instability, tensile fragmentation, and jetting resulting from four kinds of typical macro defect perturbations (chevron, sine wave, rectangle, and square) on a Cu free surface under a reflected shock wave when Cu impacts a solid wall at a speed of 2.5 km/s and found that, for the chevron and sine wave cases, the ejecta velocities of the head are 6.28 and 5.88 km/s, respectively. Some parts of the inner material are in a tensile state without any fragmentation, which is observed only in the main body of the material owing to the tension effect. Furthermore, for the other two initial perturbations (rectangle and square), the highest ejecta velocities may even reach 9.14 and 9.59 km/s, respectively. Fragmentation caused by multilayer spallation can be observed on a large scale in the Cu main body, and there are granules in the front area of the ejecta but the degree to which fragmentation occurs is much less in the Cu main body and there is a notable high-speed, low-density granule area in the ejecta head. Finally, we present a detailed analysis of the spatial distribution of the granules, ejecta mass, pressure, temperature, and grid convergence.
基金supported by the National Key Research and Development Program of China(Grant Nos.2022YFF0711400&2022YFF0503100)the Young Elite Scientists Sponsorship Program by the China Association for Science and Technology(Grant Nos.2021QNRC001&2022QNRC001)the National Natural Science Foundation of China(Grant Nos.12273044&62495034)。
文摘The Yutu-2 rover of the Chang'e-4 mission has been exploring the lunar farside since January 2019.By analyzing the visible and near-infrared spectra collected by Yutu-2 during its first five years of operation,we have identified that the pyroxene in the surrounding lunar regolith is primarily low-Ca clinopyroxene.Findings from spectral absorption analyses and mineralogical quantification indicate that the lunar regolith in the Chang'e-4 landing area predominantly consists of local mare basaltic materials rather than Finsen's ejecta.These mare basaltic substances were likely excavated by Finsen's secondary crater from the local basalt layer located at depths below about 8 m.Collaborative analyses of the mineralogy and topography along the Yutu-2 traverse suggest that the southern wall and western wall of Finsen's secondary crater may have experienced different degradation processes.Additionally,the Finsen's ejecta may be predominantly deposited at the center of its secondary crater.Our results reveal that the distal impact ejecta are capable of substantially excavating the local materials.These findings reveal the complex evolutionary processes of the lunar regolith and highlight the significance of meticulous analysis for the provenance of lunar surface materials.
基金the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No.896404-CRADLEthe European Research Council(ERC)under the European Union’s Horizon 2020 Research and Innovation Program(grant agreement No.679086-COMPASS).
文摘Scientific interest in asteroids and their physical characteristics is growing.These bodies provide insights into the primordial solar system and represent a valuable source of metals,silicates,and water.Several missions over the past few years have aimed to improve and better identify the main properties of these poorly known celestial bodies.However,these missions relied on touchdown(s)on the target asteroid to gather samples,which is complicated owing to the difficulty of accurately reaching and rendezvousing with the body.This study aims to assess the feasibility of an in-orbit asteroid sample collection mission.Such a strategy could prevent complex operations related to landing and touchdown maneuvers and avoid the dead times present in a mission requiring several landings.The presented collection scenario,which focuses on the asteroid Ryugu,proposes gathering samples using a spacecraft injected into a halo orbit around the second libration point,L2.For this purpose,the orbits in the neck region of the zero velocity curves are analyzed.A novel methodology to characterize bouncing behavior is introduced.An interpolation-based approach was used to recover the appropriate restitution coefficients for each collision occurring at a specific impact angle.This was applied to both the rigid body model and the point mass approximation studied for two different sites on the asteroid.Furthermore,the study enlarged the region of interest from only L2 to its neighboring zones to return a more global and realistic point of view.Considering the solar radiation pressure and asteroid aspherical potential,particles of different sizes ejected from different longitudes and with different ejection angles were classified according to their trajectories to finally build a database.Based on this analysis,an aerogel-based collection strategy inspired by that used in the Stardust-NExT(NASA)mission was investigated to assess its possible applicability to the analyzed scenario.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFF0503104)the National Natural Science Foundation of China(Grant Nos.42241111,62227901,and 42441826)+1 种基金the Macao Young Scholars Program(Grant No.AM201902)the Key Research Program of the Institute of Geology and Geophysics,Chinese Academy of Sciences(Grant No.IGGCAS-202401).
文摘The lunar magma ocean hypothesis suggests that the primordial KREEP(an acronym of potassium(K),rare earth element(REE),and phosphorus(P))was the final product of fractional crystallization.However,the primordial KREEP(a.k.a.urKREEP)has never been identified in previous lunar samples or meteorites.The Moon is the focus of many countries’and agencies’space exploration plans,and with the advancement of technology,crewed missions have been proposed.We propose two candidate landing sites,located respectively in the northwest(9.5°W,0.9°S)and southeast(11.1°W,6.2°S)of Lalande crater(8.6°W,4.5°S),for future crewed missions,with the primary goal of sampling the speculated urKREEP.Both sites are situated on the Th-(a critical marker of KREEP)and silica-rich Lalande ejecta in the Mare Insularum and Mare Nubium,respectively.Their geolocations at the low latitude on the lunar nearside,the flat surface,and the low rock abundance suggest the sites are safe for landing and meet the needs of real-time Earth-Moon communication.The astronauts could perform many extravehicular activities,such as collecting KREEP-rich samples,screening clast samples,and drilling regolith cores,to gather a variety of samples,such as Lalande ejecta,basalts,Copernicus ejecta,and regolith.The returned samples are valuable to explore the speculated urKREEP,to reveal the relationship between heat-producing elements and volcanism,to refine the lunar cratering chronology function,and to investigate volatiles in the regolith.
