研究小行星的暴露年龄对于理解其形成与演化具有重要意义。双小行星重定向测试(Double Asteroid Redirection Test,DART)任务的实施,不仅验证了动能撞击技术偏转近地小行星轨道的可行性,也为研究小行星暴露年龄及其成因演化提供了宝贵...研究小行星的暴露年龄对于理解其形成与演化具有重要意义。双小行星重定向测试(Double Asteroid Redirection Test,DART)任务的实施,不仅验证了动能撞击技术偏转近地小行星轨道的可行性,也为研究小行星暴露年龄及其成因演化提供了宝贵机会。基于DART撞击前后地基望远镜获得的可见近红外光谱数据,对主星Didymos表面及次星Dimorphos溅射物开展暴露年龄研究。结果表明,Didymos表面的暴露年龄约为45.7万年,表明主星在约45.7万年前发生了一次较大规模的物质脱落事件。该事件对主星的表面年龄几乎没有影响,但重置了次星的表面年龄及主星的暴露年龄。Dimorphos溅射物与主星Didymos的表面成分相同,但风化程度较低,这表明在次星形成后,主星和次星表面受到强烈的太空风化作用,而次星内部物质受到的太空风化作用相对较弱。展开更多
In a Nature Physics report published in late September 2024[1],a team of scientists and engineers at Sandia National Laboratories(Albuquerque,NM,USA)described the results of a laboratory experiment showing that a nucl...In a Nature Physics report published in late September 2024[1],a team of scientists and engineers at Sandia National Laboratories(Albuquerque,NM,USA)described the results of a laboratory experiment showing that a nuclear blast could create a burst of X-rays powerful enough to change the path of a large asteroid that might one day be on a collision course with Earth.展开更多
In the present study,we investigated the existence of arbitrary amplitude dust acoustic solitons by considering the Cairns distributed ions,negatively charged streaming dust grains along with(r,q)distributed electrons...In the present study,we investigated the existence of arbitrary amplitude dust acoustic solitons by considering the Cairns distributed ions,negatively charged streaming dust grains along with(r,q)distributed electrons in an un-magnetized dusty plasma.We used the pseudopotential technique to obtain the solitary wave solution.It is seen that the coexistence of rarefactive and compressive solitons is possible when ions and electrons are nonthermally distributed.We found that the soliton characteristics are strongly dependent on the choice of velocity distribution function through the nonthermal spectral indices r q,,a as well as on the ion and dust temperatures.For(r,q)distributed electrons,we found that the soliton amplitude increases(decreases)with smaller(higher)values of negative(positive)r.For Cairns distributed ions,we found a transition from negative to positive polarity solitary structures with the coexistence in between as the nonthermal parameter a increases.Our results gave a better explanation for the formation of dust acoustic solitary structures and their dependence on high and low energy particles in nonthermal distribution profiles in space environments.展开更多
Asteroids and comets,which have long been of interest to astronomers,are important components of the solar system.They contain rich primitive information about the early solar system,which provide a unique pathway for...Asteroids and comets,which have long been of interest to astronomers,are important components of the solar system.They contain rich primitive information about the early solar system,which provide a unique pathway for studying the formation and evolution of the solar system,and even the origin of life on planet Earth.In this review,the formation,evolution processes and the internal characteristics of the asteroids and comets in the solar system are presented.The focus of this review is on the internal characteristics especially the dielectric properties of asteroids and comets by radar observations.On this basis,the possible internal structure of these celestial bodies is discussed.Combined with the existing theories,simulations and experiments,the possible internal structure of near-Earth asteroid 2016 HO_(3) is a monolith while structure of active asteroid 311P/PANSTARRS remains unknown.In 2025,China will launch Tianwen-2 asteroid-comet exploration mission to detect 2016 HO_(3) and 311P/PANSTARRS,which will carry a penetrating radar to observe the internal characteristics of these two objects.展开更多
Integrating available instrumental records with meteorite analysis could build a link between meteorite chemical groups and their original parent bodies.However,such comprehensive source region-tracing studies have no...Integrating available instrumental records with meteorite analysis could build a link between meteorite chemical groups and their original parent bodies.However,such comprehensive source region-tracing studies have not been conducted for any meteorite fall events in China.On 2022 December 15 at 09:48 UT,meteoroid Tanxi was recorded by numerous cameras in populous northern Zhejiang.This event offers an opportunity to conduct the first systematic origin-tracing study for a meteorite fall event in China.The Tanxi meteorite was classified as an H6chondrite.This meteoroid entered the atmosphere with a velocity of 13.49 km s^(-1)and a slope of 69.52°.It most likely underwent a two-stage fragmentation process,with early fragmentation under a dynamic pressure of0.08 MPa,and main fragmentation under a dynamic pressure of 7.83 MPa.Before colliding with the Earth,the meteoroid’s heliocentric orbit had a semimajor axis of 2.363±0.107 au,an eccentricity of 0.584±0.019 and an inclination of 2.078±0.074°.A backward Dshevolution result of 5000 yr shows Tanxi’s orbit is most similar to a small near-Earth asteroid 2016 WV2.The source region analysis of the Tanxi fall indicates that the H chondrites could originate from two distinct reservoirs:the 3:1J mean motion resonance complex(51.2±3.7%)and the v6secular resonance region(41.6±2.9%).展开更多
“赫拉”(Hera)任务是由欧空局(ESA)主导并与美国国家航空航天局(NASA)合作开展的行星防御任务之一,通过对“双小行星重定向测试”(Double Asteroid Redirection Test,DART)任务撞击的“迪蒂莫斯”(Didymos)双星小行星系统开展近距离探...“赫拉”(Hera)任务是由欧空局(ESA)主导并与美国国家航空航天局(NASA)合作开展的行星防御任务之一,通过对“双小行星重定向测试”(Double Asteroid Redirection Test,DART)任务撞击的“迪蒂莫斯”(Didymos)双星小行星系统开展近距离探测、物理特性表征及精确定轨等工作,从而实现撞击后小行星偏转评估、撞击坑产生和演化评估、撞击过程能量传递效率的评估,以此验证撞击防御的有效性并为后续合理有效的撞击防御方案设计提供重要的数据支撑。此外,任务通过撞击翻出的小行星表层以下物质的探测进一步研究太阳系早期小行星形成过程等科学问题。本文概述“赫拉”探测任务探测器设计、载荷配置、立方星设计、任务过程等工程实施特点,针对未来中国小行星防御技术的发展和规划提出思考和建议。展开更多
文摘研究小行星的暴露年龄对于理解其形成与演化具有重要意义。双小行星重定向测试(Double Asteroid Redirection Test,DART)任务的实施,不仅验证了动能撞击技术偏转近地小行星轨道的可行性,也为研究小行星暴露年龄及其成因演化提供了宝贵机会。基于DART撞击前后地基望远镜获得的可见近红外光谱数据,对主星Didymos表面及次星Dimorphos溅射物开展暴露年龄研究。结果表明,Didymos表面的暴露年龄约为45.7万年,表明主星在约45.7万年前发生了一次较大规模的物质脱落事件。该事件对主星的表面年龄几乎没有影响,但重置了次星的表面年龄及主星的暴露年龄。Dimorphos溅射物与主星Didymos的表面成分相同,但风化程度较低,这表明在次星形成后,主星和次星表面受到强烈的太空风化作用,而次星内部物质受到的太空风化作用相对较弱。
文摘In a Nature Physics report published in late September 2024[1],a team of scientists and engineers at Sandia National Laboratories(Albuquerque,NM,USA)described the results of a laboratory experiment showing that a nuclear blast could create a burst of X-rays powerful enough to change the path of a large asteroid that might one day be on a collision course with Earth.
文摘In the present study,we investigated the existence of arbitrary amplitude dust acoustic solitons by considering the Cairns distributed ions,negatively charged streaming dust grains along with(r,q)distributed electrons in an un-magnetized dusty plasma.We used the pseudopotential technique to obtain the solitary wave solution.It is seen that the coexistence of rarefactive and compressive solitons is possible when ions and electrons are nonthermally distributed.We found that the soliton characteristics are strongly dependent on the choice of velocity distribution function through the nonthermal spectral indices r q,,a as well as on the ion and dust temperatures.For(r,q)distributed electrons,we found that the soliton amplitude increases(decreases)with smaller(higher)values of negative(positive)r.For Cairns distributed ions,we found a transition from negative to positive polarity solitary structures with the coexistence in between as the nonthermal parameter a increases.Our results gave a better explanation for the formation of dust acoustic solitary structures and their dependence on high and low energy particles in nonthermal distribution profiles in space environments.
基金supported by the National Natural Science Foundation of China(Grant No.12473063,12461160265,and 62227901)Shenzhen Science and Technology Innovation Commission(Grant No.20231121103211001)+5 种基金the Opening Fund of the Key Laboratory of Lunar and Deep Space Exploration,Chinese Academy of Sciences(No.LDSE202005)the Shenzhen University 2035 Program for Excellent Research(Grant No.2024C009)China National University Student Innovation&Entrepreneurship Development Program(No.202410590011)Natural Science Foundation of Guangdong Province(No.2024A1515011275)the Shenzhen Municipal Government Investment Project(No.2106_440300_04_03_901272)the team“Searching For Subglacial Water On Mars With Orbiting Ground Penetrating Radars”of the International Space Science Institute(ISSI).
文摘Asteroids and comets,which have long been of interest to astronomers,are important components of the solar system.They contain rich primitive information about the early solar system,which provide a unique pathway for studying the formation and evolution of the solar system,and even the origin of life on planet Earth.In this review,the formation,evolution processes and the internal characteristics of the asteroids and comets in the solar system are presented.The focus of this review is on the internal characteristics especially the dielectric properties of asteroids and comets by radar observations.On this basis,the possible internal structure of these celestial bodies is discussed.Combined with the existing theories,simulations and experiments,the possible internal structure of near-Earth asteroid 2016 HO_(3) is a monolith while structure of active asteroid 311P/PANSTARRS remains unknown.In 2025,China will launch Tianwen-2 asteroid-comet exploration mission to detect 2016 HO_(3) and 311P/PANSTARRS,which will carry a penetrating radar to observe the internal characteristics of these two objects.
基金supported by the National Key Research and Development Program of China(2023YFE0109900)the B-type Strategic Priority Research Program of Chinese Academy of Sciences(grant No.XDB 41000000)+4 种基金the National Natural Science Foundation of China(grant Nos.42273038,62227901,42073060 and 12150009)Space debris and NEO research project(No.KJSP2020020204)Youth Innovation Promotion Association CAS(2023332)the Science and Technology Project of Qinghai Province(2025-ZJ-T0)the Minor Planet Foundation of China.
文摘Integrating available instrumental records with meteorite analysis could build a link between meteorite chemical groups and their original parent bodies.However,such comprehensive source region-tracing studies have not been conducted for any meteorite fall events in China.On 2022 December 15 at 09:48 UT,meteoroid Tanxi was recorded by numerous cameras in populous northern Zhejiang.This event offers an opportunity to conduct the first systematic origin-tracing study for a meteorite fall event in China.The Tanxi meteorite was classified as an H6chondrite.This meteoroid entered the atmosphere with a velocity of 13.49 km s^(-1)and a slope of 69.52°.It most likely underwent a two-stage fragmentation process,with early fragmentation under a dynamic pressure of0.08 MPa,and main fragmentation under a dynamic pressure of 7.83 MPa.Before colliding with the Earth,the meteoroid’s heliocentric orbit had a semimajor axis of 2.363±0.107 au,an eccentricity of 0.584±0.019 and an inclination of 2.078±0.074°.A backward Dshevolution result of 5000 yr shows Tanxi’s orbit is most similar to a small near-Earth asteroid 2016 WV2.The source region analysis of the Tanxi fall indicates that the H chondrites could originate from two distinct reservoirs:the 3:1J mean motion resonance complex(51.2±3.7%)and the v6secular resonance region(41.6±2.9%).
文摘“赫拉”(Hera)任务是由欧空局(ESA)主导并与美国国家航空航天局(NASA)合作开展的行星防御任务之一,通过对“双小行星重定向测试”(Double Asteroid Redirection Test,DART)任务撞击的“迪蒂莫斯”(Didymos)双星小行星系统开展近距离探测、物理特性表征及精确定轨等工作,从而实现撞击后小行星偏转评估、撞击坑产生和演化评估、撞击过程能量传递效率的评估,以此验证撞击防御的有效性并为后续合理有效的撞击防御方案设计提供重要的数据支撑。此外,任务通过撞击翻出的小行星表层以下物质的探测进一步研究太阳系早期小行星形成过程等科学问题。本文概述“赫拉”探测任务探测器设计、载荷配置、立方星设计、任务过程等工程实施特点,针对未来中国小行星防御技术的发展和规划提出思考和建议。
