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
The meteor radar can detect the zenith angle,azimuth,radial velocity,and altitude of meteor trails so that one can invert the wind profiles in the mesosphere and low thermosphere(MLT)region,based on the Interferometri...The meteor radar can detect the zenith angle,azimuth,radial velocity,and altitude of meteor trails so that one can invert the wind profiles in the mesosphere and low thermosphere(MLT)region,based on the Interferometric and Doppler techniques.In this paper,the horizontal wind field,gravity wave(GW)disturbance variance,and GW fluxes are analyzed through the meteor radar observation from 2012−2022,at Mohe(53.5°N,122.4°E)and Zuoling(30.5°N,114.6°E)stations of the(Chinese)Meridian Project.The Lomb−Scargle periodogram method has been utilized to analyze the periodic variations for time series with observational data gaps.The results show that the zonal winds at both stations are eastward dominated,while the meridional winds are southward dominated.The variance of GW disturbances in the zonal and meridional directions increases gradually with height,and there is a strong pattern of annual variation.The zonal momentum flux of GW changes little with height,showing weak annual variation.The meridional GW flux varies gradually from northward to southward with height,and the annual periodicity is stronger.For both stations,the maximum values of zonal and meridional wind occur close to the peak heights of GW flux,with opposite directions.This observational evidence is consistent with the filtering theory.The horizontal wind velocity,GW flux,and disturbance variance of the GW at Mohe are overall smaller than those at Zuoling,indicating weaker activities in the MLT at Mohe.The power spectral density(PSD)calculated by the Lomb−Scargle periodogram shows that there are 12-month period and 6-month period in horizontal wind field,GW disturbance variance and GW flux at both stations,and especially there is also a 4-month cycle in the disturbance variance.The PSD of the 12-month and 6-month cycles exhibits maximum values below 88 km and above 94 km.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。
基金supported by the Fundamental Research Funds for the Central Universities,CHD(NO.300102263205 and NO.300102264916)the West Light Cross-Disciplinary Innovation team of Chinese Academy of Sciences(NO.E1294301).supported by the Fundamental Research Funds for the Central Universities,CHD(NO.300102263205 and NO.300102264916)the West Light Cross-Disciplinary Innovation team of Chinese Academy of Sciences(NO.E1294301).
文摘The meteor radar can detect the zenith angle,azimuth,radial velocity,and altitude of meteor trails so that one can invert the wind profiles in the mesosphere and low thermosphere(MLT)region,based on the Interferometric and Doppler techniques.In this paper,the horizontal wind field,gravity wave(GW)disturbance variance,and GW fluxes are analyzed through the meteor radar observation from 2012−2022,at Mohe(53.5°N,122.4°E)and Zuoling(30.5°N,114.6°E)stations of the(Chinese)Meridian Project.The Lomb−Scargle periodogram method has been utilized to analyze the periodic variations for time series with observational data gaps.The results show that the zonal winds at both stations are eastward dominated,while the meridional winds are southward dominated.The variance of GW disturbances in the zonal and meridional directions increases gradually with height,and there is a strong pattern of annual variation.The zonal momentum flux of GW changes little with height,showing weak annual variation.The meridional GW flux varies gradually from northward to southward with height,and the annual periodicity is stronger.For both stations,the maximum values of zonal and meridional wind occur close to the peak heights of GW flux,with opposite directions.This observational evidence is consistent with the filtering theory.The horizontal wind velocity,GW flux,and disturbance variance of the GW at Mohe are overall smaller than those at Zuoling,indicating weaker activities in the MLT at Mohe.The power spectral density(PSD)calculated by the Lomb−Scargle periodogram shows that there are 12-month period and 6-month period in horizontal wind field,GW disturbance variance and GW flux at both stations,and especially there is also a 4-month cycle in the disturbance variance.The PSD of the 12-month and 6-month cycles exhibits maximum values below 88 km and above 94 km.
