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arXiv 1507.01008astro-ph.EP
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潜在危险小行星(214869)2007 PA8的组成:来自外部小行星带的一颗H球粒陨石

Composition of Potentially Hazardous Asteroid (214869) 2007 PA8: An H Chondrite from the Outer Asteroid Belt

Juan A. Sanchez, Vishnu Reddy, Melissa Dykhuis, Sean Lindsay, Lucille Le Corre

摘要:

有潜在危险的小行星是在其接近地球期间进行物理特性鉴定的一个独特机会。这些小行星的距离很近,使它们能够进行采样返回和载人飞行任务,但如果发生碰撞,也可能对地球上的生命构成风险。因此,详细的矿物学分析是规划未来勘探任务和制定适当缓解战略的关键组成部分。在这项研究中,我们提出了近红外光谱(0.7-2.55微米)的PHA(214869)2007 PA 8获得与美国宇航局红外望远镜设施在其接近地球的2012年11月。对这颗小行星的矿物学分析显示,其表面成分与普通的H型陨石一致。特别地,我们发现2007 PA 8的橄榄石和辉石化学分别是Fa 18(Fo 82)和Fs 16。橄榄石-辉石丰度比估计为47%。这一低橄榄石丰度和测量的带参数,接近H4和H5方解石,表明2007年PA 8的母体经历了热变质,然后才被灾难性地破坏。根据组成的亲和力,接近J5:2共振,估计通量的共振对象,我们确定的Koronis家庭是最有可能的源区2007年PA 8。

英文摘要:

Potentially hazardous asteroids (PHAs) represent a unique opportunity for physical characterization during their close approaches to Earth. The proximity of these asteroids makes them accessible for sample-return and manned missions, but could also represent a risk for life on Earth in the event of collision. Therefore, a detailed mineralogical analysis is a key component in planning future exploration missions and developing appropriate mitigation strategies. In this study we present near-infrared spectra (0.7-2.55 microns) of PHA (214869) 2007 PA8 obtained with the NASA Infrared Telescope Facility during its close approach to Earth on November 2012. The mineralogical analysis of this asteroid revealed a surface composition consistent with H ordinary chondrites. In particular, we found that the olivine and pyroxene chemistries of 2007 PA8 are Fa18(Fo82) and Fs16, respectively. The olivine-pyroxene abundance ratio was estimated to be 47%. This low olivine abundance and the measured band parameters, close to the H4 and H5 chondrites, suggest that the parent body of 2007 PA8 experienced thermal metamorphism before being catastrophically disrupted. Based on the compositional affinity, proximity to the J5:2 resonance, and estimated flux of resonant objects we determined that the Koronis family is the most likely source region for 2007 PA8.

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