MITHNEOS的去偏成分分布：近地和主带小行星群与过量D型近地天体之间的全球匹配
The debiased compositional distribution of MITHNEOS: Global match between the near-Earth and main-belt asteroid populations and excess of D-type Near-Earth Objects
摘要：
我们报告了对420个近地天体的491个新的近红外光谱测量结果，这些测量结果是在美国航天局红外望远镜设施上收集的，是麻省理工学院-夏威夷近地天体光谱测量的一部分。这些测量结果与先前公布的数据（Binzel等人，2019年）相结合，并进行了偏差校正，以得出整个近地天体群以及来自小行星带及以外的各种逃逸路线的子群的固有组成分布。由此产生的分布很好地反映了小行星带的整体成分梯度，减少分数的硅酸盐丰富（S-和Q-型）机构和增加分数的碳质（B-，C-，D-和P-型）机构作为一个功能，增加ER距离太阳。近地天体与其预测的来源群体之间的组成密切吻合，证实了用于识别地球辐射的动力学模型的正确性，并反驳了小行星带中约5公里至约100米之间的小行星的组成随大小而发生任何强烈变化的说法。一个明显的例外是5：2 J的D型近地天体过多，3：1 J和nu 6 ER的D型近地天体数量较少，这表明主带中存在大量的D型小行星。或者，这种过量可能表明，由于空间风化，光谱优先从D型表面演变为C型和P型，或者表明，在近地天体空间，D型天体比其他光谱型天体更容易碎裂。在这项工作中，没有发现在主带中存在碰撞族的进一步证据，低于当前主带调查的检测限。
英文摘要：
We report 491 new near-infrared spectroscopic measurements of 420 near-Earth objects (NEOs) collected on the NASA InfraRed Telescope Facility (IRTF) as part of the MIT-Hawaii NEO Spectroscopic Survey (MITHNEOS). These measurements were combined with previously published data (Binzel et al. 2019) and bias-corrected to derive the intrinsic compositional distribution of the overall NEO population, as well as of subpopulations coming from various escape routes (ERs) in the asteroid belt and beyond. The resulting distributions reflect well the overall compositional gradient of the asteroid belt, with decreasing fractions of silicate-rich (S- and Q-type) bodies and increasing fractions of carbonaceous (B-, C-, D- and P-type) bodies as a function of increasing ER distance from the Sun. The close compositional match between NEOs and their predicted source populations validates dynamical models used to identify ERs and argues against any strong composition change with size in the asteroid belt between ~5 km down to ~100 m. A notable exception comes from the over-abundance of D-type NEOs from the 5:2J and, to a lesser extend, the 3:1J and nu6 ERs, hinting at the presence of a large population of small D-type asteroids in the main belt. Alternatively, this excess may indicate preferential spectral evolution from D-type surfaces to C- and P-types as a consequence of space weathering, or to the fact that D-type objects fragment more often than other spectral types in the NEO space. No further evidence for the existence of collisional families in the main belt, below the detection limit of current main-belt surveys, was found in this work.
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