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Density distribution of asteroid 25143 Itokawa based on smooth terrain shape

机译：小行星25143基于光滑地形形状的小行星分布

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摘要

The shape and internal structure of an asteroid is a result of its violent collisional history, and Asteroid 25143 Itokawa is an important target for investigating the internal structure and formation processes associated with rubble pile asteroids. The surface of Itokawa contains numerous boulders and is very rough, but 20% of the surface is covered with centimeter-sized gravels that are called "smooth terrain". These flat areas are associated with low areas of the gravitational potential and are considered to be formed by down-slope migration and accumulation of pebbles. We propose a method to constrain the interior density distribution of an asteroid by modeling the gravity field and fitting the smooth terrains to equi-potential surfaces. Density models that are composed of two distinct lobes best explain the data if the "head" and "body" have different densities of 2,450 kg/m(3) and 1,930 kg/m(3), respectively. Alternatively, the two lobes could have comparable densities if there was a compressed "neck" of higher density between the two. Three layer models that treat the densities of the head, neck and body separately are largely unconstrained. However, when using an independent estimate of the center-of-mass/center-of-figure offset as determined from modeling the YORP spin-up of Itokawa, our models require the density of the head to be larger than the global average.
机译：小行星的形状和内部结构是其剧烈的碰撞历史的结果，小行星25143 Itokawa是研究与瓦砾桩小行星相关的内部结构和形成过程的重要靶标。 Itokawa的表面含有许多巨石，非常粗糙，但20％的表面覆盖有被称为“平滑地形”的厘米大小的砾石。这些平坦区域与重力电位的低区域相关联，并且被认为是通过下坡迁移和鹅卵石的积累形成的。我们提出了一种通过模拟重力场来限制小行星的内部密度分布，并将光滑的地形拟合到平等电位表面来限制小行星的内部密度分布。如果“头部”和“身体”分别具有2,450kg / m（3）和1,930kg / m（3）的不同密度，则由两个不同的裂片组成的密度模型最佳地解释数据。或者，如果在两者之间存在压缩的“颈部”，则两个凸起可以具有相当的密度。一种处理头部，颈部和身体密度的三层模型在很大程度上是无约束的。然而，当使用从模型型号的伊托克旋转的模型中确定了质量估计的质量估计，我们的模型需要头部的密度大于全局平均值。

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