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arXiv 1003.2580astro-ph.EP
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内主带HED陨石和V型小行星的光谱比较

A Spectroscopic Comparison of HED Meteorites and V-type Asteroids in the Inner Main Belt

Nicholas Moskovitz, Mark Willman, Thomas Burbine, Richard Binzel, Schelte Bus

摘要:

内主带的V型小行星(a < 2.5天文单位)和HED陨石被认为是来自大型玄武质小行星4灶神星表面的碰撞碎片,在遗传学上彼此相关。我们通过比较39颗V型小行星的近红外(0.7-2.5微米)光谱与HED陨石的实验室光谱来研究这种关系。中心波长和面积跨越1和2微米的辉石橄榄石吸收带的行星玄武岩的特点是测量小行星和陨石的数据。谱带中心的相关性很好,但是小行星的1微米和2微米吸收谱带所占的面积比要比陨石大得多。我们认为,这种带面积比的偏移与我们目前对空间风化作用的有限理解是一致的,但是我们不能排除这种偏移是由于成分差异造成的可能性。这种偏移的其他几个可能的原因进行了讨论。在这些主带内的小行星中,我们没有发现非Vestoid矿物的证据。相反,这些小行星似乎代表了一个连续的组成,与来自单一分化母体的起源一致。此外,我们的分析表明,具有低倾角(i < 6度)的V型小行星往往具有向长波长轻微移动的带中心。这可能意味着灶神星表面不止一次的碰撞是产生观测到的内带V型小行星群的原因。最后,我们提供了几个预测,可以测试时,黎明飞船进入轨道灶神星在2011年夏天。

英文摘要:

V-type asteroids in the inner Main Belt (a < 2.5 AU) and the HED meteorites are thought to be genetically related to one another as collisional fragments from the surface of the large basaltic asteroid 4 Vesta. We investigate this relationship by comparing the near-infrared (0.7-2.5 micron) spectra of 39 V-type asteroids to laboratory spectra of HED meteorites. The central wavelengths and areas spanned by the 1 and 2 micron pyroxene-olivine absorption bands that are characteristic of planetary basalts are measured for both the asteroidal and meteoritic data. The band centers are shown to be well correlated, however the ratio of areas spanned by the 1 and 2 micron absorption bands are much larger for the asteroids than for the meteorites. We argue that this offset in band area ratio is consistent with our currently limited understanding of the effects of space weathering, however we can not rule out the possibility that this offset is due to compositional differences. Several other possible causes of this offset are discussed. Amongst these inner Main Belt asteroids we do not find evidence for non-Vestoid mineralogies. Instead, these asteroids seem to represent a continuum of compositions, consistent with an origin from a single differentiated parent body. In addition, our analysis shows that V-type asteroids with low inclinations (i < 6 degrees) tend to have band centers slightly shifted towards long wavelengths. This may imply that more than one collision on Vesta's surface was responsible for producing the observed population of inner belt V-type asteroids. Finally, we offer several predictions that can be tested when the Dawn spacecraft enters into orbit around Vesta in the summer of 2011.

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