Iron meteorites as remnants of planetesimals formed in the terrestrial planet region
Iron meteorites as remnants of planetesimals formed in the terrestrial planet region
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DOI：
10.1038/nature04536
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发表时间：
2006-02-16
期刊：
影响因子：
64.8
通讯作者：
O'Brien, DP
中科院分区：
文献类型：
--
作者：
Bottke, WF;Nesvorny, D;O'Brien, DP
铁陨石是来自分化和随后分裂的星子的核心碎片（1）。母体通常被认为是在主小行星带形成的，这是大多数陨石的来源。然而，观察证据并不表明分化的身体或其碎片在那里曾经很常见。这种观点也很难与铁陨石的母体直径小至20公里（2，3），并且它们比普通陨石的母体早形成1-2百万年（4-6）的事实相一致。在这里，我们表明，铁陨石母体最有可能形成在类地行星区域。在太阳系历史的早期，快速的吸积时间允许小的微行星通过短寿命放射性核素（如Al-26，Fe-60）的衰变而融化（7-9）。从这个种群中出现的原行星不仅引起了剩余星子之间的碰撞演化，而且还将一些幸存者分散到主带中，在那里它们停留了数十亿年，然后通过碰撞，Yarkovsky热力学和共振的组合逃离。我们预测有些小行星是主带的闯入者（如（4）灶神星）。其中一些甚至可能是形成地球的失落已久的前体物质的残留物。
Iron meteorites are core fragments from differentiated and subsequently disrupted planetesimals(1). The parent bodies are usually assumed to have formed in the main asteroid belt, which is the source of most meteorites. Observational evidence, however, does not indicate that differentiated bodies or their fragments were ever common there. This view is also difficult to reconcile with the fact that the parent bodies of iron meteorites were as small as 20 km in diameter(2,3) and that they formed 1-2 Myr earlier than the parent bodies of the ordinary chondrites(4-6). Here we show that the iron-meteorite parent bodies most probably formed in the terrestrial planet region. Fast accretion times there allowed small planetesimals to melt early in Solar System history by the decay of short-lived radionuclides ( such as Al-26, Fe-60)(7-9). The protoplanets emerging from this population not only induced collisional evolution among the remaining planetesimals but also scattered some of the survivors into the main belt, where they stayed for billions of years before escaping via a combination of collisions, Yarkovsky thermal forces, and resonances(10). We predict that some asteroids are main-belt interlopers ( such as ( 4) Vesta). A select few may even be remnants of the long-lost precursor material that formed the Earth.