The Peculiar Volatile Composition of Comet 8P/Tuttle: A Contact Binary of Chemically Distinct Cometesimals?
The Peculiar Volatile Composition of Comet 8P/Tuttle: A Contact Binary of Chemically Distinct Cometesimals?
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彗星 8P/塔特尔的特殊挥发性成分：化学上不同的彗星子的接触双星？
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发表时间：
2008
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通讯作者：
G. Villanueva
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作者：
B. Bonev;M. Mumma;Y. Radeva;M. DiSanti;E. Gibb;G. Villanueva
我们报告了使用 Keck 2 的 NIRSPEC 对彗星 8P/Tuttle 中八种天然（即直接从彗核释放的）挥发物（H2O、HCN、CH4、C2H2、C2H6、CO、H2CO 和 CH3OH）的测量结果。塔特尔彗星揭示了一种真正不寻常的成分，与迄今为止在红外波长观察到的任何彗星的成分不同。甲醇相对于水的显着富集与其他分子（尤其是 C2H2、HCN 和 H2CO）的消耗形成鲜明对比。我们认为 8P/Tuttle 的核可能包含两个具有不同挥发性成分的彗星子。 8P/Tuttle 中 C2/CN、C2/OH 和 CN/OH 的相对丰度（在光学/近紫外波长下测量）与其潜在母体（C2H2/HCN、C2H2/H2O 和 HCN/H2O）的混合比在本工作中发现有很大不同。基于此比较，我们的结果不支持 C2H2 和 HCN 分别是 Tuttle 中 C2 和 CN 的主要前体。在 8P/塔特尔中观察到的奇特的天然成分（与其他彗星相比）为彗星核中储存的挥发性物质的化学多样性提供了新的有力证据。我们讨论了这种多样性对彗星中水氘富集预期变化的影响。
We report measurements of eight native (i.e., released directly from the comet nucleus) volatiles (H2O, HCN, CH4, C2H2, C2H6, CO, H2CO, and CH3OH) in comet 8P/Tuttle using NIRSPEC at Keck 2. Comet Tuttle reveals a truly unusual composition, distinct from that of any comet observed to date at infrared wavelengths. The prominent enrichment of methanol relative to water contrasts with the depletions of other molecules, especially C2H2, HCN, and H2CO. We suggest that the nucleus of 8P/Tuttle may contain two cometesimals characterized by distinct volatile composition. The relative abundances C2/CN, C2/OH, and CN/OH in 8P/Tuttle (measured at optical/near-UV wavelengths) differ substantially from the mixing ratios of their potential parents (C2H2/HCN, C2H2/H2O, and HCN/H2O) found in this work. Based on this comparison, our results do not support C2H2 and HCN being the principal precursors for respectively C2 and CN in Tuttle. The peculiar native composition observed in 8P/Tuttle (compared to other comets) provides new strong evidence for chemical diversity in the volatile materials stored in comet nuclei. We discuss the implications of this diversity for expected variations in the deuterium enrichment of water among comets.