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arXiv 0908.2623astro-ph.EP
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用IRTF/SpeX II近红外光谱监测海卫一：冰的空间分布和演化

Near-Infrared Spectral Monitoring of Triton with IRTF/SpeX II: Spatial Distribution and Evolution of Ices

W. M. Grundy, L. A. Young, J. A. Stansberry, M. W. Buie, C. B. Olkin, E. F. Young

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22 pages, 13 figures, 5 tables, to appear in Icarus
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摘要：

这份报告来自一个正在进行的项目，该项目使用IRTF/SpeX在0.8至2.4微米范围内对海王星最大的卫星海卫一进行光谱监测。我们的目标是寻找海卫一的表面上的变化所见证的变化，其表面冰N2，CH 4，H2O，CO和CO2的红外吸收带。我们记录了海卫一在2000年至2009年的10次显灵中的53个夜晚的红外光谱。这些数据基本上证实了我们先前报道的冰吸收带的昼夜光谱变化（Grundy & Young 2004）。氮冰显示出很大的振幅变化，海卫一面向海王星的半球具有更强的吸收。我们提出了海卫一的N2冰的季节性演变的证据：2.15微米的吸收带似乎正在减少，特别是在海王星面临的半球。虽然海卫一的CH 4冰大部分溶解在N2冰中，但它显示出与N2冰非常不同的纵向变化，挑战了两种冰如何表现的假设。与Triton的CH 4冰不同，CO冰的纵向变化与N2冰非常相似，这意味着CO和N2凝结和升华在一起，保持一致的混合比例。水和CO2冰的吸收表现出可以忽略不计的变化，海卫一旋转，这意味着非常均匀和/或高纬度的空间分布，这两个非挥发性的冰。

英文摘要：

This report arises from an ongoing program to monitor Neptune's largest moon Triton spectroscopically in the 0.8 to 2.4 micron range using IRTF/SpeX. Our objective is to search for changes on Triton's surface as witnessed by changes in the infrared absorption bands of its surface ices N2, CH4, H2O, CO, and CO2. We have recorded infrared spectra of Triton on 53 nights over the ten apparitions from 2000 through 2009. The data generally confirm our previously reported diurnal spectral variations of the ice absorption bands (Grundy & Young 2004). Nitrogen ice shows a large amplitude variation, with much stronger absorption on Triton's Neptune-facing hemisphere. We present evidence for seasonal evolution of Triton's N2 ice: the 2.15 micron absorption band appears to be diminishing, especially on the Neptune-facing hemisphere. Although it is mostly dissolved in N2 ice, Triton's CH4 ice shows a very different longitudinal variation from the N2 ice, challenging assumptions of how the two ices behave. Unlike Triton's CH4 ice, the CO ice does exhibit longitudinal variation very similar to the N2 ice, implying that CO and N2 condense and sublimate together, maintaining a consistent mixing ratio. Absorptions by H2O and CO2 ices show negligible variation as Triton rotates, implying very uniform and/or high latitude spatial distributions for those two non-volatile ices.

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