深入冰冷的矮行星厄里斯的表面
Digging Into the Surface of the Icy Dwarf Planet Eris
摘要：
本文描述了用6.5米MMT望远镜和红通道摄谱仪对冰质矮行星厄里斯的光谱观测。我们报告的相关性，这是在边缘的统计意义，蓝移和最大吸收的五个甲烷冰带之间。我们解释的相关性作为一个增加稀释的甲烷冰与另一种冰成分，可能是氮，随着深度增加到表面。我们提出了一种机制来解释氮随深度的明显增加。具体地说，如果我们看到厄里斯50度从极点（布朗和Sjerier，2008），我们现在看到的极点在远日点是在冬季黑暗的近日点。在近日点附近，升华可能在阳光照射的（夏季）半球上建立起足够的大气压力，将风吹向黑暗的（冬季）半球，在那里风会凝结。因为氮比甲烷更易挥发，也更稀少，所以它在这个季节相对较早的时候就从有阳光照射的半球升华了，所以初夏的大气中富含氮，冬季极地上沉积的冰也是如此。在这个季节的晚些时候，大部分的氮从夏季极点耗尽，但还有大量的甲烷，甲烷继续升华。在这一点上，大气中的氮更加枯竭，因为冰冻结在早期沉积的富含氮的冰之上。
英文摘要：
We describe optical spectroscopic observations of the icy dwarf planet Eris with the 6.5 meter MMT telescope and the Red Channel Spectrograph. We report a correlation, that is at the edge of statistical significance, between blue shift and albedo at maximum absorption for five methane ice bands. We interpret the correlation as an increasing dilution of methane ice with another ice component, probably nitrogen, with increasing depth into the surface. We suggest a mechanism to explain the apparent increase in nitrogen with depth. Specifically, if we are seeing Eris 50 degrees from pole-on (Brown and Schaller, 2008), the pole we are seeing now at aphelion was in winter darkness at perihelion. Near perihelion, sublimation could have built up atmospheric pressure on the sunlit (summer) hemisphere sufficient to drive winds toward the dark (winter) hemisphere, where the winds would condense. Because nitrogen is more volatile and scarcer than methane, it sublimated from the sunlit hemisphere relatively early in the season, so the early summer atmosphere was nitrogen rich, and so was the ice deposited on the winter pole. Later in the season, much of the nitrogen was exhausted from the summer pole, but there was plenty of methane, which continued to sublimate. At this point, the atmosphere was more depleted in nitrogen, as was the ice freezing out on top of the earlier deposited nitrogen rich ice.
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