标题： 土卫六南极雾的发现 显示英文标题

标题： Discovery of fog at the south pole of Titan

摘要： 尽管土卫六泰坦似乎支持活跃的甲烷水文循环，但尚未出现地表与大气之间交换的直接证据。 有可能这些被识别出的湖泊特征可能充满了乙烷——这是大气光解的长期不稳定残留物；表面上看来像溪流和河道的特征可能是来自以前气候时期的古老特征；而对流层中的甲烷云虽然频繁出现，却可能从未导致降水到达地表。 我们在此报告，在土卫六的夏末，利用卡西尼号飞船上的VIMS仪器观测到南极大雾的情况。 虽然地球上的雾可以由多种原因形成，但在土卫六上这些过程大多无法实现。 土卫六上的雾只能由液态甲烷蒸发形成；雾的检测首次直接将地表和大气中的甲烷联系起来。 基于此处所展示的检测结果，在土卫六晚夏的南半球，液态甲烷似乎分布广泛，土卫六的水文循环目前仍然活跃。 显示英文摘要

摘要： While Saturn's moon Titan appears to support an active methane hydrological cycle, no direct evidence for surface-atmosphere exchange has yet appeared. It is possible that the identified lake-features could be filled with ethane, an involatile long term residue of atmospheric photolysis; the apparent stream and channel features could be ancient from a previous climate; and the tropospheric methane clouds, while frequent, could cause no rain to reach the surface. We report here the detection of fog at the south pole of Titan during late summer using observations from the VIMS instrument on board the Cassini spacecraft. While terrestrial fog can form from a variety of causes, most of these processes are inoperable on Titan. Fog on Titan can only be caused by evaporation of liquid methane; the detection of fog provides the first direct link between surface and atmospheric methane. Based on the detections presented here, liquid methane appears widespread at the south pole of Titan in late southern summer, and the hydrolgical cycle on Titan is current active.