We identify and document the instances of bright ephemeral features (BEF)—bright areas that appear, disappear, and shift from flyby to flyby on Titan's north pole, using the Cassini Visual and Infrared Mapping Spectrometer data set, thereby developing a sense of their spatial distribution and temporal frequency. We find that BEFs have differing geographic location and spatial extents. However, they have similar observation geometries and orders of surface area coverage and are mostly accompanied by specular reflections. We find the BEFs to represent either broad specular reflection off of a recently wetted surface on the north pole of Titan or a near-surface fog—both owing to probable recent rainfalls. Our surface model constrains the surface roughness to be of 9°–15° indicating the approximate vertical relief of the region to be that of cobbles. We also find that within less than two Titan days the BEF (if on the surface) might infiltrate into the subsurface. We hypothesize the...

中文翻译：

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土卫六北极明亮的临时特征的时空变化

我们使用卡西尼视觉和红外映射光谱仪数据集，识别并记录了明亮的短暂特征（BEF）的实例-明亮的区域出现，消失并在土卫六的北极上从一处掠过到另一处掠过，从而发展了它们的空间感分布和时间频率。我们发现BEF具有不同的地理位置和空间范围。但是，它们具有相似的观测几何形状和表面积覆盖范围的顺序，并且大多伴随着镜面反射。我们发现，BEFs代表了土卫六北极上最近被润湿的地表的宽镜面反射或近地表雾（均由于近期降雨）。我们的表面模型将表面粗糙度限制为9°–15°，表明该区域的近似垂直起伏为卵石区域。我们还发现，在不到土卫六天之内，BEF（如果在地表）可能会渗入地下。我们假设...