Images from the Mercury Dual Imaging System (MDIS) aboard the MErcury Surface, Space ENvironment, GEochemistry, and Ranging mission reveal low-reflectance polar deposits that are interpreted to be lag deposits of organic-rich, volatile material. Interpretation of these highest-resolution images of Mercury’s polar deposits has been limited by the available topography models, so local high-resolution (125 m pixel⁻¹) digital elevation models (DEMs) were made using a combination of data from the Mercury Laser Altimeter (MLA) and from shape-from-shading techniques using MDIS images. Local DEMs were made for eight of Mercury’s north polar craters; these DEMs were then used to create high-resolution simulated image, illumination, and thermal models. The simulated images reveal that the pixel brightness variations imaged within Mercury’s low-reflectance deposits are consistent with scattered light reflecting off of topography and do not need to be explained by volatile compositional differences as previously suggested. The illumination and thermal models show that these low-reflectance polar deposits extend beyond the permanently shadowed region, more than 1.0 km in some locations, and correspond to a maximum surface temperature of greater than 250 K but less than 350 K. The low-reflectance boundaries of all eight polar deposits studied here show a close correspondence with the surface stability boundary of coronene (C₂₄H₁₂). While coronene should only be viewed as a proxy for the myriad volatile compounds that may exist in Mercury’s polar deposits, coronene’s surface stability boundary supports the idea that Mercury’s low-reflectance polar deposits are composed of macromolecular organic compounds, consistent with the hypotheses of exogenous transport and in situ production.

来自水星表面、空间环境、地球化学和测距任务上的水星双成像系统 (MDIS) 的图像揭示了低反射率极地沉积物，被解释为富含有机物的挥发性物质的滞后沉积物。对这些水星极地沉积物最高分辨率图像的解释受到可用地形模型的限制，因此局部高分辨率（125 m 像素^-1) 数字高程模型 (DEM) 是使用来自水星激光高度计 (MLA) 的数据和使用 MDIS 图像的阴影形状技术组合而成的。为水星北极的八个陨石坑制作了本地 DEM；然后使用这些 DEM 来创建高分辨率的模拟图像、照明和热模型。模拟图像显示，在水星的低反射率沉积物中成像的像素亮度变化与从地形反射的散射光一致，不需要像之前建议的那样用挥发性成分差异来解释。光照和热模型表明，这些低反射率极地沉积物延伸到永久阴影区域之外，在某些位置超过 1.0 公里，₂₄ ħ ₁₂）。虽然只能将晕苯视为可能存在于水星极地沉积物中的无数挥发性化合物的代表，但晕苯的表面稳定性边界支持水星的低反射极地沉积物由大分子有机化合物组成的观点，这与外源运输的假设一致并就地生产。