标题： 谷神星永久阴影陨石坑中明亮沉积物的光谱特性 显示英文标题

标题： Spectral properties of bright deposits in permanently shadowed craters on Ceres

摘要： 谷神星永久阴影陨坑中的明亮沉积物被认为含有水冰。然而，迄今为止提供的水冰证据是间接的。 我们旨在直接探测谷神星极地陨坑永久阴影区域（PSRs）中存在的明亮沉积物中水冰的光谱特征。 我们分析了黎明号摄像机获取的四个最大阴影明亮沉积物的窄带图像，以重建它们的反射光谱，并仔细考虑了现场杂散光校正和图像压缩伪影等问题。 已知含有水冰的极地沉积物被阳光照射的部分在可见波长范围内相对于背景具有负（蓝色）的$-58 \pm 12$%$\mu$米$^{-1}$光谱斜率。 我们发现PSR明亮沉积物具有类似的蓝色光谱斜率，与水冰成分一致。 根据亮度和光谱特性，我们认为冰很可能以高纯度颗粒形式存在。 其他成分如层状硅酸盐可能与冰混合在一起。 鉴于盐类与低温火山活动有关，而我们未发现其痕迹，因此盐类不太可能是亮化剂。 我们的光谱分析加强了谷神星永久阴影陨坑中存在水冰的观点。 显示英文摘要

摘要： Bright deposits in permanently shadowed craters on Ceres are thought to harbor water ice. However, the evidence for water ice presented thus far is indirect. We aim to directly detect the spectral characteristics of water ice in bright deposits present in permanently shadowed regions (PSRs) in polar craters on Ceres. We analyzed narrowband images of four of the largest shadowed bright deposits acquired by the Dawn Framing Camera to reconstruct their reflectance spectra, carefully considering issues such as in-field stray light correction and image compression artifacts. The sunlit portion of a polar deposit known to harbor water ice has a negative (blue) spectral slope of $-58 \pm 12$ % $\mu$m$^{-1}$ relative to the background in the visible wavelength range. We find that the PSR bright deposits have similarly blue spectral slopes, consistent with a water ice composition. Based on the brightness and spectral properties, we argue that the ice is likely present as particles of high purity. Other components such as phyllosilicates may be mixed in with the ice. Salts are an unlikely brightening agent given their association with cryovolcanic processes, of which we find no trace. Our spectral analysis strengthens the case for the presence of water ice in permanently shadowed craters on Ceres.