Prior to 2009, the surface of the Moon was believed to be anhydrous. However, observations by three spacecraft revealed a hydrated surface by reporting a 3 μm absorption band attributed to hydroxyl and possibly molecular water. The Moon Mineralogy Mapper (M³) spectrometer on board the Chandrayaan‐1 spacecraft has been used to study the lunar 3 μm band, but its spectral range ends at 3 μm. The limited wavelength range of M³ has allowed observed variations in the strength of the 3 μm band to be called into question due to uncertainties in thermal corrections. To investigate the validity of variations in the lunar 3 μm band, we used the SpeX infrared spectrograph at the NASA InfraRed Telescope Facility at Maunakea Observatory in Hawai‘i. With SpeX, we are able to obtain lunar data over a wavelength range of 1.67 to 4.2 μm at 1–2 km spatial resolution. The long wavelengths provide strong constraints on separating thermal emission from solar reflectance. We confirm that the 3 μm band varies with lunar time of day as well as with latitude and composition. Pole‐to‐pole observation chords reveal strong variations in abundances of hydroxyl and possibly molecular water. The data reveal a decrease in abundance as lunar noon is approached, an asymmetric trend about the equator that favors the southern latitudes, and higher concentrations in highland regions. The longer wavelengths provided by SpeX have allowed us to examine variations in the 3 μm band and provide definitive evidence that the variations are due to changes in hydration.

中文翻译：

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望远镜观测月水合作用：变化和丰度

在2009年之前，月球表面被认为是无水的。但是，三个航天器的观测结果表明，由于羟基和分子水可能吸收了3μm的吸收带，从而发现了水合表面。Chandrayaan-1航天器上的月亮矿物制图仪（M ³）光谱仪已用于研究3μm的月球波段，但其光谱范围以3μm结尾。M ³的有限波长范围由于热校正的不确定性，已经允许观察到的3μm波段强度的变化受到质疑。为了调查月球3μm波段变化的有效性，我们在夏威夷毛纳基阿天文台的NASA红外望远镜设施上使用了SpeX红外光谱仪。借助SpeX，我们可以在1至2 km的空间分辨率下获得1.67至4.2μm波长范围内的月球数据。长波长对将热辐射与太阳反射区分开提供了严格的限制。我们确认3μm波段随一天的阴历时间以及纬度和成分的变化而变化。极对极观测和弦显示羟基和可能的分子水的丰度变化很大。数据显示随着临近中午，丰度有所下降，赤道偏向南部纬度的不对称趋势，以及高原地区的集中度较高。SpeX提供的更长波长使我们能够检查3μm波段的变化，并提供确凿的证据表明该变化是由于水合变化所致。