We present new optical reflectance spectra of three potentially silicate-rich trans-Neptunian objects (TNOs). These spectra were obtained with the aim of confirming past hints and detections of λ ∼ 0.7 μm absorption features associated with the presence of iron-bearing phyllosilicates. Our new spectrum of 120216 (2004 EW₉₅) presents clearly detected absorption features that are similar in shape to hydrated mineral absorption bands present in the spectra of aqueously altered outer main belt asteroids. Four new reflectance spectra of 208996 (2003 AZ₈₄) obtained at separate epochs all appear featureless, but they vary significantly in spectral gradient (between ∼3.5%/0.1 μm and ∼8.5%/0.1 μm) on a timescale consistent with this object’s nominal rotational period. We report the first four optical reflectance spectra of 90568 (2004 GV₉), finding them all to be featureless but consistent with colors previously reported for this object. We speculate that impacts are the only mechanism capable of delivering, excavating, or forming hydrated minerals at the surfaces of TNOs in detectable concentrations; as a result, any deposits of hydrated minerals on TNOs are predicted to be localized and associated with impact sites. Globally altered TNOs (as observationally suggested for 2004 EW₉₅) plausibly formed more easily at smaller heliocentric distances (r _H < 15 au) before being transplanted into the current trans-Neptunian population.

中文翻译：

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在海王星外天体上寻找水合矿物

我们提出了三个可能富含硅酸盐的海王星外天体（TNO）的新光学反射光谱。获得这些光谱的目的是为了确认过去的暗示和检测λ〜0.7μm 吸收特征与含铁页硅酸盐的存在相关。我们的新光谱 120216 (2004 EW ₉₅ ) 呈现出清晰检测到的吸收特征，其形状与水蚀外主带小行星光谱中存在的水合矿物吸收带相似。在不同时期获得的208996 (2003 AZ ₈₄ ) 的四个新反射光谱都显得没有特征，但它们的光谱梯度变化很大（~3.5%/0.1 之间）μ米和~8.5%/0.1μm) 在与该物体的标称旋转周期一致的时间尺度上。_{我们报告了 90568 (2004 GV 9} )的前四个光学反射光谱，发现它们都没有特征，但与之前报告的该物体的颜色一致。我们推测，撞击是唯一能够在 TNO 表面输送、挖掘或形成可检测浓度的水合矿物的机制；因此，TNO 上的任何水合矿物沉积物预计都将是局部的并与撞击地点有关。全球变化的 TNO（如 2004 年 EW ₉₅的观测结果所示）似乎在较小的日心距离处更容易形成（r _H < 15 au)，然后被移植到当前的跨海王星种群中。