The Main Belt Asteroid (16) Psyche is the target object of the NASA Discovery Mission Psyche. We observed the asteroid at ultraviolet (UV) wavelengths (170–310 nm) using the Space Telescope Imaging Spectrograph on the Hubble Space Telescope during two separate observations. We report that the spectrum is very red in the UV, with a blue upturn shortward of ∼200 nm. We find an absorption feature at 250 nm and a weaker absorption feature at 275 nm that may be attributed to a metal-oxide charge transfer band. We find that the red-sloped, relatively featureless spectrum of (16) Psyche is best matched with the reflectance spectrum of pure iron; however, our intimate mixture models show that small grains of iron may dominate the reflectance spectrum even if iron only comprises up to 10% of the material on the surface. We also stress that there is a limited database of reflectances for planetary surface analogs at UV wavelengths for comparison with the spectrum of (16) Psyche. The mid- and far-UV spectra (<240 nm) are markedly different for each of the four asteroids observed at these wavelengths so far, including ones in the same spectral class, indicating that UV observations of asteroids could be used to better understand differences in the composition and processing of the surfaces of these small bodies.

主带小行星 (16) Psyche 是 NASA 发现任务 Psyche 的目标天体。在两次单独的观测中，我们使用哈勃太空望远镜上的太空望远镜成像光谱仪在紫外线 (UV) 波长 (170–310 nm) 下观测了这颗小行星。我们报告说，光谱在紫外光下非常红，在大约 200 nm 处有一个蓝色上调。我们发现 250 nm 处的吸收特征和 275 nm 处较弱的吸收特征，这可能归因于金属氧化物电荷转移带。我们发现 (16) Psyche 的红色倾斜、相对无特征的光谱与纯铁的反射光谱最匹配；然而，我们的紧密混合模型表明，即使铁仅占表面材料的 10%，小铁颗粒也可能主导反射光谱。我们还强调，用于与 (16) Psyche 的光谱进行比较的行星表面类似物在紫外线波长下的反射率数据库有限。迄今为止，在这些波长下观测到的四颗小行星的中远紫外光谱（<240 nm）都显着不同，包括同一光谱类别的小行星，这表明小行星的紫外观测可用于更好地了解差异在这些小物体表面的组成和加工中。