Science. 1987 Sep 11;237(4820):1349-51. doi: 10.1126/science.237.4820.1349.
The 3 March 1987 Charon occultation by Pluto was observed in the infrared at 1.5, 1.7, 2.0, and 2.35 micrometers. Subtraction of fluxes measured between second and third contacts from measurements made before and after the event has yielded individual spectral signatures for each body at these wavelengths. Charon's surface appears depleted in methane relative to Pluto. Constancy of flux at 2.0 micrometers throughout the event shows that Charon is effectively black at this wavelength, which is centered on a very strong water absorption band. Thus, the measurements suggest the existence of water ice on Pluto's moon.
1987 年 3 月 3 日，冥王星的“卡戎”掩星现象在红外波段 1.5、1.7、2.0 和 2.35 微米处被观测到。通过从事件前后的测量值中减去第二和第三接触之间测量的通量，在这些波长下获得了每个天体的单独光谱特征。“卡戎”的表面相对于冥王星来说，甲烷含量较低。在整个事件过程中，2.0 微米处的通量保持不变，表明“卡戎”在这个波长上是有效的黑色，该波长中心位于一个非常强的水吸收带。因此，这些测量结果表明冥王星的卫星上存在水冰。
