Pluto: Evidence for Methane Frost

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Science  19 Nov 1976:
Vol. 194, Issue 4267, pp. 835-837
DOI: 10.1126/science.194.4267.835-a


Infrared photometry (1.2 to 2.2 micrometers) of Pluto provides evidence for frozen methane on the surface of the planet. This appears to be the first observational indication of this ice in the solar system. Its presence on Pluto suggests that the planet's albedo (reflectance) may be ≥ 0.4 and that its diameter may be less than that of the moon.