And in fact, New Horizons does see large very dark regions on Pluto that might be made up of
these photochemical products, generated when the methane in Pluto's atmosphere absorbs ultraviolet sunlight.
Powell, K. J., Richens, J. L., Bramble, J. P., Han L. - C., Sharma, P., O'Shea P. and Moses, J. E.,
Photochemical activity of membrane - localised polyketide derived marine natural
products, Tetrahedron, 2017, 74, 1191.