The Memory of Whiteness is a science fiction novel written by Kim Stanley Robinson and published in 1985. It shares with the Mars trilogy a focus on human colonization of the solar system and depicts a grand tour that travels from the outer planets inward toward the Sun, visiting many human colonies along the way. The different human societies on the various planets and planetoids visited are depicted in detail. The purpose of the tour is to stage concerts by the 'Holywelkin Orchestra', a futuristic musical instrument played by a selected master. Readers follow the Orchestra and its entourage together with a journalist, who after some time detects a conspiracy that seems to be connected with a group of gray-clad, sun-worshipping monks. The tour ends near the planet Mercury in a solar station belonging to these "Grays", which controls the white line energy source for the whole solar system.