10 January 1997
Vol 275, Issue 5297

About The Cover

Recalibration and mosaicking of Mariner 10 images, acquired in 1974, have allowed the identification of distinct geologic units on the surface of Mercury. Color trends inferred to be dominantly controlled by variations in iron content, opaque mineral abundance, and regolith maturity were used to identify volcanically emplaced material, which is indicative of complex differentiation of the interior as has occurred on the other terrestrial planets and the moon. See page 197. [Image: M. S. Robinson and P. G. Lucey]