title: Reflectance and color variations on Mercury: regolith processes and compositional heterogeneity.
abstract: Multispectral images of Mercury obtained by the MESSENGER spacecraft reveal that its surface has an overall relatively low reflectance with three large-scale units identified on the basis of reflectance and slope (0.4 to 1.0 micrometer). A higher-reflectance, relatively red material occurs as a distinct class of smooth plains that were likely emplaced volcanically; a lower-reflectance material with a lesser spectral slope may represent a distinct crustal component enriched in opaque minerals, possibly more common at depth. A spectrally intermediate terrain probably forms most of the upper crust. Three other spectrally distinct but spatially restricted units include fresh crater ejecta less affected by space weathering than other surface materials; high-reflectance deposits seen in some crater floors; and moderately high-reflectance, relatively reddish material associated with rimless depressions.
authors.affiliation: School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA. robinson@ser.asu.edu
authors.forename: Mark S
authors.initials: MS
authors.lastname: Robinson
authors.forename: Scott L
authors.initials: SL
authors.lastname: Murchie
authors.forename: David T
authors.initials: DT
authors.lastname: Blewett
authors.forename: Deborah L
authors.initials: DL
authors.lastname: Domingue
authors.forename: S Edward
authors.initials: SE
authors.lastname: Hawkins
authors.forename: James W
authors.initials: JW
authors.lastname: Head
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Holsclaw
authors.forename: William E
authors.initials: WE
authors.lastname: McClintock
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: McCoy
authors.forename: Ralph L
authors.initials: RL
authors.lastname: McNutt
authors.forename: Louise M
authors.initials: LM
authors.lastname: Prockter
authors.forename: Sean C
authors.initials: SC
authors.lastname: Solomon
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Watters