title: Hollows on Mercury: MESSENGER evidence for geologically recent volatile-related activity.
abstract: High-resolution images of Mercury's surface from orbit reveal that many bright deposits within impact craters exhibit fresh-appearing, irregular, shallow, rimless depressions. The depressions, or hollows, range from tens of meters to a few kilometers across, and many have high-reflectance interiors and halos. The host rocks, which are associated with crater central peaks, peak rings, floors, and walls, are interpreted to have been excavated from depth by the crater-forming process. The most likely formation mechanisms for the hollows involve recent loss of volatiles through some combination of sublimation, space weathering, outgassing, or pyroclastic volcanism. These features support the inference that Mercury's interior contains higher abundances of volatile materials than predicted by most scenarios for the formation of the solar system's innermost planet.
authors.affiliation: The Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA. david.blewett@jhuapl.edu
authors.forename: David T
authors.initials: DT
authors.lastname: Blewett
authors.forename: Nancy L
authors.initials: NL
authors.lastname: Chabot
authors.forename: Brett W
authors.initials: BW
authors.lastname: Denevi
authors.forename: Carolyn M
authors.initials: CM
authors.lastname: Ernst
authors.forename: James W
authors.initials: JW
authors.lastname: Head
authors.forename: Noam R
authors.initials: NR
authors.lastname: Izenberg
authors.forename: Scott L
authors.initials: SL
authors.lastname: Murchie
authors.forename: Sean C
authors.initials: SC
authors.lastname: Solomon
authors.forename: Larry R
authors.initials: LR
authors.lastname: Nittler
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: McCoy
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Xiao
authors.forename: David M H
authors.initials: DM
authors.lastname: Baker
authors.forename: Caleb I
authors.initials: CI
authors.lastname: Fassett
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Braden
authors.forename: Jürgen
authors.initials: J
authors.lastname: Oberst
authors.forename: Frank
authors.initials: F
authors.lastname: Scholten
authors.forename: Frank
authors.initials: F
authors.lastname: Preusker
authors.forename: Debra M
authors.initials: DM
authors.lastname: Hurwitz