title: Radar sounding of the Medusae Fossae Formation Mars: equatorial ice or dry, low-density deposits?
abstract: The equatorial Medusae Fossae Formation (MFF) is enigmatic and perhaps among the youngest geologic deposits on Mars. They are thought to be composed of volcanic ash, eolian sediments, or an ice-rich material analogous to polar layered deposits. The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument aboard the Mars Express Spacecraft has detected nadir echoes offset in time-delay from the surface return in orbits over MFF material. These echoes are interpreted to be from the subsurface interface between the MFF material and the underlying terrain. The delay time between the MFF surface and subsurface echoes is consistent with massive deposits emplaced on generally planar lowlands materials with a real dielectric constant of approximately 2.9 +/- 0.4. The real dielectric constant and the estimated dielectric losses are consistent with a substantial component of water ice. However, an anomalously low-density, ice-poor material cannot be ruled out. If ice-rich, the MFF must have a higher percentage of dust and sand than polar layered deposits. The volume of water in an ice-rich MFF deposit would be comparable to that of the south polar layered deposits.
authors.affiliation: Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, Washington, DC 20560, USA. watterst@si.edu
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Watters
authors.forename: Bruce
authors.initials: B
authors.lastname: Campbell
authors.forename: Lynn
authors.initials: L
authors.lastname: Carter
authors.forename: Carl J
authors.initials: CJ
authors.lastname: Leuschen
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Plaut
authors.forename: Giovanni
authors.initials: G
authors.lastname: Picardi
authors.forename: Roberto
authors.initials: R
authors.lastname: Orosei
authors.forename: Ali
authors.initials: A
authors.lastname: Safaeinili
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Clifford
authors.forename: William M
authors.initials: WM
authors.lastname: Farrell
authors.forename: Anton B
authors.initials: AB
authors.lastname: Ivanov
authors.forename: Roger J
authors.initials: RJ
authors.lastname: Phillips
authors.forename: Ellen R
authors.initials: ER
authors.lastname: Stofan
mesh_terms: D005118:Extraterrestrial Environment; D019015:Geologic Sediments; D007053:Ice; D018535:Mars; D011825:Radar
chemical_list: D007053:Ice