Medusae Fossae Formation - New perspectives from Mars Global Surveyor

The nature and origin of the Medusae Fossae Formation (MFF) on Mars has been debated since the return of the first Viking images. The MFF's young age, distinctive surface texture, and lack of obvious source have prompted multiple hypotheses for its origin. This study uses data from the Mars Global Surveyor (MGS) mission to examine the MFF at all available scales. We discuss and quantify observations from Mars Orbiter Laser Altimeter (MOLA) topography and Mars Orbiter Camera (MOC) images to better constrain the origin of the MFF. Topographic grid estimates yield a present extent of 2.1 x 10 exp 6 sq km and a volume of 1.4 x 10 exp 6 cu km; however, remnant yardang deposits observed far from the thicker lobes of MFF material suggest that it may have once covered up to 5 x 10 exp 6 sq km. We do not find compelling evidence for extensive fluvial reworking of the MFF; however, in several regions, buried channels are apparent in the MFF because the formation is draped over underlying topography. Layering is apparent at all scales, from submeter to hundreds of meters, with variable resistance to weathering. Continuity of layers appears to be local to regional, but not likely formation-wide. Yardangs form both parallel and bidirectional patterns, with resistant layers and jointing probably influencing their orientations. A comparative study of MFF regional topography and surface expression indicates that the MFF is quantitatively dissimilar to Martian polar layered deposits. The material is most likely a friable and irregularly consolidated air fall deposit of probable volcanic origin. (Author)